Photothermographs, a tool for climate studies in relation to the ecology of vegetable varieties

Summary

If water is supplied artificially, vegetables can be grown in various countries where rainfall is insufficient. Therefore precipitation need not necessarily be a primary climatic factor in relation to ecological studies in vegetable varieties. Most important climatic factors are day length and temperature, which control the growth and life cycle of many important species. A “photothermograph” has been designed to express a climate, or the weather conditions during a certain period, as far as the last two factors are concerned. Similarly the dependence of the growth and life cycle of a plant on the photothermic factors may be expressed. This has been worked out for a not too complicated problem: the transition from the vegetative to the generative stage, and vice versa, of some varieties of red table beet and sugar beet. For a few varieties the borderlines were found between the photothermic conditions which have a vernalizing effect, and those which result in devernalizing. A comparison of these borderlines with the climate photothermographs of some places gives rise to various considerations. It has been shown that this method, if worked out further, may probably contribute to predicting the productivity of a variety in a certain region.