不同水分条件下施磷对冬小麦穗花结实及光合特性的影响

为探究不同水分条件下施磷肥对冬小麦光合及结实特性的调控效应,明确施磷调控光合生产力促进穗花发育成粒的机制,于2020-2022年设置3种水分处理(W0:重度干旱;W1:中度干旱;W2:正常水分)和2种磷肥处理(P0:不施磷;P1:施磷)的盆栽试验,以大穗型品种周麦16(V1)和多穗型品种豫麦49-198(V2)为试验材料,通过测定不同穗位(基部、中部和顶部)的可孕小花数、结实数以及叶片净光合速率、叶绿素、叶绿素荧光参数、蔗糖含量等,分析不同水分条件下磷素对两类型品种冬小麦光合及结实特性的影响。结果表明,施磷肥可以有效增加冬小麦开花期(W10时期)可孕小花数,尤其对基部穗位的可孕小花数提升效果最显著(13.74%-27.01%),其次是顶部(9.57%-20.19%),再次是中部(6.97%-14.01%)。对成熟期的结实粒数而言,施磷肥可以提高干旱胁迫下每穗的小穗数以及各小穗的结实数,进而显著提高每穗的结实粒数。此外,施磷肥可以有效提高两类型品种叶片净光合速率、叶绿素含量、光系统II最大光化学效率(F_v/F_m)和实际光化学效率(Φ_PSII);对蔗糖含量的影响因水分而异,干旱处理下增施磷肥降低了蔗糖含量,正常水分条件下则增加了蔗糖含量。将两类型品种光合指标分别与可孕小花数和穗粒数进行通径分析发现,5个光合指标与可孕小花数和穗粒数均呈正相关,其中净光合速率和蔗糖与可孕小花数的直接通径系数为1.001和0.435,与穗粒数的直接通径系数为0.996和0.626,远高于其他指标。最终,施磷通过增加穗数、穗粒数以及千粒重来显著增加产量,其中穗粒数在不同水分下均达到显著水平,穗数在W1和W2处理下显著,千粒重提升效果不显著。综上所述,在不同水分条件下施磷肥均可以通过调控冬小麦的光合性能提高其光合生产力,以维持正常的生理代谢功能,从而减少可孕小花的退化和败育以促进穗花成粒,最终达到缓解干旱胁迫危害以实现高产稳产的目的。研究结果为小麦生产中合理施用磷肥缓解干旱胁迫提供理论依据和技术支撑。

Effects of phosphorus application on spike floret development into grain and photosynthetic characteristics of winter wheat under different water treatments

To investigate the effect of phosphorus fertilization on the regulation of photosynthetic and fruiting characteristics of winter wheat under different water treatments, and to clarify the mechanism of phosphorus application to regulate the photosynthetic productivity and promote the development of spike floret development into grains, three water treatments (severe drought treatment, W0; moderate drought treatment, W1; and normal water treatment, W2) and two phosphorus fertilizer treatments (no phosphorus fertilizer treatment, P0; and phosphorus fertilizer treatment, P1) were set up in 2020-2022 for pot experiment. Using the massive-spike variety Zhoumai 16 (V1) and the multi-spike variety Yumai 49-198 (V2) as experimental materials, we analyzed the effects of phosphorus on the photosynthetic and fruiting characteristics of winter wheat of the two types of varieties under different water treatments by determining the number of fertile florets and the number of grains in the different spikes (the basal, the central, and the apical parts of the spikes), as well as the net photosynthetic rate, chlorophyll content, chlorophyll fluorescence parameter, and sucrose content of leaves. The results showed that the phosphorus fertilization could effectively increase the number of fertile florets at anthesis (W10 stage) in winter wheat, especially the most significant effect on the number of fertile florets at the basal spike position (13.74%-27.01%), followed by the top (9.57%-20.19%), and then the middle (6.97%-14.01%). For the number of grains at maturity, the phosphorus fertilizer application increased the number of spikelets per spike as well as the number of grains in each spikelet under drought stress, and then significantly increased the number of grains. In addition, the phosphorus fertilization was effective in increasing the net photosynthetic rate, chlorophyll content, photosystem II maximum photosynthetic efficiency (F_v/F_m) and actual photochemical efficiency (Φ_PSII) of leaves of both types of varieties, and the effects on sucrose content varied according to water treatments, with phosphorus fertilization decreasing the sucrose content under drought treatments, and increasing the sucrose content under normal water treatments. Pathway analyses of the photosynthetic indexes of the two types of varieties with the number of fertile florets and the number of grains per spike respectively revealed that five photosynthetic indexes were positively correlated with the number of fertile florets and the number of grains per spike, among which the direct pathway coefficients of Pn and sucrose with the number of fertile florets were 1.001 and 0.435, and those with the number of grains were 0.996 and 0.626, which were much higher than those of other indexes. Finally, phosphorus application significantly increased yield by increasing spike number, grain number per spike and 1000-grain weight, among which grain number per spike reached significant level under different water treatments, spike number was significant under W1 and W2 treatments, and 1000-grain weight improvement effect was not significant. In summary, the application of phosphorus fertilizer under different water treatments could improve the photosynthetic productivity of winter wheat by regulating its photosynthetic performance to maintain normal physiological and metabolic functions, thus reducing the degradation and abortion of fertile florets and promoting the spike floret develop into grains, ultimately alleviating the damage caused by drought stress for the purpose of achieving high and stable yields. The results provide a theoretical basis and technical support for alleviating the adverse effects of drought stress on wheat growth through the application of phosphorus fertilizer.