ABSTRACT
The climatic elements and their effects on plant growth are far more complex than is apparent from their treatment in this book. In the field, the plant is never subjected only to a single variable at any given time, but to a constant interaction with an almost infinite number of combinations of the elements. We have not been able to isolate the various aspects of selective integration of the various climatic elements by the plants, except in a crude qualitative manner. In spite of the obvious limitations of studies on the effects of single climatic elements on plant growth, with our present knowledge we know what elements need to be measured and their relative importance in most cases. Furthermore, studies on the effect of single climatic elements are a necessary first step toward more complete understanding of our problem. For instance, under a known radiative and thermal regime, the estimation of potential yield when the water application is adequate and the yield loss caused by varying amounts of water deficit, opens up a new horizon in the assessment of various alternatives of water resources management. Starting from a different assumption, we can also estimate the potential photosynthesis as determined primarily by radiation and temperature. Should the two estimates agree with each other, we can proceed with confidence to assess their combined effects on productivity under less favorable conditions. The economic implications of this approach are many and varied.
