【目的】研究生物炭对发生对羟基苯甲酸毒害的平邑甜茶幼苗光系统功能、叶绿素含量、抗氧化酶活性及丙二醛含量的影响，以期为防治苹果连作障碍提供依据。【方法】以苹果常用砧木-平邑甜茶为试材，在水培条件下，以（1）营养液作为对照（CK），用（2）营养液+0.4 mmol·L-1对羟基苯甲酸（FS）和（3）营养液+0.4 mmol·L-1对羟基苯甲酸+0.5%生物炭（FSC）处理平邑甜茶幼苗，测定不同处理对平邑甜茶幼苗叶片光合速率、荧光参数、叶绿素含量等与光合作用相关的系统指标和超氧化物歧化酶（SOD）、过氧化氢酶（CAT）和过氧化物酶（POD）活性和丙二醛（MDA）含量的影响。【结果】与FS处理相比，FSC处理的平邑甜茶幼苗叶片净光合速率（Pn）和气孔导度（Gs）显著提高，分别提高了32.7%和25%，而胞间CO 2浓度降低，可见，FS处理平邑甜茶幼苗叶片净光合速率下降的主要原因不在气孔；FSC处理的平邑甜茶幼苗叶片PSⅡ反应中心实际光化学效率（ΦPSⅡ）、电子传递效率（ETR）和光化学猝灭系数（qP）显著高于FS处理，分别提高了15.8%、16.9%和11.1%，而FSC处理的非光化学猝灭系数（NPQ）上升幅度比FS处理降低了17.5%；同时， FS处理显著降低了平邑甜茶幼苗叶片的Chl a、Chl b、Chl (a+b)含量，处理5 d后，分别为对照的66.7%、37.5%和54.1%，而FSC处理叶片Chl a、Chl b、Chl (a+b)含量显著高于FS处理，处理5 d后，分别比FS处理高35.7%、66.7%和45%；FSC处理还大大提高了对羟基苯甲酸胁迫下平邑甜茶幼苗叶片抗氧化酶活性，处理5 d后，幼苗叶片的SOD、POD和CAT 活性明显高于FS处理，分别比FS处理提高了55.5%、44.7%和18.6%；与对照相比，FS处理致使平邑甜茶幼苗叶片的MDA含量随着处理天数的增加而显著增加，生物炭处理则减缓了酚酸胁迫下MDA含量的增加幅度。可见，生物炭的加入可提高对羟基苯甲酸胁迫下平邑甜茶幼苗叶片的抗氧化酶活性，从而增强植株对逆境的抗性，对植株起到有效的保护作用。【结论】对羟基苯甲酸导致平邑甜茶幼苗光合速率下降的主要原因是非气孔因素，生物炭可提高幼苗叶片叶绿素含量及叶片保护酶活性，降低叶片MDA含量，有效缓解对羟基苯甲酸对叶片PSⅡ系统的损伤，增强光合作用，最终缓解对羟基苯甲酸对平邑甜茶幼苗的生长胁迫。%[Objective] The experiment was to explore the effects of biochar on photosynthetic gas exchange, chlorophyll fluorescence parameters, chlorophyll content, malondialdehyde (MDA) content , and the activities of protective enzymes (including SOD, POD and CAT) in leaves of Malus Hupehensis Rehd. seedlings under p-hydroxybenzoic acid stress in hydroponics, and to provide basis for prevention and treatment of suppressive cropping problems of apple.[Method]A common rootstock of apple trees seedlings was used in this study. The seeds were stratified for 30 days under 4℃, after shoot emergence, the seeds were planted in nursery plates. The seedlings of uniform size with 3 leaves were transplanted in 1/2 Hoagland nutrient solution in greenhouse until they reached the six-leaf-stage. Three treatments were designed, i.e. 1/2 Hoagland nutrient solution (CK); 1/2 Hoagland nutrient solution+0.4 mmol·L-1 p-hydroxybenzoic acid (FS);1/2 Hoagland nutrient solution+0.4 mmol·L-1 p-hydroxybenzoic acid+0.5%biochar (FSC). The photosynthetic gas exchange and chlorophyll fluorescence parameters were measured after 24 h of treatment, and the chlorophyll content, malondialdehyde (MDA) content , and the activities of SOD, POD and CAT in leaves of M. hupehensis Rehd. seedlings were investigated at the 1, 3, and 5 day after treatment. [Result] The results showed that the net photosynthetic rate (Pn) and stomatal conductance (Gs) treated with FSC were obviously increased by 32.7% and 25%, respectively compared with p-hydroxybenzoic acid stress. While the internal CO2 concentration (Ci) was reduced; With FSC treatment, the actual PSⅡefficiency (ΦPSI ), electron transport rate (ETR) and photochemical quenching coefficient (qP) were increased, increased by 15.8%, 16.9%and 11.1%, respectively compared with FS treatment. But the increase of non-photochemical quenching of PSⅡ(NPQ) under FSC treatment was decreased by 17.5%compared with FS treatment. At the same time, the chlorophyll content treated with biochar was significantly increased, after 5 days of treatment, the Chla, Chlb and the Chla+b increased by 66.7%, 37.5%, and 54.1%, respectively. Application of biochar enhanced the activities of antioxidant enzyme in the leaves of M. hupehensis seedlings under p-hydroxybenzoic acid stress. The activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) significantly increased by 55.5%, 44.7%, and 18.6%, respectively under FSC treatment; Compared with the control, the MDA content was enhanced with the increase of days of treatment, while the MDA content declined with the biochar addition. [Conclusion] It is considered that the reduction in the net photosynthetic rate under p-hydroxybenzoic acid stress was mainly caused by non-stomatal restriction. The biochar significantly increased chlorophyll content, maintained PSII center activities and photosynthetic capacity, improved the activities of SOD, POD and CAT, decreased the MDA content. The biochar alleviated the p-hydroxybenzoic acid stress and enhanced the autotoxicity tolerance of M. hupehensis Rehd. seedlings.
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