【作者】 梁赟；

【导师】 任正隆；

【作者基本信息】 四川农业大学 ， 生物化学与分子生物学， 2009， 硕士

【摘要】 小麦是世界最重要的粮食作物,增产潜力巨大。小麦籽粒产量的形成主要来自小麦开花后的光合同化产物。但是,小麦籽粒的灌浆时期正好伴随着叶片的衰老过程,小麦叶片的衰老缩短了有效光合作用持续期进而造成产量的大幅下降。“持绿型”小麦品种开花后能有效地延缓旗叶的衰老,为籽粒合成更多的光合产物。本文以“持绿型”小麦品种为材料,研究其在开花后旗叶的生化、光合和叶绿素荧光参数特性,解释延缓旗叶衰老的机制,同时做了衰老期间旗叶主要的生物化学、光合参数及叶绿素荧光参数与籽粒千粒重的相关性分析。具体结果如下:1“持绿型”材料旗叶的叶绿素含量在整个衰老期间维持在一个较高的水平,长时间高叶绿素含量是“持绿型”小麦旗叶延缓衰老的重要生化基础。与此同时,“持绿型”小麦的可溶性蛋白质含量也高于对照小麦,这说明其衰老程度比对照材料小。2与对照材料相比,“持绿型”材料旗叶的CAT和SOD活性高,MDA含量上升慢。表明在衰老期间,“持绿型”小麦CN17和CN18具有较高的清除活性氧的能力以减轻活性氧的损害。3与对照材料相比,“持绿型”材料的Pn、Gs和Tr均显著较高。结果还表明,“持绿型”小麦高Pn值(Pn＞10)的持续时间比对照延长了12天。通过对Pn的线性回归和通径分析发现,小麦光合速率的下降在衰老前期主要受气孔因素影响,在衰老后期则主要受叶肉细胞同化能力的影响。4通过对参试材料旗叶衰老期间叶绿素荧光参数的测定,发现在荧光参数(Fv/Fm、Fv’/Fm’、ΦPSⅡ、ETR和qP)是一个下降的趋势。在衰老后期,“持绿型”材料的荧光参数(Fv/Fm、Fv’/Fm’、ΦPSⅡ、ETR和qP)显著较高于对照材料,说明“持绿型”材料的PSⅡ得到有效的保护以保持着较高的生化活性。5在衰老前期,参试材料旗叶非光化学淬灭值NPQ都有一个显著地上升,说明旗叶启动了热耗散机制耗散过剩的激发能,以减轻因PSⅡ吸收过多光能而引起的光氧化从而保护光合机构免受伤害。但在衰老后期,“持绿型”小麦品种比对照表现出较高的NPQ值,说明其叶黄素循环更为高效,进而有效地热耗散多余的光能。6对剪叶处理后的籽粒千粒重进行分析,发现“持绿型”小麦品种延缓衰老的特性有助于在衰老后期积累更多的同化物,并提高籽粒产量。7对衰老期间旗叶荧光参数与净光合速率Pn进行相关性分析,发现各荧光参数与净光合速率Pn都呈显著正相关,但随着时间推移相关性逐渐减小。8对衰老期间旗叶主要的生物化学、光合参数及叶绿素荧光参数与籽粒千粒重的相关性分析,发现籽粒干粒重与Fv/Fm、Fv’/Fm’、ΦPSⅡ、ETR和qP呈显著正相关,且相关系数随着时间推移相关性逐渐减小。另一方面,籽粒千粒重与衰老中期和后期的MAD显著呈负相关。更多还原

【Abstract】 As the most important food crop worldwide,wheat is regarded as a cereal with considerable potential to increase yield,particularly in marginal agricultural areas.The senescence of wheat leaves is accompanied by the grain filling process,k is a great significance to study the photosynthesis during the senescence of wheat leaves because it contributes greatly to grain yield.Leaves senescence during the grain-filling period causes a sharp decrease in wheat yield by shortening the duration of active photosynthesis. Senescence of flag leaf is effectively delayed in "stay-green" wheat cultivars afer Florescence.Much more photosynthates are synthesized for grain.Here we use the materials of"stay-green" wheat cultivars.We studied the changes of the biochemical,photosynthetic and chlorophyll fluorescence characteristics during the senescence period and explained mechanism of delaying senescence.Meanwhile,we analysed the correlation between the main biochemical traits,photosynthetic characteristics,chlorophyll fluorescence parameters and 1000-kernel weight.The results are shown as follow:1 The "stay green" materials maintained a high level of chlorophyll content throughout senescence stage,and long period of high level of chlorophyll content is the most important biochemical elements of delaying senescence.In this study showed that the soluble protein of the "stay green" materials higher than CK in the senescence stage,which suggests that the "stay green" materials senescence extent is slower than CK.2 The stay-green" wheat cultivars,compared with CK,had the higher activity of CAT, SOD;and the raise of MDA content was more slowly.It is showed that the "stay green" wheat（CN17&CN18） have a greater ability to remove O₂^- so as to lighten the contamination of the active oxygen during the senescence stage3 The stay-green" wheat cultivars,compared with CK,had the higher value of Pn,Gs and Tr.The results showed that the duration of high Pn value（Pn＞10） of the "stay green" wheat lasted 12 days longer than that of CK materials.The multiple linear regression and correlation analysis of Pn was studied,the results suggested that the decline of Pn mainly depended on the stomatal limitation in early period of senescence,but in the later period of senescence,it depended on the assimilation capacity of mesophyll cell.4 There was a degressive trend by the means of measuring the chlorophyll fluorescence parameter of the flag leaf in the senescence period.In later period of senescence,this study on the chlorophyll fluorescence parameter measurement of "stay-green" wheat cultivars showed that Fv/Fm,Fv’/Fm’,ΦPSⅡ,ETR and qP had the higher value than CK,indicating that the PSⅡof"stay-green" wheat were effectively protected so as to maintain the higher activity of biochemistry.5 We also detected a significant increase of NPQ in the in early period of senescence, which indicated that the mechanism of thermal dissipation had been started to dissipate excess lightenergy,and protect the flag leaf from photo-oxidation.But in the in later period of senescence,this study showed that NPQ had the higher value than CK,which indicated that the thermal dissipation depending on xanthophyll cycle was more efficient so as to dissipate excess lightenergy.6 It was showed that the trait of delaying senescence of "stay green"whaet had higher abilities to accumulate photosynthate so as to improve the yeid of the grain by the means of measuring the 1000-kernels weight of leaf-cutting treatment in n the later period of senescence.7 The conclusion was that there is significantly positive correlation by the means of analysing the correlation between chlorophyll fluorescence parameter and net photosynthesis rate.But the correlation between chlorophyll fluorescence parameter and Pn were declined as time extended under leave senescence period.8 The conclusion was that the 1000-kernels weight was significantly positive correlated to Fv/Fm,Fv’/Fm’,ΦPSⅡ,ETR qP and Pn by the means of analysing the correlation between chlorophyll fluorescence parameter,Pn,and 1000-kernels weight.But the value of correlation declined as time extended under leave senescence period.On the other hand, the 1000-kernels weight was significantly negative correlated to MAD at middle senescence stage and later senescence stage.更多还原