【作者】 白向历；

【导师】 齐华；

【作者基本信息】 沈阳农业大学 ， 作物栽培学与耕作学， 2009， 博士

【摘要】 通过田间试验与盆栽试验相结合,研究不同生育时期水分胁迫对玉米生长发育及生理生化特性的影响,比较品种间抗旱性的差异,探讨生理生化指标与玉米抗旱性的关系,进而明确玉米抗旱的机制,筛选出玉米抗旱性鉴定的生理指标,为玉米抗旱育种、高效生产提供理论依据和技术指导。得到的主要结论如下:1.供试品种的实际抗旱性（以耐旱指数表示）由强到弱依次是:京单28＞中单808＞郑单958＞京科308＞辽单565＞京科25＞吉单261＞农大108＞四单19＞丹玉39＞沈玉21＞京单508＞DH3719。根据系统聚类和隶属函数分析结果将上述品种划分为不抗品种—DH3719、京单508和沈玉21;低抗品种—丹玉39、四单19和吉单261;中抗品种—农大108、京科308、京科25和辽单565;高抗品种—京单28、郑单958和中单808。2.水分胁迫致使玉米减产程度及原因,因胁迫时期而异。不同生育时期水分胁迫的研究结果表明,任何生育时期水分胁迫均会导致玉米减产,其中抽雄吐丝期水分胁迫减产最重,其次是拔节期,苗期相对较轻。抽雄吐丝期是玉米的水分临界期,干旱可导致散粉至吐丝期间隔（ASI）加大,致使花期不遇,穗粒数大幅度下降,从而严重影响玉米的产量。拔节期水分胁迫抑制玉米叶片、株高的生长以及干物质的积累,对其营养生长影响较大。3.将各生理指标与耐旱指数进行灰色关联度分析,关联度大小依次为:PSⅡ光化学效率（F_V/Fm）＞SOD＞叶绿素a/b＞可变荧光（Fv）＞POD活性＞净光合速率（Pn）＞相对含水量＞最大荧光（Fm）＞可溶性蛋白含量＞脯氨酸含量＞可溶性糖含量＞相对电导率＞丙二醛含量＞固定荧光（F_O）。并且上述生理生化指标与品种抗旱性间均表现显著的相关关系,均可作为玉米抗旱性鉴定指标的良好参数、可用于玉米品种抗旱性的评定。4.在水分胁迫过程中,可溶性糖含量变化表现为先增后降的趋势,可溶性糖含量占对照百分率与品种抗旱性呈极显著负相关(r=-0.6952^**);脯氨酸含量和可溶性蛋白含量持续增加,与品种抗旱性呈极显著正相关(r=0.7382^**;r=0.6354^**)。抗旱性强的玉米品种渗透调节能力强于抗旱性弱的品种。5.随着水分胁迫时间的延长,SOD和POD活性呈增加趋势,与抗旱性呈极显著正相关(r=0.9365^**;r=0.8803^**)。同时,MDA含量随着水分胁迫时间的延长而逐渐增加,且MDA含量占对照百分率与品种抗旱性呈极显著负相关(r=-0.6909^**),与抗旱性弱的玉米相比,抗旱性强的玉米叶片MDA含量积累少,SOD和POD活性高,表明抗旱性强的玉米品种酶促保护系统清除自由基能力强,细胞膜受到的破坏较轻。6.水分胁迫下,叶绿素含量及叶绿素a/b比值随胁迫时间的延长逐渐降低,与品种的抗旱性则呈极显著的正相关(r=0.8869^**),水分胁迫不仅使叶绿素的生物合成能力减弱,同时由于植物体内活性氧大量积累,也导致叶绿素分解加快。水分胁迫下,叶片可通过降低叶绿素含量避免吸收过多光能对光合机构造成破坏。7.在水分胁迫过程中,硝酸还原酶活性的变化表现为先增后降的趋势。前期水分胁迫能诱导硝酸还原酶活性的提高,增强其氮代谢的能力;胁迫中后期,硝酸还原酶活性持续下降,其氮代谢能力受到抑制。水分胁迫下净光合速率较对照均有不同程度的下降,净光合速率占对照百分率与品种的抗旱性呈极显著正相关(r=0.7197^**)。水分胁迫使玉米的碳、氮代谢减弱,抑制其生长发育,抗旱性强的品种其代谢能力高于抗旱性弱的品种。8.水分状况与玉米叶片光合作用关系密切,水分胁迫下玉米叶片的最大净光合速率（Pmax）、光补偿点（LCP）、光饱和点（LSP）、表观量子效率（AQY）、CO₂补偿点（CCP）、CO₂饱和点（CSP）、CO₂表羧化效率（β）和暗呼吸速率（R_d）这些参数均降低,玉米光合能力下降。正常供水处理下玉米叶片的净光合速率日变化为双峰曲线,有明显的“午睡”现象。水分胁迫下,光合速率较低,“双峰”现象消失,光合作用基本停止,水分胁迫造成光合作用受阻。9.水分胁迫下,基础荧光（Fo）显著增加,且Fo占对照百分率与品种抗旱性则呈极显著的负相关(r=-0.8843^**);最大荧光（Fm）、可变荧光（Fv）和PSⅡ光化学效率（Fv/Fm）降低,且与品种抗旱性则呈极显著正相关(r=0.7944^**;r=0.8987^**;r=0.8987^**)。Fo增加和Fv/Fm下降,表明PSⅡ反应中心受到不易逆转的破坏,PSⅡ原初光化学活性受到抑制,PSⅡ活性中心受到损伤,抗旱性较强的品种光化学活性仍较强,损伤程度较小。10.水分胁迫下,光化学淬灭（qP）、实际光化学效率（ΦPSⅡ）和表观电子传递速率（ETR）下降,非光化学淬灭（qN）增大。qP下降表明PSⅡ反应中心开放部分的比例减少,PSⅡ潜在活性受到抑制,qN增大表明PSⅡ的潜在热耗散能力增强,过多的光能多是以非光化学淬灭等其它形式耗散掉,有效地避免或减轻因PSⅡ吸收过多光能对光合机构的破坏。水分胁迫下ETR和ΦPSⅡ低于对照,可以认为水分胁迫致使PSⅡ光化学量子产量下降,用于光化学反应的比例减少,光合电子传递速率降低。更多还原

【Abstract】 Study the impact of different periods of drought on maize growth and development, physiological and biochemical characteristics by the combination of field experiments and pot environment;Study the relationship between various physiological indicators;Compares the resistant differences exist amoung varieties;Explore the relationship between physiological and biochemical indicators and drought resistance of maize,and make mechanisms for drought resistance clear;Determine the indicators of resistance evaluation of crop drought; Set up a optimize index system with scientific and accurate evaluation of maize drought resistance to provide theoretical basis and technical guidance for the efficient production in maize drought Breeding.The main conclusions are as follows:1.The actual drought resistance of varieties（express to drought index）followed from strong to weak are:Jingdan 28＞Zhongdan 808＞Zhengdan 958＞Jingke 308＞Liaodan 565＞Jingke25＞Jidan 261＞Nongda 108＞Sidan 19＞Danyu 39＞Shen 21＞Jingdan 508＞DH3719.Uses the method of ciuster analysis and membership function to identify and evaluate frought resistance of varieties.By drought level from weak to strong they are divided into non-resistant varieties—DH3719、Jingdan 508 and Shenyu 21;Resistance varieties—Danyu39、Sidan 19 and Jidan 261;Medium resistant varieties Nongdal08、Jingke308、Jingke25、and Liaodan565:Highly resistant varieties—Jingdan28、Zhengdan958 and Zhongdan808.2.The degree and reasons of maize yields decreasing resulted from water stress vary in different stages.The results we study under water stress at different stages show that any growth stages under water stress may cause maize yields decreasing,and the yields decrease severely at tasselling silking stage,followed by the jointing stage,seedling stage seems relatively lighter.Tasselling silking is the critical period for maize moisture,drought can cause the interval which is from loose powder to silking（ASI）prolonging,result in infertility flowering,kernel number decreasing significantly,thereby seriously affect maize production. Water stress inhibits maize leaves,plant height,root growth and dry matter accumulation,and water stress at jointing stage is the greatest impact to them.3.Use the method of gray relational grade to analysis physiological indicators and drought index.The correlation sizeorder is PSⅡphotochemical efficiency（Fv/Fm）＞the SOD activity＞ch1a/b＞variable fluorescence（Fv）＞POD activity＞net photosynthetic rate（Pn）＞relative water content＞maximal fluorescence（Fm）＞Soluble protein content＞Proline content＞Soluble sugar content＞Relative conductivity＞Malondialdehyde content＞fixed fluorescence（F_O）.The physiological and biochemical indexes and drought resistance of varieties we mentioned above shows a significant correlation,they can be used as good parameters for maize drought resistance identifying indicators,it also can be used for evaluating the drought resistance of corn varieties.4.The accumulation of osmotic adjustment defense drought is one of the physiological mechanisms for maize drought.In the course of water stress,the changes of soluble protein content performance by the trend of firstly increasing and then decreasing and increasing finally,the comparison percentage of soluble sugar content and drought resistance are highly significant negative correlation(r=0.6952^**).Proline content and soluble protein content are increasing,they are in highly significant positive correlation(r=0.7382^**;r=0.6354^**) to the varieties’ drought resistance.Maize varieties of strong drought resistance have stronger osmotic adjustment ability than those of weak drought resistance.5.With the time of water stress prolonging,SOD activity and POD activity have increasing trend,they are in highly significantly positive correlation(r=0.9365^**;r=0.8803 ^**)to the drought resistance of varieties.At the same time,MDA content is gradually increasing with the time prolonging of water stress and the comparison percentage of MDA content and drought resistance are negatively correlated(r=0.6909^**),comparing to weak drought-resistance maize,the leaves of strong drought-resistance maize accumulate less MDA,have higher SOD activity and POD activity,it shows that the strong drought-resistance varieties of maize have enzymatic scavenging system which has a strong ability of scavenging radical,and less cell membrane damage.6.Under water stress,chlorophyll content and chlorophyll a/b ratio decrease gradually with the stress time prolonging,water stress not only makes the process of chlorophyll biosynthesis weakened,but also speeds up the chlorophyll decomposition because of the reactive oxygen in plants greatly accumulates.In the process of chlorophyll decomposition, chlorophyll a is probably less stable than chlorophyll b,which results in chlorophyll a/b ratio decreasing,under water stress,chlorophyll a/b ratio and varieties’ drought resistance performance highly significant positive correlation(r=0.8869^**).Under water stress, chlorophyll attenuaties so as to avoid the photosynthetic apparatus damage because of excessive absorption of solar energy.7.With the time of water stress,the nitrate reductase activity changes of corn varieties performance a trend of firstly increasing,then dropping,it shows that in the whole stress process,especislly in the early stage of water stress,it can rapidly induct nitrate reductase activity improving,enhance its nitrogen metabolic capacity,in the mid and late stress,nitrate reductase activity continues to decline,and its ability of nitrogen metabolism is inhibited. Water stress makes the leaf net photosynthetic rate of various maize varieties have varying degrees of decline than those for check.The comparison percentage of net photosynthetic rate and the drought resistance of varieties are highly significant positive correlation(r=0.7197 ^**).Water stress makes the carbon and nitrogen metabolism of corn weakening,and inhibits maize growth and development,varieties of strong drought resistance have higher metabolic capacity than the weak ones.8.Water status and photosynthesis in leaves of maize are closely related,with the light response curve of net photosynthetic rate and the CO₂ response fitting we can calculate: Under water stress,the maximum net photosynthetic rate（Pmax）,light compensation point （LCP）,light saturation point（LSP）,the apparent quantum yield（AQY）,CO₂ compensation point（CCP）,CO₂ saturation point（CSP）,apparent CO₂ carboxylation efficiency（β）and dark respiration rate（R_d）of maize leaves are significantly decreas.Maize photosynthetic capacity decreases under water stress.9.Under water stress,basic fluorescence（F_O）increas significantly,the comparison percentage of F_O and drought resistance of varieties shows significantly negative correlation(r =-0.8843^**);Maximal fluorescence（Fm）,variable fluorescence（Fv）and PSⅡphotochemical efficiency（Fv/Fm）decrease,and they are significantly positive correlation(r =0.7944^**;r=0.8987^**)to drought resistance.F_O increases and Fv/Fm declines,it indicates the damage which is not easy to reverse produces a phenomenon of photoinhibition in PSⅡreaction center,the primary photochemical activity of PSⅡis inhibited,the active center of PSⅡis injuried.Varieties of strong drought resistance still have strong photochemical activity,but the degree of their injury is lower.10.Under water stress,photochemical quenching（qP）,the actual photochemical efficiency（（?）PSⅡ）and apparent electron transport rate（ETR）decrease,Non-photochemical quenching（qN）increases.qP decline indicates that the proportion of the open parts in PSⅡreaction center reduces.Potential activity of PSⅡis inhibited.qN increase shows the potential ability of heat dissipation in PSⅡ,excessive light energy quenches by non-photochemical and many other forms of dissipation,it effectively avoids or reduces the damage to the photosynthetic apparatus which is caused by excessive light absorption of PSⅡ.Under water stress,ETR and（?）PSⅡare lower than the check,you can consider water stress results in the yield of PSⅡphotochemical quantum declining.The proportion used for photochemical reaction declines,and the photosynthetic electron transport rate decreases.更多还原