Studies on Rubber (<i>Hevea brasiliensis</i>) Trees Exist Plant Type after Planting and Available Tapping Tree of Rubber Plantation in China

Existing plant types of rubber tree after planting and available tapping tree were investigated, and there were about 28 rubber plantations with different tapping years of 8 varieties “CATAS7-33-97”, “CATAS8-79”, “CATAS7-20-59”, “PR107”, “RRIM600”, “GT1”, “INA873”, “93-114”in South China. The results showed that there were six kinds of existing plant types of rubber tree after planting of rubber plantations, which were available tapping trees, wind damaged trees, cold damaged trees, tapping panel dryness trees, absent trees and weak trees, respectively. These data investigated also showed rubber trees under available tapping, stoppage due to tapping panel dryness, absence, wind damage, cold damage and weakness were counted and calculated and made up for 72.21%, 14.75%, 5.61%, 3.86%, 2.68% and 1.89%. Tapping panel dryness trees, wind damage and absent trees are major factors for the loss of tapping rubber trees in the rubber plantations. Of these investigated varieties, available tapping trees per 100 trees of rubber plantation of “PR107”at the 1st, 12th, 14th, 16th, 20th, 24th tapping year were 96, 67, 70, 75, 66, 46 trees in Hainan planting zone, respectively. Available tapping trees per 100 trees of rubber plantation of “RRIM600”at the 9th, 15th, 20th, 22nd tapping year were 88, 62, 55, 36 trees in Yunnan planting zone, respectively. Available tapping trees per 100 trees of rubber plantation of “93-114” at the 10th, 19th, tapping year were 94, 62 trees in Guangdong planting zone. These results showed that available tapping trees of rubber plantation decreased with increasing tapping age under different planting zones in China.

Evaluation of unconstrained and constrained mathematical functions to model girth growth of rubber trees (Hevea brasiliensis) using young agemeasurements

No attempt has been made to date to model growth in girth of rubber tree （Hevea brasiliansis）. We evaluated the few widely used growth functions to identify the most parsimonious and biologically reasonable model for describing the girth growth of young rubber trees based on an incomplete set of young age measurements. Monthly data for girth of immature trees （age 2 to 12 yearsi from two locations were sub- jected to modelling. Re-parameterized, unconstrained and constrained growth functions,of Richards （RM）, Gompertz （GM） and the monomo- lecular ＇model ^（MM） were fitted to data. Duration of growth was the firsf constraint introduced. In the stagel We attempted a population aver- age （PA） model to capture the trend in growth. The best PA model was fitted as a subject specific （SS） model. We used appropriate error vari- ance-covariance structure to account for correlation due to repeated measurements over time. Unconstrainecl functions underestimated the asymptotic maximum that did not reflective carrying capacity of the locations. Underestimafions were attributed to the partial set＇ of meas- urements made during the early growth phase of the trees. MM proved superior to RM and GM. In the randomcoefficient models, both Gf and Go appeared to be influenced by tree level effects. Inclusion of diagonal definite positive matrix removed the correlation between random effects. The results were similar at both locations. In the overall assessment MM appeared as the candidate model for studying the girth-age relationships in Hevea trees. Based on the fitted model we conclude that, in Hevea trees, growth rate is maintained at maximum value at to, then decreases until the final state at dG/dt 〉 0, resulting in yield curve with no period of accelerating growth. One physiological explanation is that photosynthetic activity in Hevea trees decreases as girth increases and constructive metabolism is larger than destructive metabolism.

Preliminary Study on Seedling Growth Rhythm and Grey Correlation Analysis of Rubber (Hevea brasiliensis) Seedlings in Danzhou District, Hainan

The rubber tree physiological and ecological process quantitatively described by using mathematical method is an important means to the analysis of rubber tree growth process and mechanism. The study on growth simulation model of rubber tree will lay the foundation for the application of rubber tree cultivation intelligent decision system. A Richards equation was formulated to describe the height and stem diameter growth dynamics of the annual rubber seedlings. An area correlation analysis was done according to the closeness of the observed parameters to the dynamic curve on the gray system composed of the seedling growth increment and the meteorological factors including aerial temperature, precipitation and solar radiation hours that influence upon the seedling growth. The results showed that rubber seedling response fitted the Richards equation quite well. The growth increment displayed a distinct alternation of 'slow—fast—slow— fast—slow' rhythm. The growth course of the seedlings might be partitioned into three periods of time by the sequential clustering analysis, namely pre-growing, fast-growing, late-growing stage. The tray correlation analysis revealed that air temperature had the most significant influence while precipitation had the least impact on height growth of the rubber seedlings. In conclusion, the air temperature had the most significant influence while solar radiation hours had the least impact on stem diameter growth of the rubber seedlings.

Seasonal Changes Impact on Growth of Rubber (<i>Hevea brasiliensis</i>) Seedlings under Different Cultivation

The vegetative growth of rubber tree is an important basis for rubber tree cultivation and economic management. Stem diameter and height growth patterns of rubber seedlings and the seasonal variability are still poorly understood. Studying the annual growth patterns and seasonal variation of rubber seedling will help understanding biological characteristics of rubber tree and provide a reference for field cultivation and management. Height growth and stem diameter of field-sown rubber seedlings cultivation and polybag-raised cultivation all displayed a distinct annual pattern of “slow-fast-slow”. Height growth and stem diameter growth response fitted the logistic equation preferably, supporting the observed pattern. Fast-growth of plant height for polybag-raised rubber seedlings cultivation and field-sown rubber seedlings cultivation occurred from June to November and May to November, respectively. This period saw the greatest accumulations of plant height growth for polybag-raised rubber seedlings cultivation and field-sown rubber seedlings cultivation accounting for 83.99% and 86.65% of total growth, respectively. Fast-growth of stem diameter for polybag-raised rubber seedlings cultivation and field-sown rubber seedlings cultivation occurred from June to November and May to November, respectively. This period saw the greatest accumulations of stem growth for polybag-raised rubber seedlings cultivation and field-sown rubber seedlings cultivation accounting for 86.71% and 84.60% of total growth, respectively. Polybag-raised rubber seedlings cultivation and field-sown rubber seedlings cultivation for the whole year had nine extension units and each month had one extension unit from May to November. Extension unit of for the whole year did not stop period and plant height growth rate has the seasonal difference. However, leaf phenophase of field-sown rubber seedlings cultivation was earlier than that of polybag-raised rubber seedlings cultivation and each extension unit of field-sown rubber seedlings cultivation was greater than that of poly-bag-raised rubber seedlings cultivation. The precipitation had the greatest impact on seedlings growth under different cultivation. There was no period annually in which height growth and stem diameter growth did not occur and the fastest growth occurred during the rainy season. Plant height and stem diameter of rubber seedlings under different cultivation showed isogony phenomenon. Extension unit and leaf phenophase of polybag-raised rubber seedlings and field-sown rubber seedlings showed consistency and synchronization characteristic. Different cultivation of rubber seedling should take corresponding measures tending management and operation.

Characteristics of Soil Organic Carbon and Total Nitrogen in Rubber Plantations Soil at Different Age Stages in the Western Region of Hainan Island

[Objective]The aim was to study on the characteristics of soil organic carbon and nitrogen in rubber （Hevea brasiliensis Muell-Arg） plantations at different age stages in the western region of Hainan Island,so as to evaluate the ecological benefits of rubber plantations and provide basic data for studying the effect of tropical land utilization/cover change on the global carbon and nitrogen cycle. [Method]The situs was in Danzhou city,western region of Hainan Island,and the samples were four kinds of rubber plantations soil at different ages and one kind of control check （pepper,Piper nigrum L.） soil. In this research,four quadrats were set up in each sample,and the size of each was 20 cm×20 cm. Four specimens were gathered from four layers of 0-15,15-30,30-45,45-60,and the average of them was the last analysis result of each sample. Soil density was measured by cutting ring method,soil containing and hygroscopic water was detected by oven drying method,soil organic carbon （SOC） was measured by low temperature heated outside potassium dichromate oxidation-colorimetry method,and soil total nitrogen （STN） was detected by semimicro Kjeldahl method. [Result]SOC contents of different layers in rubber plantations soil at different age stages （including the CK pepper soil,the same as below） varied little,and the content of SOC in surface layer （0-15 cm） was higher,while the underlayer （45-60 cm） was lower than the average value; there was significant difference in SOC content among different kinds of soil,and the content was of 6.03-7.78 g/kg,tapping young trees （7 years） CK pepper mature age trees （30 years） prophase of young trees （2 years） tapping trees （16 years）; there was no significant difference in SOC storage among different kinds of soil,and the storage was of 61.33-74.29 t/hm2,mature age trees （30 years） tapping young trees （7 years） prophase of young trees （2 years） CK pepper tapping trees （16 years）; there was significant difference in STN content among rubber plantations soil at different age stages,the content was of 410.86-664.14 mg/kg2,CK pepper tapping young trees （7 years） prophase of young trees （2 years） mature age trees （30 years） tapping trees （16 years）,and STN content of tapping trees （16 years） soil was extremely lowest; there was significant difference in C/N ratio among different kinds of soil,the ratio was of 10.94-14.47,and the ratio of tapping trees （16 years） mature age trees （30 years） tapping young trees （7 years） CK pepper prophase of young trees （2 years）. [Conclusion]There wasn＇t unhealthy effect of rubber trees planted in tropical area on the content and storage of SOC,the content of STN and the ratio of C/N. there was no significant difference between rubber plantations and CK pepper soil,and the effects of rubber plantation on soil carbon-nitrogen was similar to that of other tropical crops （such as pepper）.

Visualization Analysis of the Impact of Rubber Agroforestry Ecosystem on Soil Microbial Community

Rubber agroforestry systems positively impact soil microbial communities. This study employed a bibliometric approach to explore the research status, hotspots, and development trends related to these effects. Using CiteSpace software, we visually analyzed research literature from the Web of Science (WOS) core database, spanning 2004 to 2024. The focus was on the impact of rubber agroforestry ecosystems on soil microbial communities. The results indicate significant attention from Chinese researchers, who have published numerous influential papers in this field. Authors Liu Wenjie have contributed the most papers, although no stable core author group exists. The Chinese Academy of Sciences is the leading research institution in terms of publication volume. While there is close collaboration between different institutions and countries, the intensity of researcher cooperation is low. The most cited literature emphasizes soil nutrients and structure in rubber agroforestry, laying a foundation for soil microorganism studies. Most cited journals are from countries like Netherlands and the United Kingdom. Key research areas include the effects of rubber intercropping on soil microbial communities, agroforestry management, and soil health. Research development can be divided into three stages: the initial stage (2010-2015), the development stage (2015-2020), and the mature stage (2020-2024). Current studies show that rubber intercropping and rubber-based agroforestry systems enhance soil microbial communities, positively impacting soil health. This paper provides a theoretical basis for the sustainable development of rubber agroforestry systems and improved management plans. Future research could explore the effects of species composition on soil microbiological characteristics and develop methods for species interactions. An in-depth study of the soil microbial community’s structure and function, and its relationship with rubber trees, is crucial. Developing effective, rationally designed rubber agroforestry systems and underground soil microbiome technology will promote sustainability and improve plantation productivity.

An Analysis of the Patents concerning Hevea brasiliensis

This paper mainly analyzes the application data of patents concerning Hevea brasiliensis in the world and China from the perspectives of time,research field,and the geographical distribution of applicants. It also interprets the patents for invention in China from time,research field,and types of applicants. Based on the study,it shows that although the patent applications fluctuate,the general trend is rising. And the patents are mostly concentrated in plant protection,and agricultural biotechnology. The Chinese applicants of patents for invention largely work in the research institutes,and most of these patents focus on the field of plant protection,agricultural biotechnology,and agro-processing.However,the foreign applicants mainly work in companies,and most of these patents only focus on plant protection. These findings will provide a reference for formulating development policies about natural rubber industry in China.

Exploration and Practice of Rubber Based Agroforestry Complex Systems in China

Agroforestry ecosystems are constructed by simulating natural ecosystems, applying the principles of symbiosis in nature, and organizing multiple plant populations to coexist, while conducting targeted cultivation and structural control scientifically. Rubber agroforestry complex ecosystems aim for sustainable development in terms of industry, ecology, resource utilization, and the livelihoods of producers. Rubber agroforestry complex ecosystems create a complex production structure system that integrates biology, society, and the economy through species combinations. Rubber trees and associated biological components coordinate with each other, mutually promote growth, and yield a variety of products for producers. Cultivation techniques and patterns of rubber agroforestry are essential components of these ecosystems. This study analyzes the production practices of rubber agroforestry complex cultivation, with a focus on the development and characteristics (complexity, systematicity, intensity, and hierarchy) of rubber agroforestry systems using a literature analysis and a survey approach. It explores the types and scales of complex planting, specifications and forms, and major effects of complex cultivation. This study identifies successful rubber agroforestry cultivation patterns and practical techniques, as well as the potential benefits of developing rubber agroforestry cultivation. It also points out the shortcomings in the development of complex planting, including an emphasis on production practices but insufficient theoretical research, a focus on production but inadequate attention to the market, and an emphasis on yield while overlooking the improvement of standards, brands, and added value. There are various complex patterns for young rubber plantations, but relatively fewer for mature plantations. Based on this analysis, this study suggests that future efforts should focus on in-depth research on interspecies and environmental interactions in rubber agroforestry ecosystems, clearly define key roles, accelerate the innovation of development patterns, and strengthen the foundation for development. It recommends promoting and demonstrating successful rubber agroforestry complex patterns and providing technical training, developing product branding for rubber agroforestry patterns, enhancing product value, expanding the application functions of rubber-forest mixed crop products, and establishing a stable and sustainable industry chain. This study provide practical experience and theoretical insights in rubber agroforestry complex systems from China the potential to enrich the knowledge of rubber agroforestry composite systems, provide practical experience to improve the operating income of smallholders, and even promote the sustainable development of rubber plantations.

巴西橡胶树大、小橡胶粒子在乙烯调控天然橡胶合成中的作用分析

巴西橡胶树(Heveabrasiliensis)是重要的产胶植物,胶乳中的橡胶粒子(RP)是合成天然橡胶的重要细胞器,但其响应外源乙烯刺激调控天然橡胶合成的具体机制还不清楚。为了明确不同大小RP在此过程中的作用,本研究通过分离外源乙烯刺激后胶乳中不同直径的RP,并与对照组进行差异蛋白质组学分析。结果发现:在直径较大的大橡胶粒子(LRP)中鉴定出响应乙烯刺激差异蛋白37个,分别参与天然橡胶合成、糖酵解/糖异生、碳代谢及氨基酸生物合成等代谢通路,其中包含4个REF/SRPP家族成员;在直径较小的小橡胶粒子(SRP)中鉴定出56个差异蛋白,分别参与内质网中的蛋白质加工、内吞及剪接体等代谢通路,其中包含5个REF/SRPP家族成员。关键差异蛋白REF138具有较多等电点(pI)和分子量不同的蛋白亚型,LRP中低于标准等电点(4.80)的REF138亚型响应乙烯刺激积累减少,高于标准等电点的REF138亚型响应乙烯刺激积累增加;与LRP不同,SRP上有更多的REF138亚型响应乙烯刺激发生变化,具有标准分子量(14.7kDa)的REF138亚型响应乙烯刺激积累增加,高于标准分子量的亚型响应乙烯刺激积累减少。针对关键差异蛋白的互作蛋白功能分析发现,REF/SRPP家族成员REF138、REF175、REF258、SRPP117及SRPP204间存在相互作用,可能形成蛋白复合体结合在RP上。除REF/SRPP家族成员外,REF138的互作蛋白主要参与剪接体及内吞代谢通路,REF258的互作蛋白主要参与脂代谢过程与次生代谢产物合成调控。综上,通过对LRP及SRP上响应乙烯刺激差异蛋白及其互作蛋白的功能分析初步揭示了LRP和SRP响应外源乙烯刺激调控天然橡胶合成的代谢调控机制。

海南热研73397等5个橡胶树品种全年割胶周期生胶质量变化

天然橡胶的质量和性能与橡胶树品种、割胶生产、气象、物候等遗传和环境因素密切相关。为了探明橡胶树不同品种之间及4—12月全年割胶周期内生胶质量的差异与变化规律,本研究分析比较了PR107、RRIM600、热研917、热研73397和热研879等5个橡胶树品种胶乳所制备生胶的质量,并分析了各品种5月份胶乳所制备生胶的硫化特性和硫化胶的力学性能。结果表明:5个橡胶树品种生胶的门尼黏度值、氮(蛋白质)含量、挥发物含量、P0和PRI值等在4—12月全年割胶周期内表现出增加或下降的趋势,这些质量指标既反映出橡胶树品种间的基因型差异,又表现出受气象等环境因素变化的影响。其中,4个品种12月生胶的蛋白质含量均超过3.0%;热研917混炼胶的硫化特性与其他4个品种有明显差异;在S/2 d/3割制下,热研879硫化胶的拉断伸长率和拉伸强度最小。本研究结果一方面有助于指导橡胶树品种选育和割胶生产,另一方面也可以为高性能天然橡胶生产加工提供科技支撑。

6个橡胶树新品种在德宏州的区域性试验研究

为筛选出适宜德宏植胶区的橡胶树新品种,引进了热研879、热垦628、热研73397、IAN873、热垦525、湛试32713这6个橡胶树新品种,在瑞丽市进行生产性试种,并对引进品种的茎围、产量、干胶含量、死皮率、抗寒性等指标进行了评价。结果表明:(1)开割前热垦628、热研73397、IAN873的茎围增粗表现较好,第8年达开割标准;开割后湛试32713,热垦628、热研73397和热垦525的茎围平均净增粗较高、速生特性好。(2)平均株次干胶产量表现为热研879极显著高于对照,热垦628显著高于对照;单位面积干胶产量以热垦628与热研879较高,均与对照之间差异极显著;热垦628的平均干胶含量较低,显著低于对照,其他品种与对照之间差异不显著。(3)死皮率表现为热垦628>湛试32713>IAN873>热研879>热研525>云研77-4(CK)>热研73397,4、5级死皮率表现为热垦525>热垦628>热研73397>IAN873>热研879>湛试32713>云研77-4(CK)。(4)热垦628和湛试32713的抗寒性表现较好,IAN873、热研879和热垦525的抗寒性表现较差。鉴于6个橡胶品种在德宏州种植的综合表现,立地环境较好林段可优先选择种植高产品种热研879,以往有轻微寒害发生的林段可选择高产抗寒品种热垦628。

植物激素调控橡胶树产排胶机制研究进展

巴西橡胶树(Hevea brasiliensis)是重要热带经济作物之一,其次生代谢产物天然橡胶(NR)是中国重要的工业原料及战略物资。植物激素对植物生长发育、萌发和环境应答等多方面均具有重要调控作用。本文详细介绍了乙烯、脱落酸、油菜素内酯和赤霉素4种植物激素在橡胶树生长发育、橡胶生物合成、产排胶和品质形成等关键环节中应用的研究进展,并展望4种激素在提高橡胶树产排胶机制研究中的应用前景,为支撑橡胶产业发展提供理论支撑。

机械割胶装备切割仿形机构设计与试验

割胶是收获胶乳的重要途径,传统人力割胶技术专业性强且难度大,劳动强度高,近十年,机械采胶装备研发已成为破解产业掣肘的重要方向。为进一步提高割胶机械的割胶质量和工作平稳性,减少机械割胶伤树,按照传统人工割胶方式建立橡胶树割面的割胶轨迹方程,设计一种由导向器、割胶刀体、斜度装配体等部件组成的能够限深限厚的切割仿形机构。分析导向器、割胶刀体、斜度装配体等关键部件在割胶过程中的理论受力,并以手持式自动割胶机为试验本体,对设计的仿形切割机构开展大田割胶试验。结果表明:使用切割仿形机构割胶,更加贴合割面和割线,能够沿割胶轨迹切割出条状树皮,能够进行限深限厚仿形切割,减少伤树,切割平均负载电流稳定在1.0~1.5 A,与传统割胶模式相比,耗皮量比设置的上限值平均降低约10%,割胶深度约增加8%,验证切割仿形机构的设计,满足割胶技术要求。为天然橡胶产业机械化、智能化割胶装备关键切割部件的研发提供参考。

4个引进橡胶树胶木兼优品种比较试验

为了能够客观地筛选出适合我国植胶环境的橡胶树胶木兼优新品种,基于品种比较试验对4个国外引进品种‘热试09-5’‘热试09-6’‘热试09-7’和‘热试09-10’的产量及副性状进行综合评价。结果表明,4个参试品种中,‘热试09-7’表现出速生性状,4个参试品种的产量特性不明显,仅‘热试09-5’在开割第1年与对照相当,其他年份均低于对照。胶乳生理参数分析结果表明,‘热试09-5’的干胶产量、排胶初速度与对照差异不显著,而蔗糖含量低,硫醇含量高,认为该品种产胶潜力大,胶乳稳定性好,排胶快,糖利用率高。‘热试09-6’原生皮厚度较厚,树皮中乳管列数多,与‘RRIM600’相比,干胶含量、堵塞指数高,排胶初速度和蔗糖含量差异不显著,认为该品种有较好的产胶潜力,但胶乳代谢强度低,可考虑通过刺激提高代谢强度,达到增产的目的;各参试品种的生胶性能、硫化胶的物理机械性能及分子量和分子量分布差异分析结果表明,不同指标参数在品种间存在差异,‘热试09-5’的塑性初值最低,塑性保持率最大,‘热试09-6’门尼粘度最高,‘热试09-5’最低,‘热试09-7’有较大的重均分子量,呈现出较好的物理机械性能。在抗逆性表现方面,‘热试09-5’的风害断倒率最小,‘热试09-10’最高;抗寒前哨数据结果表明,在对照品种‘93-114’无寒害发生的情况下,‘热试09-5’寒害等级为1.00,‘热试09-7’为0.17。综合分析表明,4个引进品种的速生性状明显,‘热试09-6’有较好的产胶潜力,‘热试09-5’的抗风性优于对照,‘热试09-7’的寒害适应能力较好。综上表明‘热试09-6’综合性状较好,适合在海南中西部轻风区生产性试种。

化肥减施下橡胶树有机肥替代用量研究

为实现橡胶树种植化肥减量增效的目的,在云南东风农场橡胶林开展不同有机肥替代化肥用量试验研究。结果表明:与单施配方肥相比,有机肥替代提高了土壤pH值及团聚体、有机质、全氮、有效氮含量。其中,60%配方肥+15 kg有机肥处理的pH、有机质、水解氮、团聚体指标显著高于单施配方肥处理,但有效磷、速效钾含量与单施配方肥处理差异不显著;叶片N、P、K、Mg养分含量与单施配方肥处理相当;年增产干胶5%,减少配方肥投入144 kg·hm^(-2)。通过综合评价,推荐60%配方肥+15 kg有机肥为橡胶树有机肥替代化肥的最佳用量。

橡胶/香露兜间作对香露兜香气成分的影响

香露兜是中国热带地区特色香料作物之一,其叶片香气成分含量是鉴定香露兜品质的关键指标。香露兜适宜在遮阴条件下种植,其中在橡胶林下间作香露兜是海南地区常见的栽培模式,但橡胶间作香露兜后对香露兜叶片香气成分的影响仍未探明。本研究拟通过盆栽试验,对比橡胶/香露兜间作处理和香露兜单作条件下土壤理化性质和香露兜叶片香气成分种类与含量的差异。结果表明,橡胶/香露兜间作处理与香露兜单作相比,显著提高土壤容重13.63%,土壤碱解氮含量59.71%,土壤速效磷含量193.03%、土壤速效钾含量9.78%,土壤pH降低1.00(P<0.05);间作和单作处理共检测出10类68种香气成分,间作与单作相比,酮类、呋喃类、呋喃酮类、烃类和酚类的物质种类数量分别减少56.52%、14.29%、33.33%、20.00%、28.57%(P<0.05);尽管呋喃类、烃类和酮类的香气成分含量分别显著减少65.28%、20.88%和69.00%,但醇类、呲咯类、酯类和呋喃酮类香气成分含量分别增加31.50%、597.56%、122.78%、96.89%(P<0.05)。土壤pH降低是香露兜叶片酮类、呋喃类、呋喃酮类、烃类和酚类香气成分组成减少的主要原因;间作模式通过降低pH、提高土壤速效磷和碱解氮含量显著提高醇类、呲咯类、酯类含量,减少呋喃类、烃类含量;吡咯类物质是香露兜叶片主要香气成分物质,因此,橡胶/香露兜间作模式显著促进香露兜香品质提升。研究结果对优化和推广橡胶间作香露兜具有积极作用,有助于促进胶农增收以及相关产业的可持续发展。

Divergent DNA Methylation Patterns Associated with Abiotic Stress in Hevea brasiliensis

Cytosine methylation is a fundamental epigenetic mechanism for gene-expression regulation and development in plants. Here, we report for the first time the identification of DNA methylation patterns and their putative relationship with abiotic stress in the tree crop Hevea brasiliensis （source of 99% of natural rubber in the world）. Regulatory sequences of four major genes involved in the mevalonate pathway （rubber biosynthesis pathway） and one general defense-related gene of three high-yielding popular rubber clones grown at two different agroclimatic conditions were analyzed for the presence of methylation. We found several significant variations in the methylation pattern at core DNA binding motifs within all the five genes. Several consistent clone-specific and location-specific methylation patterns were identified. The differences in methylation pattern observed at certain pivotal cis-regulatory sites indicate the direct impact of stress on the genome and support the hypothesis of site-specific stress-induced DNA methylation. It is assumed that some of the methylation patterns observed may be involved in the stress-responsive mechanism in plants by which they adapt to extreme conditions. The study also provide clues towards the existence of highly divergent phenotypic characters among Hevea clones despite their very similar genetic make-up. Altogether, the observations from this study prove beyond doubt that there exist epigenetic variations in Hevea and environmental factors play a significant role in the induction of site-specific epigenetic mutations in its genome.

Temporal Changes of Ecosystem Carbon Stocks in Rubber Plantationsin Xishuangbanna; Southwest China

Rubber(Hevea brasiliensis) plantations have been expanded rapidly in tropical regions of Southwest China and cover more than20% of land area in Xishuangbanna.Several studies have addressed changes of soil C stocks in rubber plantations;however,estimates of total ecosystem C stocks and their temporal changes in rubber plantations have been inadequately studied.This study calculated C stocks in soil,biomass,litter,and dry rubber(latex),and estimated the total ecosystem C stocks of rubber plantations in an age sequence of 3-,7-,9-,21-,27-,and 34-year-old in Xishuangbanna,Southwest China.The total C stocks in rubber plantations ranged from 150.3 to 283.7 Mg C ha^(-1),with a mean of 213.4 Mg C ha^(-1).The plantations≤9-year-old had significantly lower(P<0.05)total C stocks than those older than 9 years.Carbon stocks in soil(mass equivalent) were between 107.1–170.5 Mg C ha^(-1) and in living biomass were between 2.8–95.7 Mg C ha^(-1),representing the largest and the second largest C components in a rubber plantation ecosystem.Neglect of dry rubber C stock resulted in an underestimate of 7.8%–14.2% of the total C stock in the rubber plantations older than 9 years,which was much larger than the contribution of litter C stock(less than 2%).

In vitro Transient Expression System of Latex C-serum was used for Analysis of Hevein Promoter in Response to Abscisic Acid in Hevea brasiliensis

Hevein has been found to be an essential element in coagulation of rubber particles in latex of rubber trees. In a previous study, we cloned a 1 241-bp fragment of a 5＇ upstream region of the hevein gene by genome walking. This fragment was analyzed by a 5＇ end nested deletion method in the present study, fused with a uidA （gus） gene to produce a series of tested constructs, which were transferred into C-serum of latex and the Gus activities were detected. Results showed that the fragment from -749 to -292 was sufficient for expression of gus gene in latex, and the fragment from -292 to -168 was crucial in response to abscisic acid inducement. In a transient transgenic test of rubber leaf with particle bombardment, construct Hev749 conferred gus-specific expression in veins, in which the latex tubes mainly distributed. This implies that the fragment from -749 to -292 was laticiferous-specific.

橡胶林生态系统干季微气候特征和通量的初步观测

应用微气象法中的梯度观测系统、涡度相关系统和闭路水汽-CO2廓线系统,使用设置在海南省西部儋州地区一片刚开割的橡胶林中观测铁塔上的观测仪器所得的干季7个晴好天气的微气候观测数据和通量观测数据,对其微气候特征和通量特征进行初步分析研究。结果表明:(1)橡胶林的辐射通量与光合有效辐射(photosynthetically active radiation,PAR)呈明显的昼夜交替变化;橡胶林林内和林冠上风速昼夜变化明显,风向则多为东北风(15°～40°);林冠上方气温和树冠面表温具有显著的日变化特征,树冠表温日变化幅度大于气温;相同时刻干季橡胶林林冠上方和林冠内湿度和水汽压相差不大;林冠内CO2浓度夜高昼低;土壤温度日变化明显,土壤含水量变幅较小。(2)林冠上方显热通量与潜热通量变化趋势相同,显热通量小于潜热通量;净辐射通量日变化呈规则的倒"U"形,主要由下行短波辐射决定;土壤热通量存在日变化,随土层深度增加变化变小;CO2通量随光合有效辐射发生日变化;水汽通量随净辐射发生日变化。