ABSTRACT
This chapter examines these attributes in a number of commonly grown grain legumes within the general context of effectiveness in partitioning and utilization of host plant photosynthate for growth and fixation activity of nodules. It describes broadly how assimilate distribution to nodulated roots and other plant parts are patterned and are likely to vary among species or with age of a single species. The chapter considers basic biochemical processes associated with assimilation of nitrogen, dealing in particular with theoretically based costs of nitrogenase functioning of nodules in the presence or absence of uptake hydrogenase activity and likely differences in costs of synthesis of amides versus ureides as primary fixation products. It focuses on the carbon budget of nodules, depicting the likely amounts of net photosynthate consumption in nodule growth and respiration and the cycling of carbon through the nodule back to the parent plant as organic solutes containing fixed nitrogen.
