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以‘津优3号’黄瓜幼苗为试材,以Hoagland全营养液处理为对照(CK),研究低镁(30%Mg)胁迫对低温(昼/夜温度12℃/8℃)下黄瓜幼苗光合特性和抗氧化系统的影响.结果表明:低温下30%Mg处理黄瓜幼苗叶片Mg含量显著低于CK,而根中Mg含量与CK差异不显著.随着低温胁迫时间的延长,黄瓜幼苗叶片的叶绿素含量、净光合速率(Pn)、气孔导度(gs)和羧化效率(CE)逐渐降低,胞间CO2浓度(Ci)趋于升高.与CK相比,低温下30%Mg处理叶片叶绿素含量、Pn、gs和CE显著降低,Ci变化不大,叶绿体膜损伤严重,叶绿体数、基粒数和片层数较少,淀粉粒数增加,淀粉粒较长,丙二醛(MDA)含量升高,而超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)和谷胱甘肽还原酶(GR)活性降低.可见,低温下镁运输受阻引起的缺镁是叶片失绿的主要原因;低温引起Pn降低的主要原因是非气孔限制,低镁胁迫会加大低温对黄瓜Pn的影响,而由此引起的Pn降低的主要原因是气孔限制.
Taking cucumber seedlings of ’Jinyou 3’ as test material and Hoagland total nutrient solution as CK, the effects of low Mg (30% Mg) stress on the growth of cucumber seedlings under low temperature (day / night temperature 12 ℃ / 8 ℃) Photosynthetic characteristics and antioxidation system.The results showed that the content of Mg in leaves of cucumber seedlings treated with 30% Mg at low temperature was significantly lower than that of CK, while the content of Mg in roots was not significantly different from that of CK.With the increase of chilling time, (Pn), stomatal conductance (Gs) and carboxylation efficiency (CE) decreased gradually and the intercellular CO2 concentration (Ci) tended to increase.Compared with CK, 30% Mg treatment at low temperature Chlorophyll content, Pn, gs and CE were significantly decreased, Ci was little changed, chloroplast membrane was severely damaged, chloroplast number, base number and lamella number were less, starch grains increased, starch grains longer, malondialdehyde (MDA) ), While the activity of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase Decrease.It can be seen that the lack of magnesium caused by the obstruction of magnesium transport at low temperature is the main cause of leaf chlorosis. The main reason of the decrease of Pn caused by low temperature is non-stomatal limitation and low magnesium Force will increase the influence of low temperature on cucumber Pn, and Pn decreased mainly due to the resulting stomatal limitation.