Effect of Low Relative Humidity on δ13C Value in Two C3Grasses and in Panicum milioides, a C3–C4Intermediate Species

Abstract
When grown under conditions of low relative humidity, the C3–C4 intermediate Panicum milioides, as well as the C3 grasses Triticum aestivum and Poa pratense, exhibited δ13C values which were up to 2–7%o less negative than the δ13C values of the corresponding plants grown at high relative humidity. At both humidity levels, there was no evidence of a substantial contribution of phosphoenolpyruvate carboxylase to carbon gain in Panicum milioides