PLANT PHYSIOLOGY.

Otago Daily Times, Issue 21022, 10 May 1930, Page 7

PLANT PHYSIOLOGY.

THE MYSTERIOPS LIFE OF A PLANT. “ Gardeners have rare opportunities of thinking, Watching how queer things grow." Take first that marvellous structure the root, winch peiTornu an ~.nk in the lark silence of the earth. Most gardeners know that it is important that \ the numerous fibrous roots should not be broken when transplanting; there is a reason for this. Different sorts of roots are mainly engaged in keeping the plant firmly fixed in the ground; it is the fine root hairs that take in the greater part of the food from the soil. Therefore, if we plant a tree or shrub with - many of its fibres damaged, the plant is going to live on starvation diet until such time as it can make new root fibres. The leaves may be described as the “workshops of the plant,” wherein all the raw food collected by the root, combined with certain gases and vapours absorbed by the leaves from the air, is manufactured into the finished products required for building up the structure oi the plant. The daily work of this green part of the plant is most extraordinarily interesting. It is, of course, a commonplace piece cl knowledge that plants do exactly the opposite thin" to tiie atmosphere to that done by human beings and animals, viz., tliey purify the air during daytime by breathing out pure oxygen, and taking in the carbon from the surrounding air. This tr as j s at once seized upon by the chlorophyll the green colouring matter of the plant’ and assimilated. After entering into the cells of the leaf, ihe carbon-dioxide, together witli a certain amount of water undergoes a chemical change, which re-

suits la the- formation of a carbohydrate.

The word carbohydrate simply means a substance composed of. carbon, hydrogen, and oxygen. Starch and sugar are carbohydrates, and the first to be formed is sugar in soluble form, and in this form the leaves send it along by special cells and vessels down to the stem and roots. The next process that this sugar undergoes is to be converted into starch grains, which latter, being solid, are more easily compressed into a small space. Normally, storage of sugar goes on during the night; and each morning, directly it is light, the protoplasm seizes on the sugar, elaborates it, and once more converts it into starch for daytime storage. There are still a few old-fashioned country folk who believe in cutting their cabbages and lettuces either last thing at night or else at dawn. They will tell you that they, are more crisp and tender before the sun is on them. This is quite true, and' when the physiology of plants is studied, we see a reason for the practice. The work of seizing upon a raw gas and converting it into food can only be performed by plants, no part of an animal or human being can perform i these functions. Day and night there I | s always the same useful work going on in some part of the plant, with never a complaint, all done quickly and silently, nc words, no fuss, no bother. During the night time the green part of the plant performs an exactly opposite process to that of the day. In the daytime it breathes out oxygen, and takes in carbon, but at night time the process is reversed, and the plant breathes after the manner of human beings, taking in oxygen, giving out carbon. Therefore,' on account of this, some people say, and firmly believe, that it is most unhealthy to sleep with a giant or flowers in one's room. But as it would take pretty well a conservatory full of plants to breathe out as much carbon as is emitted by one human being, a few plants are not such dangerous room mates as one fellow human. Scientists tell ’us that if it were not for the fact of plants purifying the atmosphere by breathing in the poisonous carbon, and giving out pure oxygen, the earth would long ago have been uninhabitable; we should have been poisoned with our own gases. Every gardener should be something ot a botanist, and try to learn a (ittle or the structure and physiology of the plant, otherwise, he is working in the uaikj, and cannot feel the same interest m all the little details of ordinary everyday gardening. One is continually’ coming across little gems of scientific knowledge that help very materially in the cultivation of plants and their successful treatment.— M. G. K. B. in Amateur Gardening.” *’