EFFECT OF HEAT AND DROUGHT STRESS ON SORGHUM (SORGHUM-BICOLOR) .1. PANICLE DEVELOPMENT AND LEAF APPEARANCE

Seven sorghum lines, flowering from 50 to 87 days after sowing, were subjected to early drought stress, late stress, and both early and late stress in the field during the dry season in India. Panicle initiation was delayed by 2-25 days and flowering by 1-59 days by the drought stress treatments, the greatest effect being in the treatment subjected to both early and late stress. Stress increased the period between panicle initiation and flowering by retarding the rate of panicle development; when stress was severe panicle development stopped. Upon relief of stress following irrigation, panicle development resumed at rates comparable to those in a fully irrigated control. The rate of leaf appearance was affected in a similar manner to panicle development soon after water was withheld. Rate of leaf appearance and panicle development decreased as pre-dawn leaf water potential decreased and ceased at water potentials of -0.55 and -0.7 MPa, respectively.