不同品种小豆光合作用和生长发育对弱光的响应

为确定小豆作为林果行间套种作物的适宜性,通过田间试验和盆栽试验,测定全光和弱光处理(全光的48%)下3个小豆品种(阜南绿小豆、早熟黑小豆、晚熟黑小豆)在初花期的叶片光合特征参数、光合色素含量和RuBPCase活性,研究小豆生长发育对弱光的响应.结果表明: 弱光使3个品种小豆叶片的最大净光合速率、光饱和点、光补偿点等光合参数不同程度地向耐荫的方向变化,净光合速率、水分利用效率和RuBPCase活性也显著下降;遮阴后,阜南绿小豆的叶绿素a和b含量显著增加,Chl a/b和类胡萝卜素含量显著降低,其他小豆的叶绿素和类胡萝卜素含量无明显变化;弱光使3个品种小豆的生物量和干物质积累效率降低,根冠比降低,根瘤量减少,叶片数和叶面积指数减小;弱光胁迫下,阜南绿小豆提前开花、提前成熟,早熟黑小豆推迟开花、延迟成熟,而晚熟黑小豆只开花不结实.从遮阴后小豆的光合特性变化和生长发育差异等方面综合考虑,3个小豆品种的耐阴能力大小为:阜南绿小豆>早熟黑小豆>晚熟黑小豆.     

短小芽孢杆菌AR03对烟草赤星病菌和白粉病菌的防治

采用对峙培养法、凹玻片法、LB琼脂培养基萌发法测定短小芽孢杆菌AR03对烟草赤星病菌和白粉病菌的抑制作用.结果表明： AR03菌液对2种病菌的菌丝生长和分生孢子萌发均有明显的拮抗作用;对赤星病菌的抑制作用表现为:经AR03菌液原液(3×10⁸cfu·mL^-1)处理的菌丝隔间变短、肿胀且集结成团,内含物聚集,菌丝顶端生长膨大畸形;经该菌液处理的赤星病菌分生孢子不萌发或萌发产生畸形芽管,分生孢子变形、肿大,纵横分隔部分的组织膨胀呈泡状.AR03菌液原液、30倍液和200倍液对白粉病菌分生孢子萌发的平板抑制率分别为100%、91.4%和 69.3%,菌液对分生孢子萌发的破坏作用表现为分生孢子不萌发,细胞肿胀变形、细胞原生质解体或收缩,孢子内、外壁分离,由于原生质外泄,一些分生孢子内部呈中空状.温室防治试验结果表明： 不同浓度AR03菌悬液处理对烟草白粉病的防治效果存在显著差异,第二次药后7和15 d,AR03菌液原液的防治效果分别达到83.8%和90.3%,与对照药剂差异不显著;而100倍稀释液的防效分别为70.0%和73.3%,与对照药剂差异显著.AR03菌株防治白粉病的持效期为30 d以上.     

利用线性混合效应模型模拟杉木人工林枝条生物量

基于福建省将乐林场45株人工杉木解析木的572组枝条生物量数据,采用线性混合效应模型方法,建立杉木人工林枝条总生物量和枝、叶生物量的预测模型,并利用独立样本数据对模型进行检验.结果表明： 线性混合效应模型比传统多元线性回归模型的拟合精度高.不同随机效应参数的组合,其混合模型的精度不同.考虑异方差结构的混合模型能够消除数据间的异方差性,其精度更高,其中,对于枝条总生物量和叶生物量模型,以指数函数作为异方差结构时的模型精度最高;对于枝生物量模型,以常数加幂函数作为异方差结构时的模型精度最高.模型检验结果表明：对于杉木人工林枝条生物量预测模型,考虑随机效应和异方差结构的线性混合模型的检验精度比传统多元线性回归模型的精度有明显提高.     

Microarray expression profiling of Spodoptera litura in response to oxidative stress

To examine the expression profile of oxidative stress responsive genes in Spodoptera litura, we constructed a cDNA library from S. litura injected with hydrogen peroxide (H(2)O(2)). Using a microarray chip composed of 2,964 cDNAs, we screened gene expression at 1, 3, 5, 7, and 9 h post H(2)O(2) injection. Data were clustered into 15 groups of genes that behave similarly across each time course. Seventy-three genes were identified as being at least twofold up- or downregulated after treatment with H(2)O(2) in S. litura. We constructed expressed sequence tags (ESTs) for genes that changed at least twofold after treatment with H(2)O(2) . The functional classification of these ESTs based on Gene Ontology showed that the ESTs are rich in genes involved in oxidoreductase activity (5.7%), defense (14.3%), cellular process (22.9%), and development (17.1%).     

Plasmatocyte-spreading peptide influences hemocyte behavior via eicosanoids

Hemocyte-spreading behavior is required for expressing a cellular immune response, nodulation, which clears the vast majority of invading microbes from circulation. The nodulation response is completed by a layer of plasmatocytes, which spread over the nodule and initiate a malanization process leading to darkened nodules. Plasmatocyte-spreading peptide (PSP), the first reported insect cytokine, is responsible for mediating the spreading and attachment of some subclasses of plasmatocytes to nodules. Prostaglandins (PGs), one group of eicosanoids formed from arachidonic acid (AA), also mediate plasmatocyte spreading (PS), although the potential interactions between the PSP and PG signal transduction pathways have not been investigated. We tested our hypothesis that PSP acts via biosynthesis of eicosanoids, specifically PGs, in the beet armyworm, Spodoptera exigua. In this study, we report that (1) PSP and PGE(2) independently stimulated Ca(++)-dependent PS, (2) inhibitors of PG biosynthesis reversibly blocked PS, (3) dsRNA silencing the gene encoding proPSP blocked PS, which was rescued by PSP and by AA, (4) PSP-stimulated PS was reversibly impaired by inhibitors of PG biosynthesis, and (5) the inhibitor-impaired spreading was rescued by AA. Taken together, these points strongly support our model showing that PSP acts via a plasmatocyte-surface receptor, which stimulates biosynthesis of the PGs responsible for mediating plasmatocytes spreading.     

浮床生态场空间分布特征

在原位试验的基础上,建立浮床生态场模型.模拟结果表明,浮床生态势值在"场源"处最大,从浮床"场源"向周围水平方向以及向水下垂直方向,随着距离的增加生态势逐渐下降.同时,浮床植物的生物量对生态场效应有显著影响,浮床植物生长越旺盛、生物量越大,生态场效应越强.1 m×1m的浮床,当植物生物量为39.40 kg·m-2时,浮床系统可最远影响到距离浮床1.86 m范围内的水体,并对浮床周围10.90 m2范围内的水体产生作用.该模型可以模拟浮床生态场的空间分布特征及其随植物生长发育的动态变化过程,并可通过模型定量化反映浮床系统在其作用范围内对任意一点的作用强度及其综合影响,该模型的构建将为生态浮床的野外应用提供理论依据.     

草地贪夜蛾幼虫耐饥力及饥饿对其生长发育和繁殖的影响

本文旨在明确草地贪夜蛾Spodoptera frugiperda(J.E.Smith)幼虫耐饥力及饥饿处理对其生长发育、繁殖力的影响.选取初孵幼虫(幼虫孵化1 h内)、2、4、6、8和10日龄的幼虫进行饥饿处理,测定存活率和存活时间分析其耐饥力;进一步选取8日龄幼虫分别饥饿1、2、3和4d后再复食,分别统计和分析饥饿胁...     

Two groups of entomopathogenic bacteria, Photorhabdus and Xenorhabdus, share an inhibitory action against phospholipase A2 to induce host immunodepression

Photorhabdus and Xenorhabdus are two genera of entomopathogenic bacteria having a mutualistic relationship with their respective nematode hosts, Heterorhabditis and Steinernema. One of the pathogenic mechanisms of these bacteria includes host immunodepression, which leads to lethal septicemia. It has been known that X. nematophila inhibits phospholipase A2 (PLA2) to induce host immunodepression. Here, we tested the hypothesis of PLA2 inhibition using another bacterial species involved in other genera. P. temperata subsp. temperata is the intestinal symbiont of an entomopathogenic nematode, H. megidis. The bacteria caused potent pathogenicity in a dose-dependent manner against the fifth instar larvae of a test target insect, Spodoptera exigua, as early as 24 h after the intra-hemocoelic injection. In response to the live bacterial injection, hemocyte nodulation (a cellular immune response) and prophenoloxidase (pPO) activation were inhibited, while the injection of heat-killed bacteria significantly induced both immune reactions. The immunodepression induced by the live bacteria was reversed by the addition of arachidonic acid, the catalytic product of phospholipase A2. In contrast, the addition of dexamethasone, a specific PLA2 inhibitor to the heat-killed bacterial treatment, inhibited both immune capacities. In addition to a previously known PLA2 inhibitory action of X. nematophila, the inhibition of P. temperata temperata on PLA2 suggests that bacteria symbiotic to entomopathogenic nematodes share a common pathogenic target to result in an immunodepressive state of the infected insects. To prove this generalized hypothesis, we used other bacterial species (X. bovienni, X. poinarii, and P. luminescens) involved in these two genera. All our experiments clearly showed that these other bacteria also share their inhibitory action against PLA2 to induce host immunodepression.