Root osmotic potential and length for two maize lines differing in leaf osmotic potential

Abstract

ABSTRACTTwo maize (Zea mays L.) lines had previously been developed, one for expression in leaves of high osmotic adjustment (HOA) and the other for low osmotic adjustment (LOA). In field, these lines differed in soil water extraction depth and in plant wilting. It was hypothesized that HOA in leaves was also expressed in the root tips, and consequently it results in greater root extension and extraction of deeper soil water. Experiments reported here were undertaken in 1-m tall pots in a growth chamber and in the field to test these hypotheses. Periodic harvests of the soil columns during dry-down experiments showed no leaf OA in the two maize lines although the HOA line consistently had a lower leaf osmotic potential than the LOA line by 0.23 MPa. On the other hand, under the slow development of water deficit there was equivalent root tip OA in both lines. Consistent with this equivalency in root tip OA, no consistent difference in root length was observed in any of the experiments. Hence, the basis for the difference in wilting and water use between the two maize lines was not explained by differences in root OA and root extension.