TRANSPIRATION EFFICIENCY, SPECIFIC LEAF WEIGHT, AND MINERAL CONCENTRATION IN PEANUT AND PEARL-MILLET

Transpiration efficiency (TE) is the weight of dry matter produced per unit of transpiration. If mineral nutrients are taken up in proportio n to transpiration, then the concentration of minerals in dry matter m ay be predictive of TE, It has recently been reported that specific le af weight (SLW) is also correlated with TE. Since both mineral concent ration and SLW are easily and inexpensively measured, they may be valu able predictors of TE. Five experiments with 7 to 19 genotypes of pean ut (Arachis hypogaea L,; C-3 species) and four experiments with 9 or 1 0 genotypes of pearl millet [Pennisetum glaucum (L.) R, Br.; C-4 speci es] were conducted to assess the predictive value of mineral concentra tion and SLW for TE. In peanut experiments, samples were also analyzed for C isotope discrimination (Delta), Plants were grown in pots in th e greenhouse in sand, soil, and solution culture, Specific leaf weight , Delta, ash, and mineral element concentrations were determined at th e end of the experiments, There was a strong negative correlation betw een Delta and TE in the four peanut experiments in which Delta was det ermined. Leaf ash concentration was negatively correlated with TE in f our out of six comparisons for each of the species (r = - 0.55 to - 0. 88). In peanut, Ca and Mg were negatively correlated with TE. No other elements were consistently related to TE in either peanut or pearl mi llet. The SLW was positively correlated with TE, Thus, both leaf ash a nd SLW were predictive of TE, but further research is needed to determ ine the physiological bases for the relationships and their general ap plicability.