泊肃叶方程与苹果木质部的树液输导及矮化机理关系的研究

 利用自制的仪器深入研究了苹果品种和砧木木质部中树液的流量、压力、输导阻力、枝条长度和截面积之间存在的数量关系,证明了泊肃叶定律在苹果木质部树液输导中成立,并指出该理论在矮化机制、修剪理论和花芽分化等方面的应用价值。     

葡萄果实成熟前后一年生结果枝的养分变化

以‘巨峰’葡萄一年生结果枝为试材,采用蒽酮法测定枝条韧皮部、木质部、芽的淀粉和可溶性糖含量。结果表明,冬剪前芽、木质部、韧皮部的淀粉含量均达最高值,其中芽淀粉含量最高,木质部次之,韧皮部最少;葡萄果实转熟期韧皮部可溶性糖的含量大幅度下降,主要是输往果实,但采收后迅速提高,冬剪前达到最高值;木质部的可溶性糖含量自转熟期开始就缓慢增加,冬剪前达到最高值。这些变化均对树体安全越冬有利。     

桐花树和海桑次生木质部的生态解剖

对紫金牛科 (Myrsinaceae)的桐花树 (Aegicerascorniculatum)和海桑科 (Sonneratiaceae)的海桑 (Son neratiacaseolaris)的次生木质部的组织结构和数量特征进行了研究 ;并讨论了桐花树和海桑的木材结构与环境关系 ;它们的导管直径小、导管数量多、导管分布频率高 ,是对海滨盐渍环境的适应 ,保证水分在植物体内运输的安全性。桐花树和海桑的纤维壁厚度 (W )与纤维腔宽度 (L)的比值 (2W /L)分别为 0 6 7和 0 4 5 ,均小于 1 ,从木纤维 2W /L <1的角度看 ,桐花树和海桑的木材可用作造纸原料     

几个杨树木质部特异启动子的分离与序列分析

为了获得能在桑天牛(Apriona germari)寄主树种木质部特异表达的启动子用于害虫的防治,参照美洲山杨(Populus tremuloidMichx.)木质部纤维素合酶基因(PtCesA)序列(GenBank登录号:AF072131)设计引物,分别以三倍体毛白杨-93(Populus tomentosaCarr.-"93")、加杨-1(Populus CanadensisMoench.-"1")、意大利214杨(Populuscanadensiscv."I-214")基因组DNA为模板进行体外扩增,分离得到了MDCesAP、MXCesAP、JCesAP、YCesAP共4个片段。虽然4个片段序列之间及与美洲山杨中分离到的PtCesAP基因的同源性较低,但4个片断序列中的A/T含量都在60%~75%之间,且都有TATA box、poly(A)等启动子调控元件,因而有可能是新发现的特异启动子。     

植物激素与木材形成

综述了植物激素在树木维管组织分化中的作用．生长素是调节木质部细胞分化的主要因子；细胞分裂素在诱导分生组织发端和分生细胞分化上起重要作用；赤霉素促进纤维的形成，赤霉素和生长素结合使用，可有效地促进次生木质部中纤维分化；乙烯能促进树木韧皮部和木质部分化。还讨沦了木材形成过程中的三个主要问题：生长素含量的多少直接控制了沿树轴木质部导管、管胞的大小和密度；外界环境因子影响木质部细胞分化；温带落叶阔叶树环孔材和散孔材形成的机理，生长素控制环孔材树种早材宽导管的形成以及晚材窄导管和纤维形成的假说。对今后改善树木木材的质和量上有一定参考价值。     

不同供水条件下田间冬小麦气栓塞发生基本特征

 应用超声波技术,在田间灌水及干旱条件下对冬小麦品种9195叶片木质部气栓塞发生特征进行了研究。结果表明,超声波(AE)信号发生的基本特征为1d内一般有3个活跃期,第一活跃期以上午10:00～11:00出现频率最多,第二、三活跃期多分别出现在18:00左右和0:00前后,一般夜间0:00～2:00后信号终止。3个活跃期的AE信号发生强度可随生育进程、土壤水分及气候状况等条件变化。土壤干旱时,第三活跃期减弱或消失。灌水当日第二活跃期有增强的趋势。拔节初期,干旱小麦的AE信号发生量高于灌水小麦的。抽穗后土壤过度干旱时,AE信号量却常低于灌水小麦,笔者称其为“AE信号衰减现象”。灌水后土壤水分充足时,气栓塞也有相当程度的发生。气栓塞是伴随气孔开启、光照增强和温度升高而出现的植株水势快速下降的一种生理性反映。     

Contribution of the type II secretion system in systemic infectivity of <Emphasis Type="Italic">Ralstonia </Emphasis><Emphasis Type="Italic">solanacearum</Emphasis> through xylem vessels

Ralstonia solanacearum strain OE1-1 (OE1-1) systemically invades tobacco plants and causes bacterial wilt. A type II secretion system (T2SS)-deficient mutant of OE1-1, derived from EZ::TN<KAN-2>transposon-insertion, retained the ability of the parent strain to produce exopolysaccharide in vitro and grow in intercellular spaces immediately after invasion of host plants, but lost the ability to systemically infect the host. With transmission electron microscopy, the mutant was not observed in xylem vessels. These findings suggest that the T2SS contributes to systemic infection by enabling the bacteria to invade xylem vessels.     

The Analysis of Xylem Vessel Structure of Populus euphratica Oliv.Fresh Branch by HRCT

Analysis of the xylem vessels of Populus euphratica Oliv. (P. euphratica) branch anatomical characteristics is usually performed using microtomy. It is time-consuming to obtain an abundance of cross-sections using microtomy, and the sample was dried and sliced. The more effective technology for the analysis of the anatomical characteristics of P. euphratica fresh branch would be of significance for the study of the tolerance mechanism. In this paper, the xylem vessels structure of P. euphratica branches were investigated by high-resolution computed tomography(HRCT) and scanning electron microscope (SEM) to establish an efficient method to research the tolerance mechanism of P. euphratica. Analysis of the images allowed characterisation of the internal morphological and histology structural features of the fresh and dried branches of P. euphratica. Drying process caused distinct changes in the microstructure of the branches with shrinking in the more external regions and the interspace between vessels compared with fresh branches. The SEM slice of the same sample that clearly has a higher resolution than the HRCT slice, and the structure of the xylem vessels is distinct in the SEM. However, SEM is a destructive process that requires complex sample preparation, and the quality of the sample preparation and staining directly affect the resulting images. It can be concluded that the xylem vessel of P. euphratica branches can be observed using HRCT, which offers an effective means of obtaining the needed quantitative data on the tolerance mechanism of P. euphratica.     

Responses ofQuercus sapwood to infection with the pathogenic fungus of a new wilt disease vectored by the ambrosia beetlePlatypus quercivorus

Quercus serrata andQ. crispula wilt during the summer in wide areas along the Sea of Japan. Mass attacks of trees by an ambrosia beetle (Platypus quercivorus) are characteristic before appearance of the wilting symptoms. This study investigated the pathogenic effects of a fungus detected specifically in the wilting trees. This hyphomycete fungus,Raffaelea sp., has a distribution that correlates with the discolored xylem area called wound heartwood in which vessels are dysfunctional. Tylosis formation around the hyphae indicates vessel dysfunction. In areas with discoloration, the fungal hyphae were invading living ray parenchyma cells from the vessel lumen. As a protective reaction the ray cells exuded yellow substances into the vessels, but these substances seemed ineffective against the fungal activity, probably because the fungus disperses along the beetle's gallery before enough substance can accumulate. It should allow wide discoloration in sapwood. Cambium was not necrotic around the fungus. The cytological process in the host was as follows: (1) synthesis of secondary metabolites by the stimuli of oak fungus; (2) exudation of yellow substances into vessels; and (3) dysfunction of vessels and wound heartwood formation. In regard to wilting of trees, the pathogenicity of the fungus should be assessed by its ability to stop sap flow.     

柳苗中的变异电波传递

盐击柳树幼苗根系或烧伤其茎引发的变异电波（ＶＰ）可顺利地从环剥后的木质部通过，并再横向传递至韧皮部（树皮）。但若将柳茎中的木质部切除一段，ＶＰ的传递即被阻断。在柳茎木质部中，ＶＰ传递随水分供应的调节而定，水分供应充分时，ＶＰ传递速度正常；水分供应亏缺时，ＶＰ传递速度减慢或停止。这表明，刺激产生的伤素是借助木质部导管中的蒸腾流传递的，ＶＰ是木质部中伤素传导的反映。