PHOTOPERIODIC SENSITIVITY OF HEAD DIFFERENTIATION, CULM ELONGATION, AND HEADING IN SOME SPRING WHEAT AND SPRING BARLEY VARIETIES

Abstract

Eleven wheat and six barley varieties were tested for their sensitivity to six photoperiods ranging from 9 to 24 hours of light per day. Nine hours' daylight was supplied to plants in all treatments. Observations were made in terms of days to completion of head differentiation, rate of elongation of the main culm, and days to heading. The photoperiodic sensitivities were illustrated by means of response curves.There were marked differences among the wheat varieties in sensitivity of head differentiation and culm elongation to short photoperiods and in effects of all photoperiods on days to heading. The barley varieties differed only slightly in photoperiodic sensitivity of culm elongation at any one photoperiod and there were only small differences among photoperiods. Photoperiod had much less effect on head differentiation in the barley varieties tested but there were marked differences among varieties regardless of photoperiod. Number of days to heading was affected by photoperiod but less strikingly than in wheat.