An investigation of drought tolerance mechanisms in triticale (X 'Triticosecale' Wittmack) with particular reference to osmotic adjustment

Abstract

Triticale (X 'Triticosecale' Wittmack) is a human-made crop which has become increasingly important in Australia and other countries. Triticale is generally acknowledged as a plant with greater tolerance to biotic and abiotic stresses compared to other cereals, however, very little is known about the performance of this crop under water deficit conditions and its capacity for osmotic adjustment (OA). The work reported in this thesis sets out to examine plant water relations parameters with particular reference to OA, the variation between triticale genotypes, and the effect of OA on the yield of this crop in response to water deficit. Furthermore, the effect of factors such as the rate of development of water deficit and plant growth stage on OA was assessed. Since other physiological plant traits are also important in plant drought tolerance, and to find any possible correlation between OA and other plant traits, a number of other plant traits were also assessed. Variation was found between triticale genotypes based on plant water relations and OA in response to water deficit. The degrees of OA found in the experiment on OA and stomatal conductance (Experiment 2) were greater than those in the first experiment on variation in OA among triticale genotypes (Experiment 1). The experiment on OA and water deficit rate (Experiment 5) showed that the development rate of water deficit is important in determining the degree of OA in triticale genotypes. The different levels of OA obtained in the first two experiments were most likely due to differing rates of development of water deficit. In particular, the results of Experiment 5 showed that the relatively low level of OA in Experiment 1 was likely due to the faster rate of water deficit development. Therefore it is suggested that special consideration should be given to this matter in studies of OA.