Split application of phosphorus fertilizer increased wheat grain weight under post-anthesis drought stress by delaying programmed cell death of endosperm

Abstract

Drought is one of the important factors affecting wheat yield. However, the effect of split application of phosphorus fertilizer on the programmed cell death (PCD) of wheat endosperm cells under different post-anthesis water treatments is still unclear. In this study, three phosphorus fertilization methods (P1, all phosphorus fertilizer was applied at the spring green-up stage; P2, 50% and 50% of phosphorus fertilizer were applied at the spring green-up stage and jointing stage, respectively; P3, 40%, 30%, and 30% of phosphorus fertilizer were applied at the spring green-up, jointing, and grain filling stages, respectively) were designed. Besides, two post-anthesis water treatments were designed: WT, full irrigation treatment; DT, drought stress treatment. Then, the effects of P1, P2, and P3 treatments on the endosperm cell development, nuclear number, nuclease activity, DNA fragmentation, DNA content, grain weight, and phosphorus content of winter wheat variety “Xindong 23” under WT and DT conditions were determined at different stages after anthesis. The results showed that under WT and DT conditions, the degree of nuclear deformation and nuclear membrane depression in P3 treatment was milder than that in P1 and P2 treatments. The ACPase amount in P3 treatment was more than that in P1 and P2 treatments. The number of endosperm nuclei in P3 treatment was higher than that in P1 and P2 treatments. Under DT condition, the endosperm DNA content of wheat grains collected 14-35 days post anthesis (DPA) in P3 treatment increased, and the peak time of genomic DNA fragmentation in P3 treatment was later, compared with those in P1 treatment. Under DT condition, the grain weight and grouting rate in P3 treatment were higher than those of P1 treatment at 7-28 DPA, and the 1000-grain weight of P3 was the highest under both WT and DT conditions, reaching 47.03 and 40.57g, respectively. Under WT and DT conditions, the protein content change rate (3.16% and 5.59%, respectively) and the total phosphorus content change rate (34.36% and 35.08%, respectively) of wheat grains in P3 treatment were the highest. In summary, under the DT condition, split application of phosphorus fertilizer (P3, spring green-up stage stage: jointing stage: filling stage = 4: 3: 3) could increase the phosphorus uptake and utilization of wheat plants and grains, suppress the DNA fragmentation of endosperm cells, and delay the deformation and disintegration of nuclei, which ultimately delayed the PCD in endosperm and realized high grain weight and protein content.