Developmental anatomy of the three-dimensional structure of the vegetative shoot apex

There have been many studies of the vegetative shoot apex, but the majority of such studies have been based on median longitudinal sections. Anatomical studies based on surface views of the apex are relatively few in number. Unfortunately, three-dimensional structures, based on surface and transverse-sectional views as well as longitudinal views, have scarcely been analyzed. However, Hara attempted such analyses (1961, 1962, 1971a, b, c, 1977). He identified radial files of cells in the peripheral meristem and recognized four or five apical sectors in the three-dimensional structure of the shoot apex. The size of the central zone and the sizes and relative positions of the sectors change rhythmically in each plastochron. Further studies on the three-dimensional structure of the shoot apex are needed if we are fully to understand the morphogenesis and histogenesis of vascular plants.     

不同生境中云南松及其近缘种芽的比较形态解剖学研究

对滇东南、滇中以及滇西北地区的10个云南松种群及其近缘种的芽进行了比较形态解剖学研究,云南松种群及其近缘种芽的形态和结构特征表现为多态性,随着纬度或海拔(样带取样)的增加,从滇东南-滇中-滇西北,芽鳞长度和芽鳞排列的紧密程度等随着海拔高度的升高有增加的趋势。针叶的发育为"不对称"叶原基分化,形成不同针叶数的针束。云南松及其近缘种芽形态结构的多样性是生态环境的复杂性与生态因子组合的多样性共同作用的结果。     

RICE SALT SENSITIVE3 binding to bHLH and JAZ factors mediates control of cell wall plasticity in the root apex

Plasticity of root growth in response to environmental cues and stresses is a fundamental characteristic of plants, in accordance with their sessile lifestyle. This is linked to the balance between plasticity and rigidity of cells in the root apex, and thus is coordinated with the control of cell wall properties. However, mechanisms underlying such harmonization are not well understood, in particular under stressful conditions. We have recently demonstrated that RICE SALT SENSITIVE3 (RSS3), a nuclear factor that mediates restrictive expression of jasmonate-induced genes, plays an important role in root elongation under saline conditions. In this study, we report that loss-of-function of RSS3 results in changes in cell wall properties such as lignin deposition and sensitivity to a cellulose synthase inhibitor, concomitant with altered expression of genes involved in cell wall metabolism. Based on these and previous phenotypic observations of the rss3 mutant, we propose that RSS3 plays a role in the coordinated control of root elongation and cell wall plasticity in the root apex.     

Factors affecting in vitro shoot formation from vegetative shoot apices of apple and relationship between organogenic response and cytokinin localisation

ABSTRACT

The effects of macro- and micro-elements, benzyladenine (BA) concentration, and the period of auxin application on adventitious shoot formation from callus originating from vegetative shoot apices were tested on apple (Malus domestica Borkh) rootstock Jork 9. The putative relationship between organogenic response and cytokinin localisation was also studied by an immunolocalisation technique for in situ determination of free cytokinins. The use of MS (Murashige & Skoog, 1962) salts in the medium instead of those of LP (Quoirin & Lepoivre, 1977) had a strong positive effect both on shoot formation rate and on the number of shoots produced. The highest organogenic response from callus was induced using 17.8 μM BA in the presence of 2.7 μM NAA and by maintaining the explants for 20 days in darkness, then transferring them to fresh auxin-free medium and to the light. The in situ localisation studies, performed using antibodies with a marked specificity against zeatin and isopentenyladenine, revealed changes in the localisation of free zeatin in the tissues during the shoot-forming process, in particular during the active cell division phase leading to callus formation, and in the initial phase of bud formation. Changes in zeatin distribution in the tissues of the vegetative shoot apex during shoot formation may indicate a role for this cytokinin free base in cell differentiation and organogenesis.     

Transformation and regeneration of loblolly pine: shoot apex inoculation with Agrobacterium

Loblolly pine (Pinus taeda L.) is the mostimportant tree species in US commerce and has much to gain through geneticengineering. This species can be transformed using particle bombardment andAgrobacterium; however, the regeneration of plants fromtransgenic tissues has been difficult and the recovery of transgenic plants hasbeen rare. A shoot-based and genotype-independent transformation methodemploying Agrobacterium tumefaciens was used to facilitaterecovery of plants and permit the transformation of elite germplasm. Shootsfrom4–6 week old seedlings and adventitious shoots from culture wereinoculated with A. tumefaciens EHA101 (pGUS3), or EHA105(pSSLa.3), subjected to selection and regenerated. Shoots that survivedexhibited expression of the uidA gene (GUS) in a patterncharacteristic of the either the CaMV35S promoter (pGUS3), or the larch RbcSpromoter (pSSLa.3) transferred. Recovered plants were screened using PCRamplification. Southern DNA analyses and amplification of the T-DNA borderjunction confirmed genomic integration of both transferreduidA and nptII genes. In this proofofconcept study, the overall recovery of P. taeda shoots wasfair (10–20%), while recovery of intact rooted plants was poor (>1%)due to difficulty in rooting. Recovery of intact rooted plants from inoculatedshoots of P. eldarica and P. radiatawas more efficient (10–30%). The addition of a shoot multiplication stepand effective rooting protocols will improve the efficiency of this genotypeindependent transformation method in P. taeda, and inotherPinus spp.     

蛇瓜芽的诱导

蛇瓜的茎尖和腋芽以MS分别加入0.5～2.0 mg*L-1的6-BA和0.5～1.0 mg*L-1的6-BA与不同浓度的2,4-D、NAA、IAA组合培养时,以1.0 mg*L-1的6-BA以及6-BA与0.1～1.0 mg*L-1的IAA组合对芽的诱导效果最好.     

草莓生物技术研究进展

草莓的生物技术研究始于 6 0年代 ,但进展缓慢 ,进入 2 0世纪 90年代 ,取得了突破性进展 ,草莓的生物技术研究包括花药培养、茎尖培养、叶片和匍匐茎培养和遗传转化。     

Potassium in the Apoplast of the Root Sink Region

Using carboxyfluorescein, a fluorochrome transported along the phloem, we demonstrated that symplasmic phloem unloading in the watermelon root occurred in the basal zone of the meristem adjusting to the elongation zone. In the similar zones of maize and pumpkin roots, a high level of potassium was detected by X-ray microanalysis in the cell walls and intercellular spaces. Potassium concentration in these compartments comprised two-thirds of that in the cytoplasm. Such proportion between potassium concentrations in the cytoplasm and apoplast was characteristic of both the cortex and stele. Since potassium is a dominant osmotically active component in root tissues, such a proportion between its intracellular and apoplastic concentrations provides for a low turgor pressure in the cells of the sink region, in the phloem in particular. This might increase a turgor pressure gradient along the translocation route between source and sink tissues, which is a driving force for phloem assimilate transport.__________Translated from Fiziologiya Rastenii, Vol. 52, No. 4, 2005, pp. 591–599.Original Russian Text Copyright © 2005 by Krasavina, Burmistrova, Feshchenko, Nosov.     

新疆天山一号冰川地区十种藓类植物叶尖的微形态观察

在光学显微镜和扫描电镜下,对新疆天山一号冰川地区生长的10种藓类植物的叶尖（毛尖）的形态、齿（刺毛）、疣、角质层纹饰等微结构进行观察,其中电镜观察结果均为首次报道。结果表明：10种藓类植物叶尖的顶尖细胞和边缘细胞大部分都是透明的,并且细胞壁厚,细胞腔大;而叶尖边缘内卷、粗糙,细胞壁厚,干时细胞壁上下或侧面凹陷,其上有较多的小孔,这些都是明显耐旱特征,有利于水分的吸收及抵御长期寒冷、反射太阳辐射对其伤害,叶尖的类型对苔藓植物科、属级的分类意义不大,但其微形态如叶尖细胞及边缘细胞的形状、数目、细胞壁的凹陷程度以及其上角质层纹饰、乳突的微形态在同属的不同种之间存在明显差异,对于属下种间的鉴定具有一定的分类学价值。