高温强光下Ca2+对西葫芦幼苗膜质过氧化、抗氧化酶系统及热耗散的影响

为探明不同浓度外源Ca2+对高温强光胁迫下西葫芦植株幼苗的影响,本试验选用西葫芦(Cucurbitapepo L.)品种"阿兰一代"为试验材料,通过外源喷施不同浓度CaCl2溶液,研究了Ca2+对高温强光胁迫下西葫芦幼苗叶绿素荧光特性、膜质过氧化及抗氧化酶系统的影响。结果表明,较低浓度Ca2+处理(5~20 mmol.L 1)可有效提高高温强光下西葫芦幼苗超氧化物歧化酶(SOD)、过氧化物酶(POD)、抗坏血酸过氧化物酶(APX)、谷胱甘肽还原酶(GR)和过氧化氢酶(CAT)活性,降低丙二醛(MDA)、过氧化氢(H2O2)、超氧阴离子自由基(O2&)含量和膜透性,还原型谷胱甘肽(GSH)含量升高;同时西葫芦叶片PSII的最大光化学效率(Fv/Fm)、PSⅡ实际光化学效率(ΦPSⅡ)和光化学猝灭系数(qP)较高,而非光化学猝灭系数(NPQ)较低。说明5~20 mmol.L 1Ca2+处理对高温强光胁迫具有明显的缓解作用,同时其热耗散较小。当Ca2+处理浓度超过40 mmol.L 1时对高温强光胁迫缓解效应不明显。

Effects of Ca2+ on membrane lipid peroxide, antioxidation enzymes and thermal dissipation of squash seedlings under high temperature and light intensity

Vegetable growth and development have suffered restraints and damages by high temperatures and strong lights under rising global temperatures in recent years.The yield,quality and economic benefits of summer vegetables substantially reduced due to dual stresses of high temperatures and strong lights.Therefore an experiment was carried out in 2009 to explore the methods of alleviating of high temperature/light adversities in vegetable production.In the experiment,a squash(Cucurbitapepo L.) variety of "Alan" was used to study Ca2+ effects on the characteristics of chlorophyll fluorescence,membrane lipid peroxide and antioxidation enzymes of squash seedlings by exogenous application of CaCl2 solution under the stresses of high temperature and light intensity.The results showed that squash seedlings under the application of 5~20 mmol·L 1 of Ca2+ had higher superoxide dismutase(SOD),peroxidase(POD),ascorbate peroxidase(APX),glutathione reductase(GR) and catalase(CAT) activities and GSH content than the control experiment(CK).However,the contents of malondialdehyde(MDA),H2O2,and relative electrical conductivity were lower than those of over-40 mmol·L 1 Ca2+ and CK treatments.The maximum PSII efficiency(Fv /Fm),actual PSII efficiency(ΦPSⅡ) and photochemical queching coefficient(qP) improved under the 5~20 mmol·L 1 Ca2+ treatment.However,non-phochemical fluorescence quenching coefficient(NPQ) decreased under the 5~20 mmol·L 1 Ca2+ treatment.This indicated that the 5~20 mmol·L 1 Ca2+ treatment remarkably buffered damages caused by high temperatures and light intensity stresses and decreased excitation energy of dissipation.The best buffer effect for high temperatures and strong lights occurred under 10 mmol·L 1 Ca2+ application.No buffer effect was noted when Ca2+ concentration was more than 40 mmol·L 1.