Elevating soil water content (SWC) through irrigation was one of the simple mitigation measures to improve crop resilience to heat stress.  The response of leaf function, such as photosynthetic capacity based on chlorophyll fluorescence during the mitigation, has received limited attention, especially in field conditions.  A two-year field experiment with three treatments (control treatment (CK), high-temperature treatment (H), and high-temperature together with elevating SWC treatment (HW)) was carried out during grain filling with two maize hybrids at a typical station in North China Plain.  Averagely, the net photosynthetic rate (P_n) was improved by 20%, and the canopy temperature decreased by 1–3°C in HW compared with in H in both years.  Furthermore, the higher SWC in HW significantly improved the actual photosynthetic rate (Phi2), linear electron flow (LEF), variable fluorescence (F_v), and the maximal potential quantum efficiency (F_v/F_m) for both hybrids.  Meanwhile, different responses in chlorophyll fluorescence between hybrids were also observed.  The higher SWC in HW significantly improved thylakoid proton conductivity (gH⁺) and the maximal fluorescence (F_m) for the hybrid ZD958.  For the hybrid XY335, the proton conductivity of chloroplast ATP synthase (vH⁺) and the minimal fluorescence (F_o) was increased by the SWC.  The structural equation model (SEM) further showed that SWC had significantly positive relationships with P_n, LEF, and F_v/F_m.  The elevating SWC alleviated heat stress with the delayed leaf senescence to prolong the effective period of photosynthesis and enhanced leaf photosynthetic capacity by improving Phi2, LEF, F_v, and F_v/F_m.  This research demonstrates that elevating SWC through enhancing leaf photosynthesis during grain filling would be an important mitigation strategy for adapting to the warming climate in maize production.

N6-methyladenosine (m6A) plays a key role in mammalian early embryonic development and cell lineage differentiation. However, the role and mechanisms of 18S ribosomal RNA (rRNA) m6A methyltransferase METTL5 in early embryonic development remain unclear. Here, we found that 18S rRNA m6A methyltransferase METTL5 plays an important role in porcine early embryonic development. METTL5 knockdown and overexpression significantly reduced the developmental efficiency of porcine early embryos and impaired cell lineage allocation. METTL5 knockdown apparently decreased the global translation efficiency in blastocyst, while METTL5 overexpression increased the global translation efficiency. Furthermore, METTL5 knockdown did not affect the abundance of CDX2 mRNA, but resulted in a significant reduction in CDX2 protein levels. Moreover, the low developmental efficiency and abnormal lineage distribution of METTL5 knockdown embryos could be rescued by CDX2 overexpression. Collectively, our results demonstrated that 18S rRNA methyltransferase METTL5 regulates porcine early embryonic development via modulating the translation of CDX2.