邻苯二甲酸处理下外源硅对辣椒幼苗光合与抗氧化特性的影响OA

Phthalic acid(PA)is one of the main autotoxic substances produced in pepper under protec-ted cultivation.Its accumulation significantly affects crop growth,development,yield,and quality,and is an important cause of continuous cropping obstacles.Furthermore,exogenous silicon(Si)has been proven to effectively enhance crop stress tolerance.Based on this,the present study investigated the effects of exogenous Si on the growth and antioxidant characteristics of pepper seedlings under phthal-ic acid(PA)treatment,aiming to provide a theoretical basis for the management of continuous crop-ping obstacles in protected pepper cultivation.Using'Masuo'pepper as the experimental material and adopting the substrate pot culture method,seven treatments were set up,including different PA con-centrations(0,0.5,1.0,1.5 mmol·L-1)and 1.5 mmol·L-1 Si.The seedling biomass,root morpholo-gy,photosynthetic and fluorescence parameters,and antioxidant indexes were systematically measured.The results showed that:(1)PA had a"low-concentration promotion and high-concentration inhibi-tion"effect on the growth of pepper seedlings.0.5 mmol·L-1 PA increased the average root diameter and total volume.However,1.0 and 1.5 mmol·L-1 PA induced autotoxic stress in pepper seedlings,significantly inhibited seedling biomass,root length,root surface area,and photosynthetic parameters(Pn,Gs),reduced Fv/Fm,intensified membrane lipid peroxidation,and suppressed the activities of an-tioxidant enzymes such as SOD and POD.The autotoxic stress induced by 1.5 mmol·L-1 PA was the most severe.(2)Application of Exogenous silicon(Si)at 1.5 mmol·L-1 effectively alleviated PA-in-duced autotoxic stress.Compared with the T5(1.5 mmol·L-1 PA alone),the T6 treatment(1.5 mmol·L-1 PA+1.5 mmol·L-1 Si)significantly enhanced both shoot and root fresh weights.Total root length and root surface area increased by 20.66％and 24.80％,respectively.Chlorophyll a and b contents increased by 28.30％and 30.30％,respectively.Pn and Fv/Fm were significantly increased.Leaf MDA and superoxide anion(O-·2)contents decreased by 34.50％and 36.57％,respectively,and SOD activity increased by 85.70％.In addition,under the condition of 0.5 mmol·L-1 PA,exogenous Si and PA showed a synergistic effect on the growth,photosynthetic characteristics,and antioxidant characteristics of pepper seedlings.In conclusion,1.5 mmol·L-1 exogenous Si can alleviate PA auto-toxic stress and promote the growth of pepper seedlings by enhancing photosynthetic performance and antioxidant defense,and it has a synergistic effect at low PA levels.