外源H_2O_2对镧胁迫下裸燕麦幼苗光合作用和活性氧代谢的影响

Effects of Exogenous Hydrogen Peroxide on Photosynthesis and Reactive Oxygen Metabolism in Leaves of Avena nuda L. Seedlings under Lanthanum Stress

土壤稀土元素污染已成为中国稀土矿区农业可持续发展的制约因素。为探讨信号分子H_2O_2对La胁迫下作物生理响应的调控机制,以裸燕麦品种‘白燕7号’幼苗为试材,采用砂培方法,研究了喷施5 mmol·L^(-1) H_2O_2预处理对1.20 mmol·L^(-1) La^(3+)胁迫下裸燕麦幼苗La含量、生长参数、叶片光合色素含量、气体交换参数和活性氧代谢的影响。结果表明:La胁迫下,裸燕麦幼苗根系和地上部La含量,胞间CO_2浓度(C_i),超氧阴离子(O_2^(·-)), H_2O_2,丙二醛(MDA),类黄酮,总酚和原花青素含量,质膜相对透性(RPP),超氧化物歧化酶(SOD),过氧化物酶(POD),抗坏血酸过氧化物酶(APX)活性显著提高,而根长、株高及根系和地上部干重、叶片光合色素含量、净光合速率(P_n)、气孔导度(G_s)、蒸腾速率(T_r)、抗坏血酸(ASA)、谷胱甘肽(GSH)、可溶性蛋白质、可溶性糖含量明显降低,过氧化氢酶(CAT)活性变化不大。La胁迫下H_2O_2预处理对裸燕麦幼苗根系La含量没有影响,但地上部La含量显著下降;根长、株高及根系和地上部干重、叶片光合色素、 ASA、可溶性蛋白质、可溶性糖、类黄酮、总酚和原花青素含量、 CAT活性、P_n,G_s,T_r提高,C_i, O_2^(·-), H_2O_2, MDA含量、 RPP, SOD, POD和APX活性下降, GSH含量没有改变。表明La胁迫下外源H_2O_2能够抑制La从根系向地上部的转运,并通过调控活性氧清除系统降低膜脂过氧化程度,提高光合速率,缓解植株生长受抑程度,从而增强裸燕麦对La胁迫的适应能力。

The pollution of rare earth elements in soil is an important factor restricting the sustainable development of agriculture in China′s rare earth mining area. In order to explore the regulatory mechanism of signaling molecule hydrogen peroxide(H2O2) on the crop physiological response under the stress of lanthanum(La), naked oat(Avena nuda) cultivar ‘Baiyan 7’ seedlings were taken as the testing material and the effect of spraying 5 mmol·L^-1 H2O2 pretreatment on the La content and growth, leaf photosynthetic pigment content, gas exchange parameters, and reactive oxygen metabolism in naked oat seedlings under 1.20 mmol·L^-1 La^3+ stress were investigated using the method of sand culture. The results showed that La stress significantly increased the La contents in root and shoot, leaf intercellular CO2 concentration(Ci), contents of O2·-, H2O2, malondialdehyde(MDA), flavonoid, total phenols and proanthocyanidins, relative plasma permeability(RPP), and activities of superoxide dismutase(SOD), peroxidase(POD) and ascorbate peroxidase(APX) in naked oat seedlings, and the root length, plant height, dry weights of root and shoot, leaf photosynthetic pigment content, net photosynthetic rate(Pn), stomatal conductance(Gs), transpiration rate(Tr), and contents of ascorbic acid(ASA), glutathione(GSH), soluble protein and soluble sugar were markedly decreased, but no significant change in the catalase(CAT) activity. In comparison to La stress, spraying H2O2 pretreatment had no significant effect on the La content in root, but it decreased in shoot. Meanwhile, spraying H2O2 pretreatment also led to a marked increase in the root length, plant height, dry weights of root and shoot of naked oat seedlings, the contents of photosynthetic pigment, ASA, soluble protein, soluble sugar, flavonoid, total phenols and proanthocyanidins, CAT activity, Pn, Gs and Tr, as well as decrease in Ci, contents of O2(·-), H2O2 and MDA, RPP, activities of SOD, POD and APX, but little influence on GSH content in naked oat leaves. Consequently, exogenous H2O2 could reduce the degree of membrane lipid peroxidation induced by La stress, improve the photosynthetic rate and alleviate the inhibition of La stress on the growth, enhance the ability of naked oat seedlings against La stress by inhibiting the transport of La from root to shoot and adjusting active oxygen scavenging system.