【作者】 张蕊；

【导师】 周志春；

【作者基本信息】 中国林业科学研究院 ， 林木遗传育种， 2013， 博士

【摘要】 木荷（Schima superba）是山茶科木荷属常绿阔叶大乔木，为亚热带地带性常绿阔叶林的主要建群种，广泛分布于我国南方各省。其树干端直，木材坚重致密，结构均匀，力学性质好，是建筑、器材、木制工艺品等优质用材，同时木荷还是我国南方主栽的生物防火树种和重要的生态防护树种。然而我国南方林地有效磷缺乏，严重影响了木荷人工林的持续高产经营。林木磷效率的遗传改良成为育种学研究热点。近年来，我国南方地区大气N沉降加剧，土壤N素增加，重要环境因素的变化对植株的生长产生了重大的影响，然而有关N沉降对木荷生长、根系结构、叶片生理及磷素营养效率的影响，研究报道较少。本论文分别选取木荷不同产区的地理种源材料为试验对象，设置0、50、100和200kg N ha-1·a-1不同浓度的N素沉降模拟盆栽试验，揭示不同浓度N沉降影响下，木荷不同种源分别适应低磷胁迫的生长、生物量差异、根系生长发育状况、磷素吸收特点和叶片光合生理等的生物学机制，揭示不同种源感知N沉降的遗传反应差异，及N沉降与低P耦合作用对木荷不同种源P吸收和利用、干物质积累和分配等的作用，为选育N沉降丰富条件下觅取利用土壤有限P素等能力强、生产力高的木荷优良新品种提供理论基础和科学依据。主要研究结果如下：1.模拟N沉降对土壤pH值、N和P有效性的影响研究N沉降作用引起土壤酸化，pH值下降，低磷环境下土壤酸化更为显著；随着N沉降浓度加大和处理时间的延长，土壤pH值下降程度增大，土壤酸化程度更高。N沉降初期，随着植物吸收加强和土壤酸化活化形成的铁、铝离子的增多螯合部分有效磷，造成土壤有效磷含量降低，而随着N沉降浓度的增加，土壤有效磷的衰减速度减慢，这可能和土壤酸化加剧，植物生长受限，固定态的磷的转化有关。土壤水解氮含量随着N沉降浓度增加和处理时间的延长呈现增长趋势。N沉降对土壤N存在积累效应，这既可以增加森林生产力，但另一方面也加大了土壤有效氮流失的潜力。2.模拟N沉降对木荷根系发育及根系分泌物的影响研究采用盆栽模拟试验研究了低磷（5.49mg·kg-1）和正常磷（60mg·kg-1）条件下，模拟N沉降浓度升高和时间延长对木荷根系特征、根系分泌的有机酸成分含量变化及酸性磷酸酶活性的影响。结果表明，N沉降浓度的增加促进了根系生长，根系密度增大、生物量提高，在土壤中分布空间增大，而高浓度N沉降则对根系造成伤害。N沉降初期，低磷环境下，木荷根系的根尖分生组织形成受到抑制，根系的增粗生长明显。试验中还发现了N沉降浓度增高促进了木荷根毛形成和伸长现象。在低磷环境下，木荷根系分泌的有机酸和Apase含量均比相应高磷环境高，且N沉降对木荷根系分泌有机酸的含量具有显著的促进作用。在分泌的有机酸中，乙酸所占比例高达50%以上，其次为苹果酸，低浓度N沉降能够促进其含量的增加，而中、高浓度N沉降则具有抑制作用；随着N沉降处理时间延长和苗龄的增大，乙酸和苹果酸含量增加明显，且分泌物中新增酒石酸和丙二酸两种有机酸成分，起到活化土壤固定态磷的作用。草酸则作为一种常量次生代谢酸大量存在于根系分泌物中，对提高根际磷的有效性起到辅助作用。3.模拟N沉降对木荷光合作用及叶片可溶性蛋白和Apase活性的影响研究氮素直接影响植物体内叶绿素和可溶性蛋白含量及光合酶类的合成与活性，对植物的光合作用产生影响。本研究通过对光合光响应参数、叶绿素组成、叶片可溶性蛋白及相关酶活性等研究，进一步揭示N沉降对木荷生长、根系形态变化及养分吸收等产生影响的机理。研究结果表明，N沉降初期，木荷潜在光合能力提高，净光合速率增加，光合能力增强，物质能量消耗减少，光合产物更容易积累，有利于在贫瘠环境下提高生长量；随着N沉降浓度的提高和处理时间的延长，木荷叶片的光合能力下降，光合速率降低，物质与能量消耗增加，对弱光环境的适应性降低。N沉降明显增加了木荷叶片叶绿素含量，木荷叶片捕光能力提高，有利于光合作用的高效进行，而类胡萝卜素含量和可溶性蛋白含量减少，Apase活性降低，MDA含量下降，N沉降初期的氮素增加对提高木荷的氧化损伤具有一定的作用，高浓度N沉降下，叶绿素含量降低。长期N沉降影响下，叶片可溶性蛋白含量和Apase活性下降更为显著，总叶绿素含量和叶绿素a/b值较N沉降初期也明显下降，但总叶绿素含量和叶绿素a/b值和该水平对照相比又有所增加，说明木荷通过提高叶绿素a/b值来弥补部分因叶绿素下降引起的光合作用下降，从而提高了自身抗性。4.模拟N沉降对木荷生长特征及体内养分含量变化的影响研究采用盆栽模拟试验研究了低磷（5.49mg·kg-1）和正常磷（60mg·kg-1）条件下，喷施NH4NO3浓度升高和时间延长对木荷生长、生物量和不同器官N、P养分含量变化的影响。结果表明，无论缺磷与否，N添加均能对木荷地上部及根系生长产生不同程度的促进作用。低浓度N沉降增加了木荷幼苗的苗高、地径的生长及地上部和总生物量的积累，而高浓度N沉降则抑制了木荷苗的生长。木荷植株地上部生长在低磷低N沉降下表现出明显的生长势，而地下部根系生长发育较地上部反应滞后。低磷环境下，木荷体内N、C素含量和NAE随着N沉降浓度的增加而提高，P素含量和PAE变化不明显。PAE和NAE与生长、干物质量积累呈正相关，有效的元素吸收能迅速增加植株的生长和干物质积累，增加了C储量。PUE随着N沉降浓度的增加而增高，但在高浓度N处理下增长不大；NUE随着N沉降浓度的提高和处理时间的延长而降低。N沉降初期，木荷根冠比降低，随着N处理时间延长和苗龄的增大，低磷环境下，木荷根冠比提高，PAE增强，叶片P含量增高，根系PUE增强，说明大苗增强了对恶略环境的适应能力，抗瘠薄能力提高。5.模拟N沉降对不同种源木荷生长发育影响研究N沉降初期，木荷不同种源材料生长表现为：浙江龙泉>福建建瓯>福建古田>湖南桂阳>江西信丰和浙江杭州。木荷北部边缘产区的杭州种源光合能力最强，N沉降初期，该种源地上部生长即已表现出优势，叶片叶绿素和可溶性蛋白含量增加，光合能力增强，但同化物不易积累，地下根系生长缓慢。随着N沉降浓度的提高，杭州种源苗木的光合作用下降，呼吸消耗持续增强，地上部生长下降，而根系开始加速生长。中南部中心产区的浙江龙泉和福建建瓯种源，光合能力较强，呼吸消耗最低，同化物最易积累，对N沉降的适应性也最强，在低浓度N沉降时>0.5mm直径根系的生长较快，根系生长旺盛，根系发育健壮，生长潜力增大；随N沉降水平的提高光合能力增强，在中等浓度N沉降影响下，其地上部表现出旺盛的生长势，生产力最大，而高浓度N沉降下该区域种源虽然光合作用最大，但此时呼吸消耗也大，生物量不易积累，生产力降低。南部次中心产区的福建古田、江西信丰和湖南桂阳种源在N沉降作用下，地上部的表现与浙江杭州种源相似，光合能力较低，呼吸消耗适中，地上部生物量积累不大；这些种源的地下部根系生长迟缓，甚至出现了抑制状态。另外，高海拔地区立地较为瘠薄，气温较低，长期适应于该立地和气候的种源，根系较为发达，地上部的生长较差，N沉降作用促进了其根系发育；低海拔种源生长立地环境较优，水肥充裕，温度适宜，根系较不发达而地上部生长旺盛，在N沉降影响下其根系增粗，氮磷吸收率增大，干物质积累增多。更多还原

【Abstract】 Schima superba is a representative and widely distributed and dominant evergreenbroadleaf tree species in the subtropical forests in southern China. The timber of this species istough, dense and glossy, which can be used for both architecture and furniture. S.superba isalso an important biological fire-resisting and ecological protection species. Nowadays, lowsoil P content in southern China is serious and the forest soil fertility recession has seriouslyaffected the productivity of plantation and management. So forest phosphorus efficiency hasbeen studied more. More recently, the rate of deposition of nitrogen (N) is high in subtropicalforests in southern China. The soil N increased and much more environment factors changedand improved the plant growth. However, the changes of plant growth, root growth, leafphotosynthetic and phosphrous efficiency of S.superba under different N-deposition andP-limitation conditions have not been documented. The factorial design of the experimentincluded S.superba seedlings of eight provenances of different producting areas and and levelsof N addition using NH4NO3(0,50,100, and200kg N ha-1year-1). The results may reveal themechanisms of plant growth, biomass, root growth, phosphrouse absorpt and photosyntheticunder N deposition. It may reflect the difference in response to N and P among differentprovenances. The objectives of this study were to provide insight for selecting and breeding offavorite genotypes with higher P efficiency. The main results obtained from experiments are asfollows:1. Effects of simulated N deposition on the soil pH, N and P availabilityThe N dposition could cause the soil acidification. The effect of soil acidification wasmore significant on low P soil than in high P soil. The soil pH decreased and the soilacidification increased as the increasing of the N dposition content and treatment time. In theinitial stage of N dposition, the available P decreased as the strengtherning of plant absorptionand the chelation of iron and aluminum ion with available phosphorus. Then the available phosphorus reduced slowly with N addition, which is related to the transformation of the fixedP as the aggravating of the soil acidfication and the plant growth restriction. The content ofhydrolyzable nitrogen in soil increased with increasing of N concentration and treatment time.The accumulation effect of the N deposition on soil N may in crease the forest productivity, buton the other hand, it may increase the potential of the loss of soil available N.2. Effects of simulated N deposition on plant root morphological characteristic and rootexudation in S.superbaThe effects of elevated N deposition on root morphological characteristic, organic acidcontent and Apase activity in root exudation were studied by carrying out a pot experimentwith conditions of P deficiency and normal P suplly. The results showed that root growth,density, biomass and spatial distribution of S. superba were increased with N addition, but highconcentrations of N deposition would do harm on root. In the early time, the root apicalmeristem formation is inhibited, the root become thicken under P deficiency. It was discoveredthat N addition also significantly improved root hair development and elogation. The organicacid and Apase content were higher in P deficienvy than in normal P. Meanwhile, the Ndeposition had a promoting role on secretion of organic acids. Among the organic acid, theamount of acetic acid accounted for more than50%, and followed by malic acid. The oganicacid content was increased under50N deposition, but inhibited under100or200treatment.The acetic acid and malic acid were sharp increased with the treatment time and seedlings age,and there were another two new compositions, which was tartaric acid and malonic acid,involved in the activation of fixed soil P. Oxalic acid as a constant and a large number ofsecondary metabolites acid presented in the root exudates, and played a role to improve theeffectiveness of the rhizosphere P.3. Effects of simulated N deposition on photosynthetic character, leaf solube protein andApase activity in S.superbaThe synthesis and activity of plant chlorophyⅡ, soluble protein and photosyntheticenzymes are directly effected by N, so N addition have an impact on plant photosynthesis. Inthis study, the photosynthetic light response curve, leaf pigments and soluble protein contents were determined and further reveal the mechanism of N deposition impact on plant growth,root morphology and nutrient absorption. The results showed that N addition increased the leafphotosynthesis and maximum net photosynthetic rate (Pmax), but reduced the material andenergy consumption, so the products were easier accumulated and the plant was easy to growthin the barren environment. However, when the N concentration was higher and the treatmenttime was longer, the leaf photosynthesis was reduced and material and energy consumptionwere increased, and the adaptability to low light conditions was reduced. N depositionincreased in leaf pigments contents and capacity of leaves light-harvesting, so it was beneficialto photosynthesis. But the carotenoid and solube protein content were reduced, the activity ofApase was decreased and MDA content reduced ether. N deposition had a certain effect onoxidative damage, but high concentrations of N deposition inhibited the plant chlorophyⅡcontent. The leaf solube protein content and activity of Apase were reduced significantly underlonger N deposition, and so as to the totle chlorophy content and chlorophy a/b. whencompaired with the comparison in longer time treatment, the totle chlorophy content andchlorophy a/b were increased, that means S.superba could increas the chlorophy a/b ratio tocompensate the photosynthesis decreased, thereby imroving the resistance.4. Effects of simulated N deposition on the plant growth and nutrients content inS.superbaThe effects of NH4NO3evevated from0to200kg N ha-1year-1on plant growth, biomassand N or P content in different organ were studied by carrying out a pot experiment withconditions of P deficiency (5.49mg·kg-1) and normal P suplly (60mg·kg-1). The resultsshowed that N addition had a positive effect on the growth of shoot and root of seedlings of S.superba no matter P was deficient or not. Early on, plant height, SBD, shoot biomass and totlebiomass were the highest among specimens subjected to N50treatment, but a decreasing trendwas observed when N treatment was increased to N200levels. The shoot growth was found tobe more sensitive to added N than root growth was under P deficiency. Roots showed a delayedresponse to N addition, and their growth and PUE increased at higher levels of added N. The N and C content and NAE were increased with N addition, while P content and PAE had nochange. The PAE and NAE were positively correlated with plant growth, dry matteraccumulation, and effective elements absorbtion could increase plant growth and biomass andfurther increasing of C reserves. The PUE was increased with N addition, but no increasingunder higher N concentration. However, NUE was decreased with N addition and treatment oftime. In the early time, RAR of S.superba was decreased under P deficiency; however, it wasincreased with the treatment time and seedlings age. The PAE, leaf P content and PUE of rootwere increased also, which means aged seedlings enhanced ability to adapt to the evilenvironment and increased the anti-barren capacity.5. Effects of simulated N deposition on growth and development of different provenancesof S.superbaUnder N deposition, the growth of different provenances was showed as:ZJLQ>FJJO>FJGT>HNGY>JXXF and ZJHZ. The ZJHZ provenance in the northern edge ofthe producing areas had stronger photosysthetic capacity. The shoot growth was increasedunder low concentration of N deposition and the leaf pigment and solube protein contentincreased. But the assimilation was not easy to accumulate and the root growth was slow. Thephotosynthesis of ZJHZ provenance was reduced under higher N concentration. The respirationcontinued increasing and shoot growth was reduced, whereas root was rapid developed. TheZJLQ and FJJO provenances in the central and southern central areas had strongerphotosynthetic ability and lower respiratory consumption, so the assimilation was easier toaccumulate and more adaptive to N deposition. Under low concentration N deposition,the>0.5mm diameter root growth was growth fast and root had stronger development. Thephotosynthetic ability was increased with N addition. The aboveground grown strongly andhad largest productivity under100N deposition, while the respiration was largest, so thebiomass could not accumulated and the production was lowest under200N deposition. Theaboveground growth of FJGT, JXXF and HNGY from southern sub-centers producing areashad similar performance as ZJHZ, such as lower photosynthetic capacity, moderate respirationand lower biomass accumulation. The root growth of these provenances was slow and even inhibited under N deposition. In addition, the provenances in the high altitudes had a developedroot system but a poor shoot growth because of the barren site and low temperatures in thatareas. N addition promoted root growth of these provenances and changed the root intothinning. The provenances in the low-altitude had better site environment, which has amplewater and fertilizer and suitable temperature. The suitable environment resulted in lessdeveloped root system and vigorous shoot growth. The root turn to be thicker and strongerunder N deposition and N and P absoption efficiency increased, so there was more dry matteraccumulated.更多还原