PARTITIONING OF C-14 ASSIMILATES, TOTAL C-14 ACTIVITY AND GROWTH UNDER WATER-STRESS AND DURING RECOVERY IN INDETERMINATE CAJANUS-CAJAN L

Distribution of C-14, in different plants parts of pigeonpea (Cajanus cajan L.) was assayed by moving (CO2)-C-14-fed plants to moderate (Soi l psi(2) = -0.77 MPa) and severe (soil psi(w) = -1.37 MPa) levels of w ater stress. In shoots at the vegetative stage, the ethanol soluble fr action represented 98.7% of total C-14 content at zero time, which dec reased 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 C-14 content under dr ought. At the flowering stage a similar trend was observed for C-14 di stribution, however, in reproductive parts C-14 amount increased six t imes in the soluble fraction and two times in the insoluble fraction a fter 168 h. Under severe stress 27.1% and 27.0% of total C-14 content was diverted to reproductive parts and nodules, respectively. In plant s revived after stress C-14 was reduced to 50% in retained reproductiv e parts. High rates of respiration of nodules and leaves were noted ev en at low rates of photosynthesis under moderate stress. Total C-14 ac tivity decreased with time to 32.2% and 13.5% at moderate stress durin g the vegetative and flowering growth stages, respectively. Recovered plants showed higher C-14 activity than the control. (C) 1996 Academic Pres Limited