Alleviative effects of nitrogen fertilizer regulation on the antioxidant sys-tem and dry matter allocation of cucumber under high temperature stress

GAN Xiaolin; WANG Yanling; GAO Lei; YANG Zaiqiang; SHI Jiaqi

doi:10.16861/j.cnki.zggc.2025.0448

Abstract：To investigate the alleviating effect of nitrogen fertilizer regulation on the antioxidant defense system and dry matter allocation of cucumber under high-temperature stress,using the cucumber cultivar Jinyou 101 as material,four ni-trogen application levels were set,namely 0(N0),160(N1),240(N2),and 320 kg·hm-2(N3).With 28/18℃(day/night)as the control,three high-temperature stress treatments of mild temperature stress(35/25℃),moderate temperature stress(38/28℃),and severe temperature stress(41/31℃)were simulated using artificial climate chambers..The activities of superoxide dismutase(SOD),catalase(CAT),peroxidase(POD),and soluble protein(SP)content in cucumber leaves at different durations(3,6,and 9 d),and the characteristics of dry matter allocation were measured after 9 d of stress.The results showed that,under the N0 treatment,high-temperature stress significantly inhibited SOD and CAT activity,with reductions ranging from 20.4%-44.1%and 9.1%-63.9%,respectively.Mild temperature stress(35/25℃)increased POD activity by 12.7%-210.0%,while severe temperature stress(41/31℃)decreased SP content by 22.8%-49.9%.Moderate ni-trogen(N2,240 kg·hm-2)application significantly improved the activity of antioxidant enzymes,increasing SOD and POD activity under mild temperature stress(35/25℃)by 7.9%-53.9%and 67.5%-328.2%,respectively,and enhancing CAT activity under moderate(38/28℃)and severe(41/31℃)temperature stress by 39.5%-146.3%.It also increased the dry matter allocation rate in fruit by 9.4%-16.9%under mild and moderate stress.However,under severe temperature stress(41/31℃),the regulatory effect of high nitrogen application(N3,320 kg·hm-2)significantly dismished.In conclu-sion,in facility cucumber cultivation,appropriate nitrogen application(N2,240 g·hm-2)under 35-38℃high-temperature stress can effectively activate the antioxidant system,promote dry matter allocation to fruits,and significantly alleviate high-temperature damage.When the temperature exceeds 41℃,it is necessary to combine environmental regulation and biological management measures to achieve synergistic alleviation of high temperature stress.This study provides key the-oretical and technical support for precision nitrogen application and stress-resistant cultivation of cucumber under high temperature stress in protected environments.