Abstract
Plant responses to abiotic stresses such as drought, salt, and heat, have been studied separately, but in fact, plants are exposed simultaneously to a combination of stresses. Therefore, the objective of this study was to explore the morphophysiological responses of the guar plant to the combination of heat, drought, and salinity with respect to that to an individual stress. Five treatments including heat, drought, salinity, a combination of multiple stresses and control were applied to two guar accessions namely "BWP-5595" and "24320". The results showed that heat stress enhanced biomass, plant height, leaf number, leaf elongation, and prolonged time to flowering. However, it reduced root length and water use efficiency, but it had moderately negative effect on leaf area, stomatal conductance and number of pods. Contrastingly, drought stress improved root length, water use efficiency, and leaf elongation. It affected negatively leaf area, plant height, and prolonged days to flowering. Drought stress moderately reduced leaf number, biomass, stomatal conductance, and number of pods. Comparatively, salinity stress had a moderately negative impact on all studied traits except leaf number, which was reduced significantly. However, the combination of multiple stresses severely affected all studied traits except water use efficiency. These results show that the adverse effects of the combination of all three stresses were more pronounced than those of either of the individual stresses. Of the two guar accessions used, BWP 5595 showed better performance than accession 24320 in most of the traits measured. This indicates that the effect of multiple stresses differs among the accessions of a species.