Genotypic variation in whole-plant transpiration efficiency in sorghum only partly aligns with variation in stomatal conductance

Water scarcity can limit sorghum (Sorghum bicolor (L.) Moench) production in dryland agriculture, but increased whole-plant transpiration efficiency (TEwp, biomass production per unit of water transpired) can enhance grain yield in such conditions. The objectives of this study were to quantify variation in TEwp for 27 sorghum genotypes and explore the linkages of this variation to responses of the underpinning leaf-level processes to environmental conditions. Individual plants were grown in large lysimeters in two well-watered experiments. Whole-plant transpiration per unit of green leaf area (TGLA) was monitored continuously and stomatal conductance and maximum photosynthetic capacity were measured during sunny conditions on recently expanded leaves. Leaf chlorophyll measurements of the upper five leaves of the main shoot were conducted during early grain filling. TEwp was determined at harvest. The results showed that diurnal patterns in TGLA were determined by vapour pressure deficit (VPD) and by the response of whole-plant conductance to radiation and VPD. Significant genotypic variation in the response of TGLA to VPD occurred and was related to genotypic differences in stomatal conductance. However, variation in TGLA explained only part of the variation in TEwp, with some of the residual variation explained by leaf chlorophyll readings, which were a reflection of photosynthetic capacity. Genotypes with different genetic background often differed in TEwp, TGLA and leaf chlorophyll, indicating potential differences in photosynthetic capacity among these groups. Observed differences in TEwp and its component traits can affect adaptation to drought stress.

Psychosocial Factors That Influence Quality of Life and Potential for Self-Management in Multiple Sclerosis

Optimizing quality of life (QOL) and self-management in people with multiple sclerosis (MS) is increasingly seen as a worthwhile goal. This study aimed to investigate factors that affect QOL in MS. A large national sample of Australians with MS (n = 1848) generated from the Australian Multiple Sclerosis Longitudinal Study completed a survey addressing disease duration and severity, self-efficacy, depression, perceived stress, social support, QOL, and self-management. We tested a model of self-help in which antecedent variables are influenced by mediating variables, which in turn affects outcome variables. In the current study, the antecedent variables were disease duration and disease severity; the mediating variables were self-efficacy, depression, perceived stress, and social support; and the outcome variables were QOL and self-management. We also tested the hypothesis that disease severity, depression, and perceived stress would correlate inversely with QOL and potential for self-management, whereas self-efficacy and perceived level of social support would correlate positively with QOL and potential for self-management. The results indicated that the antecedent variables did not correlate with the mediating variables, with one exception: a negative correlation was found between disease severity and social support. No correlations were found between social support and QOL or self-management. However, significant correlations were found between depression, self-efficacy, stress, and social support and QOL. No correlations were found between either the antecedent or the mediating variables and self-management. The results confirm previous findings of statistically significant correlations between psychosocial factors and QOL.