The Fate of Acquired Carbon in Plants: Chemical Composition and Construction Costs

One of the goals of ecophysiology and agronomy is to unders tand the physiological basis of plant growth. In this respect, the process of photosynthesis has received ample attention. Large efforts have been made to analyze the physical and biochemical processes that are necessary for carbon fixation. The subsequent fate of the acquired carbon (C) has been investigated far less. Factors controlling the plant's respiration and translocation of C to several organs are only fragmentarily understood. This applies even more so to the fate of C in a specific organ or cell. In most studies related to plant growth, biomass accumulation is taken as such and not analyzed further. However, the way a plant invests its carbon as well as the other acquired elements into different compounds may have a profound effect on its growth and performance in a certain environment (e.g., Bazzaz et al., 1987). Therefore, it is crucial to unders tand the factors controlling chemical composition. So far, we only have a limited understanding of the causes and consequences of variation in chemical composition. In this chapter, we discuss first the integration level at which the chemical composition of plants will be considered. Second, we characterize the chemical composition of various plant organs at that integration level. What values for the concentrations of the various plant compounds could be taken as typical for an "average"