~PLANT PARTS~

Roots are underground parts of plants (but not all underground parts are roots). They have two main functions: 1. they anchor the plant in the ground; 2. they absorb water and minerals from the soil. Many roots, like the carrot, also serve as food storage organs for their plants.

A taproot is a single main root with distinctly smaller branch roots. Fibous roots are thin and all more or less the same size. The development of the root system depends both on the type of plant and on soil conditions, varying from the use of only a few inches of soil to 50-foot-deep forays in search of water. A single plant with a highly branching root system not untypically develops millions of roots totaling hundreds of miles in length and thousands of square feet in absorbent surface area.

Some parts of herbaceous perennial plants that many people consider roots are actually underground portions of the plants stem. These are classified as rootstocks (or rhizomes), stolons, corms, and bulbs.

A rootstock grows horizontally in the ground, sending down roots from its lower side and one or more erect stems (or sometimes leaves) from its upper side. One feature that distinguishes it from a true root is the presence of scally leaves at regular intervals along its length. The rootstock lives from year to year, sending up new growth each season. Some rootstocks are thick and fleshy; others are long and thin. Some thin rootstocks develop locally thick parts for food storage; these are called tubers (the potato being the best-known example).

A stolon is much like a rootstock, but it grows along the surface of the ground, sending roots down and stems up at intervals. A runner, like that of the strawberry plant, is a type of stolon.

A corm is a short, thick, vertical underground stem that survives from one season to the next in a dormant state. The second season it porduces one or more aerial stems and also one or more new corms. The new corms store food produced by the growing plant and then go through the next dormant period to produce their own plants and corms the following season. The 'bulbs' of gladiolus are actually corms.

Bulbs are different from croms, although the latter are often called bulbs. A bulb consists of a short, erect stem enclosed by fleshy leaves (as in onions) or leaf bases (as in daffodils) that serve to store food between growing seasons. Some bulbs survive for several years; others are replaced by new bulbs each year.

The portions of the plant that everyone recognizes as the stem is more precisely called the aerial stem. It's main functions is to bear leaves, the stem with its leaves being called the shoot. Herbaceous stems are those that contain no woody tissue; these usually die down at the end of the growing season, unlike their woody counterparts in trees and shrubs. Erect stems are those that grow more or less upward without special support; vines have stems that trail on the ground or climb by attaching themselves toother plants or objects. In addition to bearing leaves, the aerial stem performs the vital functions of transporting water and mineral up from the roots to the leaves and transporting manufactured food substances as they are distributed to all parts of the plant for use or storage.

Leaves come in all sizes and shapes (including some the look more like stems or like flowers), but the typical leaf has a flat blade and a stalk, or petiole, by which it is attached to the stem. Some leaves manage nicely without a petiole; these are called sessile. Leaves tend to grow in regular patterns on the stem; opposite leaves grow in from opposite sides at the same point along the stem; alternate leaves grow on opposite sides but at different points on the stem; whorled leaves grow in groups of three or more around the stem at one point. Radical leaves grow directly from a non-aerial stem. Simple leaves have a one-piece blade; compound leaves consist of individual leaflets which grow either from a single point (palmate leaf) or oppositely along the leaf stalk (pinnate leaf).

The typical flower consists of several whorls (circular ranks) of parts set on a receptacle, the somewhat enlarged end of a stem or flower stalk. The outermost whorl is the calyx, a set of leaf-like parts (sepals) that protect the flower before it opens. The next whorl in is the corolla, consisting of modified, usually white or brightly coloured leaves called petals. One or more whorls of club-shaped stamens come next; these are the male organs that provide the fertilizing pollen. The center of all this is the femal organ, the pistil, consisting of one or more carpels. A carpel is made up of a bulbous ovary which contains the seeds-to-be (ovules), and a stalk (the style), part of which (the stigma) is rough or sticky to capture pollen for firtilization.

Flowers that have the complete set of parts--sepals, petals, stamens, and one or more pistils--are complete; those that are missing one or more parts are incomplete. Perfect flowers have both stamens and pistils; imperfect flowers have only one or the other (a few have neither), being staminate (male) if they have stamens, pistillate (female) if they have pistils. Some plants bear both staminate and pistillate flowers on the same plant; others have the two kinds on different plants. The transfer of pollen from stamen to pistil--the polination necessary for seed to form--is accomplished in various ways, depending on the plant and physical circumstances. The usual ways are by direct contact between stamen and stigma, by insects, or by wind. Flowers can occur alone or in various kinds of clusters (inflorescences).

In botany, fruit has a much broader and yet more definte meaning than in popular usage: it is the ripened ovary or ovaries--somethimes with associated other parts--of a flower or flower cluster. True or simple fruits develop from ovaries only; accessory fruits (like strawberries or rose hips) develop from ovaries and one or more other parts of the flower. With few exceptions--seedless grapes and pineapples, for example--a fruit forms only after pollination.

Botanically, nuts, beans, corn grains, tomatoes, and dandelion 'seeds' are just as much fruits as are blueberries, oranges, cherries, and peaches. You may be suprised to find, though, that tomatoes, cucumbers, and oranges are berries; walnuts and almonds are drupes like cherries and peaches; and peanuts are lequmes like peas and beans.

The basic function of fruit is to provide for the dispersal of seed at the proper time, but the fruit also serves to protect the seeds as they mature. Considering that seeds range in size from barely visible (orchid) to over a foot in diameter (double coconut), you should not be surprised to find considerable variety in the dispersal mechanisms that differnt plants have developed. Some fruits split open spontaneously while still on the plant to scatter seeds onto the ground or into the wind; others drop from the plant intact but have wings or feathered tufts attached to help them ride the wind. And some maverick plants--collectively called tumbleweeds--abandon themselves to the wind entirely and scatter seeds as they roll along the ground. Some seeds are spread mainly by birds and other animals, which eat the fruit but excrete the undigested seeds. Prickly fruits often hitch a ride on passing animals or people who carry them elsewhare; others can float on water until they are washed up on a new shoreline. There are still other ways, but these are enought to suggest the boundless ingenuity of Nature in providing for the propagation of each species.

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