【作者】 李洪波；

【导师】 申建波；

【作者基本信息】 中国农业大学 ， 植物营养学， 2014， 博士

【摘要】 自然条件下土壤中的养分分布高度异质,而植物可以通过改变根系形态(根长、根重、侧根密度等)和生理(吸收速率)特征来适应这种异质性。本文通过搜集已发表的文献数据,利用整合分析方法,揭示植物及根系对养分空间异质性分布的响应规律,并分析这种响应在不同植物种间的变异；此外,还通过盆栽试验,研究了具有不同根系特征的农作物的根系形态对养分斑块处理的响应；最后,通过田间试验,研究了玉米在整个生育期内对局部养分供应的响应程度和动态变化过程。主要结论如下：1.整合分析的结果表明：从整体效应来看,养分空间异质性分布能够显著提高根系和地上部生长。根系对于养分空间异质性分布的响应比地上部更为敏感,根冠比显著增加。不同植物功能群之间对养分空间异质性分布的响应程度存在较大差异：与非豆科类的双子叶植物和禾本科植物相比,豆科作物对异质性环境反应不敏感。从驯化水平上说,养分空间异质性分布能够显著地提高野生型植物的根冠比,而驯养型植物根冠比提高并不显著。2.室内盆栽试验表明：局部供应铵和磷促进玉米、小麦根系在养分富集区的增生；单独局部供应铵抑制鹰嘴豆和玉米根系的生长,但磷和铵局部供应促进根系大量增生；鹰嘴豆在养分富集区的根系增生并没有提高总根长和总根表面积。局部供应养分对蚕豆的根系没有显著的影响。证明禾本科植物的根系可塑性高于豆科植物。3.田间试验表明：与撒施处理相比,局部养分供应使苗期玉米局部根长密度增加了465-667%。但这种正效应随着养分富集区氮的耗竭而逐渐降低。在十叶期,局部供应铵磷和撒施处理的生物量没有显著的差异；但在控释肥和有机肥的添加下,局部养分区氮含量能够维持到62DAS,从而使地上部生长的正效应持续到花期。根系增生与地上部的生长呈现一致的趋势。结果表明：局部供应养分促进地上部和根系的生长取决于局部富集区养分的供应强度和持续的时间长度。4.田间研究表明：根系在养分局部供应区大量增生,这种根系增生能否促进地上部生物量的增加,与局部富集区根系占整个玉米根系的比例有关,局部养分供应在苗期对地上部生长的贡献显著高于后期局部养分供应,这表明养分调控时期对于根系功能的发挥有重要作用。5.养分供应模式能够显著改变玉米生长速率和发育过程,对最终生物量并没有显著的影响；局部供应养分对玉米产量的影响很大程度上取决于竞争强度的变化,在高密度作物导致的强竞争下,优化养分的供应时期和供应强度对于发挥根系的作用,提高养分利用效率具有重要作用。更多还原

【Abstract】 In natural conditions, nutrients are heterogeneously distributed in soil. Plant roots can respond to local nutrients in order to effectively capture more nutrient resources through root morphological and physiological plasticity. Here, the related studies were conduced based on two different facets: meta-analysis and case study. Firstly, meta-analysis is performed with an extensive literature search and data collection to reveal the overall pattern (effect size and direction) and variation among plant functional group. Secondly, soil pot experiments were conducted in greenhouse to test root morphological responses to localized nutrient supply among different crop species with constrasting root traits; Five-year field experiments were conducted to examine the dynamic processes of the maize responses to localized nutrient supply over the whole growth stage. Key points of the results and progress were summarised as follows:1. The meta-analysis results showed that root:shoot ratio of plant increased or did not change under heterogeneous nutrient environments. Legume plants were generally less sensitive to the heterogeneous nutrient environments than non-legume herb and grass specie. There were significantly different effects of nutrient types on root and shoot growth, and the effect on root length density and root foraging precision increased with the decreasing level of nutrient transferability or increasing level of nutrient composition. Heterogeneous nutrient supply had a significant positive effect on the root:shoot ratio, which was also significant increase for wild species, except for domesticated species.2. The pot experimental results showed that localized supply of ammonium plus phosphorus induced maize and wheat root proliferation in the nutrient-rich zone. Localized supply of ammonium alone suppressed the whole root growth of chickpea and maize, whereas localized phosphorus plus ammonium induced the enhanced root proliferation. The localized root proliferation of chickpea in nutrient-rich zone did not increase the whole root length and root surface area. Faba bean had no significant responses to localized nutrient supply. The root morphological plasticity to localized nutrient supply could be highly modified by specific nutrients and plant species, with the greater plasticity in graminaceous than leguminous species.3. The field research showed that localized nutrient supply improved root proliferation and plant growth at seedling and jointing stages. The root length density and shoot biomass were465-667%and64-96%higher, respectively, in LNP, CF and OF than NP at seedling stage. However, despite rapid nutrient depletion, the whole-plant biomass did not differ between the LNP and NP treatments at ten-leaf stage. In contrast, the soil Nmin was kept at a high level (till62DAS) in the CF and OF treatments and the positive effect on plant growth was prolonged to flowering stage. The similar trend was also observed for root proliferation. The results indicated that localize nutrient supply elicits nutrient intensity-and duration-dependent improvement of maize root growth and nutrient uptake at vegetation stages.4. The further field research indicated that root proliferation in nutrient patches contributed more to maize growth and nutrient uptake at the early than late stages. Whether the root proliferation-based function could play a critical role for increased maize growth could highly depend on the timing of nutrient manipulation and management.5. Our results demonstrated that patterns of nutrient supply can modify the maize growth rate rather than the final biomass of individual plants; the effects of nutrient patch on plant reproductive output are highly dependent on competition intensity. How to optimize the timing and intensity of nutrient regulation and management is important to maximize root efficiency to improve crop productivity and nutrient use efficiency in intensive agriculture of China.更多还原