Partitioning of 14C assimilates, total 14C activity and growth under water stress and during recovery in indeterminate Cajanus cajanL.

Abstract

Distribution of 14C, in different plants parts of pigeonpea ( Cajanus cajanL.) was assayed by moving 14CO 2-fed plants to moderate (Soil ψ w = −0·77 MPa) and severe (soil ψ w = −1·37 MPa) levels of water stress. In shoots at the vegetative stage, the ethanol soluble fraction represented 98·7% of total 14C content at zero time, which decreased to 48·5% after 120 h. In underground portions it increased from 1·3% to 51·5%. A similar trend was observed for the ethanol insoluble fraction. Nodules showed the highest percent of 14C content under drought. At the flowering stage a similar trend was observed for 14C distribution, however, in reproductive parts 14C amount increased six times in the soluble fraction and two times in the insoluble fraction after 168 h. Under severe stress 27·1% and 27·0% of total 14C content was diverted to reproductive parts and nodules, respectively. In plants revived after stress 14C was reduced to 50% in retained reproductive parts. High rates of respiration of nodules and leaves were noted even at low rates of photosynthesis under moderate stress. Total 14C activity decreased with time to 32·2% and 13·5% at moderate stress during the vegetative and flowering growth stages, respectively. Recovered plants showed higher 14C activity than the control.