不同地区青檀叶片的解剖及表皮特征的比较研究

采用石蜡切片技术和叶表皮离析法,对我国8个省共15个居群的青檀(Pteroceltis tatarinowii Maxim.)叶片特征进行了比较和分析.研究发现:各居群的栅栏组织细胞层数多数为2层,显示出一定的稳定性,但不同居群的叶片横切面解剖特征存在显著性差异.叶片上表皮细胞有多边形和不规则形两种类型,而下表皮细胞均为不规则形.上表皮细胞垂周壁为平直形、圆形、浅波形或深波形,差异较明显,下表皮细胞垂周壁则仅有深波形和浅波形两种.叶表皮毛的分布位置在各居群间不同,而表皮毛的类型在居群间稳定,且在多数居群中表皮毛与周围细胞形成花环结构.各居群的气孔器类型均为不规则型且均仅在下表皮随机分布,但气孔器的密度、大小等特征在不同居群间存在显著性差异.生境地的气候因子对青檀叶的特征产生一定的影响.结果表明:青檀叶的解剖特征在不同居群间差异性较大,青檀叶表皮的气孔密度等特征在居群间有一定差异,而气孔器类型和表皮细胞形状等特征较稳定,有一定的分类学价值.     

亚热带常绿阔叶林冠层附生植物叶片形态结构及生理功能特征的适应性研究

以南亚热带常绿阔叶林林冠层不同部位的4种附生植物:瓜子金(Dischidia chinensis Champ.ex Benth.)、蔓九节(Psychotria serpens L.)、白背瓜馥木(Fissistigma glaucescens (Hance) Merr.)和山萎(Piper hancei Maxim.)为研究对象,比较其叶片解剖结构和光合、蒸腾等生理特性,探讨附生植物叶片形态结构、生理生态功能对冠层不同部位水、热和光资源的适应以及叶片形态结构与生理生态功能的联系.结果表明:着生在冠层上部的两种附生植物瓜子金和蔓九节叶片小而厚(厚度分别为3558±63 μm和217.1±33.1 μm),气孔面积小(分别为185.7±3.7 μm2和225 4±5.2 μm2)且覆盖角质膜,有利于降低蒸腾速率(两者分别为0.17±0.02 mmol H2O和0.34±0.05 mmol H2O),提高水分利用效率WUE(分别为11.35±0.87 μmol CO2/mmolH2O和7.88±1.31 μmol COJmmol H2O),更适应冠层顶部高温、低湿、强光照的生境.这些结构特征却不利于气体交换,会致使瓜子金和蔓九节的光合作用降低(二者最大净光合速率Pmax分别为2.2±0.1 μmol CO2 ·m-2·s-1和3.2±0 4 μmol CO2·m-2·s-1).冠层中下部的白背瓜馥木和山蒌叶片相对较薄(厚度分别为90.8±9.9 μm和114 9±18.2 μm),气孔面积较大(分别为260.6±6.3 μm2和362.5±8.7 μm2),叶肉细胞分化明显,海绵组织排列松散,有利于提高对弱光的利用,增强光合能力(二者Pmax分别为9.5±1.3 μmol CO2·m-2·s-1和7.1±0.8 μmol CO2·m-2·s-1,是瓜子金和蔓九节Pmax的3～4倍),更适应冠层中下部低温、高湿、弱光照环境.这些结构同时会导致白背瓜馥木和山蒌蒸腾速率提高(两者分别为0.67±0.10 mmol H2O和0.74 +0.13 mmol H2O),WUE下降(分别为4.4±1.01μmol CO2/mmol H2O和3.4±0.9 μmol CO2/mmol H2O,仅为瓜子金和蔓九节WUE的30％ -48％).这表明着生在林冠层不同部位的附生植物叶片形态结构特征随着光合有效辐射、温度、湿度等微环境因子的变化表现出显著的差异,并致使各自的生理生态功能发生了相应的适应,是植物适应环境条件的重要表现.     

富钟瘰螈和广西瘰螈泄殖系统研究

用解剖学技术研究和比较了富钟瘰螈Paramesotriton fuzhongensis和广西瘰螈Paramesotriton guangxiensis的泄殖系统。结果显示两种瘰螈的泄殖系统基本相同,仅生殖腺在颜色和形状上稍有差异。它们具有后位肾,雄螈肾脏由副睾肾和尾肾组成。但雄螈尾肾发出的多条集尿管并不通往后位肾管而是向后汇合成副尿管通往泄殖腔。后位肾管主要起输精作用,而副尿管则负责输尿。结果揭示雄性泄殖管道有功能分离的趋势,这在两栖类中处于较高进化水平。     

Cotton shoot plays a major role in mediating senescence induced by potassium deficiency

The objective of this study was to determine the roles of shoot and root in the regulation of premature leaf senescence induced by potassium (K) deficiency in cotton (Gossypium hirsutum L.). Two contrasting cultivars (CCRI41, more sensitive to K deficiency; and SCRC22, a less sensitive cultivar) were selected for self- and reciprocal-grafting, using standard grafting (one scion/one rootstock), Y grafting (two scions/one rootstock) and inverted Y grafting (one scion/two rootstocks) at the seedling stage. Standard grafting was studied in the field in 2007 and 2008. There were no obvious differences in senescence between CCRI41 and SCRC22 scions while supplied with sufficient K. However, SCRC22 scions showed significantly greater K content, SPAD values (chlorophyll content), soluble protein content and net photosynthetic rates than CCRI41 scions while grown in K deficient solution or soil, regardless of rootstock cultivars, grafting types, growth stage and growth conditions. Also, SCRC22 scions had greater yield and less variation in boll weight either between upper- and lower sympodials, or between proximal and distal fruit positions from the main stem in the field under K deficiency, probably owing to reduced leaf senescence. Although the effect of rootstocks on leaf senescence under K deficiency was significant in some cases, the scion cultivars explained the highest percentage of variations within grafting treatments. The shoot-to-root feedback signal(s), rather than high shoot demand for K nutrition, was involved in the shoot regulation of premature senescence in cotton plants, achieved possibly by altering root K uptake.     

Nutritional and functional biology of exudate-feeding ants

Feeding extensively on plant exudates and honeydews, many tropical arboreal ant species exhibit δ¹⁵N values characteristic of herbivores. Consistent with hypothesized herbivory, these taxa behave in feeding assays as though more N-deprived than are strictly carnivorous ants. However, to an as yet uncertain degree, relationships with N-upgrading and/or recycling microsymbionts may lower isotopic ratios, making ants appear to be more herbivorous than they actually are. Nutritional (N) contributions from microsymbionts have been inferred for a variety of ant taxa based on intracellular or extracellular associations between ants and bacteria. However, stronger and more specific inferences are possible when variability in microsymbiont locations within the digestive system is considered in the context of taxonomic variability in ant diets and digestive anatomy. Diets of exudate feeders may vary predictably in ratios of usable carbohydrates (CHOs) to N, depending on the extent to which they tend melezitose-producing Homoptera. Status of the peritrophic membrane, proventricular structure, and number and placement of Malpighian tubules can be interpreted as traits contributing to supply of N and/or CHOs to microsymbionts. In general, a more integrative understanding of ant diets, digestive anatomy, and associated microsymbionts helps to set out specific hypotheses to be tested experimentally and (where possible) in a phylogenetic context.     

The relationship between water availability and anatomical characters in Carex hirta

The effects of edaphic moisture in anatomical characters were evaluated in two different populations of Carex hirta L. with three watering treatment for 6 months to evaluate stability, and determined taxonomic value. Water availability increased (p < 0.001) leaf thickness from 239 to 289 μm, metaxylem vessel diameter from 17 to 23 μm, air cavity size from 10 to 24% and adaxial epidermal cell height from 18 to 34 μm, and abaxial from 11 to 16 μm, adaxial epidermal cell length from 54 to 105 μm, and abaxial from 35 to 86 μm, and adaxial epidermal cell width from 20 to 33 μm, and abaxial from 15 to 23 μm. Stomatal index and the number of cells in the girder of sclerenchyma did not vary with water availability, hence these traits have taxonomic value. Other characters (the length and amplitude of wall undulations in the epidermal cells, the number of bulliform cells) have a doubtful relation with water availability, because they are variable even in constant homogeneous conditions.     

Influence of a salinity gradient on the vessel characters of the mangrove species Rhizophora mucronata

BACKGROUND AND AIMS: Although mangroves have been extensively studied, little is known about their ecological wood anatomy. This investigation examined the potential use of vessel density as a proxy for soil water salinity in the mangrove species Rhizophora mucronata (Rhizophoraceae) from Kenya. METHODS: In a time-standardized approach, 50 wood discs from trees growing in six salinity categories were investigated. Vessel densities, and tangential and radial diameters of rainy and dry season wood of one distinct year, at three positions on the stem discs, were measured. A repeated-measures ANOVA with the prevailing salinity was performed. KEY RESULTS: Vessel density showed a significant increase with salinity, supporting its use as a prospective measure of salinity. Interestingly, the negative salinity response of the radial diameter of vessels was less striking, and tangential diameter was constant under the varying environmental conditions. An effect of age or growth rate or the presence of vessel dimorphism could be excluded as the cause of the absence of any ecological trend. CONCLUSIONS: The clear trend in vessel density with salinity, together with the absence of a growth rate and age effect, validates the potential of vessel density as an environmental proxy. However, it can only be used as a relative measure of salinity given that other environmental variables such as inundation frequency have an additional influence on vessel density. With view to a reliable, absolute proxy, future research should focus on finding wood anatomical features correlated exclusively with soil water salinity or inundation frequency. The plasticity in vessel density with differing salinity suggests a role in the establishment of a safe water transport system. To confirm this hypothesis, the role of inter-vessel pits, their relationship to the rather constant vessel diameter and the underlying physiology and cell biology needs to be examined.     

The integration of cell proliferation and growth in leaf morphogenesis

A number of recent publications have assessed the outcome on leaf development of targeted manipulation of cell proliferation. The results of these investigations have awakened interest in the long-standing debate in plant biology on the precise role of cell division in morphogenesis. Does cell proliferation drive morphogenesis (cell theory) or is it subservient to a mechanism which acts at the whole organ level to regulate morphogenesis (organismal theory)? In this review, the central role of growth processes (distinct from cell proliferation) in morphogenesis is highlighted and the limitations in our understanding of the basic mechanisms of plant growth control are highlighted. Finally, an attempt is made to demonstrate how sequential local co-ordination of growth might provide an interpretation of some of the recent observations on cell proliferation and leaf morphogenesis.     

The Herbivore Assemblage, Herbivory and Leaf Chemistry of the Mangrove Kandelia obovata in Two Contrasting Forests in Hong Kong

The herbivore assemblage, intensity of herbivory and factors determining herbivory levels on the mangrove Kandelia obovata (previously K. candel, Rhizophoraceae) were studied over a 13-month period at two forests with contrasting growing conditions in Hong Kong. Mai Po was part of an eutrophic embayment in the Pearl River estuary and generally offered more favourable conditions for mangrove growth, whereas Ting Kok had a rocky substratum and oceanic salinity. Twenty-four insect herbivore species were recorded on K. obovata, with lepidopteran larvae that consume leaf lamina being the dominant species. While leaf litter production was similar at the two forests, herbivory level at Mai Po (mean = 3.9% in terms of leaf area loss) was more severe than that at Ting Kok (mean = 2.3%). Peak herbivory levels were found in summer at both locations (6.5% for Mai Po and 3.8% for Ting Kok). Young leaves of K. obovata at both locations were generally preferred by the herbivores from the period of late spring to summer. Concentrations of most feeding deterrents (ash, crude fibre, and total soluble tannins) were significantly higher in both young and mature leaves at Ting Kok, whereas leaf nutrients (total nitrogen and water) were the same at the two sites. Young leaves at Ting Kok contained about 30% more tannins than their counterparts at Mai Po. Significant differences in leaf chemistry also existed between young and mature leaves at either site. The differences were concomitant with the observed patterns of leaf herbivory on K. obovata, and suggest a potential relationship between environmental quality and plant defence against herbivory.