【作者】 蔡铁；

【导师】 王振林；

【作者基本信息】 山东农业大学 ， 生物化学与分子生物学， 2013， 博士

【摘要】 小麦是最基础的粮食作物之一。人口增长与社会发展对小麦产量呈刚性需求，同时种植面积难以持续扩大，决定了我国小麦生产发展必须以提高单产来增加总产。小麦群体的结构与质量是提高小麦单产的基础，其直接受小麦个体发育的影响。而植株个体生长发育呈异质性，小麦个体由主茎和一系列分蘖构成，由于茎蘖的不同空间位置和发生时间，决定了其生长发育的明显差异性，由此预示着其茎蘖间具有不同的生产力。因此，可通过以小麦优势茎蘖为基础构建合理的群体结构以提高小麦产量。为重组群体的茎蘖构成，关键在于调控小麦分蘖的发生与发育。小麦的分蘖由分蘖芽发育而来，激素在分蘖芽生长过程中起重要作用。因而，外施激素可作为调控分蘖发生发育的有效措施。为此，本研究中，通过两个不同类型小麦品种，评价茎蘖间生产力差异；分析外源激素对分蘖发生的影响及潜在机制；调查通过外源激素处理，改变小麦茎蘖构成后，对小麦产量的影响。明确了以上问题，可为通过重组小麦茎蘖构成以构建高产的合理群体结构提供理论基础与技术支持。主要研究结果如下：1小麦茎蘖生产力差异及其生理基础低位蘖（早发生蘖）比高位蘖（后发生蘖）具有较多的穗粒数，较多的可孕小穗数、较少的不孕小穗数及较高的粒重，直接决定了其保持较高的单穗产量。通过对不同蘖位单茎单穗产量及其构成因素进行系统聚类分析，山农15茎蘖可分为2组，一组定义为强势蘖，包括0、I和II，另一组定义为弱势蘖，包含III和I-p。而山农8355则可分为3组，0和I为强势蘖，II和III为中势蘖，I-p为弱势蘖。进一步分析产生差异的相关生理生化指标，结果显示，在小麦籽粒灌浆期，旗叶光合速率呈下降趋势，且低位蘖的旗叶光合速率明显高于同期高位蘖的光合速率。两小麦品种中，强势粒和弱势粒灌浆速率均先升高后降低，呈“∧”型，而粒重增加则呈“S”型。低位蘖籽粒较高位蘖籽粒有较高的灌浆速率，且较早到达最大灌浆速率。同时，粒重在整个灌浆进程中呈增加趋势，且低位蘖一直较高位蘖保持较高的粒重。通过分析小麦不同蘖位功能叶衰老特性得出，超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）活性随灌浆进程均呈下降趋势，且低位蘖功能叶较同期高位蘖功能叶保持较高的酶活性。与抗氧化酶活性变化相反，丙二醛（MDA）含量呈上升趋势，且低位蘖较高位蘖功能叶一直保持较低的MDA含量水平。而可溶性蛋白则在低位蘖功能叶中保持较高水平。随着蘖位的升高，单茎生物量表现下降趋势，与此类似，单茎经济系数也随蘖位的升高而降低。由此表明，小麦不同茎蘖间存在明显的产量差异。低位蘖较高位蘖具有较强的光合能力、灌浆能力、抗衰老能力以及较高的单茎生物量和经济系数，决定了前者在生产力上具有明显的优势。2外源激素对小麦分蘖发生生长的调控及作用机制两小麦品种在不同外源激素处理下分蘖I、II、III、I-p均能发生。而喷施IAA和GA3显著降低了分蘖IV、I-1、II-p、II-1的发生率。与外源IAA和GA3对分蘖发生率的影响不同，喷施ABA仅降低了分蘖IV、II-1的发生率，而对分蘖I-1、II-p的发生率无明显影响。小麦分蘖由分蘖芽发育而来，进一步分析外源激素对分蘖芽的调控效应，结果显示，外源IAA和GA3完全抑制分蘖芽的生长，而外源ABA明显减缓了分蘖芽的生长速率。激素在调控小麦分蘖芽生长中起关键作用。分蘖芽生长过程中，分蘖节中内源ZT含量呈明显上升趋势。喷施IAA和GA3显著降低了ZT含量。而ABA处理中，内源ZT含量于处理后缓慢上升，但明显低于CK处理。喷施IAA和GA3于处理后明显提高了分蘖节中IAA含量。CK和ABA处理，分蘖节中IAA含量略有升高或降低，无明显规律性。CK、IAA和ABA处理中，分蘖节中GA3含量基本保持不变，且处理间无显著差异；而喷施GA3处理后，分蘖节中GA3含量呈先升高后降低趋势，于处理后2d达到峰值，随后迅速下降。在分蘖芽生长过程中，分蘖节中ABA含量保持稳定，且IAA和CK处理间无显著性差异；而ABA和GA3处理中其含量均呈先升后降趋势。同时，分蘖发生不仅受激素绝对含量的影响，还取决于激素间相对含量。外源IAA和GA3较对照和ABA处理显著提高了分蘖节中IAA/ZT水平。随分蘖芽生长，分蘖节中ABA/ZT呈下降趋势，而IAA处理中其比值基本保持不变，GA3和ABA处理中其比值则呈现先升后降的趋势。其中，外源ABA处理后，ABA/ZT于处理后2d达到峰值，而GA3处理中其峰值出现在处理后4d。相关性分析显示，分蘖芽的生长与ZT呈显著的正相关，与IAA、IAA/ZT和ABA/ZT呈显著负相关，与GA3和ABA呈不显著的负相关。由此表明，IAA和ZT在小麦分蘖发生过程中起关键作用，外源激素主要通过影响内源IAA、ZT含量，以改变IAA/ZT和ABA/ZT来影响分蘖芽的生长，进而调控小麦分蘖的发生。3外源激素对小麦群体动态和籽粒产量影响从出苗到成熟，两小麦品种单位面积总茎数变化均先升高后降低，呈“∧”型。与对照相比，外施IAA、GA3和ABA可显著降低越冬期和拔节期单位面积总茎数；同时，IAA和GA3处理下单位面积总茎数又低于ABA处理，且IAA与GA3处理间无显著性差异。随后，单位面积总茎数迅速下降，至抽穗期和成熟期，各处理间无明显差异。外源激素处理后，两品种小麦单茎生物量均明显提高。此外，喷施外源激素对山农15各蘖位单茎的经济系数无明显影响；而显著提高了山农8355各蘖位单茎的经济系数。两小麦品种，单茎穗粒数、粒重随蘖位升高而呈下降趋势。与对照相比，外施IAA、GA3和ABA明显提高了各蘖位单茎穗粒数和粒重。然而，外施激素对小麦单位面积穗数无明显影响。喷施外源激素显著提高了小麦产量，且外源IAA的增产作用优于GA3和ABA处理。由此得出，外源激素主要通过改善群体结构促进小麦个体发育进而影响穗粒数和粒重以调控小麦产量。4基于重组小麦茎蘖组成构建合理群体结构的化控途径山农15的稳定穗数为750穗·m2左右，其优势蘖为0，I和II，为实现基于优势蘖重组群体的茎蘖构成，可提高种植密度至240株·m2的同时喷施外源IAA（60mg·L1），通过抑制分蘖发生而降低越冬期和拔节期单位面积总茎数，改善群体空间环境，促进单茎个体发育，提高单茎粒数、粒重，进而提高小麦产量。而山农8355，其稳定穗数为570穗·m-2左右，通过提高种植密度至270株·m2结合喷施外源IAA（60mg·L1）构建以优势蘖（0和I）为主的群体结构。更多还原

【Abstract】 Wheat (Triticum aestivum L.) is one of the primary food crops. Social development andpopulation growth also indicate that there is rigid demand for high-yield wheat, which mainlyrely on raising yield per unit area at present. The structure and quality of wheat population arethe basis of increasing yield per unit area and directly influenced by individual plantdevelopment. Additionally, the development of individual plant is asynchronous. A wheatplant is composed of a number of tillers, which initiate at different times and differ in tillerposition. It indicates that the tillers of wheat have different production capacity, depending onthe occurrence time and spatial position of tillers. Therefore, for enhancing the yield potentialof wheat, a way is to construct rational population structure of wheat based on the superiortillers, which have superiority over the other tillers in terms of productive forces. Torestructure the tillers components of wheat population, the key is regulating the occurrenceand development of tillers. The tillers develop from tiller buds, and hormones play key rolesin regulating the growth of tiller buds. So, external hormone application can be used as aneffective measure to regulating the occurrence and development of tillers. In the present study,the objective was to elucidate the grain yield among tillers, analyse the underlyingmechanisms between endogenous hormones and the occurrence of wheat tiller induced byexogenous hormones, and investigate the effect of exogenous hormones on the grain yield ofwheat on the basis of changing the tillers components. A greater understanding of thatinformation can provide a theoretical basis to restructure the tillers components to obtain therational population structure of high-yield wheat. The main results were as follows:1The difference in grain yield and the underlying mechanisms among tillers in wheatLow position tillers (early initiated tillers) had higher yield per spike than that of high position tillers (late initiated tillers) in both cultivars，which was attributed to more grainnumber per spike, more fertile spikelet per spike, less sterile spikelet per spike and highergrain weight in low position tillers. According to cluster analysis, tillers of SN15wereclassified into2groups, one was defined as superior tiller group, which included main stem(0), the first primary tiller (I) and the second primary tiller (II); the other one was inferiortiller group, which included the third primary tiller (III) and the first secondary tiller (I-p).Meanwhile, tillers of SN8355were classified into3groups as follows, superior tiller group (0,I), intermediate tiller group (II, III) and inferior tiller group (I-p).Further analyzing the biological basis of the difference, the results showed: The flag leafphotosynthetic rate gradually declined during the grain filling periods, and the flag leaf of lowposition tillers had higher photosynthetic rate than those of high position tillers. For twocultivars, the grain filling rate increased first and then decreased in both superior and inferiorgrain, showed the ‘∧’ model, while the grain weight increase showed the ‘S’ model duringthe grain filling. Additionally, grains (superior and inferior grain) of low position tillers hadhigher filling rate and reached a maximum filling rate earlier than those of high position tillersin both cultivars. Furthermore, the grain weight gradually increased during the whole grainfilling periods, and grains of low position tillers had greater grain weight than those of highposition tillers during the entire grain filling periods. Investigating the changes in leavessenescence characteristics with depth of canopy at different tiller positions in wheat, activityof superoxide dismutase (SOD), peroxidase (POD) and Catalase (CAT) showed decreasingtendency during the entire grain filling periods in the two cultivars, and the leaf of lowposition tillers had higher activity than those of high position tillers. Contrary to antioxidantenzyme activities, the content of methane dicarboxylic aldehyde (MDA) gradually increasedduring the grain filling period and the leaves of low position tillers had lower MDA contentsthan those in the high position tillers. Furthermore, in contrast to MDA, the soluble proteincontents in low position tillers were rather higher than those in high position tillers. Thesingle-stem biological yield was decreased with rising of tiller positions. Similar tosingle-stem biological yield, the low position tillers had higher single-stem economiccoefficient than those of high position tillers.These results suggested that the grain yield among tillers in wheat differed obviously. The low position tillers had stronger leaf photosynthetic capacity, more predominance in terms ofgrain filling, better senescence resistance, higher biological yield and larger economiccoefficient than those in high position tillers, determining that the former had superiority overthe latter in terms of productive forces.2The effect of exogenous hormones on the occurrence of wheat tiller and the actionmechanismsThe occurrence of0, I, II, III and I-p were normal under different treatments. Thepercentage of IV, I-1, II-p and II-1occurrence tended to decline with external application IAAor GA3. As compared with the IAA and GA3treatment, external ABA only inhibited theoccurrence of IV and II-1. The tillers develop from tiller buds. Considering the two cultivars,exogenous IAA and GA3completely inhibited the tiller buds growth, while exogenous ABAsignificantly slowed the growth rate of tiller buds compared with the control.Hormones play key roles in regulating the growth of tiller buds. The ZT contents in thetiller nodes increased as the growth of tiller buds. Exogenous IAA and GA3significantlyreduced ZT contents after treatment. While, ABA treatment increased the ZT content in tillernodes, but the levels remained lower than that in the control plants after treatment. Theapplication of IAA and GA3significantly increased the IAA levels in the tiller nodes aftertreatment. In addition, there were irregular changes in the IAA level under the CK and ABAtreatments. The GA3levels in the tiller nodes remained nearly constant during the entireexperiment period, and had no significant difference among the CK, IAA and ABA treatmentgroups. However, the content of GA3significantly increased after GA3treatment, reaching apeak at2d post treatment and then decreasing gradually. The ABA levels remainedapproximately constant during the entire experiment period and showed no significantdifference among the CK and IAA treatment groups. While, the content of ABA increasedfirst and then decreased under ABA and GA3treatments. Numerous studies have also shownthat the mechanisms of the tiller occur depend on the balance between endogenous hormonesrather than the absolute level of an individual hormone. External IAA and GA3significantlyincreased the IAA/ZT level in the tiller nodes compared with the CK and ABA treatmentgroups. The ABA/ZT levels in the tiller nodes of the control plants gradually decreased duringthe entire experiment period. The ratio remained nearly constant in the IAA treatment groups after treatment. However, the application of ABA and GA3significantly increased the ratiofirstly, reaching a peak at2d post treatment and4d post treatment, respectively, and thendecreasing gradually.According to correlation analysis, the tiller buds growth was significantly and positivelycorrelated with the content of ZT, whereas significantly and negatively correlated with theIAA contents and the ratios of IAA to ZT and ABA to ZT. Moreover, no significantcorrelation was observed between the tiller buds growth and the contents of GA3and ABA.These results suggested that IAA and ZT play key roles in regulating the occurrence of tiller,and exogenous hormones regulated the growth of wheat tiller buds via affecting the contentsof IAA and ZT, the ratio of IAA to ZT and ABA to ZT in tiller nodes, thus regulating the tilleroccur in wheat.3The effect of exogenous hormones on the population dynamics and grain yield ofwheatFor two cultivars, the stem number per square meter increased first and then decreasedfrom seedling emergence to maturity, showed the ‘∧’ model. At the stages of wintering andjointing, the number of stem per square meter obviously decreased with external applicationof IAA, GA3and ABA compared with those under the control. And the stem number persquare meter under IAA and GA3treatment markedly lower than that in ABA groups, whilethe differences of numbers between IAA and GA3groups were not significant. Then thenumber of stem decreased rapidly. At the stages of heading and maturity, there were nosignificant differences in the stem numbers per square meter from the IAA, GA3, ABA andcontrol treatments.The single-stem biological yield all increased under exogenous hormones treatmentcompared with the control. In addition, for SN15, there were no significant differences in thesingle-stem economic coefficient from the IAA, GA3, ABA and control treatments. However,the single-stem economic coefficient obviously increased under the application of IAA, GA3and ABA when compared with those under the control in SN8355. The number of grain perspike and single-kernel weight tended to decline with rising of tiller position in the twocultivars. Compared with the control, the application of IAA, GA3and ABA obviouslyincreased the grain number per spike and single-kernel weight. However, there were no significant differences in the spike number per square meter from the IAA, GA3, ABA andcontrol treatments. Moreover, grain yield increased with external IAA, GA3, ABA application,while external IAA was more beneficial to improve the grain yield than GA3and ABAtreatments.These results suggested that exogenous hormones regulated the number of grain per spikeand single-kernel weight via promoting the growth of individual plant, which affected bypopulation density, thus regulating the grain yield of wheat.4The path of chemical control of constructs the rational population structure based onchanges of tillers components of wheat populationThe relatively stable spike numbers per area of Shannong15was about750spikes m2. Theresult showed that0, I and II were superior tiller in SN15, which had superiority over theother tillers in terms of productive forces. Therefore, the plant density was designed,240plants m2. To restructure the tillers components of wheat population based on superior tiller,increasing plant density to240plants m2with external application of IAA (60mg L1IAA)could reduce the number of stem per square meter at the stages of wintering and jointing viainhibiting more tillers occur, which could promote the development of individual plant. Thenthe wheat plant had more grain number and higher single-kernel weight than those in the highplant density treatment, resulted in increasing in grain yield. For SN8355, the relatively stablespike numbers per area was about570spikes m2. To restructure the tillers components ofwheat population based on superior tiller (0and I), the plant density was set to270plants m2,meanwhile with external application of60mg L1IAA.更多还原