Factors involved in the amelioration of retarded symbiosis in Tinaroo glycine

Abstract

Root nodules formed on Tinaroo glycine (Glycine wightii) were slow to pigment and begin fixing nitrogen. Various carbon and nitrogen compounds enhanced nodule pigmentation, the greening of the plants, and the rate of nitrogen fixation at 42 days. Of these inositol, glucose, ammonium nitrate (as both foliar and root applications) and coconut milk were most effective. Riboflavin, sodium glutamate and nodule infusion had little effect. There were no structural differences between nodules enhanced respectively by glucose and ammonium nitrate. Nodules on control plants showed slow development of the bacteroids and envelope membranes, with copious starch accumulation in uninvaded host cells. It was concluded that the retarded symbiosis in formed nodules was due initially to tardy nodule formation depleting the nitrogen reserves in the seeds before nitrogen fixation began. Because of the interaction of photosynthesis and nitrogen fixation, self-regeneration of nitrogen fixation in chlorotic plants was slow without an external stimulus. It is suggested that by selecting lines of the legume with larger seeds or by incorporating nitrogen in seed pellets the problem might be overcome.