Carbon balance and source‐sink metabolic changes in winter wheat exposed to high night‐time temperature

Abstract

Carbon loss under high night‐time temperature (HNT) leads to significant reduction in wheat yield. Growth chamber studies were carried out using six winter wheat genotypes, to unravel postheading HNT (23°C)–induced alterations in carbon balance, source‐sink metabolic changes, yield, and yield‐related traits compared with control (15°C) conditions. Four of the six tested genotypes recorded a significant increase in night respiration after 4 days of HNT exposure, with all the cultivars regulating carbon loss and demonstrating different degree of acclimation to extended HNT exposure. Metabolite profiling indicated carbohydrate metabolism in spikes and activation of the TriCarboxylic Acid (TCA) cycle in leaves as important pathways operating under HNT exposure. A significant increase in sugars, sugar‐alcohols, and phosphate in spikes of the tolerant genotype (Tascosa) indicated osmolytes and membrane protective mechanisms acting against HNT damage. Enhanced night respiration under HNT resulted in higher accumulation of TCA cycle intermediates like isocitrate and fumarate in leaves of the susceptible genotype (TX86A5606). Lower grain number due to lesser productive spikes and reduced grain weight due to shorter grain‐filling duration determined HNT‐induced yield loss in winter wheat. Traits and mechanisms identified will help catalyze the development of physiological and metabolic markers for breeding HNT‐tolerant wheat.

High night temperature induced changes in grain starch metabolism alters starch, protein, and lipid accumulation in winter wheat

“…HNT induced rapid senescence resulting in early maturity observed in this study and other reports, led to shortened grain‐filling duration (Figure ; Hurkman & Wood, ; Impa et al, ). SY Monument despite recording 12‐ and 14‐days early maturity under HNT (25°C and 27°C, respectively) compared with 15°C maintained its grain weight and number per plant, supported by the extended chlorophyll index and flag leaves and the spike QY (Figure ).…”

“…This response from SY Monument provides rationale for a possible whole plant functional stay green phenomenon having a positive impact on minimizing HNT‐induced yields and quality losses. Because HNT enhances carbon loss due to increased respiration (Impa et al, ), the ability of the plant to minimize or meet the carbon demand by maintaining photosynthesis is a possible option to minimize HNT damage in wheat.…”

“…However, significant negative effects on the physiological traits were recorded at a night temperature of 23°C, whereas grain weight and harvest index were negatively affected at 20 and 23°C compared with 14°C night-time temperature (Prasad et al, 2008). due to increased respiration (Impa et al, 2019), the ability of the plant to minimize or meet the carbon demand by maintaining photosynthesis is a possible option to minimize HNT damage in wheat.…”

“…Our recent study has explored the alterations in carbon balance and whole‐plant metabolic changes in wheat leaves, stems and spikes exposed to HNT of 23 o C (Impa et al, ). HNT induced higher night‐time respiration and alterations in whole‐plant carbon balance and affected starch and sucrose metabolism in wheat spikes and tricarboxylic acid cycle related metabolites in leaves (Impa et al, ). Our study, and others quantifying the response of HNT in wheat, have compared genotypic responses using an arbitrary HNT versus optimum conditions (Impa et al, –23°C vs. 15°C; Narayanan, Prasad, Fritz, Boyle, & Gill, –24°C vs. 15°C).…”

“…HNT induced higher night‐time respiration and alterations in whole‐plant carbon balance and affected starch and sucrose metabolism in wheat spikes and tricarboxylic acid cycle related metabolites in leaves (Impa et al, ). Our study, and others quantifying the response of HNT in wheat, have compared genotypic responses using an arbitrary HNT versus optimum conditions (Impa et al, –23°C vs. 15°C; Narayanan, Prasad, Fritz, Boyle, & Gill, –24°C vs. 15°C). However, these studies, do not address the critical night‐time temperature threshold, beyond which yield and quality losses are observed.…”