减肥配施生物刺激素对苹果植株生长、光合特性及产量的影响OA

This study aims to investigate the effects of different fertilizer reduction gradients combined with the application of biostimulants on plant growth,photosynthetic characteristics,and yield of apple plants.The experiment adopted a two-factor design:fertilizer application rate and biostimulant spra-ying.Three fertilizer levels were set:40％reduction in chemical fertilizer(CK1),20％reduction(CK2),and conventional fertilization(CK3).Each was paired with a corresponding humic acid-based biostimulant treatment—C1,C2,and C3—resulting in six treatment combinations.The study analyzed the effects of biostimulants on vegetative growth,leaf photosynthetic characteristics,yield and irriga-tion water use efficiency(IWUE).The results showed that biostimulant application under reduced fertilizer conditions significantly enhanced shoot elongation,basal shoot diameter,and leaf area.All biostimulant treatments significantly increased the leaf area index(LAI),with the highest LAImax val-ue(2.115)observed in C3 and the greatest improvement(7.51％)over the control found in C2.Bios-timulants also regulated endogenous hormone levels by increasing the concentrations of indole-3-acetic acid(IAA),trans-zeatin riboside(tZR),and gibberellin A19(GA19),while suppressing abscisic acid synthesis.Across all fertilizer levels,biostimulant spraying improved leaf SPAD values and enhanced photosynthetic efficiency.Furthermore,biostimulant application increased the commercial fruit rate,total yield,and IWUE.The C2 treatment resulted in the highest values:81.53％commercial fruit rate,60 315.07 kg·hm-2 yield,and 13.40 kg·m-3 IWUE.Based on the results,the combination of 20％fertilizer reduction with biostimulant application(C2 treatment)was identified as the optimal strategy.