Productivity and Environment

Abstract

There is little doubt that the survival of an autotrophic plant is based on its ability to maintain a positive carbon balance even under severe stress conditions, and also that its reproductive potential is dependent on its ability to gain carbon and energy by photosynthesis. These relationships are complex and it is not necessarily true that selection pressure has always favored maximization of productivity as such. Survival obviously depends on a combination of a number of characteristics, only a few of which may be fully exploited. Nevertheless, we share the view of Fischer and Turner (1978) that maximization of photosynthetic efficiency in terms of a limited resource (such as water) remains central to maximization of survival. But we wish to again re-emphasize the importance of considering characteristics of possible adaptive significance in the proper time and space perspective. As Eckardt (1975) has pointed out … “activities of living beings seem to be directed towards the attainment of goals that lie in the future, [but] their behaviour just reflects the fact that they have evolved under changing conditions which favoured great variability.” Having discussed the responses and adaptations of the photosynthetic characteristics we shall how examine the difficult subject of the relationship between productivity and the success and survival of plants in natural environments.

“While recognizing that uncertainty as to the exact long-term goals of evolution exists, we suggest that maximization of carbon gain, which in water-limited environments amounts to maximizing the efficiency with which water is acquired and ‘traded’ for carbon, remains central to other goals, such as stress resistance or survival, which may also have to be satisfied.” (Fischer and Turner, 1978)