【作者】 樊剑波；

【导师】 沈其荣；

【作者基本信息】 南京农业大学 ， 植物营养学， 2008， 博士

【摘要】 我国是水稻生产大国,每年水稻种植面积在0.28-0.30亿公顷,占全球水稻种植面积的22%,年产稻谷1800-2000亿公斤,占世界稻谷总产量的30%左右,居世界稻谷产量的第一位.水稻在我国粮食生产中有着举足轻重的作用,水稻生产中消耗的化学氮肥大约为700多万吨,氮肥利用率平均为28%。氮肥利用效率低不仅导致氮素的浪费,而且对环境产生了严重的影响.人们通常采用养分吸收量或产量作为养分效率的评价指标,但它们容易受其他因素的影响而难以真实地反映某一养分性状的遗传特性.理想的做法是寻找与某一养分性状密切相关的形态和生理指标.在水稻摄取氮素养分的过程中,根系参数的改变起了决定性的作用,根的生长和根表面积对根表的氮素养分有效性具有重要影响。因此,本试验采用根袋法(田间)和砂培法(温室),以不同氮效率基因型水稻为试验材料,研究了不同氮效率水稻根系形态和其它根系生理指标的基因型差异,为筛选氮高效基因型水稻提供试验依据.本论文在水培条件下进行了8个基因型(其中Elio为氮低效品种)水稻苗期获取氮能力的差异及其原因的研究。在不同供氮水平下,不同水稻品种苗期吸氮能力差异显著.随着供氮水平的提高,南光、豫粳7号、黔育421和武运粳7号的氮积累总量增加显著,说明这四个水稻品种对氮的响应度高;而桂单4号、Elio、云粳38和4007的氮积累总量增加不显著,说明这四个水稻品种对氮的响应度低.对氮响应度高的四个水稻品种的平均吸氮速率随着供氮水平的增加其增幅显著,而其总根长的变化幅度则小得多;水稻氮积累总量与根系总根长和平均吸氮速率的相关关系的分析结果进一步表明,平均吸氮速率对水稻苗期获取氮能力的贡献率大于其根系总长的贡献率。选用种质特性(生育期,株高等)相似的两个品种(氮低效品种Elio和氮高效品种南光),在不同施氮处理下进行田间试验,以了解苗期后不同氮效率品种氮素吸收利用与根系形态的差异.结果表明,不同氮效率水稻产量随施肥量的增加而增加,在各施氮处理下,氮高效品种南光的产量均高于氮低效品种Elio。两个水稻品种在各生育期的干物质和氮素积累量都存在基因型差异,分蘖期和拔节期,Elio的干物质和氮素积累量高于南光,而至齐穗期南光显著高于Elio。氮高效品种南光的根系形态参数明显大于品种Elio;且两品种根干重,总根长,根系表面积,根冠比等指标与氮素积累量呈很好的相关关系。在水稻生产中根系形态参数是决定其是否高效吸收和利用氮素营养的决定性因素。为进一步了解齐穗后不同氮效率品种的差异,在温室砂培条件下研究了不同氮效率水稻全生育期尤其是齐穗后的各项根系生理指标。结果表明,齐穗至成熟,氮低效品种Elio总干物质量和氮素积累量的增加显著小于氮高效水稻南光。齐穗后,高氮处理下Elio的根系出现明显衰退,其根量,总根长,根系表面积较前一生育期均显著下降,而南光的根系指标降幅较小,且根长还有所增加;低氮处理下,南光的各项根系生理指标较前一生育期无显著变化,而Elio则呈明显下降趋势,部分指标降幅显著。本试验条件下,我们认为,齐穗后氮高效水稻的根系衰退相对较慢,仍然保持着相对旺盛的代谢机能,这为其最后获得较高的籽粒产量打下了坚实基础.以另一氮高效品种4007和氮低效品种Elio为试验材料,在田间条件下比较两个品种氮素吸收利用与根系形态的差异,旨在验证根系形态参数是否确是衡量氮效率的重要指标.结果表明,氮高效品种4007和氮低效品种Elio氮素吸收利用与根系形态的差异与南光和Elio的比较试验结果一致。对于根系其它生理指标的试验结果表明,随着供氮水平的提高,氮高效品种南光的苗期根系活力显著大于氮低效品种Elio,前者大于后者35%(2mmol/L)和15%(4mmol/L).而对生育中后期水稻伤流的研究表明,不同氮效率水稻品种Elio与南光的根系活力差异显著,氮高效品种南光的伤流速率显著高于氮低效品种Elio;在生育后期南光伤流液中可溶性糖和氨基酸的浓度、总量均显著大于Elio,游离态氨基酸种类也较全.生育后期,Elio根系MDA含量显著高于南光,SOD活性低于南光,氮高效品种南光根系的衰老缓于氮低效品种Elio。更多还原

【Abstract】 China produce most rice grain in the world, the rice planting area is about 28-30 million hectares, which accounts for 22% of the total rice planting area in the world. The annual production of rice grain ranged between 1800～2000 hundred million kilograms, which accounts for about 30% of total rice production. Rice has a pivotal function in Chinese grain production. Chemical nitrogen fertilizer in rice production consumes probably more than 7 million tons, but the average N use efficiency (NUE) is about 28%. Low NUE not only waste nitrogen, but alao has serious effects on environmental condition. Nutrient absorption capacity or grain yield is major index that scientist usually used to evaluate the nutrient efficiency, but these indexes could be influenced easily by other factors. Therefore these factors could not really reflect the hereditary property of nutrient character. The ideal method is to seek the morphological and physiological target that closely related with nutrient characters. In the process of nitrogen absorption, the changes of rice root morphology parameters had a decisive function, and root growth and surface area influence the N validity. Several experiments with different rice cultivars (high and low NUE) were conducted with methods (i.e. root bags and sand culture). The studies investigated the differences of root morphology parameter and biological activity between rice cultivars, which can provide theoretic basis for screening high NUE rice cultivar.In the present study, hydroponic experiments were conducted to study the differences and mechanism of N absorption in seedling stage of 8 different genotype rice. The results showed that there were significant differences in N uptake capacity between different rice cultivars. Based on the N uptake accumulation of rice, eight cultivars could be divided into high response to N, such as Nanguang, Yujing 7, Qianyu 421 and Wuyunjing 7, and low response to N, such as Guidan 4, Elio, Yunjing 38 and 4007. The difference in N uptake response was related to N uptake rate and root characteristics. N uptake rate of high-responsing cultivars increased significantly with increasing N rate. N uptake rate exhibited much higher increase than that of total length of root. The linear regression between N uptake accumulation and root bulk and N uptake rate showed that N uptake rate was significantly correlated with N uptake across N levels, indicating N uptake rate plays a key role in studying of N uptake in seedling of rice.In the field experiment, two rice cultivars (Elio and Nanguang) which have similar development characteristic (growth stage, plant height, etc) were taken as experiment materials. Differences of absorbing nitrogen and root morphology were compared after seedling stage. The grain yields increased with N application rates. Under different N supplying level, the yields of the high NUE cultivar (Nanguang) were significant higher than that of the low NUE cultivar (Elio). There were differences in dry matter and biomass accumulation between two rice cultivars at each growth stage. Nanguang’s root morphology parameters are obviously great than Elio. Root dry weight, total root length and root surface area of two cultivars are directly correlated with N accumulation. Therefore it is concluded that the production of rice root morphology parameter are the decisive factors to determine whether the rice take and use N efficiently.Sand culture was conducted to study the root physiological parameters of different NUE rice under the whole growth stages. From heading to maturity, increase of total dry matter and N accumulation of N absorption inefficient rice cultivar Elio was significantly less than N absorption efficient rice cultivar Nanguang. After heading stage, root system of Elio on high N supplying level senesced significantly, root dry weight, total root length and root surface area were significantly decreased than front growth stage. Root system index of Nanguang decreased little, but the root length increased. Root system physiology index of Nanguang on low N supplying level were not change obviously, but that of Elio completely showed a decreasing tendency, some index decreased significantly. Under this experiment condition, we concluded that relatively root system of N absorption efficient rice declined slowly, and still maintain the exuberant metabolism function after heading stage. This result is a strong foundation for getting higher grains yield.In the field experiment, another high NUE cultivar 4007 was compared with low NUE cultivar Elio to prove that root morphology parameter is the important index for N efficiency. The results showed that differences of 4007 and Elio were sameness with it of Nanguang and Elio.Increased with N level root activity of Nanguang was significantly larger than Elio, the former had 35% (2 mmol/L N level) and 15% (4 mmol/L N level) lager than the latter. The study of bleeding sap of rice on the middle-later period showed that root system activity was significantly different between Elio and Nanguang. Bleeding rate of Nanguang was significantly larger than Elio. In later growing stage the concentration and total of soluble sugar andamino acids in bleeding sap of Nanguang were significantly larger than that of Elio, and the kinds of free amino in bleeding sap of Nanguang were more than Elio. The results of MDA and SOD show that senescence of Nanguang’root was slower than Elio.更多还原