Ovules and seeds in Euphorbioideae (Euphorbiaceae): structure and systematic implications

Ovule and seed structure in Euphorbioideae, one of the five euphorbiaceous subfamilies, is surveyed to evaluate its systematic implications on the basis of 79 species representing four of five tribes. All Euphorbioideae, like two other uniovulate subfamilies Acalyphoideae and Crotonoideae, but unlike most of two biovulate subfamilies Oldfieldioideae and Phyllanthoideae, consistently have a persistent and palisadal exotegmen composed of radially elongate, sclerotic, and pitted cells. Within Euphorbioideae, the tribe Stomatocalyceae (also with the palisadal exotegmen) is unusual in having vascular bundles in outer integument and clearly distinct from the remaining Euphorbioideae and the other uniovulate subfamilies. With the exclusion of Stomatocalyceae, Euphorbioideae are not anatomically divided into major groups such as a pseudanthial and a non-pseudanthial clade, but instead have some remarkable diversity within a tribe, a subtribe, and even a genus in the three ovule and seed characters: (1) the thickness of the inner integument, (2) the thickness of the outer integument, and (3) the presence or absence of an aril. Groups of genera and species wrapped by different combinations of their characteristics, however, are not necessarily harmonized with tribal or subtribal classifications available. Anatomical similarities and dissimilarities presented in this paper, as well as relationships among taxa presented in the classifications available, will be critically evaluated in the light of results of ongoing molecular phylogenetic analyses. Electronic Publication     

Ovules and seeds in Acalyphoideae (Euphorbiaceae): structure and systematic implications

Acalyphoideae, the largest subfamily of Euphorbiaceae, are investigated with respect to ovule and seed structure on the basis of 172 species of 80 genera in all 20 tribes of Acalyphoideae sensu Webster. All species of Acalyphoideae examined have bitegmic ovules with a non-vascularized inner integument. However, noticeable differences exist among and sometimes within the genera in the thickness of the inner and outer integument, the presence or absence of vascular bundles in the outer integument, whether ovules are pachychalazal or not, the presence or absence of an aril, seed coat structure (in terms of the best-developed mechanical cell-layer), and the shape of cells constituting the exotegmen. For the latter two characters, two different types of seed coat (i.e., "exotegmic" and "exotestal") and three different types of exotegmic cell (i.e., palisadal, tracheoidal and ribbon-like) were distinguished. Comparisons showed that three tribes Clutieae, Chaetocarpeae and Pereae are distinct from the other Acalyphoideae as well as from the other Euphorbiaceae in having an exotestal seed coat with a tracheoidal exotegmen. The tribe Dicoelieae is also distinct from the other Acalyphoideae in having an exotegmic seed that is composed of ribbon-like cells of exotegmen (i.e., cells both longitudinally and radially elongated, sclerotic and pitted). The tribe Galearieae, which should be treated as a distinct family Pandaceae, is also distinct from the other Acalyphoideae in having an exotegmic seed with a tracheoidal exotegmen (i.e., cells longitudinally elongated, sclerotic and pitted). The remaining genera of Acalyphoideae always have an exotegmic seed with a palisadal exotegmen (i.e., cells radially elongated, sclerotic and pitted). The shared palisadal exotegmen supports the close affinity of Acalyphoideae (excluding five tribes) with Crotonoideae and Euphorbioideae. Within the remaining genera of Acalyphoideae, a significant diversity is found in ovule and seed morphology with respect to the thickness of the inner and outer integument, the size of chalaza, vascularization of an outer integument and an aril.     

Structure and development of stomata on the primary root of Ceratonia siliqua L

Stomata of various sizes are produced on the primary root of Ceratonia siliqua L. Most are generated during embryogenesis, prior to seed desiccation. They can be detected on the dry embryo in a wide zone just above the root tip. Initially, large stomata are formed. These have the ability to induce divisions of their neighbouring cells, creating particular cell patterns around them. Later, small perigenous stomata are generated. As the root grows following seed germination, the stomatal zone overlaps with that of the root hairs. Although root stomata of C. siliqua undergo a structural differentiation that seems almost identical to that of the elliptical stomata formed on leaves, they are unable to move and remain permanently open. Polarizing microscopy of fully differentiated stomata and young stomata at the stage of stomatal pore formation revealed deposition of radial cellulose microfibril systems on their periclinal walls. However, these systems were less developed than those on leaf stomata, a feature that might be responsible for their inactivity. Besides, plastids of the root guard cells (GCs) do not differentiate into chloroplasts but function solely as amyloplasts. Root stomata have a short life span. During rapid and intense root growth, GCs cannot keep pace with the elongation of their neighbouring rhizodermal cells. They therefore split in their mid-region, transversely to the stoma axis. The two parts of the transversely torn stoma are dragged apart and a large opening is formed on the root surface, just above the substomatal cavity. The root stomata, together with these openings, may facilitate increased gaseous exchange during respiration and/or an increased transfer of some nutrients and water in the rapidly growing primary root.     

The genus Eugenia L. (Myrtaceae) in southern Africa: the structure and taxonomic value of stomata

The mature stomatal morphology of 11 southern African species of Eugenia , and also of E. uniflora L. (naturalized) and E. incerta Diimmer (a garden plant of unknown origin) has been studied by light and scanning electron microscopy.
Leaves of all the species are hypostomatic and water-stomata are occasionally present. Two different stomatal types, X and Y, differing mainly in their cuticular ornamentation, were found in the southern African species. The grouping of species based on stomatal characters supports a previous grouping of species on the basis of periderm and seed characters.
Conspicuous lipid bodies, usually present in the subsidiary cells, are limited to the southern African species. Although the subsidiary cells do not differ in shape and size from adjacent epidermal cells, their contents often have a higher tannin content than ordinary epidermal cells. The variable patterns of arrangement of the three to five subsidiary cells makes it difficult to identify the stomata with existing classifications based on mature topography. Thus, a new term 'anomostaurocytic' is proposed for the stomatal type found in the southern African species.
Stomata of E. uniflora and E. incerta are paracytic and anomocytic respectively, and the cuticular ornamentation of their stomata differs from those of the southern African species. The view that E. incerta is not closely related to the southern African species is supported by differences in its cuticular ornamentation, lack of lipid bodies in the subsidiary cells, anomocytic stomata and prominent T-pieces at the guard cell poles.     

大戟科叶下珠属花粉形态的研究

对叶下珠属Phyllanthus Linn.13种植物花粉进行了光学显微镜和扫描电镜的观察。研究表明,本属花粉虽然在大小、形状和外壁纹饰等方面有不同程度的差异,但差异最大的还是在于萌发孔类型上。可以把本属花粉分为3孔沟,4－5孔沟,多孔沟,散沟（沟短而纺锤形或近圆形）和散孔等类型。这些萌发孔类型虽然与李秉滔在中国植物志第44卷中所划分的组不很吻合,但或多或少有一定的相关性,并且对于属下的分类具有一定的意义。在外壁纹饰方面,均为网状纹饰,可分为具粗网眼,细网眼和中等网眼等几种类型。但纹饰类型在组间或种间的差异不大明显。     

Roles of CONSTITUTIVE PHOTOMORPHOGENIC 10 in Arabidopsis stomata development

Stomata are epidermal bi-celled structures that differentiate within special cell lineages initiated by a subset of protodermal cells. Recently, we showed that the Arabidopsis photomorphogenic repressor COP10 controls specific cell-lineage and cell-signaling developmental mechanisms in stomatal lineages. Loss-of-function cop10-1 mutant cotyledons and leaves produced (in the light and in the dark) abundant stomatal clusters, but nonlineage epidermal cells were not affected. Here we examine COP10 role in hypocotyls, cylindrical organs displaying a distinct epidermal organization with alternate files of protruding and non-protruding cells, with the latter producing a limited number of stomata. COP10 prevents stomatal clusters and restricts stomata production in hypocotyls; these roles are specific to lineage cells as in cotyledons, since COP10 loss of function does not elicit stomatal fate in nonlineage cells; COP10 also sustains the directional cell expansion of all hypocotyl epidermal cell types, and seems necessary for the differentiation between protruding and non-protruding cell files.     

小鼠卵巢囊淋巴孔的超微结构及其吸收功能

为研究小鼠卵巢囊及卵巢囊淋巴孔的超微结构 ,探讨其吸收功能 ,本实验用常规扫描电镜和透射电镜观察小鼠卵巢囊组织 ,应用Elscope软件对卵巢囊淋巴孔进行定量处理。并通过曲利本蓝吸收实验 ,测定其吸收功能。本实验首次发现小鼠卵巢囊上皮的立方细胞和扁平细胞之间存在淋巴孔 ,淋巴孔直径为 3 6 12± 1 132μm ,周长为 10 86 2± 3 4 15 μm。同时也发现小鼠卵巢囊上存在闭合淋巴孔。小鼠卵巢囊淋巴孔能吸收曲利本蓝 ,并随着时间的延长 ,曲利本蓝吸收增多。本实验的结果提示 :小鼠卵巢囊淋巴孔的大小、分布都与金仓鼠、豚鼠的卵巢囊淋巴孔有一定的差异 ,其淋巴孔的物质吸收功能具有时间依赖性。同时 ,闭合淋巴孔的发现表明淋巴孔的可调控性。卵巢囊淋巴孔使卵巢囊腔、卵巢囊淋巴系和腹膜腔沟通 ,在维持卵巢正常发育所需的体液环境方面发挥了重要作用     

宁夏大戟科植物分布新资料

报道了宁夏植物分布的1个新记录种黑水大戟.该种植物系宁夏首次发现.     

一氧化氮对大鼠胸膜淋巴孔调控及淋巴吸收的影响

实验研究了一氧化氮（nitric oxide,NO）对大鼠胸膜淋巴孔的调控和胸膜腔淋巴吸收的影响。NO供体和NOS（nitric oxide synthase）抑制剂分别经腹腔给药,示踪剂（台盼蓝）胸膜腔内注射后,处死大鼠,测定血清NO和台盼蓝浓度;在扫描电镜下观察各组胸膜淋巴孔,用计算机图像处理,统计学分析。结果显示,NO供体组血清NO浓度为49.34±18.47μmol/L,淋巴孔的面积和密度分别为6.80±1.13 μm2和170.24±66.60/0.1mm2;NOS抑制剂组血清NO浓度为17.72±6.58μmol/L,淋巴孔的面积和密度分别为5.72±1.54μm2和61.71±12.73/0.1mm2。血清NO浓度与淋巴孔开放的面积和密度成正相关（P<0.05）。在胸膜腔给示踪剂后,NO供体组血清台盼蓝的浓度为74.68±33.67mg/L,与对照组比较有显著差异（P<0.05）。提示,NO可以调控胸膜淋巴孔,促进胸膜腔淋巴吸收。     

Computer-based studies of diffusion through stomata of different architecture

BACKGROUND AND AIMS: The influence of stomatal architecture on stomatal conductance and on the developing concentration gradient was explored quantitatively by comparing diffusion rates of water vapour and CO(2) occurring in a set of three-dimensional stoma models. The influence on diffusion of an internal cuticle, a sunken stoma, a partially closed stoma and of substomatal chambers of two different sizes was considered. METHODS: The study was performed by using a commercial computer program based on the Finite Element Method which allows for the simulation of diffusion in three dimensions. By using this method, diffusion was generated by prescribed gas concentrations at the boundaries of the substomatal chamber and outside of the leaf. The program calculates the distribution of gas concentrations over the entire model space. KEY RESULTS: Locating the stomatal pore at the bottom of a stomatal antechamber with a depth of 20 microm decreased the conductance significantly (at roughly about 30 %). The humidity directly above the stomatal pore is significantly higher with the stomatal antechamber present. Lining the walls of the substomatal chamber with an internal cuticle which suppresses evaporation had an even stronger effect by reducing the conductance to 60 % of the original value. The study corroborates therefore the results of former studies that water will evaporate preferentially at sites in the immediate vicinity to the stomatal pore if no internal cuticle is present. The conductance decrease affects only water vapour and not CO(2). Increasing the substomatal chamber increases CO(2) uptake, whereas transpiration increases if an internal cuticle is present. CONCLUSIONS: Variation of stomatal structure may, with unchanged pore size and depth, profoundly affect gas exchange and the pathways of liquid water inside the leaf. Equations for calculation of stomatal conductance which are solely based on stomatal density and pore depth and size can significantly overestimate stomatal conductance.     

秋枫属的染色体数目及其进化意义

对秋枫属两个种Bischofia javanica和B·polycarpa的体细胞进行了染色体计数研究。结果表明这两个种在形态学上虽然存在差异,如秋枫是圆椎花序,重阳木是总状花序,但染色体数目均为2n=196。同时,结合细胞学、形态学和生态学特点探讨了秋枫属的染色体基数,多倍化的起源及其演化意义。     

Structure, distribution and taxonomic importance of stomata in some Indian Tephrosia Pers.(Fabaceae)

SUBBA RAO, J.V.& SHANMUKHA RAO, S. R.(1994).Structure, distribution and taxonomic importance of stomata in some Indian Tephrosia Pers.(Fabaceae).Structure, distribution and taxonomic importance of stomata in all the vegetative parts of 18 taxa of Indian Tephrosia including five species endemic to south India are described. The stomata are anisocytic, anomocytic or paracytic. In addition, brachyparacytic stomata have been recorded for the first time in this taxon. This is the first attempt to assess subgeneric treatment in the light of stomatal characteristics and it suggests certain realignments at the infrageneric level in Indian Tephrosia.     

Functional andromonoecy in Euphorbia (Euphorbiaceae)

The occurrence of cyathia containing staminate flowers but lacking a pistillate flower was studied in 17 species of Euphorbia. Male cyathia were found in the majority of species studied (88.2%) giving functional andromonoecy. In the male cyathia, the pistillate flower is generally totally absent, but sometimes a vestigial pistillate flower with a non-functional ovary is present. The proportion of male cyathia varied at both the population and species level. The position of male cyathia within the inflorescence showed a constant pattern among species: the proportion of male cyathia decreased from the first to the last levels of the pleiochasia. In general, perennial species had significantly higher proportions of male cyathia than annual species (mean 20 and 2.3%, respectively). In annual species there was a trend for production of male cyathia only in the first level of the inflorescence, whereas in perennials production up to the fourth level of the inflorescence was usual. Functional andromonoecy is common in Euphorbia and represents a new sex segregation in the genus. The selective forces causing this secondary sex segregation in Euphorbia, such as improved pollination or increased outcrossing, are discussed.     

The role of cytoskeleton in stomata functioning

The main question in this review is of whether and how the cytoskeleton of guard cells is involved in stomata movements. The main function of stomata is the regulation of the rate of gas exchange between the plant environment and underlying plant tissues. As a result of special morphology and anatomy GCs form the stomatal pore. It can open or close in a controlled manner via internal or external signal-induced changes in GCs turgor pressure, volume and shape. The mechanism of stomata movement is a complex process. A network of actin microfilaments and microtubules, dynamic polymers collectively known as the cytoskeleton forms protein fibril systems in GCs. CT elements are dynamic structures, interconnected to different cell structures. The organization of CT during morphogenesis of stomata is very important in establishing the size and shape of GCs. It is well documented that AFs and MTs are involved in stomata movements and can modify the ability of GCs to respond to environmental and hormonal stimuli. Data gathered clearly suggest that the organization of CT elements is not a direct effect of stomata movements. Several investigation procedures for study of the CT role in stomata functioning, including GCs treatment with anti-CT drugs (disrupters or stabilizers), have been analyzed and discussed in this review but the question of what role AFs and MTs play in stomata movements and how they work still remains open. The availability of new CT visualization techniques and the usage of mutants to study this problem is a good perspective for further research.     

大戟科植物学名订正

大戟科(Euphorbiaceae)是被子植物中的大科,是热带植物区系中的重要成分,还有橡胶[Hevea brasiliensis (Willd. ex A. Juss.) Muell. Arg.]、木薯(Manihot esculenta Crantz.)、油桐[Vernicia fordii (Hemsl.) Airy Shaw]等重要的粮食、经济植物和巴豆(Croton tiglium L.)、大戟(Euphorbia pekinensis Rupr.)、余甘子(Phyllanthus emblica L.)等常用药用植物,是一个具有重要经济价值的植物类群.     

Ovules and Seeds in Subfamily Phyllanthoideae (Euphorbiaceae): Structure and Systematic Implications

Lingelsheimia ) are distinct from the rest of the subfamily in having a thick inner integument (over six cells thick), an exotegmen composed of cuboidal cells (type II), and vascular bundles in the outer integument and, as molecular evidence also suggests, should be transferred to a separate family Putranjivaceae. Hymenocardieae (Didymocistus and Hymenocardia), whose positions have been controversial, are monophyletic in sharing endotestal seeds with a collapsed exotegmen which is unknown elsewhere in Euphorbiaceae. The genera seem to require separation from the Euphorbiaceae. In addition, a morphological heterogeneity of the two large genera Cleistanthus and Phyllanthus, as well as of tribe Antidesmeae subtribe Scepinae were also discussed. Received 20 October 2000/ Accepted in revised form 14 January 2001