【作者】 张仁和；

【导师】 廖允成；

【作者基本信息】 西北农林科技大学 ， 植物资源学， 2011， 博士

【摘要】 干旱是影响玉米生产的最主要的非生物胁迫因素。通过筛选抗旱玉米品种,进而对其进行生理生化研究,最终进行旱地玉米氮肥管理实现玉米抗旱节水,是研究玉米高产高效的重要课题。本研究采用大田、池栽和盆栽试验,在水分胁迫条件下对玉米苗期、开花期的形态、生长发育和生理生化等性状特征进行了系统研究和分析,初步建立玉米开花期抗旱性鉴定指标,深入研究水分胁迫对玉米形态、生理、生化、产量等指标的影响,系统揭示了玉米抗旱的生理生化特性,阐明玉米苗期水分胁迫下氮素调控生理机制,主要研究结果如下:1.干旱胁迫下玉米品种籽粒产量均比对照明显降低,雌雄开花间隔增加,株高和穗位高降低,穗短小,秃尖多,穗粒数少,粒重轻,最终导致产量下降。雌雄开花间隔、保绿性与产量抗旱指数之间呈极显著相关。通过聚类分析将51个品种分为三类:郑单958、粟玉2号、富友9号、先玉335和蠡玉13等5个抗旱性强;晋单50、冀玉9号、秦龙11、陕单9号,浚单20、沈单21和沈玉17等20个旱性中;陕单902、豫玉22、沈单16、陕单308等26个抗旱性差的品种。2.以抗旱性差异的12个品种为材料,通过对玉米开花期33个形态、生理性状指标采用灰色关联度、主成分分析和隶属度分析方法,从中筛选出净光合速率（P_n）、实际量子产量（φPSⅡ）、叶绿素含量（Chl）、叶面积、干物质等5项指标对玉米的抗旱性有显著影响,可作为玉米开花期抗旱性鉴定指标。所建立抗旱隶属函数对所选用的12个玉米品种进行了抗旱性预测,发现品种抗旱性排序结果与产量指数排序结果基本一致,表明筛选出的5个指标在开花期对玉米抗旱性进行鉴定是可行的。3.干旱胁迫抑制2个玉米品种郑单958（抗旱性强）和陕单902（抗旱性弱）植株生长和相对生长速率,导致整株生物量显著下降。随着干旱胁迫程度加剧,叶片最大净光合速率(P_nmax)、表观量子效率（AQY）、光饱和点（LSP）、气孔导度（G_s）、气孔限制值（L_s）、最大电子传递速率（ETR_m）、光能利用效率（α）、光系统Ⅱ的实际量子产量（φPSⅡ）和光化学猝灭系数（qP）均下降,而胞间CO₂浓度（Ci）,光补偿点（LCP）和非光化学猝灭系数（qN）均升高。干旱胁迫下叶片光合能力和电子传递速率降低是2个玉米品种生物量减少的主要因素。郑单958变幅小于陕单902,表明郑单958植株生长发育和光合特性比陕单902受干旱胁迫的影响小,较高的电子传递速率、较强的光能转化能力和较大的相对生长速率是郑单958适应干旱环境的重要光合生理特性。4.干旱胁迫下2个品种根系活力降低和可溶性蛋白含量降低,提高根系超氧化物歧化酶（SOD）活性,增加丙二醛（MDA）含量;随着干旱胁迫程度加剧,陕单902根系活力和可溶性蛋白含量降低幅度大于郑单958;郑单958根系超氧化物歧化酶（SOD）比对照升高幅度大于陕单902,且超氧化物歧化酶（SOD）活性高于陕单902,而陕单902根系MDA含量比对照升高幅度大于郑单958。干旱胁迫下郑单958根系活力﹑根系SOD活性以及根系可溶性蛋白含量较高能够减缓根系衰老进程,延长根系功能期。这可能是抗旱性强的郑单958在干旱环境下仍然能够获得较高产量的根系生理特性。5.吐丝期随着干旱胁迫的加剧和时间延长,叶片光合速率、气孔导度、蒸腾速率、光系统Ⅱ的实际量子产量（φPSⅡ）和光化学猝灭系数（qP）均下降下降迅速,陕单902比郑单958降速快、幅度大。花后0-10 d随胁迫时间的延长叶片内SOD,CAT和POD三种酶活性升高,郑单958增加或升高的幅度大。花后10 d后叶片SOD,CAT和POD三种酶活性降低,而MDA含量一直增加,郑单958增幅小于陕单902。在水分条件下,郑单958叶片抗氧化酶系统清除活性氧能力的增强,膜脂过氧化程度轻,有利于维持花后较高的光合产物供应强度和较长的光合持续期。6.吐丝期干旱胁迫提高了2个品种花前贮藏同化质运转量、运转率和花前同化物对籽粒的贡献率。郑单958比陕单902花前同化物运转量、运转率和对籽粒贡献率的增幅均较大。而降低了花后光合同化量和收获指数,郑单958的收获指数比陕单902大。干旱胁迫条件下,郑单958较高的花前营养器官贮藏物质运转量、运转率是其高产的物质基础。7.干旱胁迫下,适量施氮（225 kg N/hm²）不仅有利于玉米地上部干物质积累同时有利于玉米根系生长从而显著增加玉米苗期总干物质积累,从而提高水分利用效率。根冠比最小,地上部与地下部生长最为协调。提高了玉米幼苗叶片的Gs、Tr、Fv/Fm、φPSⅡ和qP;降低了胞间CO₂浓度（Ci）和qN;同时,显著提高保护酶活性（SOD、POD和CAT）,降低了膜质过氧化程度减少MDA含量,因而全面改善叶片光合功能和内在的生理特性。而施氮不足（0 kg N/hm²）使玉米遭受干旱和低氮双重胁迫,过量施氮（450 kg N/hm²）则加重了玉米干旱胁迫的程度,二者均表现出与适量施氮处理相反的变化。更多还原

【Abstract】 Drought is one of the most major envirnmental stresses influencing grain yield. It is a key and efficiencial biological way to solve the water stress to breed new maize hybrids with both stronger drought tolerance. With three experiments cultivated in pots and in fields, we studied systematically the expression of these characters such as growth and development, morphology, yield and physiological biochemistry of the different genotype maize under water stress though the methods of blurring subordination function, grey correlation degree, analysis of principal component. Appraised the drought resistance of different maize variety based on drought index（DI） of yield, analyzed the correlations between evaluation parameters and tested values of traits and evaluate N application rates management effects on physiological characteristics and grain yield of maize at the seeding stage under water stress. It got the following main conclusions:1. Comparing with contrast, the biomass and yield of maize varieties under water stress decreased obviously, and ASI added, leaves area reduced, height of plant and ear position declined, stalk became thinner, ears were shorter and smaller, barren ear tip increased more, number of grain per ear reduced less and grain weight reduced lighter, which leaded to yield decline. ASI and stay green were relatate to drought tolerance index. With comprehensive appraisement and cluster analysis by different parameters and indexes, the droughr tolerance of the hybrids were divided into three types, stronger, medium and softer. Five genotypes, Xianyu 335, Zhengdan958, Suyu2, Fuyou9, Liyu13 were with stronger drought tolerance. Twenty genotypes, Jidan50, Shandan 20, Jiyu 9, Xundan20 and Shenyu17, et al were with medium droughr tolerance. Twenty six genotypes, Shan902, Shandan308,Shendan16 and Yuyu22, et al showed the worst.2. Five indexes P_n,φPSⅡ, chlorophyll content, dry matter and leaf area were screened based on thirty three morphological and physiological traits with quantitative analyzing methods. The comprehensive drought resistance of maize varieties were calculated by the subordinate degree of drought index of screen, it was used to drought resistant sequencing in silking date, the two sequencing in accordance with the results of drought index.3. The response of plant growth, gas exchange and chlorophyll fluorescence parameters were studied in two different maize hybrids Zhengdan958 （drought resistance） and Shaandan 902 （drought-sensitive） under three different drought stresses （mild drought, moderate drought, severe drought ） and normal irrigation in pot experiment. The results showed that drought stress inhibited the growth of two maize plant growth and the relative growth rate, resulting in a significant decline in biomass. With the increasing degree of drought stress, the maximum leaf net photosynthetic rate （Pnmax）, apparent quantum efficiency （AQY）, light saturation point （LSP）, stomatal conductance （Gs）, stomatal limitation （Ls）, maximum electron transport rate （ETRm）, photosynthetic efficiency （α）, PSⅡactual quantum yield （φPSⅡ） and photochemical quenching （qP） were decreased, while the intercellular CO₂ concentration （Ci）, light compensation point （LCP） and qN were increased. But the change extents of all parameters were smaller in Zhengdan958 than in Shandan902. This finding indicated that drought stress could significantly decrease the biomass of two maize varieties, possibly caused by reduction in the photosynthetic efficiency of plants. The drought stress damaging effects of plant growth and photosynthesis was minimal on the Zhengdan958 compared to Shaandan902. Under drought stress the Zhengdan958 maintained higher photosynthetic efficiency, stronger light energy transfer capacity and greater relative growth rate may be the major physiological traits in the adapt ability to drought conditions.4. Compared with the control, the root shoot ratio was raised in drought-sensitive maize. The rate of root activity of drought-tolerant maize reduced more than drought-sensitive maize. Root SOD activity was higher than that in the control plant. In addition, root MDA content increased but root soluble protein content decreased in maize. To the increase rate of MDA content and reduced degree of root soluble protein content, drought-sensitive maize were higher than drought-tolerant maize. In a word, root activity, SOD activity and root soluble protein content of drought-resistant maize were high. So these can slower root aging process and extend the period of root function, which may be one of the important role in getting high yield of drought-tolerant maize under drought stress.5. Effects of anthesis water stress on photosynthesis, senescense of leaf and matter redistribution in maize. Water stress significantly reduced stomatal conductance, transpitation rates and photosynthetic rate, and Shaandan902 decreased much faster than Zhengdan958. Actual photosynthetic efficiency, and photochemical quenching were much lower, while non-photochemical quenching were much higher under water stress than in control, indicating damage to photosystemⅡ. Compared with CK, water stress reduced the activities of protective enzymes as superoxide dismutase （SOD）, catalase （CAT） and peroxidase （POD）, while increased the content of malondiadhyde （MDA）, thus enhanced membrane lipid peroxidation. In addition, significant relativities between root activity, root weight, catalase （CAT）, the content of malondiadhyde （MDA）. Those revealed that depressed anti-oxidative enzyme activities, and leaf photosynthetic characteristics were key physiological mechanisms in affecting the grain yield formation under anthesis water stress.6. Effects of anthesis water stress on grain yield in maize. Water stress significantly reduced grain 1000-kernel weight, grain yield. The obvious increase in the amount of pre-anthesis dry matter accumulated, translocation accumulated and contributed to the grain dry matter under water stress. While water stress reduced harvest index. In conclusion, decreased dry matter accumulation translocation were involved in the depressed grain yield in maize under water stress.7. Effects of nitrogen on the dry matter weight, nitrogen accumulation and distribution under soil water stress. Soil water stress significantly reduced dry matter weight, but increased the distributive indexes in root, and increased the Root/Shoot ratio. Nitrogen enhanced the compensative capacity.The dry matter weight and WUE were all highest at 225 kg N ha^-1 level under water stress. P_n, stomatal conductance（G_s） and T_r were declined when the soil relative water content went down under soil water stress. Nitrogen increased P_n, G_s and T_r, in maize leaf under soil water stress. These results suggest that 225 kg N ha^-1 is the optimal nitrogen application rate under soil water stress in our experiments. F_v/F_m, the quanttun yield of electron transport（φPSⅡ）, and the photochemical quenching co-efficient（qP） in maize leaf were all higher at 225 kg N ha^-1 than other two nitrogen level. 225 kg N ha^-1 was the best nitrogen application level for improving Pn among three nitrogen levels. The antioxidant enzymes activities were highest, MDA content were the lowest. The deficient(0 kg N ha^-1) and excessive nitrogen supply(450 kg N ha^-1) are of disadvantaged to the yield formation.更多还原