【作者】 张立华；

【导师】 林益明；

【作者基本信息】 厦门大学 ， 植物学， 2009， 博士

【摘要】 木麻黄是滨海沙地上重要的防护树种。本研究选择福建东山的短枝木麻黄作为研究对象，探讨了不同海岸梯度对其小枝发育和衰老过程中单宁含量、氮磷含量、N：P比和养分内吸收率的影响以及单宁含量的季节动态；并选择自然条件下对木麻黄生长影响较大的几个生态因子(养分、水分、pH值)进行控制实验，系统探讨不同生态因子及其交互效应对短枝木麻黄单宁形成的影响，以验证关于次生物质形成的不同假说，进一步揭示植物单宁的形成机制。研究结果表明：1．海岸带梯度对短枝木麻黄衰老小枝养分和单宁含量具有显著影响，基干林带短枝木麻黄衰老小枝养分含量显著高于后沿林带，而各种单宁含量和养分内吸收率则显著低于后沿林；海岸梯度对幼嫩、成熟小枝养分和单宁含量没有显著影响。2．首次利用成熟小枝的N：P比来指示短枝木麻黄林分的营养限制状况，各海岸带梯度上成熟小枝中的N：P比均高于28，表现为磷限制，相应地木麻黄小枝衰老过程中磷内吸收率显著高于相应海岸梯度上的氮内吸收率。同时，养分胁迫可能是导致木麻黄高单宁含量的重要原因之一。3．首次对短枝木麻黄小枝单宁和氮含量的季节动态进行了研究。不同季节幼嫩和成熟小枝总酚、可溶性缩合单宁和蛋白质结合能力显著高于衰老小枝；而衰老小枝蛋白质结合缩合单宁显著高于幼嫩和成熟小枝。幼嫩和成熟小枝在夏季总酚含量最高，而总缩合单宁含量最低。氮在幼嫩小枝中的含量最高，并随着小枝的成熟和衰老而降低，且最低值均出现在夏季，而氮内吸收率(51．01±3．94％～63．00±8．61％)在不同季节间的差异不显著。短枝木麻黄小枝中总酚与氮含量存在显著负相关，而总缩合单宁与氮含量存在显著的正相关。衰老小枝中较高的总缩合单宁与氮的比率(TCT：N)能够降低凋落物的分解率，从而延缓凋落物中养分的释放，是短枝木麻黄重要的养分保存机制之一。4．在养分效应的控制实验中，施加氮肥使短枝木麻黄幼苗小枝中总酚、可溶性缩合单宁含量显著降低，而促进了可溶性糖的形成，但对养分含量没有显著影响，从而导致总酚与氮的比率(TP：N)和可溶性缩合单宁与氮的比率(ECT：N)降低；施加磷肥对总酚和可溶性缩合单宁含量没有显著影响，但促进了淀粉、叶绿素、类胡萝卜素的合成和对养分的吸收。5．在养分和pH效应的控制实验中，短枝木麻黄幼苗小枝总酚和可溶性缩合单宁含量随着氮肥的施加而显著降低，氮含量和ECT：N与施加氮肥的水平也存在显著的负相关；施加磷肥对总酚和可溶性缩合单宁含量没有显著影响；随着pH值的升高，总酚含量显著升高，可溶性缩合单宁含量没有显著变化，而淀粉、叶绿素a、叶绿素a／b、类胡萝卜素和氮磷含量显著降低，因而TP：N和ECT：N水平均显著升高。6．在养分和水分效应的控制实验中，施加氮肥和磷肥对短枝木麻黄幼苗小枝总酚和可溶性缩合单宁含量均具有显著影响，且总酚和可溶性缩合单宁含量随着氮肥和磷肥水平的升高而降低；水分胁迫导致总酚和可溶性缩合单宁含量显著升高。在控制实验中，随着处理时间的延长，短枝木麻黄幼苗小枝总酚含量升高而可溶性缩合单宁含量降低；施加氮肥使小枝中的总酚和可溶性缩合单宁含量均降低，支持碳氮平衡假说和生长分化平衡假说；总酚和可溶性缩合单宁与营养物质的关系相反，表明不同类型的单宁存在不同的合成途径，但由于总酚和可溶性缩合单宁均与氮含量没有显著的相关性，故不支持蛋白质竞争模型；TP：N和ECT：N的水平在养分缺乏和干旱条件下较高，有利于提高短枝木麻黄的防御水平和降低凋落物的分解率，减少养分的损失，从而保持较高的生产力。更多还原

【Abstract】 Casuarina equisetifolia is an important shelter tree in coastal sandy areas.Changesin the N and P concentrations,N:P ratios and tannin content in C.equisetifoliabranchlets during development and senescence across a coastal gradient,and seasonalchanges in tannin content were studied at Chishan Forestry Center of DongshanCounty,Fujian Province,China.In addition,the effects of fertility,pH and soilmoisture on tannin contents of C.equisetifolia seedlings were discussed in a sandculture system,so as to find proof about secondary metabolism production.The results showed as follows:1.Nutrients and tannin contents of C.equisetifolia branchlets varied significantly inresponse to changes in a coastal gradient.Nutrient contents of senescent branchlets atseaward sites were higher,while tannin contents and nutrient resorption efficiencywere lower than those at inland sites.The coastal gradients have no significant effectson nutrient and tannin contents of young and mature branchlets.2.N:P ratios of mature branchlets was firstly used to indicate the nutrient limitationin C.equisetifolia forests.Based on N:P ratios(above 28),C.equisetifolia forestswere P-limited.Accordingly,phosphorus resorption efficiency was higher thannitrogen resorption efficiency of corresponding coastal gradient.Nutrient deficiencymay be one of the important reasons for high tannin levels in C.equisetifolia.3.The seasonal variation of tannin and nitrogen contents of C.equisetifoliabranchlets at different developmental and senescent stages were studied firstly.Indifferent seasons,total phenolics(TP),extractable condensed tannins(ECT) contentand protein precipitation capacity(PPC) in young and mature branchlets were higherthan those in senescent branchlets,but protein-bound condensed tannins(PBCT) weresignificantly higher in senescent branchlets than in young and mature branchlets.Thehighest of TP in young and mature branchlets occurred in summer,when TCT contentwas lowest.Nitrogen content in young branchlets was highest,and decreased withmaturity and senescence.The lowest of nitrogen content also was in summer,but thenitrogen resorption efficiency(51.01±3.94% to 63.00±8.61%) didn’t change withseason.In this study,TP contents were inversely related to N contents.However,therewas a positive correlation between TCT and N contents.The high TCT:N ratios in senescent branchlets was one of the important nutrient conservation strategies for C.equisetifolia.4.In fertilized soil treatment plots,TP and ECT contents of branchtets of C.equisetifolia seedlings decreased,soluble sugars increased,while nutrient contentschanged little with nitrogen fertilizer addition.TP:N and ECT:N ratios decreased.TPand ECT contents remained stable,while starch,chlorophyll,carotenoid and nutrientcontents increased with phosphorus fertilizer addition.5.In pH and fertilized soil treatment plots,TP and ECT contents significantlydecreased with nitrogen fertilizer addition.Nitrogen contents and ECT:N ratios werealso inversely related to levels of nitrogen fertilizer.Phosphorus fertilizer applicationhas no significant effects on TP and ECT contents.TP contents increased,and ECTcontents remained unchange with the increasing of pH.But starch,chlorophyll a,chlorophyll a/b ratios,carotenoid and nutrient contents decreased significantly,Accordingly,TP:N and ECT:N ratios significantly increased.6.In moisture and fertilized soil treatment plots,nitrogen and phosphorus fertilizerhave significant effects on TP and ECT contents of branchlets of C.equisetifoliaseedlings.TP and ECT contents decreased with nitrogen and phosphorus fertilizeraddition.TP and ECT contents increased under drought-stressed conditions.In controlled experiments,TP contents increased,and ECT contents decreased withprolonged treatment time.Both TP and ECT contents decreased with nitrogenfertilizer addition.This pattern lends to support source-sink hypotheses such as thecarbon-nutrient balance(CNB) hypothesis and the growth-differentiation(GDB)hypothesis.The discrepancy of relationship between nutrition with TP or ECT showedthat the biosynthetic route of different tannins were different.In this study,nosignificant correlation between TP and N,or ECT and N did not support proteincompetition model(PCM).TP:N and ECT:N ratios were higher under nutrientdeficiency and arid conditions,which was one of the important nutrient conservationstrategies for C.equisetifolia.更多还原