Effect of slope position on leaf and fine root C,N and P stoichiometry and rhizosphere soil properties in Tectona grandis plantations

Little is known about C-N-P stoichiometries and content in teak(Tectona grandis)plantations in South China,which are mostly sited on hilly areas with lateritic soil,and the effect of slope position on the accumulation of these elements in trees and rhizosphere soils.Here we analyzed the C,N,P content and stoichiometry in leaves,fine roots and rhizosphere soils of trees on the upper and lower slopes of a 12-year-old teak plantation.The Kraft classification system of tree status was used to sample dominant,subdominant and mean trees at each slope position.The results showed that the C,N and P contents in leaves were higher than in fine roots and rhizosphere soils.The lowest C/N,C/P and N/P ratios were found in rhizosphere soils,and the C/N and C/P ratios in fine roots were higher than in leaves.Nutrient accumulation in leaves,fine roots and rhizosphere soils were significantly influenced by slope position and tree class with their interaction mainly showing a greater effect on rhizosphere soils.Leaf C content and C/N ratio,fine root C and P contents,and C/N and C/P ratios all increased distinctly with declining slope position.The contents of organic matter(SOM),ammonium(NH4+-N),nitrate-nitrogen(NO3--N)and available potassium(AK)in rhizosphere soils were mainly enriched on upper slopes,but exchange calcium(ECa),available phosphorus(AP),and pH were relatively lower.Variations in the C,N and P stoichiometries in trees were mainly attributed to the differences in rhizosphere soil properties.N and P contents showed significant positive linear relationships between leaf and rhizosphere soil,and C content negative linear correlation among leaves,fine roots and rhizosphere soils.Chemical properties of rhizosphere soils,particularly C/N and NH4+-N,had significant effects on the leaf nutrients in trees on the upper slope.Correspondingly,rhizosphere soil properties mainly influenced fine root nutrients on the lower slope,and soil AK was the major influencing factor.Overall,these results offer new insights for the sustainability and management of teak plantations in hilly areas.

New insights into the carotenoid biosynthesis in Torreya grandis kernels

Torreya grandis is a characteristic rare economic tree species in subtropical mountainous areas. The nut has a variety of bioactive compounds, such as polyphenols and vitamins. However, the carotenoids compositions and its regulatory mechanisms underlying carotenoid biosynthesis in kernels remain unknown. Here, the major carotenoids in the kernel were analyzed. The result showed that lutein and β-carotene were the predominant carotenoids in the kernel, while low levels of a-carotenoid and zeaxanthin were detected. Lutein and β-carotene were decreased during the maturation of kernel. Expression analysis by RNA-seq and q RT-PCR indicated that the expressions of TgCYP97A3 and TgLCYB were also reduced during the maturation of kernel. The contents of lutein or β-carotene were obviously increased in tobacco transiently overexpressing TgCYP97A3 or TgLCYB. Moreover, DPPH radical scavenging activity and FRAP were also significantly enhanced. In addition, several MYB and WRKY transcription factors TgMYBS3, TgMYB48 and TgWRKY11 were identified to positively regulate the TgCYP97A3 expression, while TgMYB48, TgWRKY2 and TgWRKY11 could upregulate the TgLCYB expression. The illustration of carotenoids biosynthesis and its molecular mechanism in kernels not only provides a basis for understanding carotenoids biosynthesis in kernels, but also enables the use of molecular biotechnology to develop new health products rich in carotenoids based on T. grandis nuts.

Understory plant diversity and phenolic allelochemicals across a range of Eucalyptus grandis plantation ages

Allelopathy is an important mechanism in Eucalyptus plantations that causes detrimental impacts on understory diversity.Phenolic compounds are the main allelochemicals suppressing understory plants.However,the dynamic changes in phenolic allelochemicals and their relationship with understory diversity with increasing age of Eucalyptus plantations remain largely unclear.In this study,the understory plant diversity was assessed and phenolic compounds identified from leaf litter,roots,and rhizosphere soil samples in a Eucalyptus grandis plantation at two-year intervals for ten years using ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS).The abundance and diversity of under story plant species were lowest in 4-year-old plantations and increased significantly with age.Seven phenolic acids and 10 flavonoids were identified from leaf litter,roots,and rhizosphere soils.Most of the potential phenolic allelochemicals,such as salicylic acid,gallic acid,4-hydroxybenzoic acid,and epicatechin,were more abundant in younger plantations,especially at4 years old.The concentrations of phenolic compounds in the rhizosphere zone were significantly lower than in litter and root samples and did not change significantly with an increase in age.Notably,phenolic compounds contributed more to the variation in the understory plants than soil factors.Hydroxyphenyllactic acid,ellagic acid,quercetin,salicylic acid,and 4-hydroxybenzoic acid were the main phenolic compounds explaining the variation in plant diversity with plantation age.These findings indicate that young E.grandis plantations,especially at four years of age,merit a greater focus because of their lower understory plant diversity and higher allelopathic potential.

Tectona grandis (Teak Tree) Young Leaf Extract as a Histological Stain

Stains are applied to impart contrast to the tissue and identify particular features of interest. However, the use of synthetic dyes as staining reagents has been associated with significant human health challenges and pollution of the ecosystem. These developments have necessitated a shift towards using natural dyes that are eco-friendlier and readily available. We investigated the staining reaction patterns of teak tree leaves (Tectona grandis) dye extracts and explored their suitability as a cytoplasmic stain in micromorphological assessments. Dye extracts were prepared using acetone, methanol, and ethanol as solvents from air-dried (under shade) teak tree young leaves. The dye extracts were applied as a counterstain and evaluated against eosin in formalin-fixed paraffin-embedded (FFPE) bovine tissue sections at varying concentrations and different staining times. Teak tree leaves (Tectona grandis) dye extracts produced relatively varying staining intensities of reddish-brown cytoplasmic coloration when used on bovine tissue at different concentrations and staining times comparable to eosin and with blue-purple hematoxylin nuclear stain. The present study showed that Tectona grandis leaf dye extracts provide an excellent cytoplasmic staining pattern and can be used as an alternative counterstain in routine H&E staining techniques.

Effects of Torreya grandis Root Rot on Seedling Growth and Screening of Its Chemical Control Agents

[Objectives]This study was conducted to prevent the occurrence of root rot disease in Torreya grandis and improve the yield and quality of T.grandis.[Methods]One-year-old and two-year-old seedlings of Torreya grandis‘Xifei’and‘Cufei’were inoculated with the root rot pathogen Fusarium fujikuroi,and the changes in photosynthesis,chlorophyll content,malondialdehyde,and defense enzyme system(superoxide dismutase,peroxidase,and catalase)activity in leaves of T.grandis seedlings were investigated using water as a control.Meanwhile,the control effects of 80%carbendazim wettable powder,64%metalaxyl·mancozeb wettable powder,430 g/L tebuconazole suspension and 30%difenoconazole·cyproconazole EC on root rot in T.grandis were investigated.[Results]After inoculation with the pathogen F.fujikuroi,the net photosynthetic rates and transpiration rates in leaves of T.grandis‘Xifei’and‘Cufei’decreased,and the contents of chlorophyll decreased,while the contents of malondialdehyde increased,and the contents of superoxide dismutase and catalase increased with time.However,peroxidase showed a high activity in T.grandis‘Cufei’only,but a trend of"increasing-decreasing-increasing"in T.grandis‘Xifei’.Among the four chemical control agents,64%metalaxyl·mancozeb wettable powder had the best control effect on root rot of T.grandis caused by the pathogenic fungus F.fujikuroi.[Conclusions]The net photosynthetic rate,transpiration rate,chlorophyll content,malondialdehyde content,superoxide dismutase activity and catalase activity could all be used as screening indicators for T.grandis varieties resistant to root rot.Meanwhile,64%metalaxyl·mancozeb wettable powder could be used as a control agent for root rot on T.grandis.

13个柚木种源/家系生长表现研究

[目的]了解国内柚木种源/家系的遗传变异特征,选育更多适应性强的优良种质。[方法]对采集自海南尖峰岭等地的13个种源/家系进行造林试验,在5、10、37 a时测定树高、胸径,应用方差分析方法进行差异性分析和重复力估算,运用偏相关分析揭示生长因子与地理及气候因子的相关性,进而筛选优良种质。[结果](1)不同种源/家系间37 a生时保存率、树高、胸径、单株材积差异显著,其变化范围分别为68.81%~94.29%、11.72~16.03 m、11.33~17.92 cm、0.0844~0.3291 m^(3)。(2)树高、胸径、材积重复力分别为0.6077、0.5131、0.6344。(3)保存率、树高与地理坐标、气候因子相关不显著;胸径和单株材积与海拔(r=0.938^(**),r=0.868^(**))、年均温(r=0.914^(**),r=0.844^(**))显著正相关,与经度(r=-0.913^(**),r=-0.735^(*))、距离(r=-0.923^(**),r=-0.832^(**))显著负相关。(4)聚类分析结果表明,37 a生时,种源/家系7514的保存率、树高、胸径和单株材积表现最好,8440表现最差,其次是75129。[结论]不同种源/家系间保存率、树高、胸径、单株材积差异显著,树高、单株材积有较高的重复力。柚木引种宜选择年均气温相近且距离较近的种源/家系以获得较好的遗传表现,对于凭祥当地而言,种源/家系7514适宜广泛推广种植。

化橘红成花过程挥发油成分的动态变化及活性分析

本文旨在探索化橘红花挥发油成分的动态变化,为化橘红花的综合利用和其挥发油产品的开发提供理论参考。以现蕾期、花苞期、盛开期和谢花期的化橘红花新鲜样品为材料,水蒸气蒸馏法提取挥发油,采用气质联用法(GC-MS)测定挥发油成分,通过构建“化橘红花-活性成分-靶点”网络图对挥发油活性进行分析。结果表明化橘红花挥发油成分以烯类(56.84%~70.19%)和醇类(21.33%~38.34%)物质为主,包括γ-松油烯、D-柠檬烯、芳樟醇、法尼醇、橙花叔醇和β-蒎烯。烯类物质在成花过程中呈现出逐渐降低的趋势,醇类物质表现出先增多再减少的趋势,盛开期达到峰值。现蕾期、花苞期和盛开期的挥发性物质总量保持在较高水平,谢花期显著降低。法尼醇、芳樟醇、α-水芹烯、橙花叔醇和香茅醇等挥发性成分的抑菌和抗氧化活性较高。各个花期的化橘红花均含有丰富的挥发油,具有开发应用价值。

滇西南29年生柚木种源/家系多性状综合选择

[目的]通过对滇西南柚木种源/家系试验林早期与29年生的适应性、生长和形质性状进行综合评价,旨在为当地选出适应性强、速生、形质优良的柚木种源/家系。[方法]从国内外收集了34个柚木种源和家系,采用完全随机区组设计,(2×2)株小区,8次重复,调查、分析和比较试验林早期2~8年生与29年生的保存率和生长差异,对29年生种源/家系的保存率和优势木生长与形质性状采用主分量分析,综合评价出优良种源/家系。[结果]早期2~8年生柚木种源/家系间的保存率差异均不显著,而29年生保存率种源/家系间差异呈极显著;但2~8年生和29年生种源/家系间生长和形质性状的差异均达到极显著,2~8年生最好种源/家系的平均树高、平均胸径和平均单株材积分别是生长最差的1.38~1.91倍、1.63~2.18倍和3.82~5.17倍,而29年生最好种源优势木的平均树高、平均胸径、平均单株材积、树干通直度和主干材高分别是最差种源的1.81倍、1.87倍、4.84倍、2.18倍和12.89倍,通过优良种源/家系选择可获得较大的增产效益。29年生种源/家系的保存率和优势木生长性状与4~8年生优势木的生长性状均呈显著至极显著相关;29年生种源/家系的优势木树干通直度与优势木各生长性状、优势木主干材高与优势木的平均树高和单株材积生长相关显著至极显著。29年生种源/家系保存率、生长和形质性状主成分分析的前三个主分量累积贡献率达97.63%,根据种源/家系在前三个主分量的综合得分,按20%的入选率评选出7个优良种源/家系:种源8410、8603、8407、8602、85131、1007和家系7564#。[结论]29年生入选的7个种源/家系的优势木树高、胸径、单株材积、树干通直度和主干材高的遗传增益分别为7.92%、9.39%、14.74%、7.06%和12.29%,其中来自云南陇川林场种源8410和海南尖峰岭种源8603更适宜当地生长。

巨桉(Eucalyptus grandis)人工林土壤动物群落对采伐干扰的初期响应

为了解采伐干扰对巨桉（Eucalyptus grandis）人工林土壤动物的影响,于2005～2007年采用手捡法和干湿漏斗法对四川省洪雅县巨桉人工林采伐干扰前和采伐干扰后土壤动物群落进行调查,采伐干扰前四季共获土壤动物4775头,分属4门11纲27目,采伐干扰后获土壤动物4640头,分属4门10纲23目。采伐干扰后秋季（10月）、冬季（1月）和春季（4月）土壤动物个体数较采伐干扰前分别上升224头、368头和443头,而夏季（7月）下降了1170头。采伐干扰前巨桉人工林土壤动物个体数与类群数季节变化趋势基本一致,而采伐干扰后土壤动物类群数变化受土壤动物个体数变化的影响较小。与采伐干扰前相比,采伐干扰后枯落物层各季节土壤动物密度均低于采伐前,0～5 cm土层土壤动物密度与干扰前呈相反的变化趋势,其波动较5～10 cm和10～15 cm土层大。采伐干扰后土壤动物类群数四季共减少4个,采伐干扰前后土壤动物优势类群类群数波动小,采伐后常见类群类群数上升（除冬季外）,稀有类群对采伐干扰较敏感,其类群数下降幅度较大。采伐干扰前后同功能种团均以杂食性和腐食性土壤动物为主,两者百分比之和均在89%以上。密度-类群指数（DG）和多样性指数（H′）的变化趋势相似,采伐干扰前后的变化趋势相反,表明采伐干扰对巨桉人工林土壤动物季节变化有较大影响。

基于中药特色技术传承概述广东芸香科道地药材

基于中药传统特色技术,文章通过现场观摩调研与文献检索,概述在十大广药中占有1/3的芸香科药物的药用历史、产地采收加工、性状鉴别特点。芸香科药物多含挥发油,具有芳香气,大部分具有宽中理气的功效,临床应用广泛。据考证,柚类橘红始自清代,此前使用橘类橘红;广陈皮主产区在新会地区,也称新会陈皮,药用时间至今约有600年;广佛手以肇庆高要地区产量多且质优,“佛手柑”的记载最早见于元朝。化橘红的传统加工方法是将化州柚的外层果皮切成角状,加工成7角的毛橘红药材,称为“毛七爪”;新会陈皮需在新会地区内陈化三年,方可称为“新会陈皮”。化橘红鉴别特点为表面密被柔软毡状细绒毛,有油点,气清香;新会陈皮“鬃眼”明显,对光照视呈半透明状,香气浓郁。广佛手切面的外皮呈黄色,肉呈白色,俗称“金边白肉”。文章基于中药传统理论、技术对广东地区芸香科道地药材进行概述,以期守正创新,使中药的传统特色技术得到传承发展。

化橘红挥发油对罗汉果斑枯病菌的抑制作用及机理

采用平板抑菌法结合盆栽防治试验测定化橘红(Citri grandis Exocarpium)挥发油对罗汉果(Siraitia grosvenorii)斑枯病菌(Stagonosporopsis cucurbitacearum)的抑制活性。通过显微观察病原菌菌丝体的形态及测定挥发油处理病原菌菌丝体后处理液的电导率及可溶性蛋白质含量变化情况,探究化橘红挥发油的抑菌机理。平板抑菌结果表明,化橘红挥发油稀释≤1 000倍对罗汉果斑枯病病原菌菌丝生长的抑制率均达100.0%,显著高于80%多菌灵可湿性粉剂稀释1 000倍的抑制率(88.7%)。盆栽试验结果表明,化橘红挥发油稀释1 000倍,45%戊唑·咪鲜胺乳油和10%苯醚甲环唑乳油对罗汉果斑枯病病斑扩展的抑制率均在80.0%以上,且均显著高于80%多菌灵可湿性粉剂的抑制率(70.68%)。显微镜下观察发现,经化橘红挥发油处理7 d的病原菌菌丝呈念珠状膨大并有断裂现象。菌丝体与化橘红挥发油共培养结果表明,混合液的电导率及可溶性蛋白质含量均随着化橘红挥发油处理浓度的加大、互作时间的延长而提高;浓度为2.0 g/L的化橘红挥发油与病原菌菌丝共培养48 h,培养液的电导率为279.208μS/cm,为各处理最大值;挥发油终质量分数0.2%、作用60 h后,培养液中的可溶性蛋白质含量达90.6μg/mL,为各处理的最大值。

叶面喷施硒肥对香榧幼苗叶片代谢组的影响

[目的]分析亚硒酸钠叶面喷施后对香榧(Torreya grandis)幼苗叶片代谢组的影响,探究亚硒酸钠喷施后香榧叶片次生代谢物的累积情况及其对果实品质的影响。[方法]以苗龄2年的香榧幼苗为供试材料,叶面喷施亚硒酸钠(浓度为100μg·L^(-1))2次,间隔15 d。第二次喷施后15 d,采取1年生叶片进行代谢组分析,以色谱-质谱研究香榧幼苗叶片代谢物差异。[结果]在正离子模式下,处理组和对照组之间有909种差异代谢物,其中69种显著变化(27种显著上调,42种显著下调)。在负离子模式下,出现433种差异代谢物,其中43种显著变化(11种显著上调,32种显著下调)。对人体有益的一些次生代谢物显著增加,如车前苷(2.827倍)、川芎内酯(2.524倍)、6-唾液乳糖(2.021倍)、阿齐沙坦(1.931倍)。[结论]香榧叶片喷施亚硒酸钠有利于促进对人体有益的次生代谢物的生物合成及其在叶片中的累积。

大竹蛏(Solen grandis)cDNA文库中微卫星标记的筛选

利用微卫星查找软件SSRIT对大竹蛏cDNA文库(2038条EST)中2—6个碱基重复单元组成的简单序列重复进行了筛选。最少重复次数设定为5次,共发现包含微卫星位点的EST96条,占整个EST数据库的4.71%;共发现微卫星位点103个,其中含双碱基重复序列77个,数量最多,占总数的74.76%;三、四碱基重复序列分别占微卫星序列总数的22.33%、2.91%,没有发现五或六碱基的重复。对含有SSR位点符合微卫星引物设计的EST序列,利用在线引物设计软件Primer3设计合成引物14对,以南通野生群体为模板PCR扩增和聚丙烯酰胺凝胶电泳发现,其中5对有多态性位点。在5个微卫星位点上,等位基因的数目从2—7个不等,观测杂合度和期望杂合度分别为0.067—1.000和0.066—0.775,香农指数在0.146—1.545之间。结果表明,所筛选的微卫星标记可用于遗传分析。

大竹蛏(Solen grandis)不同地理群体遗传多样性的AFLP分析

应用AFLP分子标记技术对我国沿海大竹蛏(Solen grandis)群体的遗传多样性进行了分析,利用筛选出的7对AFLP引物,对丹东、烟台、莱州、日照和南通5个地理群体的141只大竹蛏个体进行了扩增,共得到了403个位点,片段大小在100—700bp之间。其中丹东、烟台、莱州、南通4个群体的大竹蛏遗传多样性水平接近,日照群体的多态位点比例高于其它4个群体,结合Shannon’s信息指数(I)和Nei’s基因多样性指数(H)看,日照群体的遗传多样性水平最高,而南通群体的遗传多样性水平最低。AMOVA分析得到群体间遗传分化系数Φst=0.2250(P<0.001),群体间的变异百分率为22.5%,群体内为77.5%,说明群体的遗传变异主要来源于群体内个体间的遗传差异,但群体间也存在一定程度的基因渗透。

巨桉EgrGBF1基因的克隆和表达模式分析

G-box结合蛋白(GBF)是一类能够识别并结合G-box的转录因子,广泛参与植物基因响应外界刺激的表达调控。通过巨桉(Eucalyptus grandis)初生生长到次生生长的转录组测序筛选出差异表达基因EgrGBF1,为探讨其在桉树生长发育中的功能,从巨桉中克隆了该基因,并进行了结构和进化分析。结果表明,EgrGBF1编码区长度为984 bp,编码327个氨基酸,存在2个转录本,分别命名为EgrGBF1α和EgrGBF1β。实时荧光定量PCR结果表明,EgrGBF1α和EgrGBF1β在不同组织中,不同激素、胁迫处理下的表达模式不同,EgrGBF1α主要在茎尖表达,沿节间向下表达量逐渐降低,而EgrGBF1β在韧皮部高表达,在节间的表达量无显著差异。在水杨酸和缺硼处理下,EgrGBF1α和EgrGBF1β的表达趋势相反。EgrGBF1α在缺磷处理168 h的表达量最高,而EgrGBF1β在处理6 h的表达量最高。因此,EgrGBF1在桉树生长发育以及响应胁迫中发挥着重要作用,且转录本EgrGBF1α和EgrGBF1β可能具有不同的功能。

我国沿海大竹蛏(Solen grandis)野生群体及增殖放流群体遗传多样性的ISSR分析

近年来,大竹蛏野生资源因过度捕捞等原因急剧减少,主要通过人工增殖放流方式进行补充。对我国沿海大竹蛏群体进行遗传多样性研究,评判增殖放流活动对野生群体遗传结构的影响,能够了解大竹蛏当前的种质资源状况,为合理保护该资源提供科学依据。采用ISSR分子标记技术,对广西北海(BH)、江苏启东(QD)、山东日照(RZ)、辽宁营口(YK)、河北秦皇岛(QH)5个野生大竹蛏群体及江苏蒋家沙增殖放流群体(JJ)共150个样品进行了研究。实验结果表明,我国沿海大竹蛏遗传多样性水平高,但各野生群体间已出现显著的遗传分化;江苏蒋家沙增殖放流群体较启东野生群体遗传多样性有所下降,但两群体间的遗传分化并不明显。所以在苗种培育过程中,应当保证亲本数量及品质,扩大亲本选择区域来提高遗传多样性水平,同时应加大本地原种保护力度来避免种质混杂。

香榧藻斑病病原的分离鉴定及防治药剂筛选

【目的】探明香榧藻斑病的病原种类及其生物学特性,筛选对香榧藻斑病具有良好防治效果的药剂,为香榧藻斑病防治提供科学依据。【方法】在浙江省香榧主产区采集藻斑病病叶,结合传统形态学方法与分子生物学手段对从病叶中分离获得的香榧绿藻进行鉴定,明确病原藻的生物学特性,通过室内毒力测定和林间防治试验筛选防治香榧藻斑病的优良药剂。【结果】1)从香榧藻斑病病叶中分离获得3种病原绿藻类群,结合藻株形态学特点以及SSU-ITS区间序列分析,3种绿藻类群分别被鉴定为链带藻、软克里藻和Tritostichococcus corticulus,均为香榧病原新记录种。3种香榧绿藻的培养条件相似,均适宜在初始pH 11、温度25℃、光照/黑暗为12 h/12 h光周期下的BG-11培养基中生长。2)以混合藻为靶标进行室内毒力测定试验显示,12%松脂酸铜悬浮剂灭藻效果最好,EC50可达8.33 mg·L^(-1),显著低于其他药剂(P<0.05),其后依次为33.5%喹啉铜悬浮剂、80%波尔多液、20%噻菌铜悬浮剂和45%石硫合剂。林间防治试验表明,施药30天后,12%松脂酸铜和33.5%喹啉铜悬浮剂的防治效果分别达78.11%和71.62%。【结论】从浙江省香榧上新发现3种病原绿藻类群,藻群生物学特性类似。室内毒力测定和林间防治试验表明,12%松脂酸铜和33.5%喹啉铜悬浮剂对香榧藻斑病有较好防治效果。

抗风桐(Pisonia grandis)的生态生物学特征

抗风桐(Pisonia grandis)为紫茉莉科常绿乔木,是西沙群岛自然植被中最常见的乔木树种,具有重要的生态、药用和观赏价值;其生长速度快,断枝可再殖,在防风、海岸固沙以及海岛植被恢复方面具有重要作用。该研究以西沙群岛永兴岛的野生抗风桐为研究对象,对其形态解剖特征、生理特征和营养成分进行了研究。结果表明:抗风桐属阳生性树种,具有叶片厚、比叶面积低、栅栏组织发达、海绵组织细胞间隙小等形态解剖特征,利于其对光能和水分的利用;其超氧化物歧化酶和过氧化氢酶活性高、脯氨酸含量较高,丙二醛含量较低,表明其具有较强的抗旱性。抗风桐生长的土壤养分含量低,但其叶片营养元素含量高,表明抗风桐对土壤养分的利用能力高,对土壤养分贫瘠胁迫具有较强的适应性。因此,抗风桐能适应强光、干旱和贫瘠等生长条件,可作为热带珊瑚岛植被恢复的重要树种。由于抗风桐生长速度快、适应环境能力强,因此在栽培过程中应适时浇水及补充生长所需的矿质元素,以维持植株生长所需要的水分和养分平衡。该研究结果为抗风桐的引种、栽培、保护及开发利用提供了科学依据。

柚树(Citrus grandis)叶片光合作用对补增UV-B辐射的响应

生长在人工光照 4 0 0μmol m- 2 s- 1 下的柚树幼树光合速率的最大值为 1 0 .2± 0 .5μmol m- 2 s- 1 ;而补增UV-B辐射 ( 3.8-4 .2μW cm- 2 ,2 4 5～ 2 97nm,4 5d)的叶片则为 6.4± 0 .8μmol m- 2 s- 1 ,较对照植株降低37.2 %。对照植物的表观量子产率 (固定 mol CO2 mol- 1量子 )为 0 .0 75± 0 .0 1 2 ,而经 UV-B辐射处理植株则为0 .0 4 1± 0 .0 0 8,明显较对照植株低。UV-B辐射处理使植株叶片的光呼吸和不包括光呼吸的 CO2 补偿点增高。对照植株叶片的最大值的 CO2 羧化速率 (μmol m- 2 s- 1 )为 57.1± 1 .5μmol m- 2 s- 1 ,较 UV-B辐射处理的高30 .9% ,而 UV-B辐射处理的植株的光合电子传递速率较对照低 30 %。同时 UV-B辐射植株叶片有较低的光能转化效率 ,其较对照低 39.1 % ,叶片亦含有较低的叶绿素含量。结果表明 ,UV-B辐射明显抑制叶片光合羧化速率和光合电子传递速率 ,UV-B辐射可能抑制包括 Rubisco羧化作用在内的多个光合生理过程 ,降低叶片光合速率。柚树叶片对 UV-B辐射敏感 ,选育抗 UV-B辐射的柚树品种势在必行。

热带柚木(Tectona grandis L. f.)人工林中不同邻体干扰强度下林木CO2气体交换特征

研究以海南岛尖峰岭21a生的珍贵树种柚木人工林为对象,以邻体干扰指数为干扰强度评价指标,用Li-6400(Li-cor,Inc.,USA)便携式光合作用测定系统研究了邻体干扰强度对柚木个体CO2气体交换的日动态和季节变化特性,光合-光响应特性及光合-CO2响应特性的影响。结果表明:邻体干扰并未改变个体叶片光合作用日进程,但对日净光合速率(Pn)的影响差异较大,表现为弱、中、强和极强度干扰下日Pn时段均值比为2.5∶2.3∶1.7∶1.0,弱干扰下日最大净光合速率为极强干扰下的2.8倍;随着干扰强度的增加,柚木叶片的蒸腾速率、气孔导度等特征参数也出现不同程度的下降。邻体干扰对光合-光响应和光合-CO2响应特征参数的影响明显,弱干扰下柚木叶Asat、Qsat、αA、CE、Vcmax和Jmax分别是极强干扰下的2.7、1.3、1.4、2.7、1.9和2.8倍,Qcomp和Rd则受邻体干扰的影响不明显。干扰强度对光合光响应和光合CO2响应特征的影响随光环境和CO2浓度的改变而有所差异,光环境的改变对弱干扰下柚木个体的影响明显要强于强度以上干扰的个体,而CO2浓度的改变对弱干扰个体的影响则明显要弱于强度干扰以上个体的影响。因此,在林分结构相对单一、经营管理措施基本一致的人工林内,邻体干扰是个体竞争的主要影响因素之一,干扰强度的不同将影响种内个体光合碳同化能力出现差别,导致个体生长差异。可以基于邻体干扰指数评价柚木人工林内种内竞争程度的大小,并以此为依据合理调整柚木人工林的林分结构,达到对环境资源的最合理利用。