Grain sorghum transpiration efficiency at different growth stages

Transpiration efficiency (TE) is an important physiological trait associated with drought tolerance of plants. Currently, little is known about the grain sorghum TE and its dynamics with the age of plants. To compare the sorghum TE at different growth stages, four studies (two in the greenhouse and two in the growth chamber) were conducted under controlled environmental conditions. Plants were grown in lid-covered boxes and harvested at six-leaf, flag leaf, grain filling and maturity stages. The mean shoot TE values were 4.47 and 4.10 kg/m(3) for two greenhouse studies, and 4.85 and 4.30 kg/m(3) for two growth chamber studies, respectively. The shoot TE was not different among four growth stages within each study, suggesting that sorghum plants used the same amount of water per unit of biomass production for different growing periods. Because crops grown under dryland environments often run out of water during reproductive periods, result supports the ideas that soil water availability at later growth stages is crucial to achieve the yield potential of dryland sorghum.