Photosynthetic physiological response of water‐saving and drought‐resistant rice to severe drought under wetting‐drying alternation irrigation

Abstract

Water-saving and drought-resistant rice (WDR) is widely grown in central China in recent years. However, studies have not explored the interaction effect of WDR and irrigation regimes on drought-resistance capacities under severe drought at sensitive growth periods. A pot experiment was conducted using a WDR cultivar Hanyou73 (HY73) and traditional high-yielding and drought-sensitive cultivar Huiliangyou 898 (HLY898). Three irrigation regimes, including flooding irrigation (W1), mild wetting-drying alternation irrigation (W2), and severe wetting-drying alternation irrigation (W3), were applied before heading. At heading, severe drought with À50 KPa soil water potential was established for all treatments and cultivars. The findings showed that cultivar HY73 under W2 treatment had the highest yield, 1000-grain yield, filled grain, relative water content, and photosynthesis potential compared with the other combinations. The higher net photosynthetic rate (P n ) was attributed to larger mesophyll conductance (g m ) in drought for cultivar HY73 under W2 treatment compared with that for cultivar HLY898 and the other water treatments. Enhanced photo-respiration rate may be an important photoprotection mechanism for achieving high P n for cultivar HY73 coupled with W2 treatment than for other combinations in drought. The relative expression level of OsPIP1;1 gene was significantly down-regulated during drought in all cultivars and water regimes. But OsPIP1;2, OsPIP2;3, OsTIP2;2, and OsTIP3;1 genes were upregulated to alleviate the significant decrease in g s and g m under drought. These results suggest that WDR and mild wetting-drying alternation irrigation (W2) have significant interaction effects in improving photosynthetic production potential by maintaining higher g m under severe drought.

Physiological and molecular mechanisms regulated mesophyll conductance under severe drought in water-saving drought-resistant rice

“…However, for WDR, g m is slight reduction compared with drought-sensitive variety, even if the g s is significantly reduced when responded to seasonal drought at heading, especially in optimized water management regime before heading (He et al, 2021).…”

“…The limitation of photosynthesis is one of the main reasons for decreasing grain yield in drought (He et al ., 2014; 2021; Wang et al ., 2021). The homeostasis mechanism of reactive oxygen species (ROS) is disrupted and ROS contents would be increased in drought due to the reduction of oxygen molecular to superoxide on the acceptor side of PSI called Mehler reaction (Christine and Shigeru, 2011; Singh et al ., 2018).…”

“…It has even become mainly-planted cultivars in the typical seasonal drought regions around Anhui Province. Compared with high-yield rice varieties, the high-yield and drought-resistant characteristics of WDR are closely related to the high photosynthetic potential of leaves in drought (He et al ., 2021; Wang et al ., 2021). In drought, stomatal conductance ( g s ) is significantly reduced to prevent water loss within cellular.…”

“…Generally, decreased photosynthetic production can be ascribed to inadequate CO 2 concentration at carboxylation sites limited by low CO 2 diffusion capacities from air to carboxylation sites in drought (Flexas et al ., 2004). However, for WDR, g m is slight reduction compared with drought-sensitive variety, even if the g s is significantly reduced when responded to seasonal drought at heading, especially in optimized water management regime before heading (He et al ., 2021). Maintaining high g m is a pivotal reason to obtain high photosynthetic production potential for WDR in drought.…”

“…Increased aquaporin activities could compensate for the negative effect of adverse leaf structure on g m in drought for conventional high-yield rice varieties (Ouyang et al ., 2017; He et al ., 2021), but for WDR, the function of aquaporin did not improve and g m did not also significantly decrease in drought (He et al ., 2021). The results suggest that WDR might be different adaptive mechanisms in structural, physiological, and molecular levels.…”