NATURE IN SHORT / Flower terminology is a language of love

Kevin Short / Daily Yomiuri Columnist

One issue when learning and teaching about botany, or any natural science, is how deep to delve into the technical jargon. Unfortunately, most basic botany textbooks rely so heavily on terminology that they discourage first-time learners. On the other hand, employing basic terms to understand how a plant works can be fun and rewarding, doubly so if you go at it bilingually in Japanese and English.

Everybody loves flowers, which makes them a good place to start. A flower (hana) is the part of a plant designed specifically for reproduction. Flowers appear complicated, and textbook explanations can rattle on for dozens of pages, but twenty basic terms are all that is required to understand how plants have sex!

A typical flower (actually, there are surprisingly few of these? most species show some sort of aberration!) consists of four basic sections. From the bottom up these are the calyx, corolla, stamens and pistil.

The calyx (gaku) surrounds and protects the young flower in the bud stage. As the flower opens, it splits into individual segments called sepals (gaku-hen). The sepals may split right down to the vary base, becoming totally independent of one another, or remain partly fused together in a single structure.

The corolla (ka-kan) is situated inside the calyx. It also splits apart as the flower opens, and the segments are called petals (ka-ben or hana-bira). In flowers pollinated by insects, it is usually (but not always) the corolla that takes on a colorful shape and pattern. Like the sepals, the individual petals may be independent from the base, or all fused together.

The stamens (oshibe), usually numbering from several to several dozen, comprise the flower's male reproductive organ. The tip of the stamen, known as the anther (yaku), is where pollen (kafun) is produced and released. The staff that supports and lifts up the anther is known as the filament (ka-shi).

At this point in the discussion, a brief diversion into the world of pollen is required. When animals reproduce, the male simply approaches the female and places his sperm (seishi) inside her reproductive organ, or in the case of fish and amphibians, sprays it on top of her eggs as she lays them. Plants, however, are stuck in one spot, and require some special system for getting the sperm from one individual to the egg of another. The ingenious solution to this need in pollen

Pollen appears as a light dusting of powder, often but not always yellowish in color, on the surface of the anther. The pollen grain, too tiny to see with the naked eye, is not the sperm cell itself. It is rather a case-like structure that surrounds and protects the sperm cell on its perilous journey from plant to plant.

The female reproductive organ, called the pistil (meshibe), is the most complicated structure on the flower, and is divided into three segments. At the upper tip is the stigma (chuto). This has a sticky or hairy surface, and is designed to grab pollen grains out of the air or collect them off the head or underside of visiting insects. The process of receiving pollen at the stigma is known as pollination (jufun).

Supporting the stigma, and lifting it up high enough to catch pollen grains, is a rod-like structure called the style (ka-chu); at the very bottom of which sits the ovary (shibo), which will eventually grow into the plant's fruit (kajitsu). Well protected inside the ovary is the ovule (haishu), or egg, which will eventually develop into the seed (shushi).

The one great goal of this whole process is to produce seeds. In order to develop into a seed, however, the ovule must first be fertilized by a sperm cell. But the sperm cells are in the pollen grain, which sits on the stigma at the opposite end of the style, high, high above the waiting ovule. At this point the sperm and ovule are just star-crossed lovers, longing for one another but separated by an insurmountable barrier.

Not to fear. That miraculous structure pollen has one last trick up its sleeve. When a pollen grain is captured by the stigma, it first produces a long, very thin tube, called the pollen tube (kafun-kan) that grows downward through the inside of the style, eventually reaching all the way to the ovule. Now the way is cleared for the sperm cells to descend to meet their soul mate. Fertilization (jusei) occurs when a sperm cell reaches the ovary and joins with the ovule.

Short is a naturalist and cultural anthropology professor at Tokyo University of Information Sciences.