Physiological studies on seed setting in sunflower I. photosynthesis and nitrate assimilation

Photosynthesis and nitrate assimilation were studied in two sunflower genotypes in relation to their seed yield. Low photosynthetic rate (as determined by CO₂ fixation rate and RuBP carboxylase enzyme) and low nitrate metabolism particularly at the time of seed filling are partly responsible for poor seed yield in sunlower.