【作者】 马溶慧；

【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】 棉纤维比强度是原棉的重要品质指标,其形成主要取决于次生壁的建成质量。氮素是棉花优质高产的主要调控因素之一,研究氮素调控棉纤维比强度形成的生理基础,可为探索改善纤维比强度的氮素营养调控提供理论依据。本研究以棉纤维比强度高(科棉1号,平均比强度为35 cN·tex-1)和中等(美棉33B,平均比强度为32 cN·tex-1)的2个基因型品种为材料,采用大田和盆栽方法,于2005-2006年在江苏南京(118°50’E,32°02’N,长江流域下游棉区)和江苏徐州(117°11 ’E,34°15N,黄河流域黄淮棉区)进行氮素水平(零氮:0 kgN·ha-1,适氮:240 kgN.ha-1,高氮:480 kgN·ha-1)试验,研究了：(1)棉纤维中蔗糖代谢、棉纤维发育关键酶(蔗糖合成酶、p-1,3-葡聚糖酶)活性变化特征对氮素的响应及其与纤维比强度形成的关系；(2)不同开花期棉铃对位叶内源保护酶活性、棉铃干物质累积分配对氮素的响应及其与纤维品质性状的关系；(3)氮素调控不同开花期棉铃纤维比强度形成的生理机制；(4)棉铃对位叶氮浓度与纤维品质指标的关系。主要研究结果如下：1.棉纤维中蔗糖代谢、棉纤维发育关键酶活性变化特征对氮素的响应及其与纤维比强度形成的关系。(1)通过研究棉铃对位叶氮浓度、棉纤维加厚发育过程中蔗糖代谢、纤维素累积及纤维比强度形成对氮素的响应特征,分析了氮素调控棉纤维中蔗糖代谢及纤维比强度形成的生理机制。结果发现：棉铃对位叶氮浓度随铃龄变化的趋势符合幂函数曲线(YN=αt-β,YN：棉铃对位叶氮浓度(%),t：铃龄(d),α,β为参数)。高氮水平下的a值显著增加,是导致铃龄24 d前纤维中蔗糖代谢相关酶(蔗糖酶、蔗糖合成酶和磷酸蔗糖合成酶)活性和蔗糖转化量、纤维素最大累积速率以及铃龄24 d纤维比强度降低的重要原因；零氮水平下的β值显著增加,与铃龄24 d后纤维中蔗糖代谢相关酶活性和蔗糖含量峰值降低、纤维素快速累积持续期缩短以及铃龄24 d后纤维比强度增幅减小的关系密切。上述变化特征在品种间保持一致,是棉纤维发育对棉铃对位叶氮浓度做出的重要生理响应,进而导致高氮、零氮水平下的成熟纤维比强度显著降低。综合分析认为,对中部果枝而言,铃龄24 d可以作为棉铃对位叶氮浓度调控棉纤维中蔗糖代谢及纤维比强度形成的转折期。(2)基于两年的盆栽氮肥试验,研究了棉纤维发育关键酶(蔗糖合成酶和β-1,3-葡聚糖酶)活性变化特征对氮素的响应及其与纤维比强度形成的关系。结果表明：氮素通过调控纤维发育关键酶活性变化特征影响了纤维素的累积进程,进而影响了纤维比强度的形成。在生化水平上,适氮水平下棉纤维发育关键酶维持高活性的时间较长,高氮、零氮分别导致铃龄24 d前、铃龄24 d后纤维发育关键酶活性显著降低；在mRNA转录水平上,适氮水平下铃龄7-24 d内蔗糖合成酶基因表达量及铃龄18-24 d内β-1,3-葡聚糖酶基因表达量显著高于其余两个氮素处理。适氮水平下纤维发育关键酶维持高活性的时间较长,且其基因表达量高,促使纤维素在较长时间内快速累积,最终形成的纤维比强度较高。2.不同开花期棉铃对位叶内源保护酶活性、棉铃干物质累积分配对氮素的响应及其与纤维品质性状的关系。(1)基于大田氮肥试验,研究了研究棉花季节桃(伏前桃、伏桃、早秋桃和秋桃)对位叶保护酶活性及纤维品质性状对氮素的响应。结果表明：与适氮相比,零氮水平下伏桃、早秋桃和秋桃对位叶中可溶性蛋白含量、SOD和POD活性均降低,MDA含量升高,且影响程度随开花期推迟而增加,相应开花期棉铃中纤维所占比例显著降低,纤维长度、比强度和整齐度均降低,马克隆值升高；高氮水平除有利于延长秋桃对位叶的功能期外,对其他季节桃对位叶中可溶性蛋白含量和内源保护酶系统的作用较小,不利于伏前桃、伏桃中的光合产物向纤维运输,进而导致纤维比强度显著下降,但对早秋桃、秋桃纤维品质性状的影响程度较小。可见,零氮处理过早打破了棉花季节桃对位叶内源保护酶系统的平衡是导致棉铃发育、纤维品质形成受阻的重要生理原因,而高氮对棉花季节桃对位叶内源保护酶系统的影响程度与纤维品质性状的关系较小。(2)以伏桃、秋桃为对象,研究了棉铃干物质积累分配对氮素的响应及其与纤维品质指标的关系。结果表明：棉铃各组成部分中以纤维受氮素的影响最大,其次为棉籽、铃壳。棉籽与纤维之间存在同步异速生长关系,这种关系可用模型y=a+bx表示(x、y分别代表棉籽、纤维干重的自然对数,a为截距,b为线性回归系数)。零氮、高氮处理均降低了伏桃的b值,相应的纤维比强度显著降低,但对其他纤维品质性状的影响较小；秋桃的b值在适氮与高氮处理间差异较小,但显著高于零氮处理,纤维长度、比强度及整齐度对氮素的响应亦呈现出相似趋势。由此推断,对相同开花期的棉铃而言,棉籽、纤维异速生长方程的线性回归系数b越大越有利于高品质棉的形成。3.氮素调控不同开花期棉铃纤维比强度形成的生理机制。以伏前桃、伏桃和秋桃为研究对象,分析了氮素调控不同开花期棉铃纤维比强度形成的生理机制。结果表明：与适氮相比,零氮处理显著降低了棉铃对位叶氮浓度,增加了C/N值,且影响程度随开花期的推迟而加大,导致伏桃、秋桃对位叶制造和运输光合产物的能力在棉铃发育中后期大幅度下降,棉纤维的相对生长速率以及纤维发育关键酶活性降低,纤维素快速累积持续期缩短,相应的纤维比强度显著降低；高氮处理显著增加了棉铃对位叶氮浓度,降低了C/N值,但影响程度随开花期推迟而降低,降低了伏前桃、伏桃发育过程中光合产物向纤维分配的比例、棉铃发育前中期的纤维发育关键酶活性及纤维素累积速率,导致伏前桃、伏桃纤维比强度显著降低。综合分析认为,适宜施氮通过协调棉花的“源库”关系,促进了不同开花期棉铃高纤维比强度的形成。4.棉铃对位叶氮浓度与纤维品质指标的关系。通过分析棉铃对位叶比叶重(LMA)、氮浓度(NM：单位干重氮含量,NA：单位叶面积氮含量)对开花期及氮素的响应特征,初步探索了棉铃对位叶NA与纤维品质指标的关系。结果表明：①棉铃对位叶NA蕴含了NM和LMA的双重信息,具有对氮素水平及开花期均较为敏感的特性,在氮素处理间差异性达显著水平,随开花期的推迟呈现出逐步上升趋势；②随着棉铃对位叶NA平均值的增加,棉纤维品质关键指标(纤维长度、比强度、马克隆值、整齐度)的变化趋势均为开口向下的抛物线型；③零氮与适氮处理间棉铃对位叶NA平均值的差距随着开花期的推迟逐渐扩大,而高氮与适氮处理间的差距逐渐缩小,相应氮素处理间纤维比强度和马克隆值的差距亦呈现出同样的变化趋势。综合分析认为,棉铃对位叶NA与棉纤维品质指标的关系密切,可以作为今后从氮素营养角度实时监测预报棉纤维品质优劣的一个重要生理指标。更多还原

【Abstract】 As an important criterion of cotton quality, fiber strength contributes highly to the yarn strength. The secondary wall thickening stage is a key period to fiber strength formation and many complex physiology mechanisms are involved in it. Nitrogen is one of the regulating factors to the production and fiber quality of cotton. Nowadays, darkly applying nitrogen fertilization significantly depressed fiber strength in production. For improving fiber strength by regulating nitrogen fertilizer application, the physiology basis of nitrogen regulating cotton fiber strength formation was studied in this research to provide theoretical basis. In 2005-2006, field or pot experiments were carried out in Nanjing (118°50’E, 32°02’N, middle lower reaches of Yangtze River Valley) and Xuzhou (117°11’E,34°15’N, Yellow River Valley), which stand for the different ecological conditions. Two cotton cultivars with difference fiber strength (KC-1, average fiber strength is 35 cN·tex-1. AC-33B, average fiber strength is 32 cN·tex-1.) were used, and three nitrogen rates (0 kgN·ha-1,240 kgN·ha-1,480 kgN·ha-1), standing for low, optimum and high nitrogen application level respectively were applied. The study focused on:(1) the response of sucrose metabolism and changing characteristics of key enzymes activities in developing cotton fiber to nitrogen rates and their relationships with fiber strength formation; (2) the response of antioxidant enzyme activities in the subtending leaf and dry matter accumulation and distribution of cotton bolls with different anthesis date to nitrogen rates and their relationships with fiber quality characteristics; (3) the physiological mechanism of nitrogen regulating fiber strength formation of cotton bolls with different blooming dates; (4) the relationship between nitrogen concentration in the subtending leaf of cotton boll and fiber quality indices. The main results were as follows: 1. Response of sucrose metabolism and changing characteristics of key enzymes activities in developing cotton fiber to nitrogen rates and their relationships with fiber strength formation(1) By studying the response of change characteristics of nitrogen concentration in subtending leaf of cotton boll, sucrose metabolism during fiber thickening, cellulose accumulation and fiber strength formation to nitrogen rates, the physiological mechanism of nitrogen regulating sucrose metabolism in cotton fiber and fiber strength formation were investigated. The results showed that the changing trends of nitrogen concentration in the subtending leaf of cotton boll followed the equation:YN=αt-β(YN, nitrogen concentration in the subtending leaf of cotton boll (%).t, boll age (d).αandβare the parameters). "a" was significantly higher under high-nitrogen rates, which, to a great extent, lead to the decrease of sucrose translation and activity of the enzymes (invertase, sucrose synthetase, phosphate sucrose synthetase) before the 24th day post anthesis (DPA), the decline of maximal speed of cellulose accumulation in cotton fiber and fiber strength at the 24th DPA. "β" was significantly higher under low-nitrogen rates, which may made negative effects on sucrose metabolism after the 24th DPA, decline the duration for cellulose speedily accumulating in cotton fiber and the increment of fiber strength from the 24th DPA to boll opening. The changes under high or low-nitrogen rates, which described above were important physiological responses of cotton fiber development to nitrogen concentration in the subtending leaf of cotton boll, and ultimately resulted in lower final fiber strength, and the changes showed similar trends in KC-1 and AC-33B. All the results indicated that, as to the bolls located at the middle fruiting-branch position, in the subtending leaf of cotton boll, the 24th DPA was an inflexion in the time course of nitrogen concentration regulating sucrose metabolism in cotton fiber and fiber strength formation.(2) By setting the three nitrogen rates through potted experiments, the response of the key enzymes activities change to nitrogen rates and its relationship with fiber strength formation were studied. The results of two-year potted experiments showed that the activities and gene expression of key enzymes during cotton fiber development were affected by nitrogen rates, and the nitrogen effects influenced the characteristics of cellulose accumulation and fiber strength formation. At the biochemical level, sucrose synthetase andβ-1,3-glucanase showed higher activities throughout boll maturation period under optimum-nitrogen rate, while significantly declined under high-nitrogen rate before 24th day post anthesis (DPA) and low-nitrogen rate after 24th DPA. At the gene expression level, the expression of the sucrose synthetase gene during 7-24 DPA, andβ-1,3-glucanase gene expression suppressed during 18-24 DPA remarkably promoted under optimum-nitrogen rate. For fiber strength is determined by characteristics of cellulose deposition during cotton fiber thickening in a great extent, meanwhile, the key enzymes of sucrose synthetase and P-1,3-glucanase play important regulation function in cellulose accumulation. Sucrose synthetase is involved in cleaving sucrose and channeling UDP-Glu, andβ-1,3-glucanase in breaking down callose to cellulose synthase. From the results above, we suggested that the high activities and gene expression of sucrose synthetase andβ-1, 3-glucanase in cotton fiber contribute to longer period of speedy cellulose accumulation under optimum-nitrogen rate, and then promote higher fiber strength formation accordingly.2. Response of antioxidant enzymes activities in the subtending leaf and dry matter accumulation and distribution of cotton bolls with different anthesis date to nitrogen rates and their relationships with fiber quality characteristics(1) Based on the field experiment, the response of antioxidant enzymes activities in the subtending leaf, boll components and fiber quality characteristics of seasonal cotton bolls to nitrogen rates were analyzed in this research. Sympodial-branch position white blooms (flowers at anthesis) were tagged on the blooming date of Jul 15, Jul 25, Aug 25 and Sep 10, and the cotton boll samples were expressed as PSB (pre-summer boll), SB (summer boll), EAB (early autumn boll) and AB (autumn boll), respectively. Results showed that compared with optimum-nitrogen rates, under low-nitrogen rates, the soluble protein content, SOD activity and POD activity and MDA content in subtending leaves of SB, EAB and AB decreased, and the effect degree under low-nitrogen rate increased with blooming date postponing, correspondingly, fiber length, strength and uniformity index correspondingly decreased, but micronaire value increased; The effect of high-nitrogen rate on soluble protein content and antioxidant enzyme activities in the leaf subtending of PSB, SB and EAB was slight, but that is favorable to prolong the functional period of leaf subtending of AB. Fiber strength significantly decreased in PSB and SB, but EAB and AB traits and fiber quality indices changed a little under high-nitrogen rates. All the results suggested that the balance of antioxidant enzyme system in the subtending leaf of seasonal cotton bolls broken too early under low-nitrogen rates played a very important role in hindering fiber quality formation, but small effects of antioxidant enzyme activities in the subtending leaf of seasonal cotton bolls on fiber quality characteristics under high-nitrogen rates. (2) Take SB and AB as research objects, response of dry matter accumulation and distribution of cotton bolls to nitrogen and its relationship with fiber quality characteristics were studied. Results showed that the effect degree of nitrogen rates on fiber is higher than seed and fiber. The decrease in seed/fiber ratio came from an allometric growth between seed and fiber, which could be expressed by the following equation:y=a+bx (x is the natural logarithm of cottonseed while y is the natural logarithm of fiber dry weight per boll, and a is intercept while b is regression coefficient for the linear equation). "b" of SB was significantly lower under low-nitrogen or high-nitrogen treatment, correspondingly, fiber strength also decreased but other fiber quality characteristics changed little. "b" of AB has a little difference between high-nitrogen treatment and optimum-nitrogen treatment, which significantly higher than low-nitrogen treatment, and the indices of fiber length, strength and uniformity showed similar trends too. All the results indicated that, as to the cotton bolls bloomed on the same date, the larger "b" is, the more favorable to form high fiber quality.3. Physiological mechanism of nitrogen regulating fiber strength formation of cotton bolls with different blooming datesThrough analysis of the effects of nitrogen rates on nitrogen concentration and C/N in the subtending leaf, allometric growth between seed and fiber, key enzymes (sucrose synthetase andβ-1,3-glucanase) activities, cellulose accumulation and fiber strength of PSB, SB and AB, the mechanism of nitrogen regulating fiber strength formation of cotton bolls bloomed in different dates were groped. The results showed that compared with optimum-nitrogen rates, under low-nitrogen rates, the nitrogen concentration significantly decreased and C/N significantly increased significantly in leaf subtending cotton boll. And the effect degree under low-nitrogen rate increased with blooming date postponing, which, to a great extent, lead to the reduction of capacity of photosynthetic product accumulation and transportation in the leaves subtending SB and AB, the decrease of relative fiber growth rate in cotton boll and the activity of key enzymes during the middle-later period of fiber development, and also the decline of cellulose speedily accumulating duration in cotton fiber and the fiber strength of SB and AB; On the contrary, the changes of nitrogen concentration and C/N under high-nitrogen rates were opposite to low-nitrogen rates, which may made negative effects on the distribution proportion of photosynthetic product to fiber, the key enzyme activities during the early-middle period of fiber development and the momentary rate of cellulose accumulation in PSB and SB fiber, resulted in significant fiber strength decreased in PSB and SB too. From above results, we suggested that source-sink relation could be optimized under the optimum-nitrogen rates, which promoted higher fiber strength formation in cotton bolls.4. Relationship between nitrogen concentration in the subtending leaf of cotton boll and fiber quality indicesBased on the analysis of the response of LMA (leaf mass per unit leaf area) and nitrogen concentration (NM, nitrogen content per unit leaf mass; NA, nitrogen content per unit leaf area) in the subtending leaf of cotton bolls with different anthesis dates to nitrogen rates, the relationships between nitrogen concentration and fiber quality indices were firstly groped. The result showed that (1) NA in the subtending leaf of cotton boll contained both the information of LMA and NM, possessed the special sensitive characteristic in response to nitrogen rates and anthesis dates. It can reflect the increasing trends with anthesis date postponing and significant difference in nitrogen treatments; (2) With the average values of NA increasing, the changing trends of pivotal quality indices (length, strength, micronaire and uniformity) of cotton fiber according with the curve of parabola with peak value; (3) With anthesis date postponing, the difference of NA between low-nitrogen and optimum-nitrogen treatments enlarged gradually, on the contrary, the difference between high-nitrogen and optimum-nitrogen treatments diminished gradually, fiber strength and micronaire also showed similar trends between corresponding nitrogen treatments. NA in the subtending leaf of cotton boll was tightly related to fiber quality indices formation. As the corresponding relationships between NA and fiber indices were not affected by cotton varieties and ecological sites, we proposed that NA in the subtending leaf of cotton boll could be used as a practical physiologic index for timely monitoring nitrogen status for fiber quality in the future.更多还原