Straw mulching combined with phosphorus fertilization increased photosynthesis rate and grain yield of wheat due to reduced stomatal and mesophyll limitations

Abstract

AbstractPhosphorus (P) has been proposed as an important factor determining photosynthesis through improvements in leaf anatomical traits and carboxylation efficiency. However, little is known about the combined effects of straw mulch and P fertilizer on the relationship between flag leaf P content and photosynthesis. This study was conducted to determine the combined effects of straw mulch combined with P fertilizer on wheat flag leaf photosynthetic capacity and grain yield. We performed field experiments during 2020–2022 to investigate the combined effects of straw mulch (0 and 8000 kg ha−1) with P fertilizer (0, 75, and 120 kg P2O5 ha−1) in Southwest China. Straw mulch with 75 kg P2O5 ha−1 gave an 18.3% yield advantage over no mulch with 120 kg P2O5 ha−1. Straw mulching with P fertilizer increased flag leaf P content and increased stomatal density. These changes increased stomatal conductance, mesophyll conductance, and net photosynthetic rate (Pn) by 17.4%, 16.3%, and 20.8%, respectively, compared with no‐mulch plots. The increased Pn was found associated with decreased stomatal and mesophyll limitation. Straw mulching with P fertilizer increased the activities of ribulose‐1,5‐bisphosphate carboxylase‐oxygenase and sucrose synthesis enzymes, thus promoting sucrose synthesis in flag leaves, which is beneficial for increasing grain number per meter square and grain yield. Straw mulching combined with 75 kg P2O5 ha−1 increased flag leaves P content and stomatal density, and increased stomatal and mesophyll conductance, resulting in improved leaf photosynthesis and grain yield.