果胶酶激发子对黄瓜叶片病程相关蛋白及细胞壁物质的影响

以草酸青霉菌(Penicillium oxalicum)的固态发酵产物———果胶酶粗提液喷雾诱导黄瓜,研究了该激发子对黄瓜细胞内几丁质酶和-β1,3-葡聚糖酶2种病程相关蛋白(PR s蛋白)以及细胞壁物质的影响.结果表明,经激发子处理后,黄瓜叶片中几丁质酶和-β1,3-葡聚糖酶活性诱导升高,木质素及富含羟脯氨酸糖蛋白(HRGP)含量也诱导增强;同时,在激发子处理后接种黑星病菌的黄瓜中,上述2种PR s蛋白及细胞壁物质被大量诱导合成.其中,两种PR s蛋白均在接种后d 4达到最高值,分别为22.72 U/mg(pro)和268.16 U/mg(pro);木质素和HRGP含量在接种后d 3后达最高,分别比对照高196.12%和272.98%.表明果胶酶激发子在接种前期对黄瓜几丁质酶、-β1,3-葡聚糖酶、木质素及HRGP的诱导产生是导致病情降低的内在机制.图4参16     

黔西北不同林龄马尾松人工林针叶-凋落物-土壤C、N、P化学计量特征

在贵州省黔西县境内选取14、26、33 a生的马尾松人工林为研究对象,比较分析"植物-凋落物-土壤"连续体中的C、N、P含量及其化学计量特征的差异,探讨它们随林龄的变化及其相互间的关系,以期为马尾松人工林的可持续经营提供参考。结果表明,(1)C和N含量表现为针叶凋落物土壤,P含量表现为针叶土壤凋落物,ω(C):ω(N)比表现为针叶凋落物土壤,ω(C):ω(P)和ω(N):ω(P)比表现为凋落物针叶土壤,且3个库之间均存在显著差异(P0.05)。(2)林龄对针叶、凋落物、土壤中的C、N、P含量及其化学计量特征均有显著影响,但是它们随林龄的变化趋势不尽相同。随着林龄的增加,针叶和土壤中的C、N、P含量呈增加趋势;凋落物中的N、P含量呈增加趋势,但是C含量则逐渐降低。随着林龄的增加,针叶和凋落物中的ω(C):ω(N)和ω(C):ω(P)比逐渐降低;土壤中的ω(C):ω(N)比则逐渐增加,ω(C):ω(P)比先降低后增加。(3)不同林龄针叶的ω(N):ω(P)比均小于14,表明研究区内马尾松的生长受N限制较严重,特别是26 a生时最严重,且不同林龄间差异显著。(4)相关分析表明,马尾松生长过程中,针叶、凋落物、土壤中的P含量及ω(C):ω(P)比均呈显著正相关关系,说明P比C和N在叶片、凋落物、土壤3个库之间的相关性更显著,ω(C):ω(P)比对3个库之间的养分转化关系最敏感。     

杉木林取代阔叶林后土壤生物学活性变化的研究

通过对福建省南平市溪后安曹下取代阔叶林的70a生杉木车产林（山坡）、32a生杉木“青年林”（山坡）及前茬阔叶林（山脊）土壤生物学活性连续2a的比较研究结果表明，与山脊上前茬的阔叶林相比，70a生杉木丰产林土壤微生物总数、生理类群的数量减少、活性下降；土壤酶活性减弱；呼吸作用强度（内源）及添加基质的外源呼吸作用强度降低，土壤中有机质分解和腐殖质再合成程度降低．32a生杉木“青年林”土壤生物学活性下降则更为明显，说明从杉木取代阔叶林（头耕土）起，土壤生化活性及土壤肥力就存在明显下降现象，轮伐期缩短或林地连栽杉木代数增加，而不采取恢复地力措施，杉木林地地力衰退将更为明显．     

禾谷孢囊线虫侵染对小麦根部防御酶的影响

以抗禾谷孢囊线虫(Heterodera avenae Wollenweber,cereal cyst nematode,CCN)小麦品系‘E-10’和易感材料‘中国春’为材料,通过人工接种禾谷孢囊线虫二龄幼虫,并在接种线虫后测定根部防御酶苯丙氨酸转氨酶(PAL)和脂氧合酶(LOX)活力变化,研究抗感性材料对线虫侵染后防御酶的响应,以了解作物的抗虫机制.结果发现,‘E-10’和‘中国春’防御酶活力变化存在显著差异,‘E-10’在线虫侵染后6 h,LOX酶活增强,在24 h达到最大值,酶活变化比‘中国春’迅速,暗示‘E-10’启动线虫防御反应更为有效直接.此外,发现小麦在接种线虫后会引起邻近未接种植株根部防御酶活力变化.‘E-10’在接种线虫后12 h,其接触组未接种材料根部PAL酶活增加0.9倍,LOX酶活增加1.1倍,并且‘E-10’未接种植株的酶活变化比‘中国春’更迅速,幅度更剧烈.表明可能有某些气态或挥发性物质参与了小麦防御线虫侵染过程,并且这种现象在抗感材料间差异显著.使用茉莉酸甲酯处理‘E-10’和‘中国春’,小麦根部PAL和LOX酶活并未产生与接触接种线虫材料相一致的变化,表明该气态或挥发性物质并非茉莉酸甲酯.     

帽峰山森林土壤碳氮随雨季月及土壤深度的时空变化特征

采用森林生态系统定位观测及对比试验方法,对广州帽峰山常绿阔叶林和杉木人工林（16年）土壤（0~90 cm）有机碳、无机碳、总氮及有机氮的雨季月（5—10月）含量动态、垂直梯度变化特征及土壤湿度影响进行了对比观测研究。结果表明：常绿阔叶林及杉木林土壤有机碳、无机碳雨季月的剖面权均含量变化趋势均为倒S型,常绿阔叶林土壤有机碳剖面权均质量分数较相应杉木林大0.14%、土壤无机碳则小0.12%。常绿阔叶林土壤表层0~10、10~30 cm有机碳雨季月含量变差较杉木林分别高出1.83%、0.61%,土壤30~90 cm雨季月含量变差相对较小;常绿阔叶林土壤70~90 cm无机碳含量在5—8月份较高、杉木林则以土壤30~50 cm在5、6及10月含量较高;常绿阔叶林群落土壤0~20 cm的总氮雨季月含量均大于相应杉木林,植被吸收作用影响使土壤20 cm以下层的雨季各月总氮相对较低;常绿阔叶林土壤剖面雨季月无机氮含量随土层深度递减变化显著,即表层0~30 cm受矿化作用影响较大、深层30~90 cm则受植被吸收作用影响较大;而杉木林土壤剖面层无机氮含量则随雨季的月变化显著,5—7月份含量相对较小、8—10月份含量相对较大。常绿阔叶林土壤有机碳、总氮含量随土壤深度的增加均呈幂函数规律的递减,而杉木人工林土壤有机碳随土壤深度的增加呈对数函数规律的递减、土壤总氮含量则随土壤深度的增加呈二次函数规律的递减。在0~10 cm处,土壤有机碳和有机氮含量与土壤湿度呈负相关。     

攀援型和矮生型四棱豆苯丙氨酸解氨酶活性和黄酮含量的研究

以攀援和矮生型四棱豆为研究对象,对不同部位苯丙氨酸解氨酶活性和总黄酮含量进行比较,结果表明：除嫩豆荚外,矮生型四棱豆不同部位的PAL活性均高于攀援型,其总黄酮含量亦高于攀援型。攀援型和矮生型四棱豆PAL活性均为种子最高,嫩豆荚最低;两者总黄酮含量均为叶最高,储藏器官块根最低。攀援型和矮生型的PAL活性和总黄酮含量之间均呈显著正相关。矮生型四棱豆不同部位的组织或器官PAL活性受外源因子影响小,类黄酮合成能力高于攀援型,具有更高的抗逆性。     

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。     

不同磷效率基因型小麦对VAM真菌依赖性的影响因子及机理

以高、中、低效３ 个磷效率基因型小麦为试材,在ｗ（Ｐ２Ｏ５） ＝２０ ｍｇｋｇ 和６０ ｍｇｋｇ 的水平下,接种或不接种两个ＶＡ菌根真菌Ｇｌｏｍｕｓ ｍｏｓｓｅａｅ 和Ｇｌｏｍｕｓｖｅｒｓｉｆｏｒｍｅ,研究了影响小麦菌根依赖性的因子及机理．结果表明,在低磷水平下,小麦菌根依赖性的大小顺序为中效＞ 低效＞ 高效;对Ｇ． ｖｅｒｓｉｆｏｒｍ 的依赖性大于对Ｇ． ｍｏｓｓｅａｅ 的依赖性;而在高磷水平下,接种菌根表现出不同程度的生长抑制作用．相关分析发现,菌根依赖性与根冠比、根长、根毛长度、根毛密度、磷利用效率之间的相关性不显著;在低磷水平下,菌根依赖性与磷效率、根吸收效率之间呈极显著的负相关,与韧皮部蔗糖运输速率之间呈显著或极显著的正相关．认为影响不同磷效率基因型小麦菌根依赖性的主要因子是根的吸收效率;菌根依赖性、磷效率和韧皮部蔗糖运输速率均受根吸收效率影响     

井冈山两种典型森林土壤有机碳密度及其影响因素的比较

森林土壤有机碳是土壤有机碳库的重要组成部分,研究森林土壤有机碳及其影响因素对于应对气候变化具有非常重要意义。以井冈山自然保护区两种典型森林类型（常绿阔叶林和人工杉木林）为研究对象,各选取12个样地,对比分析了两种森林土壤有机碳密度的垂直分布特征以及与年均温、年降雨量之间的相关性。结果表明：①常绿阔叶林0-100cm层平均土壤有机碳密度为（25．65±3,27）kg-^2,大于人工杉木林0-100cm层平均土壤有机碳密度为（20．37±3．37）kg·m^2;②常绿阔叶林和人工杉木林土壤有机碳密度均随土壤深度的增加显著减少;③常绿阔叶林与人工杉木林土壤有机碳密度随年均温的变化趋势差异较明显,常绿阔叶林0-100cm层土壤有机碳密度随年均温的上升呈显著增加趋势（P〈0．05）,而人工杉木林随年均温的上升先减小后增加再减小,且变化趋势显著（P〈0．05）;④常绿阔叶林与人工杉木林土壤有机碳密度随年降雨量的变化趋势差异亦明显,常绿阔叶林0-100cm层土壤有机碳密度随年降雨量的增加呈显著减小趋势（P〈O．05）,而人工杉木林随年降雨量的增加先增加后减少再增加,且变化趋势极显著（P〈0．005）;⑤森林土壤有机碳质量分数与土壤容重呈极显著负相关（P〈0．0001）。     

不同林龄马尾松（Pinus massoniana）人工林碳氮磷分配格局及化学计量特征

为了解长江上游低山丘陵区马尾松（Pinus massoniana）人工林生态系统的C、N、P分配格局及化学计量特征,本文采用时空互代的方法,在宜宾高县来复林区选取三种不同林龄（5年生幼龄林、14年生中龄林、39年生成熟林）,但立地条件相近、样地情况基本一致的马尾松（Pinus massoniana）人工林作为研究对象,对马尾松针叶、凋落物及土壤中的C、N、P含量及 w（C）？w（N）？w（P）化学计量特征进行测定和分析。结果表明,（1）C、N、P 含量均表现为针叶〉凋落物〉土壤,且在三个库之间差异显著;（2）林龄对针叶、凋落物、土壤的 C、N、P 及 w（C）？w（N）、w（C）？w（P）计量比均有显著影响。（3）土壤 C、N、P含量在成熟林中最高;针叶和凋落物的C含量在成熟林中最低,N、P含量则在中龄林中最高。（4）随林龄增加马尾松对N、P的利用效率降低,针叶、凋落物及土壤的w（C）？w（N）与 w（C）？w（P）均表现为下降。（5）马尾松针叶w（N）？w（P）比值在14.37~15.53之间,说明该地区马尾松人工林受N和P的共同限制,但林龄对N、P养分限制的影响不显著。为提高该区马尾松人工林的生产力,建议在人工林的抚育管理中要适当增加N肥和P肥,同时也可在马尾松人工林引入豆科固氮植物以提高地力。该研究将马尾松针叶、凋落物及土壤结合起来探究随林龄增长C、N、P养分元素的分配格局及化学计量特征的变化,有助于全面、系统地揭示马尾松人工林生态系统的养分循环,对指导马尾松人工林生产,调节和改善林木生长环境,提高系统的养分利用效率及林地生产力具有重要意义。     

内生真菌感染对黑麦草若干抗旱生理特征的影响

对周期性干旱胁迫下内生真菌感染（EI）和非感染（EF）的黑麦草植株的几项生理指标进行了比较。结果表明，干旱胁迫导致EI和EF叶片相对水分含量下降，细胞膜透性增加，游离脯氨酸累积，叶绿素，类胡萝 纱和淀粉含量下降，可溶性糖含量增加，与EF植株相比，干旱胁迫下EI植株可溶性糖含量较高，膜透性及脯氨酸含量均较低，从生理生化角度说明内生真菌可提高其宿主植物的抗旱性。图3参39     

壳寡糖诱导转反义mapk基因烟草的TMV抗性和PAL活性研究

壳寡糖具有诱导植物对病原物防御反应的作用,而PAL活性的升高通常被认为是发生抗性反应的标志之一.本文以mapk基因受到反义抑制的转基因枯斑三生烟草为试材,比较了壳寡糖诱导后转基因型和野生型烟草的PAL活性变化及对TMV抗性的变化.由实验结果初步推测,在壳寡糖诱导的植物抗性信号通路中,mapk可能为PAL的一个重要的上游基因,同时mapk在烟草抗TMV信号转导中亦为一个重要组分.图4表2参13     

Oviposition of carrot fly (Psila rosae) in response to foliage and leaf surface extracts of host plants

Summary. Foliage of twelve host and two non-host species and surrogate leaves treated with the respective leaf extracts were presented to laboratory populations of the carrot fly (Psila rosae) in oviposition choice assays. The stimulatory activity of dichloromethane surface extracts and the diethyl ether fraction of hot water extracts did not reflect accurately the differences in acceptability observed among intact leaves. A better correlation was found using hexane extracts prepared in a microwave oven. Two out of five fractions of this crude hexane extract obtained by silica gel column chromatography stimulated oviposition. The diethyl ether fraction, which contained the previously identified oviposition stimulants (propenylbenzenes, furanocoumarins, polyacetylenes), could account for only a minor part of the variation in the acceptability of host leaves. The preference hierarchy for intact leaves corresponded better to the ranking of species according to activity of the methanolic fraction, which apparently contains unknown stimulatory compounds.? The water fractions of the hot water extracts were shown to reduce egg-laying underneath surrogate leaves treated with a stimulatory extract. This oviposition-deterring effect was particularly strong with the non-preferred species Pimpinella major, which is also highly resistant in the field. Hence, unidentified inhibitory compounds may also contribute to differential accept ability of host plants. It is concluded that antixenotic (non-preference) resistance of host plants to carrot fly attack depends on complex mixtures of semiochemicals. Received 11 June 1997; accepted 26 November 1997.     

重庆四面山杉木群落物种多样性研究

通过对重庆四面山杉木(Cunninghamia lanceolata)林样地的调查,运用丰富度指数、Shannon-Wiener多样性指数、Simpson多样性指数和Pielou均匀度指数,分析了该地区杉木群落物种多样性特征,将该地区现存杉木群落划分为2个群系组(杉木林和杉木针阔混交林),8个群系,10个群丛。结果表明,杉木群落可分为乔木层、灌木层和草本层。在杉木林群系组中,丰富度指数、多样性指数和均匀度指数均表现为灌木层>草本层>乔木层。在杉木针阔混交林群系组中,丰富度指数表现为灌木层>乔木层>草本层;多样性指数多数表现为灌木层>乔木层>草本层;均匀度指数变化较为复杂,没有统一规律。杉木群落各层的丰富度指数随海拔高度的升高总体上呈下降趋势。群落各层的多样性指数随海拔高度的升高在特定区间内表现出一定规律性:在海拔1180m以下低海拔区域,随海拔高度的升高呈下降趋势;在海拔1180～1351m范围内,随海拔高度的升高呈波动状态;而在海拔1351m以上高海拔区域,又呈下降趋势。群落各层的均匀度指数随海拔梯度变化较为复杂,未表现出明显规律。     

杉木拟赤杨混交林土壤肥力的研究

通过对杉木拟赤杨混交林及杉木纯林土壤团聚体结构、土壤养分状况及酶活性的研究表明，与杉木纯林相比，混交林土壤结构性能得到改善，供肥和保肥能力加强，各种土壤酶活性提高，土壤肥力较好。表明杉木拟赤杨混交林具有良好的培肥土壤功能，对杉木人工林的地力维持和提高有重要意义。     

杉木观光木混交林和杉木纯林群落细根生产力、分布及养分归还

研究了福建三明27a生杉机光木混交林和杉木群落细根（d＜2mm）的生产力、分布、和养分归还。结果表明，混交林细根生物量、N、P养分现存量分别为5．381thm^2、48．085kghm^-2和4．174kghm^-2，分别比杉木纯林增加17．4％、27．2％和20．0％，混交林林细根的年净生产力达4．124thm^-2a^-1，比纯林高出16．9％，混交林杉木和观光木细根均在表层土壤富集，而在较深层土壤再会得分布具镶嵌性；与混交林杉林相比，纯林杉木土吉表层细根量较少，最大分布层次下移，混交林中观光木细根的周转速率咪1．16，杉木为0．96和0．95；而林下植被层细根周转速率（1．46－1．52）均同于相应的乔木层，混交林细根的年死亡量、N和P养分年归还量分别达2．119thm^-2、18．559kghm^-21．565kgkhm^-2，分别是纯林的1．21倍、1．23倍和1．14 倍，其中林下植被细根占有较为重要位置，对细根分布与土壤性质的相关分析表明，细根的垂直分布与土壤全N的相关性最强（0．87－0．89）。     

Ranking of individual mountain birch trees in terms of leaf chemistry: seasonal and annual variation

Summary. The quality of tree leaves as food for herbivores changes rapidly especially during the spring and early summer. However, whether the quality of an individual tree in relation to other trees in the population changes during the growing season and between years is less clear. We studied the seasonal and annual stability of chemical and physical traits affecting leaf quality for herbivores. Rankings of trees in terms of the contents of two major groups of phenolics in their leaves, hydrolyzable tannins and proanthocyanidins (condensed tannins), were very stable from the early spring to the end of the growing season. There were also strong positive within-season correlations in the levels of some other groups of phenolics in the leaves (kaempferol glycosides, myricetin glycosides and p-coumaroylquinic acid derivatives). The contents of individual sugars and the sum content of protein-bound amino acids showed patterns of seasonal consistency in mature leaves, but not in young developing leaves. The seasonal correlations in leaf water content and toughness were also strongest in mature leaves. The correlations between two years at corresponding times of the growing season were strongly positive for the major groups of phenolics throughout the season, but were more variable for the contents of proteins and some sugars. Leaf toughness and water content showed strong positive correlations in mature leaves. Despite the consistency of tree ranking in terms of leaf phenolics, the relative resistance status of trees may, however, change during a growing season because there was a negative correlation between the content of hydrolyzable tannins (early-season resistance compounds) in leaves early in the season and the content of proanthocyanidins (late-season resistance compounds) late in the season, and vice versa. Thus, assuming that phenolics affect herbivore preference and performance, different plants may suffer damage at different times of the growing season, and the overall variation between trees in the fitness consequences may be low. In addition, the adaptation of herbivorous insects to mountain birch foliage in general, as well as to specific tree individuals, may be constrained by variation in the relative resistance status of the trees.     

Species richness and stand stability in conifer forests of the Sierra Nevada

Theoretical and empirical studies have long suggested that stability and complexity are intimately related, but evidence from long-lived systems at large scales is lacking. Stability can either be driven by complex species interactions, or it can be driven by the presence/absence and abundance of a species best able to perform a specific ecosystem function. We use 64 years of stand productivity measures in forest systems composed of four dominant conifer tree species to contrast the effect of species richness and abundance on three stability measures. To perform this contrast, we measured the annual growth increments of > 900 trees in mixed and pure forest stands to test three hypotheses: increased species richness will (1) decrease stand variance, (2) increase stand resistance to drought events, and (3) increase stand resilience to drought events. In each case, the alternate hypothesis was that species richness had no effect, but that species composition and abundance within a stand drove variance, resistance, and resilience. In pure stands, the four species demonstrated significant differences in productivity, and in their resistance and resilience to drought events. The two pine species were the most drought resistant and resilient, whereas mountain hemlock was the least resistant and resilient, and red fir was intermediate. For community measures we found a moderately significant (P = 0.08) increase in the community coefficient of variation and a significant (P = 0.03) increase in resilience with increased species richness, but no significant relationship between species richness and community resistance, though the variance in community resistance to drought decreased with species richness. Community resistance to drought was significantly (P = 0.001) correlated to the relative abundance of lodgepole pine, the most resistant species. We propose that resistance is driven by competition for a single limiting resource, with negative diversity effects. In contrast resilience measures the capacity of communities to partition resources in the absence of a single limiting resource, demonstrating positive diversity effects.     

杉木人工林不同经营模式树冠的分形特征

对杉木纯林、杉木拟赤杨混交林、杉木观光木混交林的不同树种冠幅的分形维数进行计算和比较 .结果表明 :杉木观光木混交林中杉木种群冠幅分形维数 >杉木拟赤杨混交林中杉木种群冠幅分形维数 >杉木纯林冠幅分形维数 ;杉木观光木混交林中观光木种群冠幅分形维数 >杉木拟赤杨混交林中拟赤杨种群冠幅分形维数 .说明杉木混交林种间竞争小 ,而杉木种内竞争激烈 ,同时杉木同观光木之间的种间竞争小于杉木同拟赤杨之间的种间竞争 .图 4表 2参 16