杉木对炭疽病的抗性与苯丙氨酸解氨酶的关系

接种前的杉木（Cunninghamia lanceolata）针叶中，苯丙氨酸解氨酶（PAL）比活力与抗感病性之间不呈规律性相关。不同抗病性的杉木接种炭疽菌（Glomerella cingulata）后，PAL比活力均上升，接种5d后，抗病性强的杉木PAL比活力比抗病性弱的杉木高，接种前以及接种后的各个时间段内，木质素含量都是抗病杉木比感病杉木高。绿原酸的含量与杉木的抗病性之间不呈规律性的相关，从绿原酸对炭疽菌菌丝生长影响的测定结果可知，杉木针叶的绿原酸浓度不足以构成对炭疽菌的影响。可见，接种后针叶的PAL比活力以及接种前、后针叶的木质素含量可作为衡量杉木抗病性的指标。图3表2参14     

杉木人工林针叶养分含量对模拟氮沉降增加的响应

由于人类活动加剧,世界许多地区的大气氮沉降出现明显的增加,对森林植物和土壤产生明显影响.在福建沙县,通过野外模拟试验研究了杉木人工林针叶养分含量对氮沉降增加的响应.试验设计为4种处理,分别为NO (N,0kg hm-2 a-1,对照)、N1(N,60 kg hm-2a-1)、N2(N,120 kg hm-2a-1)和N3(N,240 kg hm-2a-1),每处理重复3次.通过3a监测发现,相对于NO处理,N1、N2和N3处理分别使杉木针叶平均N含量增加18.25%、11.68%和13.14%,而C/N比值分别下降15.07%、9.96%和12.01%.尽管养分含量随时间变化表现出一定的波动,但氮沉降增加在一定程度上降低了针叶中的P、K、Ca、Mg含量,致使N/P、N/K、N/Ca、N/Mg比值上升,影响了针叶的养分平衡.图2表1参33     

亚热带6种针叶和阔叶树种凋落叶分解比较

针叶和阔叶树种分别代表了不同的生活型,其凋落叶片具有不同的分解速率.应用分解网袋法,在中国亚热带地区,选取了具有代表性的3种针叶树种(马尾松Pinus massoniana、水杉Metasequoia glyptostroboides和杉木Cunninghamia lanceolata)和3种阔叶树种(木荷Schima superb、乐昌含笑Michelis chapensis和青冈Cyclobalanopsisgtauca)的凋落叶,放置于样地杭州千岛湖的林地中,经过1 a的分解实验,分析不同类型树种凋落叶的分解特征.6种树种凋落叶质量损失过程基本符合Olson指数模型,其中,3种针叶树种(马尾松、水杉和杉木)凋落叶的分解系数k值(分别为0.51、0.30和0.44),明显小于3种阔叶树种(木荷、乐昌含笑和青冈)凋落叶的分解系数k值(分别为0.55、1.12和0.66);同时,针叶树种(马尾松、水杉和杉木)凋落叶分解50%和95%所需时间(分别为1.36、2.31、1.78 a和5.87、9.99、7.68 a),大于阔叶树种(木荷、乐昌含笑和青冈)凋落叶的分解时间(分别为1.26、0.62、1.05 a和5.45、2.68、4.54a).多元回归分析表明,凋落物分解系数与初始钾元素含量显著相关(P<0.05).一元线性回归分析表明,凋落物的分解系数与初始钾元素和初始木质素含量均具有显著性差异(P<0.05).亚热带地区针、阔叶树种凋落叶分解的差异与自身质量密切相关,其中初始木质素与钾元素含量是控制凋落物分解的主要因素.图2表2参23     

大气CO2浓度和温度升高对岷江冷杉（Abies faxoniana）幼苗针叶化学特性的影响

以6年生岷江冷杉(Abies faxoniana)幼苗为研究对象,利用控制环境生长室进行了2个生长季的大气CO2浓度倍增和增温(+2.2℃)处理,旨在探讨岷江冷杉幼苗针叶化学特性对CO2浓度倍增和增温的响应.结果表明:大气CO2浓度倍增对岷江冷杉幼苗针叶的叶绿素含量无显著影响,但降低了针叶N、P和纤维素含量,并增加了针叶可溶性糖和淀粉含量.增温显著降低了1年生针叶的叶绿素b含量,同时降低了当年生和1年生针叶的N、P和纤维素含量;显著提高了针叶的可溶性糖和淀粉含量.CO2浓度倍增和增温同时作用显著增加了针叶叶绿素含量,但降低了针叶N、P和纤维素含量,而对针叶可溶性糖和淀粉含量无显著影响.大气CO2浓度倍增和增温对针叶的叶绿素、N和碳水化合物含量有显著的交互作用.在大气CO2浓度倍增和增温条件下,岷江冷杉针叶化学性质将发生改变,可能影响针叶的生物化学过程和凋落物分解.     

间伐对杉木人工林林下植被多样性及其营养元素现存量影响

间伐改变了林分结构,影响林下植被的生长和发育,但长期间伐对杉木Cunninghamia lanceolata林下植被多样性的影响尚缺乏系统研究。在浙江开化通过样地调查,采用Simpson指数、Shannon-Wiener指数和Pielou均匀度指数研究3种间伐处理下杉木人工林林下植被多样性的变化;分析林下植被主要营养元素含量,研究间伐对营养元素现存量的影响。以试验区传统经营方式为对照,即林木生长中期（第14年）进行1次轻度间伐（间伐强度约15%,T1）;中度（总间伐强度约35%, T2）和强度（总间伐强度约50%,T3）间伐均在第7年和第14年进行了2次间伐。间伐15年后的结果表明,3种间伐处理下,林下植物种类数分别为18种（T1）、17种（T2）和20种（T3）,林下植被总密度和盖度均随间伐强度增加而增大;林下植物Simpson指数、Shannon-Wiener指数和Pielou均匀度指数在不同间伐处理之间均没有显著差异（P＞0.05）。林下植被全碳（TC）、全磷（TP）和全钾（TK）含量在不同间伐处理之间差异不显著（P＞0.05）,全氮（TN）含量随间伐强度增加而降低,其中T3处理显著低于T1（P＜0.05）。林下植被生物量随间伐强度增大而增加,林下植被TC、TN、TP和TK现存量在不同间伐处理之间均没有显著差异（P＞0.05）。这些试验结果说明杉木人工林间伐15年后间伐强度不会显著影响林下植被多样性和营养元素的积累。     

闽西北马尾松人工林营养元素的积累与分配格局

通过定位监测与取样分析,研究了41 a生马尾松人工林生态系统中的林木、林下植被、地被物及土壤等各组分营养元素含量、积累及分配特征.对林木的养分含量分析显示,除Ca元素外,针叶的养分含量最高,其次是枝、根、皮,树干的养分含量最低.林下植被层的养分含量比较高,其养分含量大小排列顺序为Ca＞N＞K＞Mg＞P;凋落物中各元素的含量与林木养分含量基本一致;土壤中K含量最高,其次是Mg,而Ca、N、P的含量则比较低.通过对林木生产力的分析表明,马尾松的养分年积累量为110.79 kg·hm-2·a-1,其中叶占34.47%,树干占22.56%,皮、枝和根分别占21.43%、10.91%和10.63%.马尾松林生态系统养分总贮量为187864.77 kg hm-2,其中土壤占98.70%,林木占1.18%,林下植被和凋落物养分元素总贮量较低,仅占总贮量的0.12%.     

菌根真菌处理下滇重楼对营养元素的吸收和积累

通过室温盆栽接种实验,研究在灭菌土壤中,不同丛枝菌根(arbuscular mycorrhizal,AM)真菌处理对滇重楼不同采收期的根际土壤和药材中N、P、K、Mg、Na、Ca等10种营养元素吸收积累的影响.结果表明,接种不同AM真菌可增加果熟期重楼药材中Mg、Na、Zn、Ni等营养元素的含量,并能降低重金属离子Cu的含量,而衰老期无明显差异;还可对滇重楼根际土壤中N、P、K、Mn、Ni等营养元素浓度产生一定影响,增强滇重楼对Mg、Zn、Ni的富集能力.在滇重楼的生长过程中,根际土壤和药材中的营养元素含量间存在相关性:成熟期根际土壤中Na含量与药材中N含量呈正相关,衰老期根际土壤P含量与药材中N、Mg含量呈负相关.土壤与药材中的营养元素含量相互影响,并对药材的品质形成有较大影响.故可通过接种AM真菌增加根际土壤和滇重楼药材中相关营养元素的含量,从而起到提高重楼品质的作用.     

间作杉木对茶园土壤及茶树叶片重金属含量与分布的影响

以单作茶园和杉木—茶间作茶园为研究对象，测定间作杉木对茶园土壤及茶树叶片重金属元素含量及分布的影响。结果表明：（1）间作杉木可降低茶园土壤Pb、Ni、Mn、Zn元素含量，尤其对Mn有较强吸收能力，其次为Ni、Pb、Zn；（2）间作茶园茶树叶片Pb、Mn、Cu、Zn含量均显著低于单作茶园，说明间作杉木对减少茶叶中4种重金属含量，改善茶叶品质可起到明显作用。     

福建三明两种人工林叶片碳氮磷化学计量特征的季节变化

为了解不同人工林叶片C、N、P含量及其化学计量特征的季节变化规律,以福建三明格氏栲和杉木人工林为研究对象,分不同季节采集其新鲜成熟叶片进行分析.结果显示:(1)格氏栲叶片C、N、P及其计量比(C:N、C:P、N:P)分别为488.48 g/kg、15.67 g/kg、0.93 g/kg和31.87、537.16、17.32,杉木为501.99 g/kg、13.67 g/kg、1.00 g/kg和37.32、511.55、13.97,其中格氏栲叶片N含量、N:P显著高于杉木,C含量、C:N显著低于杉木,P含量和C:P与杉木无显著差异.(2)格氏栲和杉木叶片C含量均表现为从春季到冬季先升高后降低,秋季达到最大,格氏栲叶片N含量为秋季最低,而杉木叶片N含量为秋季最高,格氏栲叶片P含量为夏季最高、春季最低,杉木叶片P含量则为春夏季显著低于秋冬季.(3)格氏栲和杉木叶片C:N、C:P变化趋势与其N、P含量变化趋势相反,叶片N:P与其P含量变化趋势相反,说明叶片N、P含量对叶片C:N与C:P起主导作用,叶片N:P主要由P含量决定.(4)除叶片C含量和C:P外,其他指标均受季节和树种及其交互作用的显著影响;叶片C:P主要受季节的影响,其他各指标受树种的影响最大.本研究表明杉木人工林N的利用效率高,格氏栲人工林P的利用效率高;格氏栲在春冬季受P限制,秋季受N限制,夏季同时受N、P限制,杉木在秋冬季受N限制,春夏季同时受N、P限制.(图1表3参38)     

象山港表层沉积物中营养元素的分布特征及影响因素

通过对象山港表层沉积物中不同形态氮、磷含量的调查,分析了该海区表层沉积物中氮、磷的分布特征,象山港表层沉积物中氮、磷含量较高,已对底栖生物产生生态毒性;海产养殖是造成本海域营养元素超标的最主要因素,也是控制营养元素在空间和时间上变化的主要因素.     

紫花苜蓿品种间根系发育过程分析

从根系发育角度分析了不同紫花苜蓿品种在甘肃黄土高原丘陵沟壑区的适应性．研究表明：品种间侧根发生总数差异较大，Ameristand201和Sandili均为14个，陇东苜蓿(Longdong)仅为6个，65％的侧根发生于营养生长阶段；品种间主根生长，根系体积、根系生物量的积累在各个生育期的表现分为3种类型，Ameristand201，Sandili，Ameri-graze401在整个生育期内的生长速率较快，且速率基本保持一致；陇东苜蓿，Derby，Sitel在整个生育期内生长速率较慢，但在盛花期(7月中旬)后，生长速率急剧增加；Goldenempress，Defi，Algonqiun介于前两者之间．从根系发育过程分析，Amefistand201，Sandili，Amerigraze401对黄土高原丘陵沟壑区的季节性降水反映相对迟钝，在干旱半干旱生境中具有较好的适应性．     

苏云金芽胞杆菌生物活性成分研究进展

自1901年Ishimata从家蚕(Bambyx mori)中分离出第1株苏云金芽胞杆菌淬倒亚种(Bacillus thuringiensis subsp.sotto)以来,对苏云金芽胞杆菌研究已有百年的历史.现在国际上确认的苏云金芽胞杆菌菌株已有69个血清型[6],近40000株. 由于苏云金芽胞杆菌的巨大经济利益,不断地引起了广大科研人员和产品开发商的极大兴趣.到目前为止,科学家们已     

树体自动滴输微肥对果树生理和果实品质的影响

研究了树体自动滴输技术在苹果树、核桃树及柿树上的应用．结果表明：通过输施微肥可以促进树体营养生长和发育，提高核桃树花粉生活力及坐果率．节果树经输施后，果实着色显著增加，微量元素含量显著提高，铁(Fe)、锌(Zn)元素可分别比对照提高13．28％～22．90％、42．54％～43．22％，处理果实中硒(Se)及锗(Ge)的增幅较大，分别是对照的9．545倍及4．7173倍．该技术是提高我国果树生产力和改善苹果营养价值的有效方法．图1表7参18     

Resting spore formation and biochemical composition of the marine planktonic diatom Chaetoceros pseudocurvisetus in culture: ecological significance of decreased nucleotide content and activation of the xanthophyll cycle by resting spore formation

The biochemical composition of vegetative cells and resting spores of Chaetoceros pseudocurvisetus Mangin was compared in cultures under various nutrient and light conditions. The cellular content of major nucleotides such as AMP, ADP, ATP and UTP decreased in the order: vegetative cells, nutrient-starved (vegetative) cells and resting spores, indicating that the general metabolism of resting spores is relatively inactive. ADP-glucose was only abundant in nutrient-starved vegetative cells, suggesting metabolic imbalance in these cells. The chl a–specific fluorescence yield of vegetative cells grown under all culture conditions was low, but very high in resting spores. The ratios of the cellular contents of diadinoxanthin to chl a and of diatoxanthin to chl a were higher in resting spores and nutrient-starved vegetative cells than in nutrient-replete vegetative cells. The diadinoxanthin–diatoxanthin xanthophyll cycle was active in resting spores; the xanthophyll cycle was synchronized with a 14 h light:10 h dark photoperiod. Also, the ratios of cellular content of diadinoxanthin and diatoxanthin to cellular content of chl a in resting spores were relatively high in high irradiance, and decreased gradually in conditions of darkness over long culture periods. Under conditions of strong light and high temperature, most resting spores survived more than 40 d while nutrient-starved vegetative cells died within 33 d. These results suggest that resting spore formation is a strategy for enhancing protection and lowering metabolic rate for survival. These physiological changes accompanying spore formation enable resting spores not only to overwinter but also to “oversummer” in the coastal euphotic layer. Received: 23 March 1999 / Accepted: 11 August 1999     

Life-form population responses of a marine planktonic diatom,Chaetoceros pseudocurvisetus,to oligotrophication in regionally upwelled water

Life-form population responses of a centric planktonic diatom,Chaetoceros pseudocurvisetus Mangin, were investigated in summer 1986 and 1988 in the Izu Islands, Japan, in regionally upwelled water where nutrient concentration changed from favorable to unfavorable conditions for active growth and reproduction (oligotrophication). Two types of life form were observed: vegetative cells of healthy and unhealthy looking conditions and resting spores. The observed life-form responses were experimentally evaluated along with a depletion of limiting nutrients. The algal population ceased vegetative growth and initiated resting spore formation with a disappearance of limiting nitrate, and this life-form response seemed to be triggered by the decrease of cellular nitrogen content below a certain level. Since a large amount of silicon was required for the resting spore formation, a part of vegetative cells were unable to form resting spores and formed unhealthy looking vegetative cells under insufficient concentrations of silicic acid. Percentage shares of the resting spores in the population were linearly related to the amounts of available silicic acid. Vegetative cells which did not form resting spores showed greater mortality than resting spores by attack of bacteria and protozoa; however, vegetative cells could respond quickly to possible nutrient replenishment.     

Animals on marine flowers: does the presence of flowering shoots affect mobile epifaunal assemblage in an eelgrass meadow?

Eelgrass, Zostera marina, produces two types of shoots: morphologically simple vegetative shoots and highly branched flowering (reproductive) shoots, the latter found only in summer months. We examined whether the abundance and diversity of mobile epifaunal assemblage are affected by the presence of flowering shoots in an eelgrass meadow of Otsuchi Bay, northeastern Japan. Comparisons of epifauna in natural vegetation revealed that density and species richness did not differ significantly between sites consisting of both flowering and vegetative shoots, and those only of vegetative shoots. A transplant experiment, conducted to examine the colonization rates of epifauna to defaunated eelgrass planted with different combination of vegetative and flowering shoots, showed no obvious variation in abundance and species richness. At species level, the density of some species such as a tanaid Zeuxo sp. and a polychaete Platynereis sp. was higher at sites and/or treatments with flowering shoots, whereas that of some gastropods, such as Lirularia iridescens and Siphonacmea oblongata was higher at sites without flowering shoots. The species-specific response led to dissimilarity of epifaunal assemblage between sites and among treatments with different densities of vegetative and flowering shoots. Similar patterns observed for natural vegetation and the transplant experiment suggest that the variation in assemblage structure is caused by habitat selection of each species, for example, the utilization of flowering shoots as feeding ground and nursery by Zeuxo sp.     

Survival and recovery of resting spores and resting cells of the marine planktonic diatom Chaetoceros pseudocurvisetus under fluctuating nitrate conditions

Of the two resting life-forms of the planktonic diatom Chaetoceros pseudocurvisetus Mangin formed during periods of nitrate depletion, resting spores survived at least 1 month after spore formation at 24 °C, while resting cells survived only for about 10 d at the same temperature. Under nitrogen limitation, resting cells exhibited higher specific death rates than resting spores at temperatures ranging from 5 to 30 °C. After nitrogen replenishment, resting spores required a certain lag period of about 1 d to initiate vegetative growth at levels of nitrate supply from 0.5 to 20 M, while resting cells initiated vegetative growth almost immediately. Resting spores exhibited an intracellular accumulation of the supplied nitrate during germination and initial vegetative growth. The resting cells, however, exhibited more active vegetative growth, closely coupled with the uptake of the supplied nitrate. The resting spores and resting cells appear to play different roles in the maintenance of populations under nutrient fluctuations depending on the interval length between nutrient fluxes in natural waters. Received: 27 April 1998 / Accepted: 1 March 1999     

The role of cysts on population dynamics of Scrippsiella spp. (Dinophyceae) in Onagawa Bay,northeast Japan

The seasonal behavior of both vegetative cells and cysts of dinophytes Scrippsiella spp., mostly S. trochoidea, which is the dominant group among dinoflagellate populations in Onagawa Bay on the northeastern coast of Honshu, Japan, was investigated between 1990 and 1992. The germination of the cysts after 8 d incubation under favorable laboratory conditions was examined using the extinction dilution method. Incessant germination occurred throughout the year, but the germination ratio (no. of germinable cysts/total cysts) varied seasonally with a marked fluctuation during summer when vegetative cells in the water column were abundant. Although such fluctuation largely reflects the variable flux of newly deposited immature cysts produced by the vegetative cells, the regulation of germination caused by a lowered saturation of dissolved oxygen (DO) under thermally stratified conditions was also suggested. During winter, while the cysts germinated in the laboratory, vegetative cells were not found in the water column. These facts suggest that germination in situ is regulated by low temperature in winter and possibly by lowered DO and by cyst age as well in summer. Such regulation prevents simultaneous germination of all the cysts, which is disadvantageous for the population because it would be more difficult to survive adverse conditions such as successive nutrient depletion and higher grazing risk.     

Effect of light on apical length growth of Fucus distichus spp. edentatus (Phaeophyta)

The length growth of Fucus distichus L. ssp. edentatus (Pyl.) Powell in continuous light is compared to growth in natural daylight. In continuous light the length growth of vegetative and fertile apices were saturated at 25 to 40 Wm^-2 and 15 to 30 Wm^-2, respectively. In natural daylight vegetative apices reached saturation at about 300 Wm^-2 (in May), while fertile apices were not saturated at 180 Wm^-2 (in March). This shows that saturation levels are dependent on the light regime and that they may be greatly underestimated when continuous light is used. At 20 Wm^-2 vegetative and fertile apices were daylength saturated at 8 and 12 to 16 h, respectively. Maximum growth in vegetative apices occurred in July, but growth rates were high also during wintertime (45% of July maximum in March at 4.0°–4.2°C). This corresponds to the experimental results which indicate that F. d. edentatus grows well at low irradiances and during short photoperiods.     

Photosynthesis and sink activity of wasp-induced galls in Acacia pycnantha

Although insect galls are widely known to influence source-sink relationships in plants, the relationship between photosynthesis and gall activity has not been extensively studied. In this study we used 14CO2, photosynthesis, and respiration measurements to examine the capacity of bud galls induced by the wasp Trichilogaster signiventris (Pteromalidae) as carbon sinks in Acacia pycnantha. Galls of this species develop either in vegetative or reproductive buds, depending on the availability of tissues at different times of the year, and effectively eliminate seed production by the plant. Photosynthetic rates in phyllodes subtending clusters of galls were greater than rates in control phyllodes, a result we attributed to photosynthesis compensating for increased carbon demand by the galls. Contrary to previous studies, we found that photosynthesis within galls contributed substantially to the carbon budgets of the galls, particularly in large, mature galls, which exhibited lower specific respiration rates allowing for a net carbon gain in the light. To determine the sink capacity and competitive potential of galls, we measured the proportion of specific radioactivity in galls originating from either vegetative or reproductive buds and found no difference between them. The proportion of the total amount of phyllode-derived 14C accumulated in both clustered and solitary galls was less than that in fruits. Galls and fruits were predominantly reliant on subtending rather than on distant phyllodes for photosynthate. Solitary galls that developed in vegetative buds constituted considerably stronger sinks than galls in clusters on inflorescences where there was competition between galls or fruits for resources from the subtending phyllode. Wasps developing in solitary vegetative galls were correspondingly significantly larger than those from clustered galls. We conclude that, in the absence of inflorescence buds during summer and fall, the ability of the wasps to cause gall formation in vegetative tissues tempers intraspecific competition and substantially increases the availability of plant resources for the development of wasps in such galls.