钙对铝胁迫下油茶生长及生理特性的影响

Effects of Calcium on the Growth and Physiological Characteristics of Camellia oleifera under Aluminum Stress

【目的】探究钙对铝胁迫下油茶幼苗生长和生理特性的影响,为揭示钙缓解油茶铝胁迫的生理机制提供理论依据。【方法】采用盆栽试验的方法,测定铝胁迫(4 mmol/L)下施加不同浓度钙(0、0.5、1.5、3和5 mmol/L)对油茶幼苗生长、叶片光合作用、根系渗透调节物质及抗氧化酶活性的影响。【结果】铝胁迫显著抑制了油茶幼苗的生长,施入3 mmol/L钙明显缓解了铝对油茶生长的抑制,植株干质量提高40.58%。对于光合参数而言,铝胁迫降低了油茶叶片叶绿素a、叶绿素b、类胡萝卜素和总叶绿素含量,净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)分别比对照(CK)降低32.28%、51.02%和53.91%,胞间CO_(2)浓度(Ci)提高20%;添加适量钙(1.5~3 mmol/L)能够显著提高叶片光合色素含量、Pn、Gs和Tr,降低Ci。与铝胁迫相比,钙的施入可以有效减少根系游离脯氨酸积累,提高可溶性糖含量。铝胁迫下,油茶根系超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)和叶片抗坏血酸过氧化物酶(APX)活性显著降低,根系质膜透性和丙二醛(MDA)含量明显增加,施钙后能显著增强抗氧化酶活性,钙浓度为1.5 mmol/L时POD和AXP活性最高,分别为35.13和234.11 U/g,钙浓度为3 mmol/L时SOD和CAT活性最高、分别为533.20和48.42 U/g。同时,添加适量浓度钙(1.5~3 mmol/L)显著降低了根系质膜透性和MDA含量,分别比铝胁迫处理降低19.52%~31.40%和23.32%~27.86%。【结论】添加适量浓度钙(1.5~3 mmol/L)可以显著提高油茶叶片光合作用能力和抗氧化酶活性,降低活性氧胁迫和膜脂过氧化产物的生成,并通过调节渗透物质缓解铝胁迫对油茶幼苗的毒害作用,但是当钙浓度达到5 mmol/L时,则对油茶幼苗生长产生抑制作用。

【Objective】The study aims to investigate the effects of calcium on the growth and physiological characteristics of Camellia oleifera seedlings under aluminum stress,with a view to providing theoretical basis for revealing the physiological mechanism of calcium alleviation of aluminum stress in C.oleifera.【Method】The effects of different calcium concentrations(0,0.5,1.5,3 and 5 mmol/L)applied under aluminum stress(4 mmol/L)on the growth,leaf photosynthesis,root osmoregulatory substances and antioxidant enzyme activities of C.oleifera seedlings were determined through a pot experiment.【Result】Aluminum stress inhibited the growth of C.oleifera seedlings significantly,and the application of 3 mmol/L calcium significantly alleviated the inhibition of aluminum growth in C.oleifera,and the plant dry weight increased by 40.58%.For photosynthetic parameters,aluminum stress reduced chlorophyll a,chlorophyll b,carotenoids and total chlorophyll contents of C.oleifera leaves.Net photosynthetic rate(Pn),stomatal conductance(Gs)and transpiration rate(Tr)decreased by 32.28%,51.02%and 53.91%,respectively,compared with those under CK treatment,while intercellular CO_(2)concentration(Ci)increased by 20%.The addition of appropriate amount of calcium(1.5-3 mmol/L)significantly increased the photosynthetic pigment content,Pn,Gs and Tr,and decreased Ci of leaves.Compared with aluminum stress,calcium application could reduce the accumulation of root free proline and increased the soluble sugar content effectively.Under aluminum stress,the activities of superoxide dismutase(SOD),peroxidase(POD),catalase(CAT)in the roots and ascorbate peroxidase(APX)in the leaves were significantly reduced.The plasma membrane permeability and malondialdehyde(MDA)content in the roots were significantly increased.Calcium application significantly enhanced antioxidant enzyme activities.POD and AXP activities were highest when the calcium concentration was 1.5 mmol/L,which were 35.13 and 234.11 U/g,respectively;and SOD and CAT activities were highest when the calcium concentration was 3.0 mmol/L,which were 533.20 and 48.42 U/g,respectively.Meanwhile,the addition of appropriate concentration of calcium(1.5-3 mmol/L)significantly reduced root plasma membrane permeability and MDA content,which were 19.52%-31.40%and 23.32%-27.86%lower than those under aluminum stress treatment,respectively.【Conclusion】Calcium at moderate concentrations(1.5-3 mmol/L)significantly improved photosynthetic capacity and antioxidant enzyme activity of C.oleifera leaves,reduced reactive oxygen stress and production of membrane lipid peroxidation products,and alleviated the toxic effects of aluminum stress on C.oleifera seedlings by regulating osmotic substances.However,when the calcium concentration reached 5 mmol/L,it inhibited the growth of C.oleifera seedlings.