Light and Its Importance To The Plant

  • Practically all that has been said in the first chapter relates to what plants are, their organs, or what we may call the architecture or plan of their framework. But what they do with this elaborate structure is as important as what we do with a house that may contain every modern improvement but is never a home until these things have been put to use. One of the chief concerns of any architect is to see to it that the house has as much sunshine by day and as attractive illumination by night as possible. Nature, that greatest of all architects, also sees to it that plants get the utmost necessary sunlight, but for a much more important reason than the mere attractiveness of sunshine, be that ever so beautiful. For light, the life-giver of all green things, is so absolutely essential to plants that experiments to grow them in the dark have always failed, and many gardeners now use electric light in greenhouses in order to prolong the short daylight of winter. It is the lack of light that makes celery blanch.

    Plants grown in the house inevitably turn toward the windows, even plants growing against a wall turn their leaves away from it—nowhere can one find living green things that do not find the light as surely and persistently as men try to get their food or their mates. Many examples of this could be given and must have been noticed by everyone.

  • These successive steps in the degradation of food habits, are not always the clean-cut things they might be inferred to be from the foregoing. There are many intermediate stages; it may even prove to be the case that some plants are wholly autophytic at certain stages of their life, and slip partially into more devious practices at other stages. The whole affair is not yet thoroughly understood and may well be the result of competition, as it is quite conceivable that if the getting of food in normal ways became difficult or impossible plants may have had to resort to other methods.

  • Included in this group are several different kinds of compounds which have similar physical properties, and which, in general, belong to the type of organic compounds known as esters, i.e., alcoholic salts of organic acids. The terms "oil," "fat," and "wax," are generally applied more or less indiscriminately to any substance which has a greasy feeling to the touch and which does not mix with, but floats on, water. There are many oils which are of mineral origin which are entirely different in composition from natural fats. These have no relation to plant life and will not be considered here.