Changes in leaf trichomes and epicuticular flavonoids during leaf development in three birch taxa

BACKGROUND AND AIMS: Changes in number of trichomes and in composition and concentrations of their exudates throughout leaf development may have important consequences for plant adaptation to abiotic and biotic factors. In the present study, seasonal changes in leaf trichomes and epicuticular flavonoid aglycones in three Finnish birch taxa (Betula pendula, B. pubescens ssp. pubescens, and B. pubescens ssp. czerepanovii) were followed. METHODS: Trichome number and ultrastructure were studied by means of light, scanning and transmission electron microscopy, while flavonoid aglycones in ethanolic leaf surface extracts were analysed by high-pressure liquid chromatography. KEY RESULTS: Density of both glandular and non-glandular trichomes decreased drastically with leaf expansion while the total number of trichomes per leaf remained constant, indicating that the final number of trichomes is established early in leaf development. Cells of glandular trichomes differentiate before those of the epidermis and produce secreted material only during the relatively short period (around 1-2 weeks) of leaf unfolding and expansion. In fully expanded leaves, glandular trichomes appeared to be at the post-secretory phase and function mainly as storage organs; they contained lipid droplets and osmiophilic material (probably phenolics). Concentrations (mg g(-1) d. wt) of surface flavonoids decreased with leaf age in all taxa. However, the changes in total amount ( microg per leaf) of flavonoids during leaf development were taxon-specific: no changes in B. pubescens ssp. czerepanovii, increase in B. pendula and in B. pubescens ssp. pubescens followed by the decline in the latter taxon. Concentrations of most of the individual leaf surface flavonoids correlated positively with the density of glandular trichomes within species, suggesting the participation of glandular trichomes in production of surface flavonoids. CONCLUSIONS: Rapid decline in the density of leaf trichomes and in the concentrations of flavonoid aglycones with leaf age suggests that the functional role of trichomes is likely to be most important at the early stages of birch leaf development.     

Silica deposition in relation to ageing of leaf tissues in Sasa veitchii (Carriere) Rehder (Poaceae: Bambusoideae)

BACKGROUND AND AIMS: Silica deposition is one of the important characteristics of plants in the family Poaceae. There have been many investigations into the distribution, deposition and physiological functions of silica in this family. Two hypotheses on silica deposition have been proposed based on these studies. First, that silica deposition occurs passively as a result of water uptake by plants, and second, that silica deposition is controlled positively by plants. To test these two apparently contradictory hypotheses, silica deposition in relation to the ageing of leaf tissues in Sasa veitchii was investigated. METHODS: Tissues were examined using a light microscope and a scanning electron microscope equipped with an energy dispersive X-ray microanalyser. KEY RESULTS: The deposition process differed depending on cell type. In mesophyll tissue, fusoid cells deposited large amounts of silica depending on leaf age after maturation, while chlorenchyma cells deposited little. In epidermal tissue, comprised of eight cell types, only silica cells deposited large amounts of silica during the leaf's developmental process and none after maturation. Bulliform cells, micro-hairs and prickle hairs deposited silica densely and continuously after leaf maturation. Cork cells, guard cells, long cells and subsidiary cells deposited silica at low levels. CONCLUSIONS: The significance of these observations is discussed in relation to the two hypotheses proposed for silica deposition in Poaceae. The results of the present study clearly indicate that both hypotheses are compatible with each other dependent on cell types.     

Modeling the vertical foliage distribution of an individual <Emphasis Type="Italic">Castanopsis cuspidata</Emphasis> (Thunb.) Schottky,a dominant broad-leaved tree in Japanese warm-temperate forest

The vertical foliage distribution of Castanopsis cuspidata (Thunb.) Schottky was examined in trees of various sizes to clarify its variation in relation to tree size and the light environment in a stand. As indices of these parameters, we analyzed crown social position (CSP: percent of stand height) and specific leaf area (SLA). The vertical foliage distribution of trees was expressed by a Weibull function. The variation in the vertical foliage distribution of C. cuspidata could be categorized into three types using crown social position and light environment. In the first type, leaves were concentrated to the top 20% of the tree; such trees are canopy trees that can receive full sunlight. The second type had a large relative crown depth and an asymmetric distribution with the maximum foliage located near the top of the tree; such trees are suppressed trees whose crowns do not receive sufficient light. The third type had a large relative crown depth and a symmetric distribution; such trees occur in high light environments, although their crowns are in the understory layer. The differences in the vertical foliage distribution are related to the strategies used to capture light. Multiple regression analysis showed that CSP and SLA at the top layer of the tree explained successive changes in the vertical foliage distribution. These results will contribute to scaling-up the vertical foliage distribution to the community level in pure stands of C. cuspidata using an individual-based model.     

分根区施保水剂对玉米气孔导度和单叶WUE的影响

盆栽条件下,研究了陕单9号玉米(zea mays L．)在根区不施保水剂(对照)、分根区施保水剂和根区全施保水剂3种处理下,叶片气孔导度、CO2吸收和H2O蒸腾的变化。结果表明,在75％土壤饱和持水量下,各指标在3种处理之间没有明显差别;在50％土壤饱和持水量下,分根区施保水剂显著降低了叶片气孔导度,叶片CO2吸收量和H2O蒸腾量也同时降低,但H2O蒸腾量下降幅度更大;在两种水分条件下,分根区施保水剂均能提高玉米单叶水分利用效率(water use efficiency,WUE)。     

银缕梅叶器官的宏观与微观结构及系统意义

银缕梅〔Ｓｈａｎｉｏｄｅｎｄｒｏｎｓｕｂａｅｑｕａｌｅ（Ｃｈａｎｇ）Ｄｅｎｇ,ＷｅｉｅｔＷａｎｇ〕叶表皮毛为星状毛,气孔器为平列式中周缘型,叶缘齿型为弗特吉型,叶肉栅栏组织一层细胞厚,三叶隙三叶迹的节,从茎节到叶之间的维管束呈分离合并分离的变化格局,并且呈续次合并和续次分离发育模式。这些结果进而说明银缕梅属的独立性,也从一个侧面证明它应属于狭义的弗特吉族（Ｆｏｔｈｅｒｇｉｌｅａｅ）。     

人为干扰对闽北森林群落物种多样性的影响

本文从群落及其组成结构等方面分析了闽北长期封禁保护的森林（ｃｏｎｓｅｒｖｅｄｆｏｒｅｓｔ,ＣＦ）和人为干扰后的退化森林（ｄｅｇｒａｄｅｄｆｏｒｅｓｔ,ＤＦ）群落物种多样性,结果认为,ＤＦ群落的植物物种丰富度和ＳｈａｎｎｏｎＷｉｅｎｅｒ指数与ＣＦ群落相近或略高,但ＤＦ群落植物种类组成和层次结构的物种多样性发生明显变化,群落物种种群基础已改变,稀有种和渐危种缺乏,这正是ＤＦ与ＣＦ群落物种多样性的本质差异。     

耐低钾基因型水稻品种孕穗期剑叶生理及根系活力

高耐低钾基因型水稻品种“湘早糯１号”比不耐低钾品种“双白－２１１－竹印”在缺钾和不缺钾营养液生长,孕穗期剑叶叶绿素及可溶性蛋白质含量高、光合速率、呼吸速率及ＮＲ酶活性高、根系活力强,而根导电率低、气孔阻力小．在缺钾（［Ｋ＋］３ｍｇ／Ｌ）营养液时,高耐低钾品种孕穗期剑叶的Ｍｇ,Ｆｅ,Ｃａ,Ｎａ含量增加,［Ｋ＋］含量稍小,但［Ｋ＋］的下降比率相对较低,吸Ｋ功能仍强     

杂交水稻开花结实期间叶片衰老

在杂交水稻开花期间,通过剪去穗部部分枝梗和叶片等处理,形成不同的库源比,叶片衰老的生理生化指标变化和结实率的测定表明,杂交水稻组合的库源矛盾大,叶片衰老快;但谷粒数与旗叶面积比不一定高,降低库源比,能明显减缓杂交水稻叶片中蛋白质、叶绿素含量及倒3、4、5片叶叶绿素含量的平均值与旗叶叶绿素含量的比率的下降和丙二醇含量的升高。这些都说明杂交水稻叶片功能早衰与其库源矛盾较大有关。     

植物的水容特征与其耐旱性的关系

在自然风晾条件下,研究了不同植物器官的相对含水量、水势及比水容之间的相互关系。结果表明：植物叶片阻止体内蒸腾失水的能力大小顺序依次为：花生（Arrachishypogaea）＞甘薯（Ipomoeabatatas）＞大豆（Glycinemax）＞玉米（Zeamays）,各植物茎的保水能力相差不大;甘薯的茎、叶在风晾4h后仍未永久凋萎,其他植物的茎、叶在风晾1～3h就出现永久凋萎;花生、甘薯、大豆和玉米叶片风晚3～4h后,其水势的下降幅度分别为：1．00,1．30,1．80和2．70mPa,花生、甘薯、大豆茎的水势下降幅度分别为：1．95,1.40和1．30mPa;植物茎、叶的水势与其相对含水量具有较好的对数关系;植株茎、叶的比水客值范围在0．0258～0．6835mPa-1之间,叶片的比水容大于茎的比水容。因此,植物的水容特征表明不同植物茎、叶的保水、释水能力不同,因而其耐旱、抗旱性不同。玉米和大豆的耐旱性小于花生、甘薯的耐旱性。     

应用离体叶片法鉴定棉花种质抗螨性的研究

应用离体叶片法,对9个棉花种质进行了鉴定,试验结果表明;种质间抗生性和忌避性差异显著;同株棉花不同部位的叶片对朱砂叶螨的抗生性无显著性差异。通过对叶螨在不同棉花种质上种群增长动态进行系统聚类,可将9个棉花种质划分为3类:斯字棉825-91、杞县86789、鄂棉314、苏联8911为1类,中棉164、潼南接龙棉、新库861517-2、南农NAC90-2为1类,美棉7-15独立为1类。依据朱砂叶螨在不同种质上的种群增长曲线和高峰期螨量增长倍数,可将9个种质划分为3个类型;斯字棉825-91、新库861517-2为抗性类型,潼南接龙棉、美棉7-15、南农NAC90-2为感性类型,其余为中抗类型。从忌避性看:斯字棉825-91、美棉7-15表现出较高的忌避性。