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Vines - we know what they are, but what makes a vine a vine, and how are they unique? In some places, the word “vine” is only used to refer to grapevines. But kiwifruit grows on vines. Pumpkins, watermelons, cucumbers, peas, and pole beans also grow on vines. Or do they?  Melon and grapes (Daria Shevtsova) Public Domain Types of vines Climbing plants use a variety of methods to reach the sun. They can be climbing or trailing woody-stemmed or herbaceous plants. In general, we call them all vines. Stems tend to be very long and often lack the supportive tissue needed for upright growth. This allows plants to grow upward without the same investment of energy and resources used by trees and other self-supporting plants.
To the purists, grapes grow on vines, all other woody climbers are lianas, and our pole beans, peas, and cucurbits are herbaceous vines.
Now you know. Your chewing gum is made from trees. Well, it used to be.  Unwrapped stick of chewing gum (Lusheeta) Tree gums have been used as a chewable treat for over 9,000 years. Mayans and Aztecs used gum from the chicle tree. Ancients Greeks used gum from the mastic tree. Native Americans used gum from spruce trees. It was the Americans, however, who make chewing gum famous to the point that there were not enough trees to produce the gum needed to make gum. It is estimated that over 100,000 tons of chewing gum are consumed each year. Most modern chewing gum is made with natural and/or synthetic rubber and not botanical gums. But gum isn’t the only goo produced by plants. Plant oozes Plants ooze several different substances. Gum is only one of them. Plants also produce fats and oils, latex, mucilage, resin, and waxes. The fats and oils produced by plants are more commonly known as essential oils. Essential oils can be responsible for a plant’s unique smell or flavor. Latex is the milky white emulsion of defensive chemicals seen oozing from broken dandelion stems. Mucilage is used to store food and water, thicken membranes, and in seed germination. Succulents and flax seeds have particularly high mucilage contents. Resin is a viscous mixture of antibacterial, antimicrobial acids commonly seen in conifers. Resin dries to a hard, crystalline structure. And then there is plain old sap. Sap has different components, depending upon where it is found. Xylem sap carries water, hormones, and minerals from the roots to the leaves. Phloem sap conducts sugars, hormones, and minerals from leaves, where carbohydrates are produced through photosynthesis. Sap generally stays fluid. Gums are a specialized type of sap produced by woody plants.  Natural gum of plum tree (Rencas) CC BY-SA 3.0 [Plum gum? Sorry, I couldn't resist.] How do plants use gums?
Gums are produced in a process called gummosis. Gumming refers to the way some plants can break down internal tissues, particularly cellulose, to create a high-sugar sap, or gum, used to seal off wounds and surround invading insects. Gums are commonly found in conifers, such as pine and spruce. Some plants, such as Western poison oak, use gums as protective, gummy seed coatings that delay germination. How do we use botanical gums? Botanical gums are water-soluble sugars that are commonly used in the food industry as emulsifiers, thickening agents, and stabilizers. They are also used as adhesives, in printing, candy-making, paper-making, and to make chewing gum. If you look at ingredient lists on packaged food (and I urge you to do so), you may see some of these botanical gums:
Gums are frequently collected by tapping or otherwise wounding trees with incisions or by peeling back sections of bark. The trees respond to these wounds by gumming. Tapping is the method used to collect the sap from sugar maple trees to make maple syrup. A tap consists of a metal tube with a downward-pointing lip and a notch or hook from which to hang a bucket. The tube end is hammered into a tree to reach the xylem and a bucket hung from the lip. Sap from the xylem flows (very, very slowly) through the tube, down the lip, and into the bucket. From there, the sap is cooked down to reduce the water content. More modern set-ups use plastic tubing. My students and I once made a delicious syrup/caramel from silver maple trees. Some of these gums stay soft, while others harden into “tears” which are broken off for processing. If you see gums oozing from your trees, take a closer look. The red juicy bits found inside a pomegranate are called arils. Arils are a type of accessory fruit, or false fruit.  Pomegranate arils (Kate Russell) True fruits and false fruits Fruit is the tissue that surrounds the seeds of angiosperms (flowering plants). Fruit is made from a plant’s ovary. Except when it isn’t. In some cases, a fruit develops from both the ovary and nearby tissue. These tissues can be either the perianth (flower whorls) or the hypanthium (the flower base). When this occurs, the part we eat is called an accessory fruit, or false fruit. Common accessory fruits include figs, mulberries, pineapples, and strawberries. Arils are specialized versions of these false fruits.
The same is true for soapnuts. And yew creates a cup-shaped aril fruit, rather than a traditional cone.  The edible white part of lychee is an arillode or false aril. (Peggy Greb, Public Domain) Like other fruits, the aril serves as an attractant to herbivores. As birds, animals, and people eat these fruits, the seeds are spread farther and wides, improving the odds of continuing that particular line of genetic information.
Now you know. Root hairs are where water absorption occurs. Since that water contains nutrients found in the soil, root hairs are important. And fragile. You might expect root hairs to grow along the entire length of a root system, but that’s not what happens. Root hairs only occur in specific areas, or zones, of a root system. Root zones Roots start out as undifferentiated cells. The very tip of a root is called the root cap, which protects the growing root as it moves through the soil. The next zone is where cell division takes place. As more cells are produced, the root cap is pushed forward. This growth is a relatively continuous process throughout the life of a plant. As new cells are produced and the root moves forward, the older cells stretch and create storage pockets called vacuoles. This is called the zone of elongation. Finally, growth and elongation are complete and root hairs can begin to emerge. This is called the zone of maturation. The reason root hairs do not appear right away in the growth process is because they are so delicate that they would be sheared off as the root moves through the soil. This is also what causes transplant shock. The act of transplanting can shear off a majority of the root hairs as the soil gets jostled about and uninformed gardeners tamp down the soil. Rather than crushing delicate root hairs, mudding in new transplants protects those important root hairs.
How root hairs absorb water and nutrients
Nutrient-rich water is pulled into the cytoplasm of root hair cells by osmosis. Root hairs also secrete malic acid, which helps convert minerals into ionic forms that are easier to absorb. Organic molecules in the soil, called chelates, also help root hairs absorb nutrients. Root hairs as defense mechanism Because root hairs are so small, they make it very difficult for harmful bacteria to enter the plant through the xylem. When beneficial bacteria, such as those which help legumes fix atmospheric nitrogen, appear, root hairs curl around the welcome visitor. This allows an infection thread to connect the two for everyone’s benefit. Helpful soil microorganisms, called mycorrhizae, are small enough to enter a plant’s root system through the root hairs. Root maggot larvae feed on root hairs. Plants use phosphorus to grow healthy roots. Before you add more phosphorus to your soil, be sure to send out a sample for a soil test. Too much phosphorus can be just as bad, or worse, than not enough. The way veins are arranged on a plant leaf can tell you a lot about that plant. That pattern of arrangement is called venation or veination. There are complex classification systems for leaf venation, but all you really need to know is that there are four basic patterns: pinnate, palmate, parallel, or dichotomous.  Orange leaf (Kate Russell) Pinnate Pinnate venation looks like a feather, with the primary vein emerging from the center of the base of the leaf and smaller veins, called veinlets, occurring at intervals and pointed outward at an angle. Pinnate venation is seen on citrus, walnut, and pistachio.
Palmate Palmate venation looks more like a hand with three or more veins radiating from the base. Grape, pumpkin, rhubarb, and sunflower are all examples of the palmate venation seen in most dicots and eudicots.  Millet leaves (Kate Russell) Parallel Two or more equal veins start and end together at the leaf ends while running parallel to each other through the middle. Parallel venation is common to monocots, such as millet and other grasses.  Ginkgo biloba leaves (Jakub Fryš, CC BY-SA 4.0) Dichotomous
Dichotomous venation is seen as repeated forking or Y-branching, as seen in Ginkgo biloba leaves. Other venation patterns You may also run into a few other leaf vein arrangements that don’t conveniently fall into one of those four groups. For example:
When you are trying to identify an unknown plant, venation can help solve the mystery! Heartwood is the dead center of a tree. It is usually a different color from the living wood and it provides the support needed to hold up a tree that might weigh several tons  Section of yew branch showing pale sapwood, dark heartwood, and pith (MPF CC BY-SA 3.0) Tree anatomy
Tree trunks are made up of several layers of tubes, surrounded by an outer layer of bark. These tubes are the vascular bundles that carry water and nutrients to the rest of the tree. One type of tube, called the xylem (or sapwood), pulls water and nutrients up from the roots. The majority of the trunk is made up of xylem cells. Another type of tube, called the phloem (or inner bark) carries the sugars made by the leaves through photosynthesis down into the rest of the tree. [I remember these two by saying, “Food flows down the phloem, while water and food rise in the xylem.”] Just between the xylem and the phloem is the cambium layer. This is where the actual tree growth occurs. At the very center of the tree is the pith, surrounded by layers of xylem cells. As these xylem cells age, they eventually go through chemical changes that make them solid, losing their ability to transport water and nutrients. There is debate about whether or not these cells are still alive. This is the heartwood. Characteristics of heartwood Heartwood is very strong. The amount of heartwood present depends on the species. Some trees, such as ash, maple, and pine, have very thick heartwood. Other species have only a little heartwood. This group includes chestnut, mulberry and sassafras trees. Some tree species have no heartwood at all. Heartwood gets larger over time. Young trees have very little heartwood, whereas older trees have significantly more. Heartwood is resistant to decay, but wood that looks like heartwood might also be infected with disease or dealing with an insect invasion. Louisiana homes built over 100 years ago out of of bald cypress heartwood appear to be as good as new because of the decay resistance of heartwood. The next time you need to remove a large branch or tree trunk, take a closer look at the layers and see if heartwood is present. If you have ever canned jelly or fruit preserves, you have probably used pectin. Pectin is found in many plants and it has some unique properties.  Cell wall and middle lamella (LadyofHats, Public Domain) The word pectin comes to us from the Greek word for “congealed” and with good reason. Pectin converts liquids into jelly, much the way gelatin does, the difference being that gelatin is made from animal skin and bones, and pectin is made from plants.
Pectin is found in most fruits, to one degree or another: But fruits are not the only plants that contain pectin. Carrots hold an average 1.4% pectin. Commercially, most pectin is made from citrus peels and apple pulp. Soft fruits, such as grapes and strawberries also contain pectin, but at very low levels. How do plants use pectin? Pectin is a structural chain of molecules used in cell walls. Pectin is a major component of cellulose, specifically a layer called the middle lamella. The middle lamella is an outer layer to plant cells that is used to bind cells together. This allows plants to grow larger. The level of pectin present in a plant varies over time due to factors such as plant age and seasonal changes. As fruits ripen, the pectin begins to break down, which is why the fruit becomes softer. A similar process occurs during abscission, when parts such as leaves naturally die and fall from the plant. In some desert plants, pectin has been shown to help repair DNA by creating a mucous layer that captures dew. How do we use pectin? Pectin is used for more than jelly making. Pectin also provides dietary fiber and it acts as a thickening agent and stabilizer for desserts, cosmetics, and medicines. Pectin also binds to cholesterol and slows the rate at which we absorb glucose. This is especially true when the pectin is from apples and oranges. You know that old saying about an apple a day? I guess they were right! The pectin found in apple pulp is also one of the best throat lozenges I know. The mucilaginous pectin provides a surprising amount of soothing relief. Next time your have a sore or scratchy throat, skip the menthol (an irritant) and slowly eat an apple. Cabbage and mustard plants are probably not your first thought when it comes to fruit. As strange as it may seem, the seeds and seed pods of radishes, broccoli, cauliflower, mustards, and other members of the cabbage family produce long, narrow, pod-shaped fruits called silique [se-LEEK]. If you only have one, it is called a siliqua [sil-eh-KWA].  Radish silique (Folini CC BY 2.5) More to pods than peas
Pods are a type of fruit that can be dehiscent or indehiscent. Dehiscent means that the structure opens spontaneously when its contents are mature. If a pod does not open automatically, it is called indehiscent. In either case, pods are made up of two identical long halves and they contain seeds. Those halves are called valves. Valves are the outer walls of the ovary. The two halves are joined along a seam, called a suture. Held between those two halves is a ribbon of seed-bearing tissue called the septum. Siliquose fruit anatomy If allowed to bolt, or go to seed, members of the cabbage family produce long, skinny fruits, commonly referred to as seed capsules or seed pods. These pods are each made from two fused carpels. The pods of legumes, such as peas and beans, are made from a single carpel. If a seed capsule is more than three times as long as it is wide, it is called a silique, or siliqua. If a seed capsule is less than three times longer than wide, it is called silicle or silicula. If you allow your radishes and other Brassicas to go to seed, you will see siliquae for yourself, plus you will have seeds for next year’s crop. Now you know. Did you know that pine cones are actually modified branches and leaves? It's true!
Cone anatomy Female cones are covered with plates called scales. Female cones start out as a central stem covered with bracts. Bracts are modified leaves or scales with a small flower or flower clusters in its axil. The bright red “petals” of poinsettia are not actually flowers. They are bracts. In some cases, the bracts harden and fuse to the woody seed scales.  Female cone anatomy (Nefronus) CC BY-SA 4.0
Types of cones The cones of holiday decoration fame are only one of many different types of cones. The scales can be arranged in one of two ways: imbricate or peltate. Imbricate scales overlap much like roof tiles and are attached along a common axis. Peltate scales do not overlap and are attached from a central point, more like an umbrella. Some cones look more like berries than cones. Araucariaceae (monkey-puzzle tree, kauri, and the nearly extinct Wollemia tree) - fused scales create a spherical cone; imbricate  Monkey-puzzle tree with seed cones (MPF) CC BY-SA 3.0 Cupressaceae (arborvitae, cypress, juniper, redwood, sequoia) - bracts and seed scales are fused; peltate
Pinaceae (cedar, fir, larch, pine, spruce) - archetypical cone; imbricate Podocarpaceae (Prince Albert’s yew, Matai) - many of the scales are fused into a brightly colored, often edible aril; imbricate
Sciadopityaceae (Japanese umbrella pine) - imbricate
Taxaceae (yew) and Cephalotaxaceae (plum yews) - female cones have only one scale, with a single poisonous ovule; the surrounding fruit is sweet but the seed is deadly While not conifers, cycads and welwitschia, or tree tumbo, also produce cones. Tree tumbo plants are considered living fossils and are unique in that female plants produce female cones and male plants produce male cones. How many cone-producing plants do you have? Plants are particularly thin-skinned. Did you know that a plant’s epidermis is only one cell thick? Just under that skimpy outer layer is a plant’s cortex. [This is one reason why using dish soap on plants is such a bad idea.]  Cross-section of non-woody eudicot root (Kate Russell) Cortex description The cortex is made up of thin-walled cells called parenchyma. Some of those cells are purposefully torn or separated to create air spaces. This porous tissue is called the aerenchyma [a-REN-ky-ma], from the Greek word for ‘infusion’. This word makes sense when you learn that the phloem is not the only part of a plant that transports nutrients. The cortex does, too! The cortex is responsible for transporting nutrients and carbohydrates into the central core of a plant’s roots through diffusion. But there is even more to the cortex than just nutrient transportation. Functions of the cortex Depending on the plant, cortical cells may also store carbohydrates, essential oils, latex, resins, and tannins. in many cases, the cortex also contains chloroplasts that are able to perform photosynthesis, converting carbon dioxide and water into simple carbohydrates. Taking things one step further, the cortex can then convert those simple carbohydrates into the complex carbohydrates found in bulbs, tubers, and root vegetables, such as beets, carrots, and turnips. The cortex also manufactures the bark seen on the outside of woody plants and the underlying cork. Cortex and water flow In herbaceous plants, the innermost layer of the cortex is called the endodermis and the outermost layer is called the exodermis. The endodermis and exodermis are unique in that all of the cell walls have a woody band, called the casparian strip, except those facing the center or the outside of the plant. These casparian cells help regulate the flow of water between the vascular bundles, found just inside the cortex, and the outer cells of the cortex and epidermis. #/media/File:Stem-histology-cross-section-tag.svg) Flax stem cross-section: 1. Pith 2. Protoxylem; 3. Xylem; 4. Phloem 5. Bast fiber 6. Cortex 7. Epidermis Pests and diseases of the cortex
Several bacterial diseases invade the root cortex through injury sites and natural openings. These diseases include bacterial wilt of beans (Curtobacterium), ring rot of potatoes (Clavibacter), cucurbit bacterial wilt (Erwinia), black rot of cucurbits (Xanthomonas), and Pierce’s disease of grapes (Xyella). The Pythium oomycete, which causes blackleg, also moves through the cortex. Dry, brown lesions seen in the main or taproot cortex can indicate Fusarium crown and root rot. The next time you cut a plant stem or root, use a magnifying glass or hand lens to see what’s really going on in there. There are some amazing things going on in there! Long, long ago, there were no flowers.  Nasturtium flower It wasn’t until the Cretaceous period, some 130 million years ago, that a handful of renegade cone-bearing gymnosperms started protecting their naked seeds with a new structure. This new, flimsy bit of color was so successful at boosting pollination rates that it spread far and wide, making flowering plants (angiosperms) one of the most successful types of plant life on Earth. That structure is the petal. Of course, that’s a pretty big claim for such a delicate flap of plant tissue. Too frequently discounted as an unimportant fashion accessory to more vital, functional parts of plant anatomy, there is far more to a flower petal than meets the eye! Before we get to the really astounding stuff, let’s make sure we know what we are talking about when we talk about petals. What are petals? You may be surprised to learn that petals are modified leaves. In fact, sepals, stamens, and carpels are all genetic twists on the leaf. As a modified leaf, a petal has a broad, flat area called a blade. At the narrow end, where the petal attaches to the plant, is the claw, which is very similar to a petiole, or leaf stem. Where petals are attached to one another is called the limb. The petals that make up a flower are called its corolla.  Primrose willowherb flower showing petals and sepals (Eric Guinther) CC BY-SA 3.0 Just under a collection of petals is another set of modified leaves, called sepals. Sepals are usually green. When discussing the combined petals and sepals of a flower, it is called the perianth. When sepals and petals are indistinguishable from one another, they are called tepals. [Aloes and tulips are tepals.] Sometimes, sepals look more like petals than leaves. When that occurs, they are said to be petaloid. Petals of parentage The number of petals present in a flower, the way the petals are arranged, whether or not they are fused to neighboring petals, or how much they are fused, as well as color are used by pollinators to find the pollen and nectar they seek. We can use the same information to identify unknown plants
First, flowers with 3 or 6 petals tend to be monocots, while flowers with 4 or 5 petals, or groups thereof, are most often eudicots, though not always. Petal arrangement, or floral symmetry, can also help with plant identification:
 Sunflower Petal power Petals, in particular, evolved to protect the reproductive part of a flower and to attract or repel specific pollinators. We know that flowers come in every color imaginable, but did you know that they also feature colors we cannot see, with glowing flight lines, traffic patterns, and welcome mats? It’s true! Flowers exist to attract the type of pollinator that will help them to procreate their species. Not all pollinators are created equally. It is a waste of resources for a plant (or any living thing) to attract the wrong sort. The story of floral scent Orchids produce floral scent in specialized sacs, but most flowers get their scent from chemicals produced by the petals. While many of us, along with most insect and bat pollinators, find floral aromas appealing, herbivores and disease-carrying insects often disagree with that evaluation. Combined with the colors, petal arrangement, and floral placement, floral scent works to increase a flower’s chance at becoming pollinated and/or fertilized. Did you know that plants use floral scent to communicate with each other? It’s true! The volatile chemicals that give a flower its fragrance trigger a behavioral response in a surprising number of neighboring life forms and no two floral scents are identical, sort of like snowflakes. Sensing a reproductively fertile neighbor, another flower may shift its chemical production to attract pollinators of its own. On the other hand, a fertilized flower will often release ethylene, a ripening agent, to discontinue the scent so that local pollinators will turn their attentions to neighboring flowers in need of pollinating. Also, injured flowers produce different scents than those being chewed on by herbivores. We can’t see it or smell it, but it’s going on all the time.  Scanning electron image of pollen grain resting on spiderwort petal (Public Domain)  Scanning electron image of clover petal surface (Public Domain) In the world of botany, a cane can refer to a stalk of bamboo or other grass, a reed, sugar cane, or new growth on a grape vine. Canes are also used to refer to blueberry, currant, rose, and kiwi stems, but we will leave them out for the sake of this discussion, which is more accurately geared toward blackberries and raspberries. Canes are the long, arching stems of perennial bramble fruits. These canes are filled with spongy pith and normally covered with sharp prickles. Because of those sharp points, bramble canes have traditionally been used in pleaching. Pleaching is method by which living bramble are cut in half, bent over and woven together. As the canes repair themselves, they create a dense, prickly barrier that few thieves or predators would care to cross.  Raspberries Cane lifecycle Brambles have perennial roots and crowns that grow new canes each year. New green canes are called primocanes. They turn brown and go dormant over the winter, to one degree or another. In spring, these now 2-year old canes are called floricanes. Flowers and fruit are only produced on floricanes, so you don’t prune them out. Once fruit set has occurred, canes should be allowed to die back before being removed. Cane growth forms Raspberry and blackberry canes can grow in one of two forms: erect or trailing. Erect brambles have stiff canes that arch. While not completely self-supporting, erect brambles tend to grow into huge thickets if not pruned. Trailing blackberry cultivars, also known as dewberries, will spread horizontally across the ground. If you live in a cold area, there are even late-season blackberry varieties that can produce late summer crops. The University of California provides an excellent list of blackberry cultivars. Cane fruit production Cane fruit production varies between everbearing and summer-bearing varieties. Summer-bearing canes bear one crop in summer on two-year old canes, while everbearing cultivars have two crops, one small crop in summer on new canes and one heavier crop in fall on two-year old canes. Everbearing cultivars are sometimes called fall-bearing. It is a good idea to check with your local Cooperative Extension Office to find the best cultivar for your location. Cane propagation Brambles can easily be propagated by a method of layering called tip layering. Tip layering consists of digging a small hole, 3 or 4 inches deep, and putting the tip of a cane into the hole and covering it with soil. At first, the tip will grow downward. Then, it will complete a U-turn in the soil and emerge above ground. That bend will develop roots, allowing the new plant to be separated from the parent plant in spring and replanted elsewhere. Cane management New canes should be trimmed to a 6” height. First-year canes can be pruned to a manageable size with renewal pruning, or trained onto a trellis. Stimulate lateral (fruit-bearing) growth by tipping, or cutting off the ends. When working in bramble canes, it is a good idea to wear long sleeves, long pants, and heavy gloves. Those prickles are sharp! Pests and diseases of canes Canes are susceptible to a number of different pests and diseases. Bacterial diseases, such as crown gall, viral diseases, such as tomato ringspot, and a slew of fungal diseases, including a number of blights, such as petal blight, spur blight, and cane blight, along with leaf spot, anthracnose, rust, and Verticillium wilt may also appear. If that weren’t bad enough, treehoppers, raspberry cane borers and another type of borer called the rose stem girdler, along with sawflies, lygus bugs, raspberry horntails, vine mealybugs, leafrollers, and tortricid moths (leaf roll) may feed on or damage bramble canes. For all those threats, canes are durable plants, once established. You do need to monitor for environmental conditions, such as dieback, insufficient calcium combined with infrequent irrigation, iron deficiencies, and sunburn damage.  There's nothing quite so delicious as ripe raspberries! Whichever cane fruit you decide to grow, you will receive many, many years of delicious summer fruits with surprisingly little effort. Just watch out where you plant them, they can spread!
The Daily Garden is all about plant vocabulary. Today, we are looking at overall plant anatomy because it can be difficult to talk about something if you don’t know the words. By taking a closer look at plant anatomy, we will be better able to understand each other, we can get more out of plant descriptions, and be better able to identify those mystery plants that always seem to pop up in the yard. Plant anatomy, or phytotomy, starts with simple descriptions of the outside and inside of plants. Remember those black-line masters from grade school used to teach parts of a plant? Well, let’s start there.  Parts of a plant: 1. Shoot system. 2. Root system. 3. Hypocotyl. 4. Terminal bud. 5. Leaf blade. 6. Internode. 7. Axillary bud. 8. Petiole. 9. Stem. 10. Node. 11. Tap root. 12. Root hairs. 13. Root tip. 14. Root cap (Bigman24225) CC BY-SA 4.0 Basic plant systems Plants are have two basic systems: roots and shoots, with the root system below ground and the shoot system above ground. Roots provide anchorage and often store nutrients. Roots can develop as a taproot or fibrous root system. Roots have hairs that absorb water and nutrients. The shoot system consists of vegetative parts (leaves and stems) and reproductive parts (buds, fruits, seeds, and flowers or cones). Let’s take a closer look at each of those parts. Buds are shoots that may develop into leaves or flowers. Buds are identified by their location on a stem: lateral buds are found along the sides of a stem, while terminal buds are found at the end. Lateral buds usually grow where leaves meet the stem and are called axillary buds. Renegade adventitious buds may show up at injury sites, on roots, or even at the edge of a leaf. The place where buds fall off leave a mark called a bud scar. Tree leaf buds have scales, while leaf buds of annuals and herbaceous perennials have delicate naked buds. Potato eyes are clusters of buds.
Individual petals may produce nectar or scent. All of the petals together are called the corolla. The combined corolla and calyx are called the perianth. The tip of a flower stalk, called the receptacle, contains the plant’s reproductive organs. Flowers can be male, female, or both, though not always at the same time. The female part, or pistil, consists of a pollen-receiving stigma, supportive style, and the ovary. The male part, or stamen, consists of a pollen-producing anther and a supporting filament. Flowers are very useful in plant identification. Fruits are ripened plant ovaries. Fruits can be simple (formed with one ovary), as in the case of stone fruits, or compound (formed with several fused ovaries). Compound fruits can be multiple or aggregate. Apples and other pomes are multiple compound fruits. You can tell by the 5-pointed star shape in the center of the fruit. Raspberries, which are drupes, not berries, along with pineapples and figs are formed by many flowers fusing together and are called aggregate fruits. By the way, strawberries are not berries, either. They are ripened receptacles. Berries, such as pumpkins, cantaloupes, cucumbers, eggplants, and tomatoes, all have many seeds inside an outer shell of varying thicknesses and hardnesses. Dry fruits, such as peas and beans, grow in pods that either open down a seam (dehiscent), or stay closed (indehiscent), as in the case of peanuts and most cereal grains, such as wheat and barley.  Parts of a leaf 1. Apex 2. Midvein (Primary vein) 3. Secondary vein. 4. Lamina. 5. Leaf margin 6. Petiole 7. Bud 8. Stem (Jessekar0524) CC BY-SA 4.0 Leaves are the sugar factories of the plant world, absorbing sunlight and converting it into sugar through photosynthesis. The wide, flat part of a leaf is called the blade, or lamina. The shape of the leaf blade is very useful in plant identification, as is the way those leaves are arranged along a stem and the pattern of veins within a leaf. The edge of the leaf is called its margin. Leaves are coated with a waxy protective cuticle. There are tiny holes, usually found on the underside of a leaf, called stoma, that allow plants to exchange gases with the environment and to regulate water flow within the plant. The stem that connects a leaf to a stem is the petiole. Leaflike structures seen at the base of the petiole are called stipules, Plant cells Genetic research and electron microscopes have brought plant anatomy to exciting new levels. Assumptions about kinship have been wrecked asunder and colorized scanning electron microscope (SEM) images can be breathtaking. Different types of plant cells gather together to create tissues. Those tissues come together to create the functional parts of a plant.  Colorized SEM image of Spiderwort pollen and stamens (Wikiwand)  Colorized SEM image of Mexican ivy pollen (Wikiwand)
Modified stems occur both above and below ground. Bulbs, corms, rhizomes, and tubers, such as potatoes, are below ground modified stems. Crowns, spurs, and stolons are aboveground modified stems. Thorns are also modified stems, but rose thorns are not really thorns. They are prickles, which are modified epidural, or skin cells. Stubby stems, called spurs, produce fruit buds.
Seeds have three parts: the embryonic plant, stored food, called endosperm, and a protective seed coat. As temperatures rise and moisture is absorbed through the sed coat, a primary root, called the radicle, will emerge, followed by the first stem, or hypocotyl. First leaves, or cotyledons often look very different from adult leaves. Ultimately, all those functional parts grow into delicious, nutritious foods that we can cultivate in our yards for decades. For me, feet up in the yard with a nice glass of wine beats standing in line at a grocery store any day! What do wedges of citrus, hard walnut shells, the white bits inside a pomegranate, and the paper coating around avocado pits have in common? They are all endocarps.  Grape interior (Courtesy of Carlos Conde's "Biochemical Changes throughout Grape Berry Development and Fruit and Wine Quality") How can this be? How can structures so very different be the same part? Let’s find out by starting with some basic fruit facts. Fruit anatomy The fruits and seeds we eat are plant ovaries. When a flower is pollinated and fertilized, three new structures form: seeds, pericarp, and placentae. Embryonic seeds attach to the placenta, and pericarp begins to grow, to feed and protect the embryonic seed, and to attract seed-spreading herbivores. There are three different types of pericarp tissue: exocarp (outer skin), mesocarp (flesh), and endocarp (inner layer). So, endocarp is the interior fruit that surrounds seeds. But what about all those differences? Types of endocarp Endocarp is generally not fruit in the way you would expect, unless you are talking about peppers or citrus. The fleshy parts of sweet peppers and chili peppers is the endocarp, as are those membranous wedges of fruity goodness found inside lemons, limes, and oranges. If you look inside an apple, the endocarp is the hard clear plate-shaped bits close to the seeds.  Parts of an apple (Eric Guinther) CC BY-SA 3.0 If you take a close look at a stone fruit, such as a nectarine or cherry, the endocarp is very hard and inedible. To us, it looks more like the shell of a nut. And guess what? The hard outer shell of walnuts, pecans, and almonds, that shell is the endocarp, even though, to us, it looks as though it is on the outside. Confused? Read on! Nuts about endocarp When a nut develops on a tree, the exterior rarely looks like what you see in the grocery store. Many nut species have smooth or furry green exteriors (exocarp). That exocarp coats a hard, familiar shell. That shell is the endocarp of a nut.  Immature almonds Stamens are the male aspect of a flower.  Pollen-coated stamens of Amaryllis Flowering plants, or angiosperms, have flowers that can be male, female, or both, though not usually at the same time. The word stamen comes to us from the Latin word for ‘thread’. This is because the stamen is a threadlike stalk, called a filament, which has a pollen-producing anther on top. The stamen usually surrounds the female part, or pistil, though not always .jpg) Stamens and stigma of ‘Stargazer’ lily (Subhrajyoti07) CC BY-SA 4.0 Plant families Different plant families have different arrangements of pistils and stamens. For example:
 Thorny caper flower (Wilson44691) Public Domain Edible flowers When eating edible flowers, it is a good idea to remove the stamen and pistils and just eat the petals and other parts. The only exceptions are violas and Johnny-jump-ups. In these cases, the other parts add good flavor. Saffron threads are the dried [female] styles and stigmas of a specific crocus flower species, not the stamen.  Nasturtium Melons, zucchini and other squashes can easily be hand-pollinated by breaking off a pollen-carrying stamen and touching each of the flowers flowers with it.
Now you know.
You’ve heard of tannins, but what are they? The word tannin comes to us from Medieval Latin and it refers to oak bark. Oak, chestnut, and other tanbarks were used in tanning leather. Now, I do not mean some cow slathered itself with cocoa butter and lounged on the beach. Hardly. The process of tanning a raw animal skin and converting it into durable leather requires a lot of hard work and some powerful chemicals. Tannins.  Chestnut tree (Public Domain) Tannin molecules Tannins are large acidic molecules that bind to and alter proteins, which is why they were used in tanning leather. Tannins also bind to starches, minerals, and cellulose. This binding action slows decomposition. You may have seen ponds in forest environments with brownish water. That brown color is likely caused by tannins leaching out of nearby plants and into the water. In the plant world, tannins are used as pesticides, to protect against predators, and to regulate growth. Protective tannins Plants produce tannins to make themselves less palatable and harder to digest. This discourages feeding by some herbivores. To counteract the presence of those tannins, some plant eaters have evolved to include a tannin-binding protein in their saliva. [Isn’t the world amazing?] The latex produced by dandelions contains tannins.  Chickpea seedlings contain tannins Tannins as growth regulators Tannins also have antimicrobial and allelopathic actions. Allelopathy is a type of plant chemical warfare in which one plants releases chemicals that inhibit the growth of neighboring plants. This growth regulation can occur by reducing the available nitrogen or oxygen in the soil, killing nearby beneficial soil microorganisms that support plant life. Edible tannins If you bite into an unripe fruit, it is the tannins that cause your mouth to pucker. As fruits approach maturity, the level of tannins decreases. Many popular garden plants contain tannins, to one degree or another, including:
 Persimmon tree in autumn (Gphoto) In autumn, when leaves turn color, the golds and yellows you see are the result of tannins.
Now you know. Botanical stigmata are part of the female reproductive system.  Closeup of stigma surrounded by stamen of White Lilium ‘Stargazer’ lily (Subhrajyoti07) CC BY-SA 4.0 Tiny stigmata may not grab your attention at first glance, but maybe they should. Before we learn why, let’s do a quick review of flower anatomy.
Carried by insects, bats, or wind, pollen is received at the stigma by sticky, specialized cells (stigmatic papillae). Once the pollen has been captured, the stigma, which is often quite moist, helps to rehydrate the pollen after its lengthy travels. Once hydrated, the pollen grain germinates, sending a pollen tube down the style to the ovary. To ensure that the proper pollen is collected, stigmas have evolved some very fancy attraction and capture methods. You may be surprised to learn, as I was, that high temperatures, usually above 104°F, for 2 or more days prior to pollination, can exhaust the stigma of tomato plants to the point they cannot capture pollen. This may explain why, during particularly hot summers, we see lots of tomato blossoms, but no fruit. High temperatures (above 100°F) also reduces pollen germination.  Delicate nectarine blossom stigmas Specialized stigma Besides being sticky, stigmas use various shapes, flaps, and hair arrangements to help ensure that the correct pollen is captured and all others are rejected. These shapes can be simple tubes, truncated tubes, threadlike, bulbous, conical, lobed, feathery, hairy, beaked, fan-shaped, brush-like, leaflike, or disc-shaped. The familiar threads found on ears of corn, called silk, are stigmata.
The long, bright orange stigmata of autumn crocus are harvested as one of the world’s most expensive spices: saffron.
How many different stigmata shapes are there in your garden? The word rachis comes to us from the Greek word for backbone. But, plants don’t have backbones!  Vertical fern rachis with horizontal leaflets (Christian Guthier) CC BY-SA 3.0 That’s true. But they often have a main axis or shaft, similar to those seen in feathers. In fact, the shaft of a feather is also called its rachis [ray-KIS].  ‘Buddleja paniculata’ inflorescence arranged along a central rachis (Ptelea) CC BY-SA 3.0 Botanically, the rachis can be the central stem seen in ferns, in compound leaves, or in the portion of an inflorescence found above the peduncle. Rachis is a type of stipe. Stipes are stalks that support other structures.
Now, when someone mentions a rachis or a stipe, you will know what they are talking about! When you cut flowers for a bouquet, you are generally cutting the peduncle. Peduncles are simply flowering stems, but they may surprise you.
Peduncles and inflorescences When clusters of flowers grow together, it is called an inflorescence. An inflorescence is also supported by a peduncle, but the stems within the cluster, supporting the florets, are called pedicels, or strigs. For example, clusters of grapes grow on a peduncle, while the individual grapes hang from pedicels. Peduncles can occur in plants without stems, they may continue to grow indefinitely, and some peduncles grow underground. The peduncle of a simple flower is easy to recognize. It is the classic stem you hold, cut, or put into a vase to admire. Its job is to support the flower. An artichoke stem is a peduncle, and for the same reason. Accrescent peduncles While many plants are hardwired to stop growing once they reach a certain size, other plants, such as the mighty redwoods, continue growing throughout their lifetime. In other cases, certain parts of a plant will continue to grow larger. These plants are called accrescent. In some cases, only the peduncle is accrescent, and then only until the flower reaches maturity
 Peanut pegs penetrating the ground (Alain Busser) CC BY-SA 1.0 Now you know.
A flower is a flower, unless it is a bunch of flowers growing on the same stem, then it’s an inflorescence.  Yarrow Anatomy of an inflorescence A singular flower appears at the end of a stem, called a peduncle, nestled in a (normally) green cup, called the receptacle, and surrounded by modified leaves, called sepals. When there are multiple stems or branching stems (rachis), or flowers that occur on a disk, it is an inflorescence. The stalks of individual flowers within an inflorescence are called pedicels. These flowers are called florets, and their leaves are called bracts.  Parts of a flower (USDA) Types of inflorescences Inflorescences can be determinate or indeterminate. The oldest flowers of a determinate (cymose) inflorescence are found at the end of the stem, as other flowers bloom in succession, down the stem, with the youngest flowers at the base. Indeterminate inflorescences are just the opposite, with older flowers at the base and younger flowers occurring closer to the tip.
There are also catkins (mulberry), spadix (cobra plant), and many subdivisions of each category, but this is a good start.
When an inflorescence produces fruit, such as sunflower seeds, it is called an infructescence. Now you know. We’ve all heard of a “hill of beans”, but did you know that beans have hilums? #/media/File:BlackEyedPeas.JPG) Cowpeas with visible hilums (Toby Hudson) CC BY-SA 3.0 Beans, peas, and other legumes produce fruits, called pulses, in pods. If you look closely, you can see where the seed attaches to the pod. Once the fruit or seed is mature, the pod opens along a seam, which means they are dehiscent. After the pod opens, the seeds fall to the ground where they are protected by a hard, water-resistant seed coat.
Seed coats have scars. When the seed separates from its pod, one scar is formed. This scar is called the hilum. On beans, the hilum is called the “eye”. Another scar, called the raphe, is a seed’s bellybutton. This is the scar that forms when the seed was separated from its placenta, within the pod. If you look even closer, you can see a tiny opening, called the micropyle, at one end of the hilum. This opening is where water is absorbed to allow germination to occur. Chestnuts have hilums, too. Now you know. You’ve read the word countless times but what, exactly, are bracts? Bracts are specialized or modified leaves  Purplish-pink bougainvillea bracts surround tiny white flowers (Lumbar) CC BY-SA 3.0 Bracts are generally associated with a reproductive structure. That reproductive structure may be a flower, a cone, or an inflorescence. An inflorescence is a cluster of flowers. Bracts rarely look similar to other leaves on the same plant. They may be smaller, larger, a different shape, or a different texture. Plants with bracts are said to be bracteate or bracteolate, while plants without bracts can be referred to as ebracteate or ebracteolate. Very small bracts are called braceoles or braclets. Botanically speaking, bracteole are any bracts that occur on a pedicel, instead of under it. Pedicels are the tiny stems that hold individual flowers within an inflorescence. The presence of bracts, or lack thereof, can help you identify plants. Many shaped bracts The tiny leaves seen at the base of pineapples and dandelions are bracts. [Note that bracts are not the same thing as sepals. You can see the difference easily when looking at the base of a dandelion.] In many cases, what you think are flower petals are actually specialized bracts, called epicalyx. Dogwood, hibiscus, poinsettia, and bougainvillea are common examples of bracts looking like flowers. Occasionally, you may see an epicalyx formation in strawberry flowers.
Two large bracts coming together, or one large bract forming a sheath, is called a spathe. Iris, crocus, and palm spathes enclose flower structures as they develop. Peace lilies form flowers on a spike, called a spadix, which is shielded by a large white spathe. Grass family bracts Cereal grains, such as wheat and millet, and the grasses found in your lawn, have tiny florets that are held in a pair of bracts. The upper half is called the palea and the lower half is called the lemma. Each group of grass flowers, called spikelets, also have a pair of bracts, called glumes, at the base. When grain is winnowed to remove the chaff, the chaff being removed is made up of those bracts.  Bracts of a grain spikelet (Aelwyn) CC BY-SA 3.0 Conifer bracts
Pine cones are covered with scales used to protect seeds. Female cones have two types of scales, bract scales and seed scales. Bract scales grow under seed scales. This positioning is called subtending. Bract scales are more obvious at the time of pollination. Very often, seed scales will grow over bract scales as seeds mature. The next time you walk past a flower, take a moment to enjoy its fragrance and see if you can spot the bracts, while you’re at it. Because now you know. Apple trees produce fruit on spurs. Spurs are stubby stems that form along longer stems. Bourse shoots are vegetative growths that do not produce fruit, but they are an important part of fruit production, and we are still not entirely sure why. [Being cousin to apples, all of this information is relevant to pears, as well.]  Bourse shoot on apple stem (USDA Extension) CC BY-SA 3.0 US Apple tree anatomy
Before we learn about bourse shoots, we need a quick review of apple tree anatomy. Apple trees tend to grow long stems. If those stems grow upright, your apple tree is of the alternate bearing variety. If those stems tend to hang downward, your apple tree is a regular bearing type. [Many commercial apple growers spray chemicals on apple trees to cause artificial fruit drop on heavy production years to encourage a bigger return bloom the following year. Return bloom refers to the blossoms that appear after the current crop is under way. This evens out annual fruit production, maintaining supply and keeping prices consistent.] One study, published in the Journal of Horticultural Science, explains how the removal of too many bourse shoots significantly reduces return bloom. Along those stems, whichever way they happen to grow, are little stubby growths called spurs. The majority of an apple crop is found on the ends of spurs. Each spur can produce fruit for 8 to 10 years, or more. Those spurs grow out of swollen areas, called bourses. Bourse shoots Not to be confused with bourses, bourse shoots are vegetative stems that emerge just below flower buds. In some cases, new spurs can suddenly shift their growth to become a bourse shoot instead of a spur. These bourse shoots feature a whorl of leaves. In the center of those leaves, a bud may form later in the season, but they tend to be less productive than spurs. This transition from vegetative growth to floral growth, called floral inflation, is believed to be caused by an abundance of sunlight and sugar. Other causes of floral inflation include fruit thinning, summer pruning, and bending upright shoots to a more horizontal orientation. Bourse-over-bourse A common term among apple growers is bourse-over-bourse. This refers to bourse shoots emerging from existing bourse shoots, in a waterfall style growth pattern. Too many bourse shoots on one stem can lead to spur extinction. Spur extinction describes the point where a spur is no longer productive. If you see multiple bourse shoots on a stem, you can improve fruit production by pruning back to the innermost bourse shoot. Pruning apple trees Standard dormant season apple pruning involves removing all dead, diseased, or rubbing branches, as well as 15 to 20% of the previous year’s growth. Next, you should remove excessive bourse-over-bourse growth, and bourse shoots that are especially long, as they tend to be less productive than shorter or medium-length bourse shoots. Don’t remove too much, however. One study, published in the Journal of Horticultural Science, explains how the removal of too many bourse shoots significantly reduces return bloom [next year’s crop]. Bottom line: next year’s apple (or pear) crop is highly dependent on the number of leaves produced during the current year. If your apple tree has more bourse shoots, it is more likely to have more leaves, ergo, more fruit. But this is only true if those bourse shoots are spread evenly throughout the tree. Today, we are looking at some cutting-edge research in the world of plants. It may not make you a better gardener, but you’ll know more about plants than pretty much everyone else, and you may look at your plants a little differently.  Exosomes (Maximus155) CC BY-SA 3.0 Plant cells Imagine, if you will, a tiny plant cell. Within that cell is a bubble of fluid, called a vesicle. Vesicles form naturally as plant cells eat and poop and go about their business. You can think of these bubbles as microscopic burps that stick around. Plant cells can also create vesicles on purpose. When this happens, they are called liposomes. [Keep in mind that this is an extreme oversimplification of what is actually going on, but you’ll have the basic idea.] A plant cell may have several vesicles, which cluster together into groups, called multivesicular bodies (MVB). Vesicles Vesicles are extremely small. They range in size from 30 to 150 nanometers (nm). A nanometer is one billionth of a meter. By comparison, plant cells range from 10 to 100 micrometers, while animal cells can be 10 to 30 micrometers. Micrometers (μm) are one millionth of a meter. A strand of human hair ranges from 17 to 181 µm. Ergo, one human hair = 10 plant cells = 300 vesicles What do vesicles do?
Plant cells use vesicles to move materials around, process proteins, maintain buoyancy, and all sorts of other things that we are only now learning about, though scientists have known about the existence of vesicles for a while now. What we didn’t know, until very recently, is that plant vesicles perform the same function as a type of animal cell vesicle, called an exosome, does. Their job is to take material from the interior of the cell, attach itself to the inner plasma membrane, create an opening, and then release the material into the apoplast, which includes the cell wall and the space between cells. Fungal cells do the same thing, but we didn’t know plants did until very recently. In animal cells, there are specialized vesicles that check the load being carried by other vesicles, to see if the contents should be destroyed or moved to the apoplast. Plant cells do not have those specialized gatekeepers, so there is still plenty to learn. Now, this may not sound like a Big Deal, but this is how cells communicate with each other, triggering plant growth and defensive measures. In fact, exosomes are directly related to the production of defensive proteins and RNAs used to fight disease. Exosomes are also used to move those defensive proteins from nearby healthy cells to a cell under attack by a pathogen, to create protective barriers against disease, and they can even enter invading cells to inhibit their growth. [If you are interested in this sort of thing, it is called host-induced gene silencing.] On the down side, exosomes also play important roles in malignancy. In the not-too-distant future, we may be seeing artificially generated plant exosomes crafted to boost our plants’ ability to fight disease. Similar studies are being conducted to see if plant exosomes can be used in human medicine, such as exosomes found to reduce alcohol-induce liver damage in mice, or how vesicles of the ginger plant may be able to reduce inflammation in the human digestive system. For now, I will stick with ginger tea, but maybe exosomes were the reason it has been helping all along… Lenticels are porous tissues used in plant respiration. Plant respiration involves exchanging oxygen, carbon dioxide, and water vapor as part of photosynthesis and other cellular functions to generate or release energy. The words ‘lenticel’ and ‘lenticular’ refer to the more common lentil-shape of these openings, but theses raised areas can be round, oval, or elongated. In some cases, such as silver birch, lenticels appear as horizontal cracks.  Dark horizontal lenticels on silver birch (Sue Sweeney) CC BY-SA 3.0 There are two types of lenticels: those found in the stems, trunks, and roots of woody plants and trees, and those found in the skin of certain fruits, such as apples. Fruit lenticels Many apples and pears, in particular, have fruit skin lenticels. These are the tiny nicks of color seen on the skin. These lenticels start out light colored and then darken as the fruit reaches maturity and is ripe for picking. This darkening occurs because of the formation of cork cells. These openings are often the site of failing stoma, broken off trichomes, or other points of early damage, rather than planned growth. The number of lenticels seen on pome fruits can vary by species and by the availability of water during early development.
Bacterial and fungal disease can enter the fruit through these openings. There is a global skin disorder of pome fruits, called ‘lenticel breakdown’, in which 1-8 mm pits develop at the lenticels just after processing. Tree lenticels Trees and other woody plants have lenticels in their bark (periderm), both above and below ground. These openings facilitate the necessary exchange of oxygen, carbon dioxide, and water vapor. Since different species have uniquely shaped lenticels, knowing the characteristic shape of a tree’s lenticels can help in identification  Lenticels on birchbark cherry (Rosser1954) Public Domain Trees growing in low oxygen environments, such as mangroves, have lenticels on specialized roots. Grapes, on the other hand, have lenticels on their pedicels, or flower stems. Grape lenticels react to changes in temperature, rather than oxygen levels.
Did you know that potatoes have lenticels? Now you know. |
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