【作者】 刘瑞显；

【导师】 周治国；

【作者基本信息】 南京农业大学 ， 生态学， 2008， 博士

【摘要】 近年来,花铃期季节性干旱在我国各大棉区均时有发生,严重降低棉花产量和品质。氮肥的合理施用一直是调控作物生长发育及产量品质形成的重要措施.研究花铃期短期土壤干旱及复水后氮素调控棉花生长发育及产量与品质形成的生理生态基础,可为棉花的抗逆高产优质栽培提供科学的理论依据。本研究以美棉33B为试验材料,设置正常灌水与花铃期土壤短期干旱处理,同时对两个水分处理的棉花设置3个氮素水平,于2004～2006年在江苏南京农业大学卫岗试验站进行盆栽试验,研究:（1）氮素对花铃期土壤干旱及复水后棉花各器官干物质重、氮素累积与分配的影响,及与产量、品质形成的关系;（2）氮素对花铃期土壤干旱及复水后棉花叶片光合作用、蒸腾作用与水分利用率的影响,并从叶绿素荧光特性、内源保护酶活性、内源激素平衡的角度探索氮素影响光合作用的生理机理;（3）氮素对花铃期土壤短期干旱及复水后棉花根系干物质与氮素累积、内源保护酶活性、细胞膜脂过氧化及根系活力的影响,及与地上部生长发育的关系;（4）氮素对花铃期土壤短期干旱及复水后棉花纤维加厚发育相关酶与内源保护酶活性的影响,及与纤维比强度形成的关系。主要研究结果如下:1.氮素对花铃期干旱及复水后棉花干物质和氮素累积与分配的影响花铃期土壤干旱显著降低了棉株各器官的干物质重与氮素累积量,同时降低了干物质与氮素在叶片中的分配指数,但提高了根系的分配指数,从而增大了根冠比。施氮可以提高棉株的干物质重与氮素累积量,但亦增大水分胁迫指数.复水对棉株生长具有明显的补偿效应,尤其是根系,其干物质重与氮素累积量显著高于相应正常灌水处理,而增施氮肥可以提高棉株的补偿效应。花铃期土壤干旱结束时与复水后,干旱处理棉株均以240 kg N hm^-2水平下的生殖器官干物质重最高,而根冠比最小,地上部与地下部生长最为协调,最终籽棉产量最高、纤维品质最优。而施氮不足(0 kg N hm^-2)与过量施氮(480 kg N hm^-2)均不利于棉花产量的提高与纤维品质的改善。2.氮素对花铃期干旱及复水后棉花叶片光合与蒸腾特性及水分利用率的影响及其内在生理机制。花铃期干旱条件下,随土壤相对含水量的减少,棉花叶片净光合速率与蒸腾速率迅速降低。施用氮肥易加重棉株受胁迫程度,棉花土壤相对含水量,净光合速率与蒸腾速率的降低幅度随氮素水平的提高而增大。但是与蒸腾速率相比,施氮相对提高了净光合速率,从而提高了水分利用率。适量施氮(240 kg N hm^-2)有利于提高棉花净光合速率,其内部机理表现为气孔导度与胞间CO₂浓度最高,光系统Ⅱ最大光化学效率、量子产量、电子传递速率与光化学促灭系数均最高、叶片对光能的吸收利用率最高;内源保护酶活性强、膜脂过氧化程度最低;内源激素ABA的含量最低而ZR、IAA、GA的含量以及ZR/ABA、IAA/ABA、GA/ABA最高。施氮不足(0 kg N hm^-2)棉株遭受干旱与缺氮双重胁迫,过量施氮(480 kg N hm^-2)则加重了棉株的干旱胁迫程度,二者的净光合速率均较低,其叶绿素荧光特性、内源保护酶活性、内源激素含量的变化均表现出与适量施氮相反的趋势。复水后,干旱处理棉花叶片的内源保护酶活性可迅速恢复到正常灌水水平,其MDA含量与正常灌水处理间差异较小;但ABA含量明显低于正常灌水处理,ZR、IAA、GA含量以及ZR/ABA、IAA/ABA、GA/ABA却显著高于正常灌水处理.施氮有利于提高复水后干旱处理棉花叶片的内源保护酶活性,降低细胞膜脂过氧化程度,降低ABA含量,增大ZR、IAA、GA含量以及ZR/ABA、IAA/ABA、GA/ABA,其净光合速率亦随氮素水平的提高而增大。3.氮素对花铃期干旱及复水后棉花根系生理特性及生长的影响花铃期干旱条件下,棉花根重与氮素累积量显著降低,但根冠比增大;根系超氧化物歧化酶（SOD）和过氧化物酶（POD）活性明显升高,而过氧化氢酶（CAT）活性降低,同时,丙二醛（MDA）含量相应增大,根系活力显著降低,施氮可提高干旱处理棉花根重与氮素累积量,降低SOD活性,增强POD与CAT活性,以240 kg N hm^-2水平最有利于根系生长,其内在生理机制表现为根冠比最小、膜脂过氧化程度最低、根系活力最强。复水后,干旱处理棉花根系生长迅速恢复,根重与氮素累积量显著高于正常灌水处理;内源保护酶活性相应变化,MDA含量与正常灌水处理已无显著差异;根系活力亦显著高于正常灌水处理.施氮有利于增加根重与氮素累积量,提高POD与CAT活性,降低细胞膜脂过氧化程度,增强棉花根系活力,提高叶片净光合速率。4.氮素对花铃期干旱及复水后棉纤维发育的影响花铃期干旱条件下,棉纤维可溶性蛋白含量显著降低,而内源保护酶SOD、CAT、POD活性升高,MDA含量增加,细胞膜脂过氧化程度加重;纤维发育相关酶蔗糖合成酶、磷酸蔗糖合成酶、β-1,3-葡聚糖酶、IAA氧化酶的活性均显著降低。复水后,棉纤维SOD、CAT、POD活性迅速恢复到正常灌水水平,MDA含量亦降低,但棉纤维蔗糖合成酶、磷酸蔗糖合成酶、β-1,3-葡聚糖酶、IAA氧化酶等的活性仍低于相应正常灌水处理,最终棉纤维比强度亦显著低于正常灌水处理。棉纤维加厚发育期土壤干旱及复水条件下240 kg N hm^-2是高强纤维形成的最适施氮量,其内在生理机制表现为干旱处理期间棉纤维内源保护酶活性较高,细胞膜脂过氧化程度最低,棉纤维蔗糖合成酶、磷酸蔗糖合成酶、β-1,3-葡聚糖酶、IAA氧化酶等加厚发育相关酶活性均最高,复水之后纤维内源保护酶活性迅速恢复,MDA含量最低,棉纤维加厚发育相关酶活性仍处于最高值,有利于纤维素的合成与累积,最终纤维比强度亦最大。施氮不足(0 kg N hm^-2)或过量施氮(480 kg N hm^-2)均表现出相反的趋势。更多还原

【Abstract】 Flowering and boll-forming stage is the key yield determinant period of upland cotton. Short-duration drought stress occurring during this stage significantly reduced cotton final productivity and fiber quality.Nitrogen as a mineral nutrient is required in large amounts by plants and nitrogen application could improve drought resistance in plants.The study on the effects of nitrogen on physiological mechanism for cotton yield and quality formation under water stress has obvious implication for improving drought resistance and guiding cultural management in cotton.Pot experiments were conducted to short-term water stress during flowering and boll-forming stage of cotton in 2004～2006 at the research field area of Nanjing Agricultural University.Within each water treatment,three nitrogen levels(0, 240 and 480kg·N ha^-1) were imposed.The study focused on:（1） effects of nitrogen on the dry matter weight,nitrogen accumulation and distribution,yield and fiber quality under water stress and afterward re-watering;（2） responses of net photosynthetic rote（P_n）, transpiration rate(T_?) and water use efficiency（WUE） of cotton to nitrogen under water stress and afterward re-watering,and the relationship between chlorophyll fluorescence characteristic,antioxidant enzyme activity,endogenous hormone content and net photosynthetic rate in cotton leaf;（3） effects of nitrogen on root growth,N accumulation, antioxidant enzyme activities and root vigor under soil water stress and afterward re-watering;（4） effects of nitrogen on the cotton fiber thickening and fiber strength development under water stress and afterward re-watering.The main results were as follows:1.Effects of nitrogen on the dry matter weight,nitrogen accumulation and distribution under soil water stress and afterward re-wateringSoil water stress significantly reduced dry matter weight,nitrogen accumulation,but increased nitrogen content in different organs of cotton.Water stress reduced the distributive indexes of dry matter weight and nitrogen accumulation in leaf,but increased the distributive indexes in root,and increased the Root/Shoot ratio.Nitrogen could increased dry matter weight and nitrogen accumulation of cotton,and augmented the water stress indexes.There was notability compensative growth for cotton after re-watering, especially for root,the dry matter weight and nitrogen accumulation in root of Water-stress treatments were higher than that of Well-water treatments.Nitrogen enhanced the compensative capacity.The dry matter weight of reproductive organs,seed cotton yield and fiber quality were all highest at 240 kg N ha^-1 level under water stress.These results suggest that 240 kg N ha^-1 is the optimal nitrogen application rate under soil water stress in our experiments,deficient(0 kg N ha^-1) and excessive nitrogen supply(480 kg N ha^-1) are of disadvantaged to the yield and fiber quality.2.Effects of nitrogen on the net photosynthetic rate,transpiration rate and water use efficiency,and the relationship between chlorophyll fluorescence characteristic, antioxidant enzyme activity,endogenous hormone content and net photosynthetic rate in cotton leaf under soil water stress and afterward re-watering.（1） P_n,stomatal conductance（G_s） and T_? were declined when the soil relative water content went down under soil water stress.Nitrogen reduced P_n,G_s and T_?,but increased WUE in cotton leaf under soil water stress.（2） Nitrogen has significantly effect on chlorophyll fluorescence characteristic,antioxidant enzyme activity,endogenous hormone content in cotton leaf.According the data,240 kg N ha^-1 was the best nitrogen application level for improving Pn among three nitrogen levels. The maximum photochemical efficiency of photosystemⅡ（PSⅡ） photochemistry（F_v/F_m）, the quanttun yield of electron transport(φ_PSⅡ),the electron transport rate（ETR） and the photochemical quenching co-efficient（qP） in cotton leaf were all higher at 240 kg N ha^-1 than other two nitrogen level.Under soil water stress,CAT activity,soluble protein content, ZR content,IAA content,GA content,ZR/ABA,IAA/ABA,GA/ABA of 240 kg·ha^-1 cotton was highest among the three nitrogen levels,and MDA content and ABA content of 240 kg N ha^-1 cotton was smallest.Deficient(0 kg N ha^-1) and excessive(480 kg N ha^-1) nitrogen supply were of disadvantaged to the ehiorophyll fluorescence characteristic,antioxidant enzyme activities,endogenous hormone content and photosynthesis under soil water stress, because the deficient nitrogen treatment cotton suffered drought stress and nitrogen deficit stress,and the excessive nitrogen treatment cotton increased the water stress.After re-watering,there was no difference of SOD activity,CAT activity,MDA content and photosynthesis between water-stress and well-water treatments.ABA content in water-stressed cotton leaf were significant lower than that in well-water treatments,but ZR, IAA,GA content,ZR/ABA、IAA/ABA、GA/ABA in water-stressed cotton leaf were significant higher than that in Well-water treatments.Nitrogen supply could promote the SOD activity,CAT activity,POD activity,ZR content,IAA content,GA content,ZR/ABA, IAA/ABA,GA/ABA and P_n,and reduced MDA content and ABA content in water-stress and well-water treatments.3.Effects of nitrogen on the cotton root growth under water stress and afterward re-wateringSoil water stress significantly reduced cotton root dry matter production and N accumulation.The Root/Shoot ratio（R/S） and Root-N/Shoot-N（R_N/S_N）,increased with water stress,was smaller at 240 kg N ha^-1 level than at 0 and 480 kg N ha^-1 level.Nitrogen decreased the SOD activity,but increased the activities of POD and CAT.Malondialdehyde （MDA） content was greater in water-stress treatments than in well-water treatments,and MDA content of 240 kg N ha^-1 level was smallest among the three nitrogen levels under soil water stress.After re-watering,MDA content of 240 kg N ha^-1 level was the same as that of 480 kg N ha^-1 level,but less than that of 0 kg N ha^-1 level.The root vigor,debased by soil water stress,was the highest at 240 kg N ha^-1 level.After re-watering,nitrogen promoted the root vigor under two watering managements.The trends of net photosynthetic rate were the same as that of root vigor,but opposite to that of MDA content under soil water stress.These results suggest that appropriate nitrogen supply(240 kg N ha^-1) may contribute to drought resistance of cotton plants by adjusting the antioxidant enzyme activities of root,debasing lipid peroxidation and boosting root vigor under short-duration soil water stress,but excessive nitrogen(480 kg N ha^-1) was deleterious.4.Effects of nitrogen on the cotton fiber development under water stress and afterward re-wateringDuring soil water stress,soil water stress significantly reduced soluble protein content in cotton fiber,increased the antioxidant enzyme activities of SOD,CAT and POD and MDA content,but reduced the fiber thickening key enzymes activities of sucrose synthetase,β-1,3-glucanase,sucrose phosphate synthetase,and IAA oxidase,and the cotton fiber strength.On the 10th day after re-watering,there was no significant difference of SOD,CAT and POD activity between soil water-stressed and well-water treatments,MDA content were declined,and the fiber thickening related key enzymes activities were still lower than Well-water treatments.The result of 2-year experiment showed that 240 kg N ha^-1 was the optimal nitrogen application rate for forming high-strength fiber under soil water stress and afterward re-watering during the flowering and bell-forming stage.The antioxidant enzymes activities were highest,MDA content were the lowest,and the fiber thickening key enzymes activities of sucrose synthetase,β-1,3-glucanase,sucrose phosphate synthetase,and IAA oxidase were the highest at 240 kg N ha^-1 nitrogen level, thus leading to the greatest fiber strength.Deficient(0 kg N ha^-1) and excessive(480 kg N ha^-1) nitrogen supply are of disadvantaged to the fiber thickening key enzymes activities and cotton fiber strength.更多还原