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A while back, lectins made their way into the media. They were held responsible for practically every illness known to man, thanks to Steven Gundry’s book, The Plant Paradox. He claimed that lectins were responsible for disease and obesity. He was wrong. There is no scientific evidence to support his claims. But lectins can hurt you. Let’s learn the truth about lectins and how they impact the plants in your garden (and your body).  Toxic lectin found in fava beans (Thamelry) Public Domain What are lectins? Lectins are protein molecules that bind to specific carbohydrates. The word lectin comes to us from the Latin word for choose, which is a good description of what scientists believe lectins do inside your plants. While more research is needed, lectins appear critical to cell recognition. Plants use lectins to facilitate interactions between pollen and the stigma during pollination. They also play a role in maintaining seed hull integrity. When a plant cell bumps into harmful bacteria, beneficial microorganisms, or fellow plant cells, lectins initiate the proper response. That response can be anything from toxic warfare, a welcome mat, or cell-to-cell communication.
Lectins as toxins
The toxic warfare response may be what triggered Mr. Gundry's belief that lectins cause human disease. Lectins are toxic in specific situations. They are the reason why beans and other legumes are difficult for us to digest. That’s why we cook them. The heat breaks down the lectins (among other things). Can lectins hurt me? Some plants contain enough lectin to cause illness or even death. Castor oil beans are one example - but who wants to eat those?
In most cases, we typically can not eat enough lectin-containing plants to hurt us. As always, take sensational media with a grain of salt. And cook your beans.
We’ve all heard more about pandemics in the past couple of years than anyone would care to know. But the plants in your garden are in a PAN-demic of their own. PAN is short for peroxyacetyl nitrate. [You can see why we call it PAN.]  Symptoms of air pollution damage (Mary Ann Hansen, VA Polytechnic Institute, Bugwood.org) CC BY 3.0 PAN is second only to ozone in its toxicity to plants. As a type of air pollution, it is hardest on small plants and young leaves. What is PAN? PAN occurs when sunlight hits car exhaust and industrial gases. We won’t get into the chemistry of it or the different types of PANs. It’s enough to say that hydrocarbons interact with nitrogen in the air, creating problems for plants. PANs occur in high-traffic areas and industrialized regions. Vulnerable plants Like other garden issues, not all plants are affected equally. Beets, cane fruits, celery, dill, endive, escarole, fennel, lettuces, melons, oats, peppers, pinto beans, potatoes, spinach, sunflowers, Swiss chard, and tomatoes are all vulnerable to PANs in the air. If you live in an area where PAN might be a problem, broccoli, cabbages, corn, cucumbers, lima beans, onions, radishes, sorghum, and wheat should perform better than more sensitive plants.  Air pollution damage to blackberry (Robert L. Anderson, USDA Forest Service, Bugwood.org) CC BY 3.0 Symptoms of PAN PAN causes the tissues that make up the underside of leaves to collapse. This damage may appear as bronzing, glazing, or silvering. These discolorations commonly appear in bands or blotches. When pinto beans and tomatoes are affected by PAN, the tissue collapse may affect the whole leaf. In grasses, like corn and millet, leaves affected by PAN look bleached. Chlorosis, early maturity, premature leaf drop, stunting, and weather flecking also occur.  Air pollution causes weather flecking of tobacco (R.J. Reynolds Tobacco Company, Bugwood.org) CC BY 3.0 PAN can combine with ethylene to make matters worse. Healthy plants produce ethylene as part of the ripening process. But ethylene is also found in vehicle exhaust and industrial fumes, which means there is often too much of it available. Ethylene acts as a plant hormone. And we’ve all seen what happens when people take too many steroids.
Symptoms of PAN combined with ethylene include downward leaf and stem curling (epinasty), inward petal curling and the failure of buds to open (sleepiness), and stunting. Color breaking in blossoms and early petal drop may also occur. Bottom line: air pollution is harmful to all of us. A mosquito the size of an elephant?!!? Now that would be terrifying. _(22086368412).jpg) Close-up of elephant mosquito (Christopher Johnson) Public Domain Luckily for us, elephant mosquitos, and their siblings in crime, treehole mosquitos, are mosquito predators. This means they eat mosquito larvae. They eat a lot of mosquito larvae. Each one may consume 5,000 mosquito larvae before they reach adulthood. And you don’t need to start worrying about the adults either. Instead of blood, adults use sugar from nectar to produce their eggs.  Elephant mosquito (Judy Gallagher) CC BY 2.0 Predatory mosquito description Elephant mosquitos (Toxorhynchites rutilus septentrionalis) and treehole mosquitos (T. r. rutilus) are larger than blood-sucking varieties. The wingspan is similar to an American quarter. They are also more brightly colored than biting mosquitos. These predators have bright yellow markings with green or blue metallic bars. The larvae are also larger than their blood-sucking counterparts.  Treehole mosquito (PA Dept. of Conservation and Natural Resources - Forestry, Bugwood.org) CC BY 3.0 Predatory mosquito development
Predatory mosquitos start out like other mosquitos. White, football-shaped eggs are laid in tree cavities and other spaces that contain water. They also use all the other stagnant waters that pesky mosquitos use: flower pots, pet watering bowls, patio furniture, and tires. Mosquito eggs are the size of a grain of sand. The eggs hatch into larvae. Predatory mosquito larvae go through four growth stages or instars. As they grow, they feed on anything nearby that moves, including each other. And this presents a problem. The problem with predatory mosquitos is that you generally haven’t been able to buy them. Unlike our cheery ladybugs and voracious praying mantis, predatory mosquitos don’t take kindly to mass commercial breeding programs. They simply eat each other. Instead of hundreds of helpful predators, you’d end up with a handful of overfed gluttons. Scientists are working on this. For now, the best thing you can do is maintain a healthy environment with lots of biodiversity and use pesticides judiciously. While Bacillus thuringiensis (Bt) will kill biting mosquitos, it doesn’t seem to affect their predatory cousins. As someone who grew up in the San Fernando Valley of Los Angeles in the 1960s and 70s, I am no stranger to air pollution. I recall days when we had to stay indoors at school because the air quality was so bad. And, no, we did not have air conditioning. It was terrible. Luckily, I had a great 6th-grade teacher, Ms. Melching. She would dim the lights and read to us about blizzards. It helped. But the polluted air gave us headaches and respiratory problems.  Smog in Utah, 1950 (CDC) Public Domain Plants need clean air to grow and thrive too. But it can be hard to recognize the damage caused by air pollution. It often looks like a disease, heat stress, mite feeding, nutrient disorders, or water stress. If you can rule those problems out, consider air pollution. Types of air pollution Air pollution is estimated to cost US agriculture over one billion dollars annually. This damage can be chronic or acute. The smoky yellow skies from fires or fumes from a chemical spill fall are acute forms of air pollution. More likely, your plants are feeling the effects of long-term exposure to low levels of pollutants from industry, power generation, and vehicles. The most common pollutants include nitrogen oxides, ozone, peroxyacetyl nitrate (PAN), and sulfur dioxide. Ammonia, chlorides, chlorine, and fluorides may also be in the mix choking your plants.
 Ozone damage to maple (Robert L. Anderson, USDA Forest Service, Bugwood.org) CC BY 3.0  Tip burn after 4-hours of 6.5ppm of ozone (USDA Forest Service, Bugwood.org) CC BY 3.0 Protecting your plants
Healthy plants can protect themselves better, so keep them well-fed and watered. Also, the damage occurs most often during warm, humid days with no wind. Monitor air quality in your area and give your plants a light shower from the hose on days with poor air quality. You can also help your plants (and yourself) by learning about the industries currently or recently active in your area (or upwind). And think about how you spend your money. Are you supporting companies that protect the environment or opting for cheap stuff? |
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