WATER RELATIONS AND GASEOUS EXCHANGE STUDIES IN PIGEONPEA UNDER DEPLETING SOIL-WATER POTENTIAL

Plants of pigeonpea (Cajanus cajan) were subjected to drought by with holding irrigation in earthen pots at vegetative and flowering, i.e. 35-45 and 70-80 days after sowing, under screen house conditions. The stress levels were described as moderate (soil water potential of -0.77 MPa) and severe (soil water potential of -1.34 MPa), as compared to control (soil water potential of -0.37 MPa). Depleting in soil water potential resulted in decrease of leaf water potential, photosynthesis, respiration, chlorophyll b and total chlorophyll, chlorophyll a behaved differently at two stages. Stomatal conductance of both the surfaces decreased linearly with decreasing leaf water potential and soil water potential and this decrease was more on abaxial surface. Lesser reduction and better recovery was noticed for respiration than photosynthesis. Loss of turgor from 0.76 to 0.34 MPa affected the gaseous exchange. Severe stressed plants showed partial recovery for all the parameters after reirrigation.