THE EFFECTS OF ELEVATED CARBON-DIOXIDE, TEMPERATURE AND SOIL-MOISTUREON THE WATER-USE OF STANDS OF GROUNDNUT (ARACHIS-HYPOGAEA L)

Stands of groundnut (Arachis hypogaea L. cv. Kadiri 3) were grown in c ontrolled environment glasshouses at two mean air temperatures (28 deg rees C and 32 degrees C), two atmospheric CO2 concentrations (375 ppmv and 700 ppmv) and two soil moisture treatments (irrigated weekly to f ield capacity or allowed to dry from 22 d after sowing). The transpira tion equivalent, Omega(W) (g kPa kg(-1))-the product of the accumulate d biomass/transpired water ratio and the saturation deficit-was calcul ated for all the treatments using aboveground harvest, root core and n eutron probe measurements. Neither temperature nor soil moisture treat ment was found to have an effect on Omega(W). Increased CO2 concentrat ion raised Omega(W) from 6.21 +/- 0.30 to 7.67 +/- 0.29 g kPa kg(-1), an increase of 24% (P < 0.005). The importance of accounting for root material and pod composition when calculating Omega(W) was highlighted .