Ask Mr. Smarty Plants

A plant grows in the same way as animals, including humans, grow--by cell division. A cell is a very tiny building block of living organisms, visible only in a microscope. A typical plant cell can be thought of as a large factory, capable of manufacturing thousands of different products from the raw materials of water, soil and air. The factory uses sunlight rather than electricity or oil as an energy source. Whenever increased productivity is needed, the cell simply builds an exact copy of itself, within a day or two. This incredibly sophisticated process is a chain of chemical reactions called metabolism. The individual cell is approximately 1/2000 of an inch square. The really cool thing is, these cells "know", from the very first cell, that they will divide and combine to make a specific living thing; perhaps a tiny wood violet or a giraffe, a giant redwood or Aunt Elsie. Electronic engineers are justifiably proud of the tiny chips they have invented and manufactured containing immense amounts of information, but Nature beat them to it by several million years!

So, to deal specifically with how plants grow by cell division, and forget about the giraffe and Aunt Elsie. Each cell is designed to function as an independent unit. As the plant grows and develops, the cells will act in concert, adapting to needs of the plant, lengthening and developing in parallel with the general vertical growth of the roots and stems. This is called "primary growth" and ensures that leaves are quickly elevated into sunlight and roots penetrate deeply into the soil. Secondary growth occurs as the need arises for thickening at the base of the plant, extending into the roots, for stability and support. And each time a cell divides, the exact genetic instructions exist in both divisions so that the plant continues to "remember" what it is supposed to grow up to be, and how to go about it.

Now, to jump ahead. Every living organism has a built-in instinctive requirement to make more organisms like itself. A plant will at some point bloom, the blooms will be pollinated and seeds will be created. In an annual like the bluebonnet, which must grow and reproduce quickly while conditions are favorable, emerging from the soil, blooming and setting seeds takes place in about 3 months. A larger perennial flowering plant or shrub may take a year or so to mature to seeding, while trees that will grow much larger could take several years. A plant called the Agave havardiana (Havard's century plant) will take 20 to 40 years to bloom, bloom once and magnificently, make seeds and then the plant dies.

However long or short a time, all plants will produce some sort of reproductive matter, usually seeds but it could be spores as are found in ferns. It's easier to illustrate the development of a plant from a seed. Seeds come in all sizes and shapes, from something that looks like a grain of dust to a fairly large pinto bean. The seeds have evolved over eons to survive the habitat in which they find themselves, and to be transported hopefully to a fertile spot for them to grow. Many, many more seeds are produced than ever manage to find a place of their own, many of those seeds are consumed by predators or fall where they cannot grow, like cement. And, of those who do find a place to sprout, there are more predators that love a tender, fresh sprout, and the tiny plants can also be damaged by drought or drowning or some toxin in the earth or air. The wonder is that any of them survive, but adaptation to conditions determines whether a species will continue to exist or disappear.

Finally, the seed has found a good piece of dirt to call its own. It may have to wait years until there is moisture in the soil, the air is warming to a temperature at which growth is possible, and the seed can come out of dormancy and get a new plant started. We found a California State University website with illustrations of "How Seeds Germinate" that will help understand this incredible transformation. And then the whole process begins again, to grow stems and leaves and branches, to flower and be pollinated and make seeds to cast out for reproduction. And that's how a plant grows.