Apoptosis

Everything dies. The programmed death of cells within a plant is called apoptosis.

Sooner or later, the end comes for all living things. In the world of plants, the timing of death is used as a major classifying factor. That’s why we say a plant is perennial, annual, or biennial. Within the world of plants, there are three types of death:

• necrosis - uncontrolled method of death, such as being stepped on, or hit by a car
• autophagy - ‘self-eating’; the absorption of a plant’s own tissues leading to death
• apoptosis - planned release of certain proteins that cause the uninterruptible death of a plant

Annual, biennial, and perennial

Annual plants complete their entire life cycle in one growing season. That may sound like a raw deal, but the male luna moth only gets three days and no mouth. (See, perspective is everything.) Within an annual plant’s DNA is a series of instructions that drive the plant to produce seeds for the next generation before the seasons change for the worse. Biennials get a two year cycle to accomplish the same ends. Perennial plants are, well, perennial. They keep on going. Some perennials last 10 to 20 years, or upwards of 50, in the case of most fruit and nut trees. Some perennials, however, have seen the coming of electricity, Christ, and even the Bronze Age, and the invention of writing! If you count clones as the same plant, there is one Tasmanian shrub, King’s lomatia (Lomatia tasmanica), that has been around for somewhere between 43,000 and 135,000 years! It boggles the brain. Even these ancients will eventually succumb to senescence. Senescence refers to the stage in a plant’s life when its metabolism slows prior to death.

The process of apoptosis

The programmed cell death of a plant begins with instructions from the mitochondria, activating certain proteins, called caspases. These proteins trigger other proteins that lead to cell shrinkage, bulging (called ‘blebbing’ - how cool is that?), and fragmentation of the nucleus and DNA. The individual cells technically commit suicide in response to predetermined growth and survival factors.

The end is nigh!

So, what does all this have to do with your garden? First, understanding that some plants are preprogrammed for a short life, you can select the plants that best suit your purposes. Do you want trouble-free perennials, such as rhubarb and asparagus, that will come back, year after year, or do you prefer the more tender annuals of cucumber, peppers, and corn? Taking into account a plant’s lifespan can help you to design your garden and landscape more effectively.

And, hey, with words like blebbing and senescence, your friends are sure to be impressed!