When gardeners learn about the structure of a flowering plant, they also gain an understanding of the natural world as a whole. This knowledge allows a gardener to troubleshoot problems with a plant's growth and, as Barbara Damrosch says in "The Garden Primer," allows the gardener to "think like a plant."
Variations in Flowering Plants
Annuals, like snapdragons or squashes, grow for one season only; biennials, like foxgloves and carrots have a two-year life cycle. Perennials, such as potatoes or chrysanthemums, live for more than two years. All annuals are herbaceous, with soft, green stems. Perennials are either herbaceous or woody flowering plants, with brown bark-like stems.
A plant's roots serve many functions---they keep the plant in place in the soil, they absorb water and nutrients from the soil, and they transport the water and nutrients to the stems and leaves. Some roots are joined underground by rhizomes and tubers, which are really an underground portion of the plant's stem that store nutrients when the leaves die in winter.
A flowering plant's stems support the plant, leaves, buds and flowers. Stems also transport water and minerals from the roots to the leaves and from the leaves to the other parts of the plant. The stems are composed of bundles of tissue covered by an outer protective skin that is soft in herbaceous plants and made of bark in woody plants. The tissues include both the transporting tissues (vascular tissue) and the packing or protective tissues (parenchyma).
Photosynthesis takes place inside the leaves. Here, chlorophyll absorbs energy from sunlight, mixes it with water and carbon dioxide, forms sugar glucose that the stems will transport to the entire plant and releases oxygen as a waste product. All leaves contain veins to do this work. However, some are simple, single leafs, while others are compound, composed of separate leaflets. Compound leaves are either pinnate, with leaflets on both sides of the leaf's center axis, or palmate, with leaflets formed from a single point at the tip of the leaf stalk.
Flowers, where sexual reproduction takes place, begin in the outermost layer with the mostly green sepals protecting the developing flowers. Next to the sepals are the petals which surround and protect the male and female organs of the flower. The male stamens appear as slender stalks with yellow anthers containing pollen at the tip. The female organs in the center of the flower are called the pistil and consist of an ovary, style and stigma. The ovary appears as a bulge at the base of the style, which is a thicker, longer version of the male stamen; the stigma is the tip of the style, similar to the anther.