Magnesium Application Promotes Rubisco Activation and Contributes to High-Temperature Stress Alleviation in Wheat During the Grain Filling

Abstract

Inhibited photosynthesis caused by post-anthesis high-temperature stress (HTS) leads to decreased wheat grain yield. Magnesium (Mg) plays critical roles in photosynthesis; however, its function under HTS during wheat grain filling remains poorly understood. Therefore, in this study, we investigated the effects of Mg on the impact of HTS on photosynthesis during wheat grain filling by conducting pot experiments in controlled-climate chambers. Plants were subjected to a day/night temperature cycle of 32°C/22°C for 5 days during post-anthesis; the control temperature was set at 26°C/16°C. Mg was applied at the booting stage, with untreated plants used as a control. HTS reduced the yield and net photosynthetic rate (Pn) of wheat plants. The maximum carboxylation rate (VCmax), which is limited by Rubisco activity, decreased earlier than the light-saturated potential electron transport rate. This decrease in VCmax was caused by decreased Rubisco activation state under HTS. Mg application reduced yield loss by stabilizing Pn. Rubisco activation was enhanced by increasing Rubisco activase activity following Mg application, thereby stabilizing Pn. We conclude that Mg maintains Rubisco activation, thereby helping to stabilize Pn under HTS.

Magnesium Fertilization Increases Nitrogen Use Efficiency in Winter Wheat (Triticum aestivum L.)

“…The influence of Mg on the activity of Rubisco increases in conditions of water shortage, which is often accompanied by elevated temperatures [ 36 , 37 ]. Rubisco activity increases during the GFP of wheat growth, as recently documented by Shao et al [ 25 ]. This specific effect was probably observed in 2015 on the main plot fertilized with 50 kg Mg ha −1 and double Mg fertilization.…”

“…It requires, however, a higher dose of the in-soil applied Mg and its frequent application to wheat foliage [ 14 , 19 , 20 ]. The yield-forming effect of the applied Mg can be explained both by the increase in the GD and the maintenance of the photosynthetic activity of leaves during the grain-filling period [ 24 , 25 , 32 ]. The second Mg fertilization strategy can be recommended in the years or regions of the world with favorable growth conditions for winter wheat.…”

“…The strong relationship between the amount of extra N accumulated in wheat grain, as a result of the of Mg fertilization, was due to the critical role of both nutrients in photosynthesis. Nitrogen is the limiting component of Rubisco, the key plant enzyme responsible for CO 2 fixation [ 24 , 25 ]. The influence of Mg on the activity of Rubisco increases in conditions of water shortage, which is often accompanied by elevated temperatures [ 36 , 37 ].…”

“…Its key function is to capture and then fixate the CO 2 molecule, which is the basic substrate for the production of elementary sugar compounds [ 23 , 24 ]. The key function of Mg is to maintain Rubisco activation, which results in the stabilization of the net photosynthetic rate, as was demonstrated for wheat by Shao et al [ 25 ]. Crop plants well supplied with Mg since the beginning of their growth increases N uptake, resulting in an increase in its unit productivity [ 26 , 27 ].…”

Heat stress effects on the reproductive physiology and yield of wheat

“…The application of different osmoprotectants improves wheat performance and grain yield under heat stress (Table 3). Nutrient management, in particular application of micronutrients, can also help improve heat tolerance (Shao et al, 2021; Ullah et al, 2019).…”