【作者】 宋海星；

【导师】 李生秀；

【作者基本信息】 西北农林科技大学 ， 植物营养学， 2002， 博士

【摘要】 作为吸收水分和养分、合成多种生理活性物质的器官，根系生长发育状况直接影响作物的生长及产量形成，在土壤供水受到较大限制的旱作农业中，根系的作用显得更为突出。然而，由于分离根系技术上的困难，涉及根系各方面的研究还远没有地上部深入。本文以玉米和小麦为供试作物，在遮雨棚内进行了微区田间试验，在不同栽培措施及水、氮供应条件下，研究了根系生理特性与作物养分吸收、植株生长之间的关系，主要结果如下： 1．氮素对玉米根系生理特性、养分吸收、光合作用及植株生长的影响受水分供应制约，水分供应较好(如本研究中的灌水处理)或水分胁迫较轻(如本研究中的未灌水、未限根处理)时，氮素供应促进了根系生长；增加了根系总吸收面积、活跃吸收面积和根系的TTC还原总量；增加了植株的伤流量和伤流液中硝、铵态氮、游离氨基酸及磷、钾含量；促进了根系对养分的吸收；改善了光合作用有关生理特性；从而增加了产量，减轻了限制根系生长的不良影响。水分胁迫严重时(如本研究中的未灌水、未覆膜、限制根系生长的处理)，供氮导致了根系生长量、根系吸收面积和TTC还原总量降低；也导致了植株的伤流量和伤流液中硝、铵态氮、游离氨基酸及磷、钾含量下降；养分吸收减少；光合作用的气孔因素和非气孔因素限制均增加，光合速率下降；从而降低了作物养分吸收量与产量，加重了限制根系生长的不良影响。 2．限制根系生长虽然严重抑制了根系发育，但却增加了根系的活跃吸收面积、提高了根系的TTC还原强度(单位根重TTC还原量)。在根系自然生长情况下，作物旺盛生长时期根系活跃吸收面积和TTC还原强度，与养分吸收量及地上部分的生物量密切相关。这说明，在限制根系生长的逆境条件下，作物并不是被动地忍受逆境的胁迫，而是主动地调节其生理代谢过程，增强其对水分和养分的吸收能力，减缓逆境伤害。但由于尼龙袋中原有的水分和养分早期已消耗殆尽，根系又无法透出袋外由其他地方获取这两种生长要素，内在吸收功能改善并未改变作物吸收养分下降和产量降低的结局。 3．在不同水、氮供应条件下，植株氮、磷、钾吸收量与伤流量及其养分数量的变化趋势基本相同；植株氮、磷、钾吸收量与伤流吸收的养分量(伤流液养分浓度与植株消耗的水分乘积)呈显著正相关。这一结果表明，伤流量及其养分数量，既是作物生长势的反映，也是作物吸收、转运水分与养分能力的标志。 4．玉米干物质和养分吸收量，随生育期持续增加，其变化动态可用S曲线方程描述。玉米生长期间干物质与养分吸收并非同一速率，前期上升快，至最高峰后缓慢2 水、氮供应对作物根系生理特性及吸收养分的影响下降。在氮、磷、钾三要素中，氮、钾吸收速率高，上升快，下降也快；磷吸收速率低，上升慢，下降亦慢。养分最大吸收速率出现的时间，钾最早，氮次之，磷最晚。但三者均早于干物质最大累积速率出现的时间。氮肥利用率与干物质累积、养分吸收速率有类似变化趋势；氮肥最高瞬时利用率与氮素最大吸收速率出现的时间基本一致。灌水明显提高氮肥累积和瞬时利用率；水分和氮素供应增加养分吸收及干物质累积速率，但未改变其变化趋势。水分和氮素供应促进了营养体养分向籽粒的运转，提高了养分在籽粒中的分配比例，从而提高了籽粒产量。 5．玉米根系发育状况及水分供应明显影响硝态氮的迁移及分介。根系自然生长时，离主茎不同距离的各位点硝态氮浓度差异小；而限制根系生长时，各位点硝态氮浓度差异大。离主茎 0－10cm范围的耕层土壤中硝态氮含量的变化趋势是，d］远到近逐渐降低，这一变化趋势与耕层士壤中根系吸收面积的变化相反。灌水可缩小远、近不同位点的硝态氮浓度差异，而且限制根系生长时，各位点的硝态氮浓度与土壤水分有相当一致的变化规律。后者表明，硝态氮随着植物吸收水分的过程，作为溶质而向根面迁移。 6．小麦根系及其生理特性的空问分布变化是：离主茎 0—10cm范围水平方向上，根系干重、土壤样方内全部根系的hC还原量（TTC还原量）和土壤样方内全部根系的吸收面积，随着离主茎距离的增加而逐渐减少。离地面0～60cm范围垂直方向上，根系干重、TTC还原量和根系吸收面积，随着土层深度的加深而逐渐降低；随生育期的后延，深层土壤的TTC还原强度有所加强。单位根重吸收面积，在上述范围的水平和垂直方向上，均变化较小。根系总吸收面积与TTC还原量的变化趋势相一致，二者呈极显著正相关。更多还原

【Abstract】 Plant root, as an important organs absorbing water and nutrients and synthesizing growth regulation, have a direct influence on the crop growth and yield. Roots play a remarkable role in dryland agriculture with serious soil water restriction. Because of the difficulty in separating root techniques, the studies involved plant root system have not been deepened as against the studies of plant aboveground. Micro-plot field experiment was conducted under rain-proof shelter for studying the relationship to root physiological characteristics and nutrient uptake of crop, plant growth, with different N and water supply under different cultivating measures. The results are shown as follows:1. The effects of N on root physiological characteristics, nutrient uptake, photosynthesis and plant growth were limited by water supply. When water supply was relatively sufficient (irrigated water) or slightly stressed (non-irrigated water and grown naturally), N supply stimulated root growth development, increased total absorbing area, actively absorbing area and TTC reductive amounts of roots, raised the bleeding sap amounts and the contents of NOs", NH4+, free amino acid, P and K in the sap, promoted the nutrient uptake of root, improved the physiological characteristics of photosynthesis, and consequently resulted in increasing crop yields and easing the harmful effects of restricting root growth. In contrast, when water was seriously stressed (non-irrigated water and non-mulching and grown naturally), input of N did not only decline the root growth biomass, root absorbing area and TTC reductive amount of root but also decreased the bleeding sap amounts and the content of NOs", NH/, free amino acid, P and K in the sap, reduced the nutrient uptake, inhibited the stomatal factors and the non-stomatal factors of photosynthesis, decreased the photosynthesis rates, therefore, this reduced nutrient absorbing amounts and crop yields, aggravated the harmful effects of restricting root growth.2. Although restricting root growth seriously inhibited the root development, it increased root actively absorbing area and improved TTC reductive intensity of root. Under the natural growth condition, the root actively absorbing area and TTC reductive intensity closely related to the nutrient uptake and aboveground biomass during crop vigorous growth stages. It showed that crop did not passively suffer stress, but initiatively adjust its physiological metabolism processes, strengthened its absorbing ability to water and nutrients, reduced the injure of root with the stressed environment. Being early consumed water and nutrient in the nylon bags, root could not go through nylon bags, and not assimilate the water and nutrients, hence the improvement of root inherent adsorptive ability can not change the decrease of nutrient uptake amounts and yields.3. Under the condition of different water and N supply, the trend was almost same for N, P and K uptake of crop and bleeding sap amount as well as nutrients in sap, the amounts of taking up N, P, K had remarkable positive correlation with the nutrients in bleeding sap. The results strongly suggested that the bleeding sap was not only the indication of plantgrowth vigor, but also the capacity of plant absorbing, and transferring water and nutrients.4. The total dry matter of maize and N, P, K uptake amounts were continuously increased with plant growth, and the dynamics of its change could be described by S-curve equations. The dry matter accumulation and nutrient uptake was not in the same rate at all time, the rate was increased fast at early stage, and gradually decreased after reaching their peak. Of N, P and K, the uptake rate for N and K was higher, and their increase and decrease were both fast while P was in reverse case. The time for maximum absorbing rate appeared earlier for K, followed by N, then by P. In any case, the time for maximum nutrient uptake rate appeared earlier than did the dry matter. The N recovery rate was similar in trend to those of dry mat更多还原