Stomata regulate photosynthesis and transpiration, and these processes are critical for plant responses to abiotic stresses such as salinity. A barley double haploid population with 108 lines derived from a cross between CM72 (salt-tolerant) and Gairdner (salt-sensitive) was used to detect quantitative trait loci (QTLs) associated with stomatal and photosynthetic traits related to salinity tolerance. A total of 11 significant QTLs (LOD > 3.0) and 11 tentative QTLs (2.5 < LOD < 3.0) were identified. These QTLs are distributed on all the seven chromosomes, except 5H and explain 9.5–17.3% of the phenotypic variation. QTLs for biomass, intercellular CO2 concentration, transpiration rate and stomatal conductance under control conditions co-localised together. A QTL for biomass also co-located with one for transpiration rate under salinity stress. A linkage was found between stomatal pore area and gas exchange. A QTL for salinity tolerance also co-localised with QTLs for grain yield and biomass on chromosome 3H. Based on the draft barley genome, the candidate genes for salinity tolerance at this locus are proposed. The lack of major QTLs for gas exchange and stomatal traits under control and saline conditions indicates a complex relationship between salinity and leaf gas exchange due to the fact that these complex quantitative traits are under the control of multiple genes.

Capsaicinoids are pungent alkaloid compounds enriched with antioxidants, anti-microbial, anti-inflammatory, analgesics, anti-carcinogenic, anti-obesity and anti-diabetic properties. These compounds are primarily synthesised in the placenta of the fruit and then transported to other vegetative parts. Different varieties of capsicum and chillies contain different capsaicinoid concentrations. As capsicums and chillies are grown extensively throughout the world, their agricultural and horticultural production leads to significant amount of waste generation, in the form of fruits and plant biomass. Fruit wastes (placenta, seeds and unused fruits) and plant biowaste (stems and leaves) can serve as sources of capsaicinoids which can provide opportunities to extract these compounds for development of nutraceutical products using conventional or advanced extraction techniques. Capsaicin and dihydrocapsaicin are two most abundantly found pungent compounds. Considering the health benefits of capsaicinoids, these compounds can help in reducing metabolic disease complications. The development of an advanced encapsulation therapy of safe and clinically effective oral capsaicinoid/capsaicin formulation seem to require evaluation of strategies to address challenges related to the dosage, limited half-life and bioavailability, adverse effects and pungency, and the impacts of other ligands antagonising the major capsaicinoid receptor.

The recent advances in plant biology have significantly improved our understanding of reactive oxygen species (ROS) as signaling molecules in the redox regulation of complex cellular processes. In plants, free radicals and non-radicals are prevalent intra- and inter-cellular ROS, catalyzing complex metabolic processes such as photosynthesis. Photosynthesis homeostasis is maintained by thiol-based systems and antioxidative enzymes, which belong to some of the evolutionarily conserved protein families. The molecular and biological functions of redox regulation in photosynthesis are usually to balance the electron transport chain, photosystem II, photosystem I, mesophyll and bundle sheath signaling, and photo-protection regulating plant growth and productivity. Here, we review the recent progress of ROS signaling in photosynthesis. We present a comprehensive comparative bioinformatic analysis of redox regulation in evolutionary distinct photosynthetic cells. Gene expression, phylogenies, sequence alignments, and 3D protein structures in representative algal and plant species revealed conserved key features including functional domains catalyzing oxidation and reduction reactions. We then discuss the antioxidant-related ROS signaling and important pathways for achieving homeostasis of photosynthesis. Finally, we highlight the importance of plant responses to stress cues and genetic manipulation of disturbed redox status for balanced and enhanced photosynthetic efficiency and plant productivity.