【作者】 高洪波；

【导师】 郭世荣；

【作者基本信息】 南京农业大学 ， 蔬菜学， 2005， 博士

【摘要】 无土栽培中营养液供氧不足或基质根垫的形成均会造成低氧胁迫,影响植株正常生长发育,成为困扰无土栽培技术大规模应用于生产的限制性因子,提高作物在低氧胁迫下的耐性和抗性对无土栽培生产意义重大。Ca²⁺作为植物生长所必需的大量元素和偶联胞外信号与胞内生理反应的第二信使,在逆境胁迫下细胞内含量显著提高,与胞内CaM形成Ca²⁺·CaM复合物,能维持细胞壁、细胞膜及膜蛋白的稳定性,缓解逆境胁迫对植物的伤害。植物体内氮素代谢可分为无机氮代谢和有机氮代谢,无机氮代谢包括NO₃^--N、NH₄⁺-N、硝酸还原酶等,有机氮代谢包括氨基酸、蛋白质、多胺等含氮物质的代谢。在逆境胁迫下植物体内活性氧代谢平衡受到破坏,活性氧产生速率高于清除速度,导致活性氧大量积累。但低氧胁迫对植物体内氮素代谢和活性氧代谢的影响还不清楚,外源钙、钙抑制剂和钙调素拮抗剂以及γ-氨基丁酸（GABA）处理对低氧胁迫下植株低氧耐性的影响未见系统研究。 本文首先从23个网纹甜瓜（Cucumis melo L.var.raticulalus Naud）品种中筛选出低氧耐性较强、中等和较弱的品种,并用低氧耐性具有显著差异的2个品种为材料,其中低氧耐性较强的品种有‘东方刚强’和‘东方星光’,低氧耐性较弱的品种为‘西域一号’,研究了低氧胁迫对网纹甜瓜植株生长、氮代谢和活性氧代谢的影响,结合营养液加减Ca²⁺、叶面喷施Ca²⁺抑制剂La³⁺和Ca²⁺螯合剂EGTA、CaM拮抗剂TFP和W7处理,研究了Ca²⁺、CaM对低氧胁迫下网纹甜瓜幼苗根系和叶片氮代谢、活性氧代谢的影响及其与低氧耐性的关系,利用外源喷施γ-氨基丁酸处理研究了低氧胁迫下活性氧代谢的变化及γ-氨基丁酸与植株低氧耐性的关系。 结果表明,根际低氧逆境胁迫下,植株体内硝态氮和氨态氮含量、硝酸还原酶活性、Pro、PAs含量均显著提高,可溶性蛋白质含量降低,根系热稳定蛋白含量增加,而叶片热稳定蛋白质含量呈下降的变化趋势;低氧胁迫下根系硝态氮和氨态氮含量、硝酸还原酶活性、Pro、PAs含量变化幅度显著高于叶片;与“西域一号”相比,“东方刚强”植株体内含氮物质的含量较多,表明在低氧胁迫下,植株体内氮代谢途径发生变化,硝态氮快速还原成氨态氮以及热稳定蛋白、Pro、PAs的快速合成,对提高网纹甜瓜低氧耐性起着重要的作用。 根际低氧逆境胁迫下,植株体内H₂O₂和MDA含量以及O₂·^-产生速率显著增加,更多还原

【Abstract】 Hypoxia stress in the root-zone is thought be a major determinant in the adverse effect of O₂ deficiency in hydroponic culture and root-cushion formation in substrate culture on plant species. Now hypoxia stress has become a limited factor of soilless culture application to large area production. Therefore, improving the hypoxia tolerance of crops plays a vital role in soilless culture. Ca²+ is the necessary major element of plant growth and a second messenger of coupling extracellular signal and intracellular physiological reaction. It has been known that [Ca²+]_cyt increase rapidly under environmental stress and Ca ²+.CaM compound formation after Ca ²+ combined with target enzyme CaM, which played an important role in stabling the cell wall, cell membrane and membrane protein and relieving the harm of stress to the crops. In plant, nitrogen metabolism can be divided in to inorganic nitrogen metabolism （including N0₃ --N, NH₄⁺-N, NR,） and organic nitrogen metabolism （including amino acid, protein, PAs）. Environment stress change the ROS metabolism which cause overproduction of ROS and plants have developed sophisticated mechanism of scavenging ROS. But little is known about the effect of hypoxia stress and exogenous compound such as Ca²+, Ca²+ and CaM inhibitor, GABA on nitrogen and ROS metabolism and whether Ca²+, CaM, GABA are involved in the regulation hypoxia tolerance of crops.Different cultivars were sorted according to the different hypoxia tolerance from 23 muskmelon cultivars. And hypoxia-tolerance muskmelon cultivars ’Dongfang gangqiang’ and ’Dongfang xingguang’ and hypoxia-sensitivie cultivars ’Xiyu No.l’ were choose as experimental materials to investigate the effect of hypoxia stress on growth, nitrogen metabolism and ROS metabolism in muskmelon seedlings. Under hypoxia stress, combined with treatment of exogenous application Ca²+, exogenous foliar spraying La ³+, EGTA, TFP, W7 and GABA to investigated effect of Ca²+, CaM, GABA on intrinsic hypoxia resistance of muskmelon seedlings and elucidate the relationship between Ca²+ , CaM, GABA enhance hypoxia resistance and the nitrogen and ROS metabolism.The result showed that NO₃^--N and NH₄^--N, Pro, PAs contents and NR activities in roots and leaves all increased under root-zone hypoxia stress, but the soluble protein contents decreased, the heat-stable protein contents in roots increased while heat-stable protein in leaves decreased. The increase degrees of NO₃^--N and NH₄⁺-N, NR, Pro, and PAs were root>leaves. And the nitrogenous substance contents of ’Dongfang gangqiang’ were more than those of ’Xiyu No.1’. It indicated that the nitrogen metabolism pathway changed under hypoxia stress, NO₃^--N rapidly reduced to NH₄⁺-N and heat-stable protein, Pro, PAs synthesis rapidly played an important role in enhancing hypoxia resistance in muskmelon seedlings.Root-zone hypoxia stress caused the increase antioxidant enzyme （SOD, POD, CAT） activities which could scavenge the ROS, while H₂O₂, MDA contents and O₂^- productive rate also obviously increased. The speed of ROS accumulation was more rapid than that of ROS scavenge and ROS scavenge pathway is different between leaves and roots. The activities of antioxidant enzyme in ’Dongfang xingguang ’ were higher than those in ’Xiyu No.1’ while the H₂O₂, MDA contents and O₂^- productive rate were lower. It suggested that accumulation of ROS and peroxidation of membrane lipid aggravated under hypoxia stress and ROS metabolism existed difference of different site of muskmelon seedlings and different cultivars.Exogenous application Ca²+ in nutrient solution could relieve the harm caused by hypoxia stress and result in the increase of NO₃^--N and NH₄⁺-N, amine acid, heat-stable protein, ion bond conjugated protein and covalent bond conjugated protein in cell wall, PAs （free, conjugated, bound） and antioxidant enzyme activities as well as the decreased of PAO activities in cell cytoplasm and cell wall and ROS contents in roots and leaves of muskmelon seedlings as compared with the hypoxia stre更多还原