Over 270,000 species populate the plant kingdom. With the exception of mosses and ferns, plants reproduce by seed. Plants feed the planet, offering nutrition, oxygen and shelter to humans and animals. Fruits and vegetables, herbs, trees, shrubs, grasses, grains and countless flowers populate every continent and climate. In addition to the life-sustaining benefits, plants inspire us with a wealth of colors, shapes and sizes that develop and change with each season.
Seeds, comprised of an embryo, nutrients and a protective coating, begin the growth cycle when temperature and moisture conditions are optimal. Most seeds require temperatures of 70 degrees Fahrenheit or higher to sprout. Depending on soil conditions, temperature and the type of plant, germination takes anywhere from three to 30 days.
Once seeds sprout, the root and shoot systems begin to develop. Seed plants possess either a taproot or fibrous root system. Taproots bear one central root that grows deep into the soil and sprouts smaller roots along the way. Fibrous roots are comprised of many small roots that spread shallowly, in horizontal and vertical directions. Shoot systems begin to form once the root is established, producing one or two sets of leaves that will form the base for the plant.
Stem and Foliage
The stems and branches of a plant, depending on type, can be either woody or herbaceous in nature. Woody plants start with thicker, denser stems and branches that turn to wood over time. Herbaceous plants grow thinner, weaker branches and stems that die off at the end of the growth cycle. Leaves, either simple (one leaf) or compound (fragmented leaflets), form on branches
Once foliage is established, the seed plant forms the reproductive system, enclosed in the flower. Fruit and vegetable plants form flowers for the purpose of fertilization, which results in the final fruit or vegetable. These plants are referred to as angiosperms, meaning that the seeds are enclosed within the fruit. Gymnosperms are those plants that produce seeds that are exposed, such as conifers.
After fertilization, the seeds begin to develop within the ovary of the plant. In flowers, the seeds mature as the flower ages, blooms and dies. In fruits and vegetables, the seeds mature during the growth of the fruit and can be harvested once it completely ripens.
When seeds mature, the plant passes into the final cycle, death. Seeds move into a dormant phase unless they are dispersed and germinated. Dispersal can occur naturally, through insects, animals, rain and wind, or by human hand through collection. After dispersal, the stems, foliage and roots of annual plants die. In perennial plants, foliage dies away, but the root system, stems and branches remain to produce through subsequent seasons.