【作者】 王伟；

【导师】 曹敏建；

【作者基本信息】 沈阳农业大学 ， 作物栽培与耕作学， 2008， 博士

【摘要】 大豆是我国北方主要的油料作物,其产量和品质受钾素影响较大。近年来,我国土壤供钾能力逐年降低,投入钾肥不仅增加生产成本,降低肥料利用率,且易对环境造成危害,对大豆的生产十分不利。研究表明,种植耐低钾品种是缓解我国钾肥资源匮乏、促进农业可持续发展最为经济有效的途径。本文以前期筛选出的典型大豆品种为试验材料,在土培和溶液培养两种条件下分析了不同耐性品种对低钾胁迫的生物学响应差异,并对植株干物质积累、钾离子的动态吸收、植株含钾量以及钾吸收效率、利用效率进行研究,从而探讨耐性品种对低钾的耐性机制。试验主要结论如下:1.不同耐性品种的生物产量及经济产量对低钾胁迫响应不同,品种间差异明显。两品种百粒重对低钾胁迫的响应并不大。不耐品种单株荚数和收获指数在低钾胁迫下降低显著。2.溶液培养可以很好的反应不同耐性品种对低钾胁迫的反应差异,与田间试验相比,具有更好的可控性和可重复性。缺钾条件下,各品种植株干物重与高钾处理相比显著降低,不同耐性品种间没有差异;在低钾胁迫下,不耐低钾品种植株干物质积累减小幅度明显大于耐低钾品种;在中度低钾胁迫下,干物重变化的差异在不同耐性品种间表现不明显。低钾胁迫降低了植株的根/冠,耐性品种的下降幅度小于不耐品种。从培养时期来看,前期不同耐性品种处理间没有显著差异,在培养20d以后差异表现明显,耐性品种处理间植株干物重的降低幅度较小,而不耐品种则具有显著差异。因此,溶液培养中这一时期是分析生物学响应差异的关键时期。3.低钾胁迫下不同耐性品种培养前期根系形态的变化较小,处理间差异不明显。在培养20d左右,根系形态参数的变化在不同耐性品种间开始表现出一定差异,耐性品种在低钾胁迫下变化较小,根系表面积、平均直径降低幅度不明显,而不耐品种各参数受低钾胁迫变幅较大。显微结构观察结果表明,低钾胁迫下不同耐性品种根系皮层薄壁细胞明显较对照增厚,内部中柱变细。4.低钾胁迫下耐性品种叶片面积没有发生显著变化,比叶重在前期有所增加,后期变化并不明显,不耐品种叶面积在培养后期较对照显著降低,比叶重增幅显著;茎秆表皮厚角组织、维管束变薄,内部髓腔变细;不耐品种表现较耐性品种明显。叶脉的主脉变细,薄壁细胞层变薄,韧皮部、形成层和中间木质部均小于对照,但耐性品种叶脉内细小维管束部分及厚角组织没有发生显著变化,而不耐品种细小维管束发育与对照相比明显变弱。栅栏组织的排列规律是靠近主脉部分较为集中,而远离叶脉部分较为松散,在不同耐性品种各处理间表现并没有显著差异。5.低钾胁迫下根系钾吸收动力学参数中Km值有所降低,耐低钾品种变化幅度大于不耐品种,I_max有不同程度的提高,不耐品种增加幅度大于耐性品种,Cmin值也发生显著变化,尤其是耐性品种,增加幅度极为显著。高钾处理下两品种植株经过饥饿处理后吸收钾的量并没有增加,耐性品种甚至出现植株中的钾外泌现象,而低钾胁迫下两品种的植株经过钾饥饿处理后表现出了对吸收液中的钾快速吸收,不耐品种表现尤为明显,吸收液中K⁺的浓度持续降低,耐性品种在测定后期对吸收液中的钾离子吸收逐渐减弱。此外,低钾胁迫下不耐品种根系伤流量发生显著降低,耐性品种没有明显变化,但两品种根系质膜H⁺-ATPase活性都有所提高,耐性品种表现尤为突出。6.低钾胁迫下不耐品种茎秆纤维素含量有显著的降低,而耐性品种处理间没有差异;低钾胁迫下耐性品种叶片可溶性糖含量显著降低,淀粉含量则没有显著变化,不耐品种叶片可溶性糖含量降低幅度较小,但叶片淀粉含量降低十分明显;不耐品种Ca²⁺-ATPase和Mg²⁺-ATPase活性也较高钾处理显著降低,而耐性品种处理间两种酶活性变化差异并不显著。7.在低钾胁迫下,耐性品种的叶绿素a、b及a+b总含量与对照之间没有差异,a/b值较对照显著提高,而不耐品种的叶绿素a及a+b总量较对照显著降低,叶绿素b的含量及a/b值没有显著变化;低钾胁迫下耐性品种仍保持较高的光合速率,但气孔导度和胞间CO₂浓度则显著低于对照,不耐品种的各参数下降幅度远大于耐性品种,处理间均达到极显著差异。气孔限制值在不同耐性品种间的变化表现一致,而耐性品种水分利用效率降低幅度则明显小于不耐品种;随着供钾水平的降低,耐性品种叶绿素荧光各参数中仅F_v显著增加,而不耐品种F_o、F_m、F_v、F_v/F_m、F_l、Area、N、ET_o、（?）_Po、（?）_Eo、（?）_Do、RC等参数的变化均达到显著或极显著水平;低钾胁迫下不耐品种反应中心耗散的能量较多,用于电子传递的能量减少,而耐性品种处理间无明显变化。8.供钾水平对植株钾效率影响较大,不同耐性品种间表现出一定的差异。低钾胁迫下植株体内钾的累积量较对照显著降低,植株体内钾的分布也发生变化,不耐品种吸收的钾主要富集在茎秆中,叶片中的钾量显著降低,耐性品种各部分钾积累量没有发生明显变化。两品种在不同供钾水平下钾效率比的变化间并没有差异,但在钾利用效率方面的变化幅度却表现出了显著的差异,说明其耐性的差异不在于植株对钾素的吸收,钾在植株体内的利用情况如运输、同化才是其钾效率差异的关键。更多还原

【Abstract】 Soybean[Glycine max（L.）Merr.]is the main oilseed crop in north of China,which yield and quality were extremely affected by potassium fertilizer.In recent years,the decline of K content in soil need input mineral fertilizer,which not only increase cost of agricultural production,but also decrease fertilizer use efficiency.Low fertilizer utilization increased the potential hazards of environmental pollution.All these could limit soybean production. Various studies on crops showed that planting tolerant varieties was an economic and effective way of alleviating potassium resource shortage and prompting sustainable development of agriculture in China.In former experiments,potassium tolerant and non-tolerant genotypes had been screened in field.The present study is an attempt to identify the physiological mechanisms implicated in tolerance to low potassium by testing difference of biological responses,dry matter accumulation of plants,K kinetic parameters and K efficiency of two typical genotypes that differ in tolerance to low K stress.The main conclusion of study were as followed:1.Responses of biomass and economic yield of different tolerance varieties to low potassium stress was different,and difference between varieties was significant.The changes of weight per 100 seeds were slight to low potassium stress for two types of varieties,but for non-tolerant variety,greatly changes has been determined on pods per plant and harvest index under low potassium stress.2.There were distinct differences of stress symptom when tolerant and non-tolerant varieties transplanted in solution culture.Compared with field plant,tank farming was more controllable and repeatable.In general,plant dry matter and root/shoot ratio decreased consistently with the decline of K levels in the growth medium.The two types were hardly reduced dry matter weight of plant under heavy low K stress,but this difference became progressively smaller with the increase of K levels in solution.During culture period,the first noticeable influence of K deficiency on the growth parameters of plant organs appeared at 14^thdate and difference in total biomass between treatments was more acute at 21^stdate for non-tolerant varieties.There was,however,little change in tolerant varieties.These results suggested that 21^stdate could potentially be used as the crucial time for investigating differences of biological responses.3.Morphological and physiological characteristics of root are important for absorbing K efficiently from culture solution.Effect of low K stress on root morphological characteristics was tiny at early stage of growth.By 21^stdate,low K stress produced significant effect on root morphological characteristics for non-tolerant variety.Total root length,average root radius,root surface area,and root volume were all declined due to K deficiency,while those parameters of tolerant variety were slightly reduced by low K stress.Plants had evolved some mechanisms to maximize the efficiency of potassium acquisition.Changes in root architecture are one such mechanism.When soybean seedlings were grown under conditions of low potassium availability,the ply of cells in the cortex of root tip was increased,but the stele was thin,compared with seedlings grown under conditions of high potassium availability.4.The change of leaf areas was tiny for tolerant variety under low potassium stress.And positive effects of low K stress on special leaf weight were slight at the early growing stage for non-tolerant variety,and marked increase was observed at later stage,but there was no difference between two K levels for tolerant variety.Collenchyma and vascular bundle in stem was weaker than that of adequate K plants for non-tolerant than tolerant variety.Those changes were same in comparison with pith in stem.When plants were subjected to low K stress,main veins were slenderer and parenchyma cell were smaller than that of K-adequate plants.Indeed we found that phloem,cambium,and xylem were all affected by the applied low K stress.And greater decreases in vascular bundle and collenchyma of leaf vein occurred for non-tolerant than for tolerant variety.Anatomical traits of leaf cross-sections performed that palisade tissue layer arrayed densely near the veins,but loosely away from veins. However,basic difference between tolerant and non-tolerant genotypes did not exist.5.When the roots of plants grown in K deficient solution are exposed to ample K concentration solution,the rate of K uptake previously in short supply is much increased compared with control plant maintained with an adequate K provision.Representative depletion curves showed the marked contrast between unstressed controls and plants under low K stress.In our uptake experiments,the decline of K concentration was initially rapid and near linear with time,but became more gradual as the concentration approached zero.The non-tolerant variety was superior over the tolerant variety in uptake both speed and time. Potassium kinetic study indicated that K deficiency in plants result in a decrease in K_m value and increase in I_maxand C_minvalue.However,change extent of each parameter was harsh different between tolerant and non-tolerant varieties.Furthermore,root bleeding sap and cation exchange capacity of non-tolerant variety were all declined under low K stress,while that of tolerant variety changed slightly affected by K deficiency.The plasma membrane H⁺-ATPase activities were dramatically greater than those at adequate K supply,especially to tolerant variety.6.Cellulose content of stem of non-tolerant variety at deficient K supply was much lower than that at adequate K supply.Soluble sugar content in leaf significantly declined due to low K stress,while starch content in leaf varied slightly for tolerant variety,but the content of soluble sugar and starch changed on the other way round for non-tolerant variety.Besides, low K stress produced significantly negative effect on Ca²⁺-ATPase and Mg²⁺-ATPase activities in leaf for non-tolerant variety,while those of tolerant variety were slightly reduced by low K stress.7.For non-tolerant variety it was combined with a decrease of chlorophyll content under low K stress,especially decline of Chl a.There was a slightly change in chlorophyll content of tolerant variety,but the ratio of Chl a/b remarkably increased due to K deficiency,which was benefit to capturing more photo electron.Photosynthetic rate,stomatal conductance,and intercellular CO₂ concentration of non-tolerant variety were all significantly reduced in K-deficient compared to K-sufficient leaves at 21^stdate.By contrast,photosynthetic rate of tolerant variety kept a relatively high level under low K stress in spite of heavy decline of stomatal conductance and intercellular CO₂ concentration.Decrease of intercellular CO₂ concentration indicated that in tolerant and non-tolerant variety the stomata were more closed, which was reflected by a high value of stomatal limitation.There was also a decrease of WUE at the same time,especially for non-tolerant variety,which decline was noticeable.In the experiment all CF parameters were affected by low K stress:also F₀ was affected and varied for the non-tolerant but the tolerant.Except for that,the ratio of energy dissipated by reaction center increased in low K stress for non-tolerant variety,and the ratio of transfer energy decreased at the same time,while those change of tolerant variety were tiny.8.With plant growth,potassium accumulation and distribution in plant varied significantly between deficient and adequate K supply.Low K stress reduced the accumulation of K in root followed by leaf and stem,which lead to a change in K partition between organs.Marked differences existed in the non-tolerant variety.K accumulation in plant was the function of K content and dry matter weight,and was positively correlated with dry matter weight.So the potassium contents of tolerant and non-tolerant genotypes were close in the same K level. There were no difference between change of K uptake efficiency for tolerant and non-tolerant varieties,but change of K utilization efficiency between two genotypes in low and normal K. level was dramatically distinct.更多还原