Eating Plants

This came up at lunch today. To distinguish between fruits and vegetables, it is necessary to remember how plants reproduce. Most plants reproduce sexually but have both male and female sexual organs. The androgynous reproductive organ of the plant is the flower.

The male portion of the flower is called the stamen, which consist of a filament, upon which pollen sacs are usually kept, and a perianth, which are the petals or other outward display of the flower intended to aid in pollination (by attracting bees or other pollinating animals, for instance).

The female portion consists of several pistils. Each pistil consists of a stigma, which is an open portion of the tissue that receives pollen; the style, which is a stalk that moves nutrients to and pollen from the stigma, and the ovary, which contains the seed in a placenta, and fleshy tissue that contains nutrients that can be used by the seed to grow before the immature plant produces roots and leaves.

A vegetable is any edible part of a plant. It can be the flower (broccoli), the seed (beans), the stem (asparagus), the leaf (spinach), the leaf stem (celery), the root (carrot), or the bulb (onion). A fruit is a ripened ovary, including the seeds, of a flowering plant. All fruits are vegetables, but not all vegetables are fruits.

A pome is a kind of fruit in which the fleshy ovary tissue retains the distinction between the ovary and the seed-bearing placenta, which is less edible than the ovary. Pears and apples are examples of this kind of fruit.

A drupe is a seed that is surrounded by ovary tissue when ripe. The placenta is subsumed into the seed. All drupes are fruits. Some drupes have edible fleshy portions and inedible seeds (peaches) and some have inedible flesh and edible seeds (almonds). Others have both edible flesh and edible seeds (coconut).

A berry is the opposite of a drupe; the placenta is subsumed into the ovary. A grape is a berry. But most of the vegetables we think of as “berries” are not actually true berries, like raspberries and blueberries.

An aggregate fruit is an assembly of many drupes, like a blackberry. A multiple fruit contains ovary material from multiple flowers, like a pineapple. The difference between a multiple fruit and an aggregate fruit is that aggregate fruits are made from drupes but multiple fruits are other kinds of fruit, like pomes. Neither are true berries other than in common parlance.

An accessory fruit is one in which the fleshy, nutritive food for the seed is derived from a part of the plant other than the ovary, like a strawberry. Technically, a strawberry is not a fruit at all; it is a false berry. Other false berries include watermelons, bananas, cucumbers, and blueberries. Melons are distinguished from other accessory fruits by their common traits of being grown on vines and protecting the seeds and stored nutrients with an inedible husk. A coconut is not a melon because the coconut is the actual ovary of the plant; a true melon contains more than the ovary.

A tuber is a fruit in which the ovary and seed are grown underground, typically as an evolutionary adaptation to cold winters or other hostile environmental conditions. Thus, the ovary is located in a place different than the rest of the flower. Some tubers put their ovaries in their stems (potatoes) and others in their roots (yams).

A nut is a fleshy portion of a fruit, in which the seed and the ovary are indistinguishable. Thus, all nuts are fruits. A legume is a simple fruit which forms in a pod of some kind. The pod may be edible (peas) or may not be edible (peanuts). When the seed itself contains the bulk of the nutrition used for the seed to grow instead of the ovary flesh in which the seed is found, the legume is called a pulse (like wheat). Some legumes are nuts (like cashews), some are not (like rice).

Now you know.