福建大田栲树次生林优势种群结构与动态

在福建大田栲树(Castanopsis fargesii Franch.)次生林内,应用相邻格子法设置3 200 m2样地,进行优势种群结构和空间格局的研究.结果表明, 栲树种群、罗浮栲(C. fabri Hance)种群、樟树[Cinnamomum camphora (Linn.) Presl]种群结构呈金字塔型,栲树种群和罗浮栲种群从Ⅰ、Ⅱ级幼苗到Ⅲ级幼苗发育过程中出现死亡高峰; 3个优势种群从Ⅲ级幼苗向第4立木级的生长过程中,死亡率也很高.栲树、罗浮栲和樟树种群在不同发育阶段空间分布格局差别较大,栲树种群在幼树阶段为集群分布,中树及大树阶段为随机分布;罗浮栲种群在幼树阶段呈集群分布、中树阶段呈均匀分布、大树阶段呈随机分布;樟树种群在幼树及大树阶段呈均匀分布,中树阶段为随机分布.不同区组规模对种群空间分布格局产生影响.     

栲树种群的年龄结构及其生长特征

为了了解栲树的更新方式和更新动态,研究了栲树的生长特征和种群年龄结构.结果表明：栲树种群的年龄结构呈“间歇型”,经历了两个死亡高峰,并存在一个长达30年的断层;栲树的生长受光照的影响,具有很强的可塑性;由于林下光照弱且在垂直空间上不存在差异,栲树生长5～8年后进入生长的第1个抑制期,其年高生长速度可小于0.1 m,并可维持10年;栲树生长的第1个抑制期的起始时间对应着种群第1个死亡高峰期的结束时间,而其结束时间对应着种群第2个死亡高峰期的起始时间,表明栲树生长特征是影响其种群年龄结构的关键因素.     

缙云山大头茶种群林窗动态的初步研究

采用空间序列代替时间序列的方法,从种群的斑块结构特征,年龄结构和静态生命表的生存分析等方面,研究了缙云山大头茶种群的林窗动态特点,结论如下：（１）在常绿阔叶林中,存在着该种群的林窗相循环更替,从而保证了种群的世代延续;（２）种群生活史中,生存与死亡,死亡密度与危险率都存在着波动起伏,种群数量动态具有不停止的振荡特点;（３）林窗初期,群种年龄结构处于稳定的平衡态,而在生活史的较长时间内,一直处于不稳     

常绿阔叶树种栲树开花物候动态及花的空间配置

 基于定株观测和随机枝取样法,对浙江天童常绿阔叶林内栲树（Castanopsis fargesii）的开花物候动态及其雌花、雄花的空间配置进行了研究。结果表明：在栲树的生殖枝上,并非所有的芽都分化、萌发生成花序,栲树花芽的分化和发育集中在一级生殖枝上。生殖枝上花芽的分化与该枝的空间位置密切相关。栲树花期明显晚于春季的展叶期,与叶片生长时间重叠。盛花期集中于5月下旬,约持续8 d左右,属于同步发生的花期。栲树雄花序的数量明显高于雌花序,雄花序约占花序总数的77.88%,雌花序仅占22.12%。大量雄花和花粉的存在是保证雌花接受花粉和完成受精的基础。花序在植冠层中的空间配置明显不同：在同一植冠内,向阳面和背阴面生殖枝上芽萌发成花序的比率存在明显差异(p<0.01),阳面生殖枝上顶芽萌发成花序的比率高于阴面生殖枝的比率,并且,阳面的每个生殖枝上平均花序数和雄花数量均高于阴面生殖枝,花序的分化和发育与枝系的生长发育状况有密切关系。     

昆虫物候模型研究进展

物候是昆虫的重要生物学性状之一。物候模型预测昆虫发育事件的时间,在种群动态、物种分布和进化动态等科学研究以及农林业生产中具有重要作用。本文回顾了常见的物候模型及在昆虫学研究上的应用,包括热性能曲线、生物物理模型、基于概率的模型、分布时滞模型、发育进度曲线、物候匹配模型和物候变迁模型。     

大花百子莲的开花物候与生殖特性

连续2年对引种植物大花百子莲在中国上海市人工种群的开花物候、结实情况进行观测记录,从不同水平分析了大花百子莲的开花物候对其生殖的影响。结果显示:（1）大花百子莲在引种地的开花时间为6月初至7月末;种群花期历时40 d左右,单株花期在14～31 d波动,单花寿命主要为2～3 d;2年的开花振幅平均在6朵·株^-1·d^-1左右,花朵开放百分率值在3.69%~4.87%左右,平均开花式样为11~17朵。（2）大花百子莲种群内2007年比2008年的各项开花物候指标均提前6～9 d;种群开花进程为渐进式的双峰曲线;种群花期重叠时间较长,2年的平均开花同步指数分别为0.663、0.695;植株个体相对开花强度主要分布频度为50%～70%。（3）开花物候指数与座果率的相关分析表明,始花时间与开花数目、座果数、花期长度呈显著负相关关系,开花数目与座果数、花期长度以及花期长度与座果数均呈显著正相关关系,同一花序内单花所发育成果实的数量与单花开放时间呈极显著负相关关系。研究表明,大花百子莲始花时间早的植株比始花时间晚的植株花期更长,开花数目多的植株比开花数目少的植株花期更长,花期长的植株比花期短的植株座果率更高;而且在同一花序上,越早开放的单花其结实的可能性越大。作为引种植物,大花百子莲开花物候年度间具有相似性,说明其在引种地可以适应环境压力,形成稳定的开花时间与开花模式;较长的花期重叠和大量的开花数目可以吸引较多的传粉者访问,为其生殖成功奠定了良好基础。     

濒危植物长柄双花木开花物候与生殖特性

研究了长柄双花木开花过程中花部表型的变化。连续4a对其野生种群、1a对人工种群的开花物候进行了观察,并运用相对开花强度和同步性等开花物候指数分析了开花物候对其生殖的影响。结果如下：长柄双花木开花时间为9月上、中旬至11月中、下旬;单花花期一般为6～7d,单花依其形态和散粉特征可以分为4个时期：散粉前期、散粉初期、散粉盛期和凋谢期。个体开花持续时间49～55d,种群花期历时63～71d。种群内不同年度间开花物候指数没有显著差异,而种群间则存在显著差异,野生种群开花进程为渐进式单峰曲线。人工种群则为“钟”形曲线,二者均属于“集中开花模式”。长柄双花木具有2个相对开花强度的分异趋势,这种分异趋势具有进化意义。开花物候指数与生殖间的相关分析表明,始花时间与开花数量、座果率及花期长度之间均具显著负相关关系,而开花数量与花期长度之间则呈显著正相关,但均为线性相关。长柄双花木开花物候在种群间的差异和种群内年度间的相似性说明,其开花时间可能是由与其相关的复杂的微生境特征和(或)由其遗传因子决定的,同时也反映了种群间的遗传分异和种群内个体间的遗传一致性。作为一种濒危物种,长柄双花木在这种环境的选择压力之下,形成了“大量、集中开放的花”的开花模式,吸引到更多的传粉者的访问,从而达到生殖成功。     

人为干扰对闽北栲树和木荷种群的影响

对闽北森林群落中的栲树（Ｃａｓｔａｎｏｐｓｉｓｆａｒｇｅｓｉ）和木荷（Ｓｃｈｉｍａｓｕｐｅｒｂａ）种群的数量特征和等级度结构分析表明：栲树和木荷均是闽北阔叶林迹地上的建群种群。中等强度的人为干扰可促进栲树种群发展,缺乏干扰或强烈的人为干扰均产生抑制作用。木荷种群在受自然干扰的森林群落中相对稳定,重要值和高等级度比例增加,而人为干扰使木荷种群减小,低等级度比例增加。人为干扰强度越大,木荷种群越难以发展。     

三峡库区残存的常绿阔叶林及其意义

三峡库区世坪森林公园的常绿阔叶林处在中亚热带北部,群落中４８．６５％的物种具热带性质,３５．１４％的物种具温带性质;３３．７８％的物种集中在忍冬科（Ｃａｐｒｉｆｏｌｉａｃｅａｅ）、壳斗科（Ｆａｇａｃｅａｅ）等７个科,全部３８个科中８１．５８％的科仅有１～２种植物在群落中出现;群落含有具先锋意义的伴生种。这些都反映出该地带的次生常绿阔叶林的一般特点。栲树（Ｃａｓｔａｎｏｐｓｉｓｆａｒｇｅｓｉ）的重要值在乔木层和灌木层均居第一,特别是在乔木层该值显著高于其它种,说明此处的常绿阔叶林是以栲树为建群种的单优群落,而且栲树种群径级结构符合其正常发育规律,因而群落相对稳定。该群落对于中亚热带地带性植被的生态学和生物多样性的基础研究具有重要意义,对于退化生态系统的恢复和三峡水库的水源涵养具有典范作用。     

中国特有植物血水草开花物候与生殖特性

于2008年3-5月对分布在井冈山的血水草(Eomecon chionantha Hance )5个自然种群的开花物候进行了观察,运用开花振幅、相对开花强度和开花同步性等指数研究了其开花物候特征及其对该种生殖成功的影响.结果表明:血水草开花时间为3月下旬-5月上旬,种群花期历时24 ～46 d,个体平均开花持续时间为11～21 d,单花花期一般为3～5d;井冈山血水草种群的开花物候进程呈单峰曲线模式具有一个开花高峰期,表现出一种“集中开花模式”;与大多数亚热带植物一样,血水草具有较低的相对开花强度,分布频率集中在10％ ～30％.开花物候指数与生殖间的相关分析结果表明:始花时间与花期持续时间呈显著负相关,而与开花数和坐果率呈显著正相关;花期持续时间与开花数和坐果率呈显著正相关;同步性指数与始花时间、开花数、花期持续时间呈负相关.血水草“集中开花模式”是其在长期的进化过程中适应周围气候条件及生境的一种生殖保障.     

The Anillin-Related Region of Bud4 Is the Major Functional Determinant for Bud4's Function in Septin Organization during Bud Growth and Axial Bud Site Selection in Budding Yeast

The anillin-related protein Bud4 of Saccharomyces cerevisiae is required for axial bud site selection by linking the axial landmark to the septins, which localize at the mother bud neck. Recent studies indicate that Bud4 plays a role in septin organization during cytokinesis. Here we show that Bud4 is also involved in septin organization during bud growth prior to cytokinesis, as bud4Δ shs1Δ cells displayed an elongated bud morphology and defective septin organization at 18°C. Bud4 overexpression also affected septin organization during bud growth in shs1Δ cells at 30°C. Bud4 was previously thought to associate with the septins via its central region, while the C-terminal anillin-related region was not involved in septin association. Surprisingly, we found that the central region of Bud4 alone targets to the bud neck throughout the cell cycle, unlike full-length Bud4, which localizes to the bud neck only during G₂/M phase. We identified the anillin-related region to be a second targeting domain that cooperates with the central region for proper septin association. In addition, the anillin-related region could largely mediate Bud4''s function in septin organization during bud growth and bud site selection. We show that this region interacts with the C terminus of Bud3 and the two segments depend on each other for association with the septins. Moreover, like the bud4Δ mutant, the bud3Δ mutant genetically interacts with shs1Δ and cdc12-6 mutants in septin organization, suggesting that Bud4 and Bud3 may cooperate in septin organization during bud growth. These observations provide new insights into the interaction of Bud4 with the septins and Bud3.     

Localization of the Rsr1/Bud1 GTPase involved in selection of a proper growth site in yeast

Yeast cells organize their actin cytoskeleton in a highly polarized manner during vegetative growth. The Ras-like GTPase Rsr1/Bud1 and its regulators are required for selection of a specific site for growth. Here we showed that Rsr1/Bud1 was broadly distributed on the plasma membrane and highly concentrated at the incipient bud site and polarized growth sites. We also showed that localization of Cdc24, a guanine nucleotide exchange factor for the Cdc42 GTPase, to the proper bud site was dependent on Rsr1/Bud1. Surprisingly, Rsr1/Bud1 also localized to intracellular membranes. A mutation in the lysine repeat in the hypervariable region of Rsr1/Bud1 specifically abolished its plasma membrane localization, whereas a mutation at the CAAX motif eliminated both plasma membrane and internal membrane association of Rsr1/Bud1. Thus the lysine repeat and the CAAX motif of Rsr1/Bud1 are important for its localization to the plasma membrane and to the polarized growth sites. This localization of Rsr1/Bud1 is essential for its function in proper bud site selection because both mutations resulted in random bud site selection.     

Kar9p-independent microtubule capture at Bud6p cortical sites primes spindle polarity before bud emergence in Saccharomyces cerevisiae

Spindle orientation is critical for accurate chromosomal segregation in eukaryotic cells. In the yeast Saccharomyces cerevisiae, orientation of the mitotic spindle is achieved by a program of microtubule-cortex interactions coupled to spindle morphogenesis. We previously implicated Bud6p in directing microtubule capture throughout this program. Herein, we have analyzed cells coexpressing GFP:Bud6 and GFP:Tub1 fusions, providing a kinetic view of Bud6p-microtubule interactions in live cells. Surprisingly, even during the G1 phase, microtubule capture at the recent division site and the incipient bud is dictated by Bud6p. These contacts are eliminated in bud6 delta cells but are proficient in kar9 delta cells. Thus, Bud6p cues microtubule capture, as soon as a new cell polarity axis is established independent of Kar9p. Bud6p increases the duration of interactions and promotes distinct modes of cortical association within the bud and neck regions. In particular, microtubule shrinkage and growth at the cortex rarely occur away from Bud6p sites. These are the interactions selectively impaired at the bud cortex in bud6 delta cells. Finally, interactions away from Bud6p sites within the bud differ from those occurring at the mother cell cortex, pointing to the existence of an independent factor controlling cortical contacts in mother cells after bud emergence.     

Gic2p may link activated Cdc42p to components involved in actin polarization, including Bni1p and Bud6p (Aip3p)

Gic2p is a Cdc42p effector which functions during cytoskeletal organization at bud emergence and in response to pheromones, but it is not understood how Gic2p interacts with the actin cytoskeleton. Here we show that Gic2p displayed multiple genetic interactions with Bni1p, Bud6p (Aip3p), and Spa2p, suggesting that Gic2p may regulate their function in vivo. In support of this idea, Gic2p cofractionated with Bud6p and Spa2p and interacted with Bud6p by coimmunoprecipitation and two-hybrid analysis. Importantly, localization of Bni1p and Bud6p to the incipient bud site was dependent on active Cdc42p and the Gic proteins but did not require an intact actin cytoskeleton. We identified a conserved domain in Gic2p which was necessary for its polarization function but dispensable for binding to Cdc42p-GTP and its localization to the site of polarization. Expression of a mutant Gic2p harboring a single-amino-acid substitution in this domain (Gic2p(W23A)) interfered with polarized growth in a dominant-negative manner and prevented recruitment of Bni1p and Bud6p to the incipient bud site. We propose that at bud emergence, Gic2p functions as an adaptor which may link activated Cdc42p to components involved in actin organization and polarized growth, including Bni1p, Spa2p, and Bud6p.     

Specific residues of the GDP/GTP exchange factor Bud5p are involved in establishment of the cell type-specific budding pattern in yeast

Cells of the budding yeast undergo oriented cell division by choosing a specific site for growth depending on their cell type. Haploid a and alpha cells bud in an axial pattern whereas diploid a/alpha cells bud in a bipolar pattern. The Ras-like GTPase Rsr1p/Bud1p, its GDP-GTP exchange factor Bud5p, and its GTPase-activating protein Bud2p are essential for selecting the proper site for polarized growth in all cell types. Here we showed that specific residues at the N terminus and the C terminus of Bud5p were important for bipolar budding, while some residues were involved in both axial and bipolar budding. These bipolar-specific mutations of BUD5 disrupted proper localization of Bud5p in diploid a/alpha cells without affecting Bud5p localization in haploid alpha cells. In contrast, Bud5p expressed in the bud5 mutants defective in both budding patterns failed to localize in all cell types. Thus, these results identify specific residues of Bud5p that are likely to be involved in direct interaction with spatial landmarks, which recruit Bud5p to the proper bud site. Finally, we found a new start codon of BUD5, which extends the open reading frame to 210 bp upstream of the previously estimated start site, thus encoding a polypeptide of 608 amino acid residues. Bud5p with these additional N-terminal residues interacted with Bud8p, a potential bipolar landmark, suggesting that the N-terminal region is necessary for recognition of the spatial cues.     

栲树不同生长发育阶段的枝系特征分析

对浙江天童国家森林公园内常绿阔叶优势树种栲树(Castanopsis fargesii)不同发育阶段植冠内的分枝式样特征进行了统计分析。结果表明：栲树在不同发育阶段的总体分枝率和逐步分枝率有显著变化,幼苗和幼树阶段的分枝率较低,而成株阶段的分枝率较高;幼树阶段的枝条长度、枝倾角和叶倾角明显大于幼苗和成株阶段,表现为明显的高生长对策;叶片配置在不同枝系上有较大差异,叶片主要集中于植冠内一级枝和二级枝上;叶片的大小从幼苗、幼树到成株阶段逐渐增大。研究结果表明栲树在生活史的不同生长发育阶段,分枝式样表现出一定的可塑性,反映了不同的适应对策。     

The roles of bud-site-selection proteins during haploid invasive growth in yeast

In haploid strains of Saccharomyces cerevisiae, glucose depletion causes invasive growth, a foraging response that requires a change in budding pattern from axial to unipolar-distal. To begin to address how glucose influences budding pattern in the haploid cell, we examined the roles of bud-site-selection proteins in invasive growth. We found that proteins required for bipolar budding in diploid cells were required for haploid invasive growth. In particular, the Bud8p protein, which marks and directs bud emergence to the distal pole of diploid cells, was localized to the distal pole of haploid cells. In response to glucose limitation, Bud8p was required for the localization of the incipient bud site marker Bud2p to the distal pole. Three of the four known proteins required for axial budding, Bud3p, Bud4p, and Axl2p, were expressed and localized appropriately in glucose-limiting conditions. However, a fourth axial budding determinant, Axl1p, was absent in filamentous cells, and its abundance was controlled by glucose availability and the protein kinase Snf1p. In the bud8 mutant in glucose-limiting conditions, apical growth and bud site selection were uncoupled processes. Finally, we report that diploid cells starved for glucose also initiate the filamentous growth response.     

Phosphorylation of Lte1 by Cdk prevents polarized growth during mitotic arrest in S. cerevisiae

Lte1 is known as a regulator of mitotic progression in budding yeast. Here we demonstrate phosphorylation-dependent inhibition of polarized bud growth during G2/M by Lte1. Cla4 activity first localizes Lte1 to the polarity cap and thus specifically to the bud. This localization is a prerequisite for subsequent Clb-Cdk-dependent phosphorylation of Lte1 and its relocalization to the entire bud cortex. There, Lte1 interferes with activation of the small GTPases, Ras and Bud1. The inhibition of Bud1 prevents untimely polarization until mitosis is completed and Cdc14 phosphatase is released. Inhibition of Bud1 and Ras depends on Lte1's GEF-like domain, which unexpectedly inhibits these small G proteins. Thus, Lte1 has dual functions for regulation of mitotic progression: it both induces mitotic exit and prevents polarized growth during mitotic arrest, thereby coupling cell cycle progression and morphological development.     

Differential activities and regulation of Saccharomyces cerevisiae formin proteins Bni1 and Bnr1 by Bud6

Formins are conserved proteins that nucleate actin assembly and tightly associate with the fast growing barbed ends of actin filaments to allow insertional growth. Most organisms express multiple formins, but it has been unclear whether they have similar or distinct activities and how they may be regulated differentially. We isolated and compared the activities of carboxyl-terminal fragments of the only two formins expressed in Saccharomyces cerevisiae, Bni1 and Bnr1. Bnr1 was an order of magnitude more potent than Bni1 in actin nucleation and processive capping, and unlike Bni1, Bnr1 bundled actin filaments. Profilin bound directly to Bni1 and Bnr1 and regulated their activities similarly. However, the cell polarity factor Bud6/Aip3 specifically bound to and stimulated Bni1, but not Bnr1. This was unexpected, since previous two-hybrid studies suggested Bud6 interacts with both formins. We mapped Bud6 binding activity to specific residues in the carboxyl terminus of Bni1 that are adjacent to its diaphanous autoregulatory domain (DAD). Fusion of the carboxyl terminus of Bni1 to Bnr1 conferred Bud6 stimulation to a Bnr1-Bni1 chimera. Thus, Bud6 differentially stimulates Bni1 and not Bnr1. We found that Bud6 is up-regulated during bud growth, when it is delivered to the bud tip on Bni1-nucleated actin cables. We propose that Bud6 stimulation of Bni1 promotes robust cable formation, which in turn delivers more Bud6 to the bud tip, reinforcing polarized cell growth through a positive feedback loop.