Influence of Osmotic Adjustment on the Growth, Stomatal Conductance and Light Interception of Contrasting Sorghum Lines in a Harsh Environment uri icon


  • Two drought resistant sorghum lines IS 13441 and IS 1347, with a high capacity for osmotic adjustment and 2 susceptible lines, IS 12739 and IS 12744, were subjected to drought in the field during a summer season at Patancheru. Most of the osmotic adjustment occurred within 3 weeks after withholding water and at high predawn leaf water potentials (values above -1.0 MPa). As a result, resistant lines were able to maintain a positive turgor to lower leaf water potentials (-2.8 MPa) than susceptible lines (-2.0 MPa). Nevertheless, DM production was negligible in both resistant and susceptible lines when predawn leaf water potentials fell to -0.55 MPa. Furthermore, throughout the drought period the leaf area of all water-stressed plants was similar when expressed relative to the control regardless of the level of osmotic adjustment. Resistant lines had similar stomatal response to leaf water potential as susceptible lines. Large changes occurred in stomatal conductance and leaf rolling soon after withholding water while there was considerable osmotic adjustment in the leaves. Leaf rolling coincided with a reduction in the ability of the plant to utilize radiation, indicating that even if osmotic adjustment had delayed leaf rolling, the gain would be small. On the basis of these turgor related processes it was concluded that there would be little advantage in selecting for plants with a higher capacity for osmotic adjustment in this harsh environment

publication date

  • 1990