Comparison of Two Sorghum Lines with Contrasting Transpiration Use Efficiencies.

Two sorghum lines TX7078 and Liang Tang Ai were planted into insulated soil bins in a minilysimeter system and allowed to develop to boot stage. At boot, the soil bins were placed onto analog scales to measure whole plant transpiration. Diurnal leaf level gas exchange was measured with a portable photosynthesis system. Though Liang Tang Ai had higher leaf areas, whole plant transpiration efficiency increased. AC_i, leaf level light curves, and maximal quantum use efficiency as F_v/F_m revealed only slight overall differences between cultivars. Results suggest that either stomatal resistance or decreased leaf internal CO₂ concentration may be responsible for increased transpiration use efficiencies in Liang Tang Ai.