【作者】 章爱群；

【导师】 贺立源；

【作者基本信息】 华中农业大学 ， 植物营养学， 2008， 博士

【摘要】 土壤缺磷是农业生产中限制作物生长与产量的主要因素之一。但是施磷肥后,至少有700%～90%的磷在土壤中转化为难被作物吸收利用的形态。玉米是重要的粮食和饲料作物,其磷效率存在广泛的基因型差异,形成所谓的遗传学缺乏。由于缺磷是酸性土壤的特征之一,本研究室前期对国内外不同遗传背景的大量玉米自交系进行了苗期土培筛选,并对部分材料进行全生育期盆栽鉴定,获得了一些典型的耐低磷和耐酸铝基因型。本文进一步研究了同时具有耐低磷和耐酸铝玉米种质材料的耐低磷营养特性,同时以本地区三种pH值低磷土壤和三种低分子量有机酸为对象,研究了不同磷源对无机磷形态转化及有机酸对提高磷素有效性的作用。主要研究结果如下:1.本研究采用土培和水培方法系统研究了不同酸铝（铝）、磷处理下玉米自交系苗期生物学及营养学特性。结果表明,低磷和酸铝都严重抑制玉米植株的生长,低磷胁迫下干重受影响较大,酸铝胁迫对下部叶叶色和干重影响显著。耐低磷基因型适应低磷的能力较强,它们具有较长的根系和较大的根干重,且株高受低磷的影响明显小于敏感基因型。低磷胁迫增大了植株的根冠比,改变了植株对营养元素的吸收及其在地上部和根系的分配。铝胁迫下,铝敏感玉米基因型根伸长受到铝的抑制作用大于耐铝基因型,耐铝基因型地上部和根系相对干重下降较少,而敏感基因型相对干重显著下降。2.营养学特性研究表明,低磷胁迫下,低磷敏感基因型磷吸收效率低,耐低磷基因型的吸收能力较强,其绝对和相对吸磷量都明显高于低磷敏感基因型。低磷抑制玉米幼苗对N、K的吸收和累积,但耐低磷自交系受抑制程度较敏感自交系小。低磷敏感基因型M05根系和地上部Zn含量下降,耐低磷基因型M02、M08和M11根系和地上部Zn含量升高,且耐低磷自交系植株体内Zn的相对累积量高于敏感自交系。低磷胁迫使M05地上部和根系中Ca、Mg、Fe累积量显著下降,但M02、M08地上部和根系中钾、镁、锌的绝对和相对累积量显著高于敏感基因型。铝处理使自交系地上部和根系中各营养元素含量和累积量普遍下降,加磷可缓解酸铝对玉米生长的毒害作用。不同自交系之间存在耐低磷和耐酸铝基因型差异,相互间存在一定的关系,但耐胁迫能力不同。自交系M12属于酸铝低磷双敏感类型;耐酸铝自交系,如M02和M08同样耐低磷,耐低磷自交系M01也较耐酸铝,为双耐基因型。3.用营养液培养方法研究了不同耐低磷玉米幼苗对低钾、低铁和缺锌胁迫的适应性差异。结果表明,低钾胁迫对玉米株高和叶片数有显著的抑制作用,但对根系生长没有明显影响,甚至刺激多数基因型的根系生长。低钾胁迫对耐低磷基因型玉米地上部生长的抑制作用显著大于低磷敏感基因型,因此耐低磷基因型的根冠比增幅较大。低钾处理显著降低了植株的地上部和根系吸磷量,尤其是低磷敏感基因型植株的根系吸磷量;同时还使玉米根效率比大幅下降,6个基因型在对照和低钾处理中根效率比的差异均达到显著水平,但以耐低磷基因型降低的程度更为明显。低钾处理使地上部和根系的磷利用率增加,但基因型间无明显差异。低铁胁迫对低磷敏感基因型玉米地上部生物重的抑制作用显著大于对耐低磷基因型。在低铁胁迫时,耐低磷基因型玉米地上部和根系积累的磷量与正常供铁条件下相比变幅较小,而低磷敏感基因型积累的磷量显著下降。低铁胁迫显著降低了不同耐低磷基因型玉米幼苗叶片的叶绿素含量,但基因型间无明显差异。总的来说,玉米地上部更易受低铁胁迫的影响。低磷敏感基因型在缺锌时植株各部位锌含量和吸收量变幅均明显高于耐低磷基因型。缺锌处理影响玉米幼苗的磷含量,低磷敏感基因型地上部磷含量较对照显著上升,根系磷含量变幅不大:耐低磷基因型地上部磷含量变幅较小,根系磷含量则显著下降。低磷敏感基因型在缺锌时地上部磷利用率显著下降,根系磷利用率无明显变化,而耐低磷基因型的变化情况正好相反,根系磷利用率受影响的程度大于地上部。4.土壤大部分磷以难溶性磷形式存在,是影响作物生产的重要限制因素之一。作物根分泌物活化难溶性磷的能力对改善其磷素营养具有重要意义。采用室内培养方法,研究三种土壤不同磷（KH₂PO₄）处理后有效磷动态变化情况;同时将不同玉米基因型分别置于全磷和低磷的营养液中生长15d后,收集根系分泌物,然后加入预先采用磷酸钙和磷酸铝处理并已培养95d的土壤样品中进行试验。不同磷处理研究结果表明,所有施磷处理短期内速效磷含量急剧上升,并随培养时间推移不断下降,60d后趋于稳定。酸性土对磷的吸附和固定作用较强,磷处理后有效磷增加量显著小于中、碱性土。土壤加根系分泌物的试验反映,磷酸钙和磷酸铝有效磷的含量具有提高,其中加入耐低磷基因型M02低磷根系分泌物浸提的土壤有效磷含量显著高于去离子水的浸提量,且根系分泌物对磷酸铝的活化能力大于磷酸钙。5.以湖北省三种不同pH值的低磷土壤为材料,加入不同磷源和有机酸,经过室温培养后,测定有效磷含量和无机磷组分的变化。结果表明:施磷显著提高了土壤中有效磷含量,中、酸性土Fe-P和Al-P含量大幅上升,Fe-P占增加量的50%以上,而碱性土中Ca-P含量显著增加。由于有机酸的作用,三种土壤中O-P含量均有所增加,中、酸性土中Al-P含量一般呈下降趋势,碱性土中Ca-P含量有不同程度的减少。更多还原

【Abstract】 Phosphorus is often sparingly soluble in soils and consequently P deficiency in plants represents a major constraint to world agricultural production.High phosphate fertilizer inputs intensive crop areas have been the practice for several decades.Generally,the P was widely considered to be firmly fixed onto the soil particles,and it was largely unavailable to plants,which results in "P deficiency in heredity".Consequently much research has concentrated on the potential to manipulate plants either through conventional breeding of genetic engineering to enhance their capability to mobilize P in soil.Maize was an important grain and forage crop in the world,there were P-efficiency difference among different maize genotypes.Most of cultivated land in acid soil was in heavy P-deficiency,after screen more than 300 maize genotypes in seedling stage with soil culture,and identify some of them in full-life stage with pot culture experiment,we achieved some typical low-P tolerant and Acid-tolerant maize genotypes.In this study, obtained typical lines were selected to research their nutritional characters and physiological mechanism.Meanwhile,three types of low-P soils collected from Hubei province were tested to analyze their inorganic phosphorus fractions after incubated with added various organic acids and different phosphorus sources.The main results of this study were summarized as follows:1.Aluminum（Al） toxicity and phosphorus（P） deficiency often coexist in acid soils that severely limit crop growth and production,including maize.Understanding the physiological mechanisms relating to plant Al and P interactions should help facilitate the development of more Al-tolerant and/or P-efficient crops.In this study,both nutrient solution and soil experiments were conducted to study the effects of Al and P interactions on maize biology and nutrient characteristics.The results demonstrated that P deficiency and acid stress severely hinder the growing of maize.P deficiency had a negative influence on biological traits,especially on plant dry matter weight.Low-P tolerant maize genotypes,had longer roots and larger dry root weight than low-P sensitive maize genotype;and the plant heigh of low-P tolerant maize genotypes were less affected by the phosphorus defficiency than that of sensetive genotypes.Under low phosphorus condition, the ratio of root to shoot in all genotypes increased;uptaking and distribution of P,K,Ca, Mg,Fe,Zn between roots and shoots also changed.Under stress of aluminum condition, the root lengtht and relative dry weigh of Al-tolerant maize genotypes were less affected by the Al toxicity than those of Al-sensetive genotypes.2.Nutrient characteristics of seedling stage were studied for different maize genotypes.The efficiency of P uptake is the main contributor to low-P tolerance.And the P uptake amounts of P-tolerance lines M02、M08 and M11are significantly higher than P sensitive line M05 under low P stress.P deficiency has some influence on the uptake of N, P,K,Ca,Mg,Fe,Mn and Zn at seedling stage.P deficiency restrains the uptake of N and K for the maize.However,it affects less of P tolerant lines than that of P sensitive lines. The P tolerant lines show stronger abilities of Ca,Mg,Fe uptake and accumulation than P sensitive lines.P deficiency decreases concentration and accumulation of Zn in root and shoot of P sensitive lines but increases that of P tolerant lines.Under stress of aluminum condition,accumulation of P,K,Ca,Mg,Fe,Zn was seriously affected,the addition of P could alleviate the toxicities of acid and aluminum.There were genotypic differences in tolerance to low-P and acid stress among different lines.It was also found that there are some relation between low P tolerance and acid tolerance.M12 is sensitive line to both acid-aluminum stress and low P stress;The acid and aluminum tolerant lines M02 and M08 show the same tolerance to low P,whereas the low P tolerant line M01 has some tolerance to acid and aluminum stress,which are tolerant lines of both stress.3.The genotypic differences in response to K、Fe、Zn deficiency of maize with different phosphorus efficiency were investigated in nutrient solution under controlled conditions.K deficiency was significant effect on shoot growth and number of leaves. The genotypic differences existed in response to K deficiency,which decreased the dry weight of shoot in low-P tolerant genotypes more significantly than in low-P sensitive genotypes,and root/shoot ratio of low-P tolerant genotypes sharply droped.The K deficiency was also significant decreased P uptake in root、shoot and the root efficiency ratio,but increased P utilization efficiency,and P uptake in root in P sensitive genotypes more significantly than in low-P tolerant genotypes.Fe deficiency decreased the dry weight of shoot in low-P sensitive genotypes more significantly than in low-P tolerant genotypes.Compared with supplying Fe treatment （+Fe）,in-Fe treatment,the P accumulation in shoot and root of low-P sensitive decreased significantly,but was not significant effect on that in low-P tolerant genotypes. The same response to Fe deficiency existed in chlorophyll content between P sensitive genotypes and P tolerant genotypes,the contents of different genotypes in chlorophyll decreased greatly respectively.Shoot of maize appears to be the causative factor of the different phosphorus efficiency genotypes.The genotypic differences existed in response to Zn deficiency,which decreased the content and uptake of Zn of seedling in low-P sensitive genotypes more significantly than in low-P tolerant genotypes.Compared with supplying Zn treatment,in-Zn treatment,the P content in shoot of low-P sensitive genotypes increased significantly than in root;but the P content in root of low-P tolerant genotypes decreased signifecantly than in shoot; the P utilization efficiency in shoot of low-P sensitive and in root of low-P tolerant genotypes decreased respectively.4.Low phosphate availability is one of the major limitations to crop production. Organic acids are a principal component of root exudates and have been hypothesized by many authors to be involved in the mobilization of nutrients within the rhizosphere. Mobilization of insoluble phosphates by root exudates plays an important role in improving P nutrition of crops.The effect of different phosphorus level on dynamic of available phophorus in soils had been studied.At the same time,two maize inbred lines were grown for 15 days in nutrient solution with different phosphorus treatment.The root exudates were collected and added into the three types of soil which had incubated for 95days.The results showed that the available phosphorus content quickly increased by application of different phsphate,and then constantly decreased by time,and were steady after 60 day;and the available phosphorus from acid soil is significant lower than alkali soil and neutral soil.The soil available phosphorus content was extracted by the root exudates of M02 collected under low phosphorus condition significant pronounced with the addition of insoluble phosphate to the deionized soil;and AlPO₄ mobilization by root exudates was significantly higher than Ca₃（PO₄）₂.5.Three types of soils collected from Hubei province were tested to analyze their inorganic phosphorus fractions and content of available P after incubated with added various organic acids and djfferent phosphorus sources.The results indicated that application of phosphorus sources increased content of available P in all soils.On soils of pH value 4.6 and 6.8 the fertilized phosphorus was transformed into Fe-P and Al-P mainly.However,on soil of pH value 8.3 the fertilized phosphorus significant increased content of Ca-P.The release of phosphorus by organic acids from soils is significant, especially Al-P in acid soil and neutral soil,Ca-P in Alkali soil.更多还原