The occurrence of long chain polyprenols in leaves of plants of Rosaceae family and their isolation by time-extended liquid chromatography.

The long chain polyprenols composed of 30 and more isoprene units from leaves of plants belonging to the genera Potentilla and Rosa have been described. They occur in the form of fatty acid esters. The composition of polyprenol mixture was species dependent and its content reached ca. 0.5% wet weight. Large scale preparation of individual polyprenols from a natural polyprenol mixture was performed using time-extended liquid chromatography on the hydrophobic gel Lipidex-5000.     

The search for polyprenols in dendroflora of Vietnam

The occurrence of polyprenols in leaves of over 340 species of dendroflora in natural habitats in the regions of Hanoi and Hue in Vietnam was studied. Plant material was collected in the late autumn (October/November) during the end of a vegetation season. Leaves of about 200 plant species did not contain detectable amounts of polyprenols in contrast to few systematic families, e.g. Moraceae, Euphorbiaceae, where polyprenols were highly abundant and their pattern could be used as a chemotaxonomic criterion. Most often dominating polyprenols were prenol-11 and prenol-12. In several angiosperm species prenol-13 and detectable amounts of prenol-14 were also found. The incidence of prenol-13 and -14 was not restricted to a specific taxonomic group since species exhibiting domination of such longer chain polyprenols belonged to various systematic families. In some plants (e.g. Ceiba pentandra) alpha-cis polyprenols were accompanied by alpha-trans counterparts. This report describes several new plant species that may serve as natural sources of long chain polyprenols.     

Search for polyprenols in leaves of evergreen and deciduous Ericaceae plants.

Various species and cultivars of Ericaceae family were checked for the presence of long-chain polyprenols in their leaves. In the genus Rhododendron no polyprenols were found in the ever-green species, while they were present in the deciduous type. The polyprenols were of chain-length of 14-20 isoprene residues and they occurred in the form of acetic acid esters. The polyprenol accumulation is discussed with respect to senescence of leaves.     

Long-chain polyprenols in gymnosperm plants

Over 100 species of gymnosperm plants were checked for the presence of long chain polyprenols. Poly-cis long chain prenols, mainly as acetates, were found in green needles of about 60 species. In Cycadopsida either prenol-18 or prenol-20 were the main components of the natural polyprenol mixture. In Coniferopsida either a single polyprenol family was present like in all species of Pinaceae, or polyprenols consisted of two families differing in the size of polyprenol molecules: one family in which prenol-17 was the dominating component, and the other family of prenol-23. These complex mixtures of polyprenols were present in Araucariaceae, Cupressaceae, Taxodiaceae and also in Taxopsida. Seasonal variations were observed in the polyprenol content in green leaves.     

银杏叶聚戊烯醇抗肿瘤的生物活性研究

目的 :从银杏叶中分离聚戊烯醇新的有效部位 ,研究聚戊烯醇抗肿瘤的药效。方法 :通过提取、分离、精制 75 %以上银杏叶聚戊烯醇 ,以氟脲嘧啶 (5 Fu)为对照 ,选择肝癌 (Heps)实体型、肉瘤 (S180 )、艾氏癌 (EC)实体型等瘤谱 ,用不同剂量的聚戊烯醇进行小鼠移植性抗肿瘤药效实验。结果 :银杏叶聚戊烯醇对Heps、S180 和EC等移植性瘤谱的最高抑瘤率分别为 4 9 2 9%、6 0 89%和 5 2 4 7% (p <0 .0 0 5 )。结论 :银杏叶聚戊烯醇具有明显的抑制肿瘤的生物活性。     

Long-chain betulaprenol-type polyprenols from the leaves of Ginkgo biloba.

A long-chain betulaprenol-type polyprenol mixture was isolated from the leaves of Ginkgo biloba mainly as acetate. The structure was determined by mass spectroscopy, 1H-n.m.r. spectroscopy and 13C-n.m.r. spectroscopy. The mixture contained polyprenols-14-22, predominantly polyprenols-17, -18 and -19, and consisted of the dimethylallyl terminal unit (omega-terminal), two trans-isoprene residues, a sequence of 11-19 cis-isoprene residues and a terminal hydroxylated isoprene unit (alpha-terminal) aligned in that order. The concentration of these polyprenols in leaves increased from 0.04 to 2.0% of dry wt. with maturing of the leaves, though the content of total lipids was constant. The distribution of chain length in these polyprenols showed little variation throughout the whole life of the leaves.     

Effects of leaf age,nitrogen nutrition and photon flux density on the distribution of nitrogen among leaves of a vine (Ipomoea tricolor Cav.) grown horizontally to avoid mutual shading of leaves

Effects of leaf age, nitrogen nutrition and photon flux density (PFD) on the distribution of nitrogen among leaves were investigated in a vine, Ipomoea tricolor Cav., which had been grown horizontally so as to avoid mutual shading of leaves. The nitrogen content was highest in newly developed young leaves and decreased with age of leaves in plants grown at low nitrate concentrations and with all leaves exposed to full sunlight. Thus, a distinct gradient of leaf nitrogen content was formed along the gradient of leaf age. However, no gradient of leaf nitrogen content was formed in plants grown at a high nitrate concentration. Effects of PFD on the distribution of nitrogen were examined by shading leaves in a manner that simulated changes in the light gradient of an erect herbaceous canopy (i.e., where old leaves were placed under increasingly darker conditions with growth of the canopy). This canopy-type shading steepened the gradient of leaf nitrogen content in plants grown at a low nitrogen supply, and created a gradient in plants grown at high concentrations of nitrate. The steeper the gradient of PFD, the larger the gradient of leaf nitrogen that was formed. When the gradient of shading was inverted, that is, younger leaves were subjected to increasingly heavier shade, while keeping the oldest leaves exposed to full sunlight, an inverted gradient of leaf nitrogen content was formed at high nitrate concentrations. The gradient of leaf nitrogen content generated either by advance of leaf age at low nitrogen availability, or by canopy-type shading, was comparable to those reported for the canopies of erect herbaceous plants. It is concluded that both leaf age and PFD have potential to cause the non-uniform distribution of leaf nitrogen. It is also shown that the contribution of leaf age increases with the decrease in nitrogen nutrition level.     

The occurrence and seasonal distribution of C50-C60-polyprenols and of C100-and similar long-chain polyprenols in leaves of plants

Large amounts of fully unsaturated, mainly-cis, higher isoprenoid alcohols consisting of 17-30 isoprene units were found in several plants of the Rosaceae family. They occur as mixtures of several prenologues with either C85 - or C100 - prenol dominating in the form of acetates. The highest level of these polyprenols (0.5-1.0% of wet weight) were found in Crataegus crus- galli , Cotonoaster lucida, Prunus serotina and Sorbus suecica (intermedia). Their content increased with increasing age of the leaves. The dynamics of this rise is different from that observed in the case of accumulation of free C50- C60 - prenols (up to 0.5% of wet weight) in leaves of various plant species.     

Role of polyisoprenoids in tobacco resistance against biotic stresses

Infection with avirulent pathogens, tobacco mosaic virus (TMV) or Pseudomonas syringae pv. tabaci induced accumulation of polyisoprenoid alcohols, solanesol and a family of polyprenols [from polyprenol composed of 14 isoprene units (Pren-14) to -18, with Pren-16 dominating] in the leaves of resistant tobacco plants Nicotiana tabacum cv. Samsun NN. Upon TMV infection, solanesol content was increased seven- and eight-fold in the inoculated and upper leaves, respectively, while polyprenol content was increased 2.5- and 2-fold in the inoculated and upper leaves, respectively, on the seventh day post-infection. Accumulation of polyisoprenoid alcohols was also stimulated by exogenously applied hydrogen peroxide but not by exogenous salicylic acid (SA). On the contrary, neither inoculation of the leaves of susceptible tobacco plants nor wounding of tobacco leaves caused an increase in polyisoprenoid content. Taken together, these results indicate that polyisoprenoid alcohols might be involved in plant resistance against pathogens. A putative role of accumulated polyisoprenoids in plant response to pathogen attack is discussed. Similarly, the content of plastoquinone (PQ) was increased two-fold in TMV-inoculated and upper leaves of resistant plants. Accumulation of PQ was also stimulated by hydrogen peroxide, bacteria ( P.  syringae ) and SA. The role of PQ in antioxidant defense in cellular membranous compartments is discussed in the context of the enzymatic antioxidant machinery activated in tobacco leaves subjected to viral infection. Elevated activity of several antioxidant enzymes (ascorbate peroxidase, guaiacol peroxidase, glutathione reductase and superoxide dismutase, especially the CuZn superoxide dismutase isoform) and high, but transient elevation of catalase was found in inoculated leaves of resistant tobacco plants but not in susceptible plants.     

Methods for assessment of light leaf spot (Pyrenopeziza brassicae) on winter oilseed rape (Brassica napus) in the UK

Light leaf spot (Pyrenopeziza brassicae) was assessed as % plants with light leaf spot, % leaves with light leaf spot or % leaf area with light leaf spot in winter oilseed rape field experiments done at different sites (Rothamsted, Hertfordshire; Boxworth, Cambridgeshire; near Aberdeen, Scotland), with different cultivars (e.g. Bristol and Capitol), different fungicide treatments, on plants sampled at different dates. Regression analyses on data from these experiments showed that there were consistently good relationships between % leaves with light leaf spot and % plants with light leaf spot for plants sampled during the autumn and winter, until the % plants with light leaf spot approached 100%. The slopes and positions of regression lines were sometimes affected by cultivar, fungicide treatment or sampling date, but not by site. The relationship between % leaf area with light leaf spot (square root-transformed) and % leaves with light leaf spot was less consistent than that between % leaves with light leaf spot and % plants with light leaf spot and was sometimes affected by cultivar, fungicide treatment or sampling date but not by site. The relationship between % leaf area with light leaf spot (square root-transformed) and % plants with light leaf spot was also inconsistent and was sometimes affected by cultivar, fungicide treatment, sampling date and site.     

Always on the bright side: the climbing mechanism of Galium aparine

Galium aparine is a herbaceous climbing plant that attaches to host plants mainly via its leaves, which are covered by hooked trichomes. Although such hooks are found on both leaf surfaces, the leaves of G. aparine are mainly positioned upon the leaves of supporting plants and rarely beneath. In order to understand the mechanism underlying this observation, we have studied structural and mechanical properties of single leaf hooks, frictional properties of leaf surfaces, turgor pressure in different leaf tissues and bending properties of the leaves in different directions. Abaxial and adaxial leaf hooks differ significantly in orientation, distribution, structure and mechanical properties. In accordance with these differences, friction properties of leaves depend on the direction of the applied force and differ significantly between both leaf surfaces. This results in a ratchet mechanism. Abaxial leaf hooks provide strong attachment upon the leaves of adjacent plants, whereas adaxial hooks cause a gliding-off from the underside of the leaves of host plants. Thus, the leaves of G. aparine can function as attachment organs, and simultaneously orient themselves advantageously for their photosynthetic function. Further adaptations in turgor pressure or concerning an anisotropy of the flexural stiffness of the leaves have not been found.     

Concentration and retention of chlorophyll around the extrafloral nectary of Mallotus japonicus

Plants need to allocate some of their limited resources for defense against herbivores as well as for growth and reproduction. However, the priority of resource allocation within plants has not been investigated. We hypothesized that plants with extrafloral nectaries (EFNs) invest more chlorophyll around their EFNs—to support a high rate of carbon fixation there—than in other leaf parts of young leaves. Additionally, this chlorophyll may remain around EFNs rather than in the other leaf parts. We used Mallotus japonicus plants to investigate the chlorophyll content at leaf centers and edges and around EFNs at four stages of leaf development: middle‐expanded young leaves, fully expanded mature leaves, senior leaves, and leaves prior to abscission. These four stages of development were located at the third, fifth, eighth, and eleventh leaf positions from the apex, respectively. The results revealed that the chlorophyll content around the EFN side of the third‐position leaves was higher than that at the leaf center or edge. Although the chlorophyll content in the fifth‐position leaves did not differ between those at the leaf edge and around EFNs, the chlorophyll content around EFNs in the eighth‐position leaves was higher than that at the leaf centre and edge. The volume of EF nectar was positively correlated with the chlorophyll content around EFN during the leaf stage, but it was not correlated with the chlorophyll content in the leaf center and edge, except in fifth‐position leaves. These findings suggest that M. japonicus plants facilitate and maintain secretion of EF nectar in their young and old leaves, respectively, through the concentration and retention of chlorophyll around EFNs.     

The Effects of Increased Illumination and Shading on the Low-Light-Induced Decline in Photosynthesis in Cotton Leaves

An experiment was carried out to study whether low-light-induced damage to the photosynthetic system in leaves of cotton (Gossypium hirsutum cv. Deltapine) which are below the compensation point in the canopy can be arrested and reversed by increased illumination. In addition it was intended to find out whether the photosynthetic system in leaves of shade plants show a greater resistance to low-light-induced damage than leaves of plants from more exposed habitats. The plants were grown at high density, and increased illumination to the shade leaves in the canopy was achieved by thinning the stand. Thinning was carried out at two stages and its effects on the decline in the photosynthetic capacity of the 4th leaf were followed. An early thinning was carried out shortly after the 4th leaf dropped below the compensation point and a late thinning 2 weeks later. Comparison was also made between the low-light-induced damage to the photosynthetic capacity of the 4th leaf in plants grown under two light regimes during the progressive increase in self-shading of the 4th leaf within the canopy. It was observed that both types of thinning arrested the low-light-induced damage to the photosynthetic system in shade leaves. The decline in photosynthetic capacity of the 4th leaf was stopped after both early and late thinning. The dry weight of the shoot system in the early and late thinned plants was not significantly different. It was double that of the control plants. The plants thinned early did not have higher shoot weight than the late thinned plants since there was a rapid shedding of flowers and fruits after early thinning. The 4th leaf in the early thinned plants showed a 30% increase in chlorophyll content and dry weight per unit leaf area. It is suggested that shedding of flowers and fruits, and increases in chlorophyll and dry weight per unit leaf area in the early thinned plants were caused by a change in the hormonal balance of the plants. The photosynthetic system in leaves of shade plants showed a greater resistance to damage by low light intensity than the photosynthetic system in leaves of plants grown at higher light intensities.     

Exposure of cottonwood plants to ozone alters subsequent leaf decomposition

Summary Cottonwood saplings were exposed to ozone or charcoal-filtered air in a closed chamber. After leaf abscission, decomposition of individual leaf discs was measured in containers of stream water. Exposure of plants to 200 ppb ozone for 5 h caused early leaf abscission and changes in the chemical composition of leaves at time of abscission. Early-abscised leaves from O₃-exposed plants had higher nitrogen, but decomposed more slowly than leaves from control plants. Leaves from O₃-exposed plants that abscised at the normal time had lower nitrogen content and lower specific leaf mass than control leaves, but decomposed at the same rate as leaves from control plants. The results imply that O₃ exposure can alter fundamental processes important to the functioning of detritus-based aquatic ecosystems.     

罗汉松雌雄株叶形态结构的比较研究

该研究以雌雄异株植物罗汉松(Podocarpus macrophyllus)成熟叶为研究材料,采用光学显微镜、扫描电镜和透射电镜观察比较罗汉松雌、雄植株叶在形态、显微结构和超显微结构的差异,以明确罗汉松雌、雄株在进化过程中叶对环境功能的适应性。结果显示:(1)罗汉松雌株的叶片大于雄株,且两者的叶长、叶宽和叶柄长差异极显著,而叶柄厚、叶面积、叶体积、叶质量、比叶重(SLW)、面积与体积之比(A/V)等性状无显著差异。(2)雌株叶片的气孔相对较大,密度较高,且雌株气孔宽度极显著大于雄株;雌株叶片的上表皮长细胞宽度和下表皮短细胞宽度均显著大于雄株,但雌株叶片的上表皮长细胞和短细胞的长度则显著小于雄株。(3)罗汉松雌株叶片的栅栏组织厚度、海绵组织厚度、传输组织长度和宽度、上下角质层厚度、维管束厚度、叶片紧密度(CTR)及疏松度(SR)均极显著大于雄株,而雌株的下表皮厚度极显著小于雄株,但雌雄株叶片的上表皮细胞厚度和栅海比差异不显著;雌株叶片的栅栏组织细胞、叶绿体和线粒体均较雄株的长而细,且雌株的线粒体宽度极显著小于雄株。(4)罗汉松雌株叶片上表皮蜡质饰纹、下表皮角质层纹饰、气孔外拱盖纹饰及内缘类型等4个微形态特征与雄株差异明显。(5)叶表皮蜡质层能谱分析表明,罗汉松雌株叶片含有9种元素,而雄株叶片仅有8种(缺少K元素);且雌株的Si元素含量高于雄株,而雄株的C、O、Na、Mg、Al、Ca和Au元素含量均高于雌株。研究表明,罗汉松雌、雄植株之间存在明显的第二性征,雌株叶片结构有助于提高光合等性能以满足生殖需求;罗汉松雌、雄株叶形态结构的差异是其长期进化形成的有利于物种繁衍的适应策略。     

The effect of early blight disease caused by Alternaria solani on shoot growth of young tomato plants

The effect of increasing spore concentration of Alternaria solani (Early blight disease) on the shoot growth of young tomato plants was analysed. Changes in growth were related to the severity of infection which increased with increasing inoculum. Leaf production was not affected but dry weights and especially leaf expansion were decreased. The effective leaf areas of the five inoculated leaves (L1-L5 numbered from the plant base) were drastically decreased by expanding necrotic lesions and, to a lesser extent, by premature leaf fall. Healthy leaves expanding soon after inoculation (L6, L7) were markedly affected by the disease on the lower leaves and had decreased specific leaf areas (ratio of leaf area to leaf dry weight) but later formed (from L8) leaves were less affected and had greater specific leaf areas than equivalent leaves on uninoculated plants.     

Role of roots in regulating the growth rate and cytokinin content in leaves

The role of roots in the enhancement of cytokinin content and leaf growth of Phaseolus vulgaris plants after decapitation and partial defoliation was investigated. Partial excision of the roots of plants which were decapitated above the primary leaf node resulted in a reduction of leaf growth and soluble proteins accumulation in the primary leaves. Roots excision was done at time of decapitation and repeated 8 days later. Endogenous cytokinins, known to be involved in enhancing shoot growth, accumulated in the leaves and stems of decapitated and partially defoliated plants. Lower levels of cytokinins were detected in the leaves of decapitated plants with only a partial root system. The level of cytokinins in the roots of decapitated plants was reduced by partial root excision. The growth and accumulation of cytokinins in leaves were, however, not totally suppressed by removing a large proportion of the roots. At the commencement of the experiment the stem had a higher cytokinin content than both the leaves and roots. This suggests that the stem could be an alternative source of cytokinins to the leaves. The cytokinin complement in the leaves of decapitated plants is not identical to that in the roots. It appears that cytokinins supplied by the roots are metabolized in the leaves, or that alternatively certain cytokinins are synthesized in the leaves themselves.     

The effect of light intensity on stomatal frequency in leaves ofIris hollandica hort., var. wedgwood

Stomatal frequency in leaves of plants of Iris hollandica, cultivated under four light intensities, about 12%, 37%, 75% and 100% of natural daylight, was studied. The stomatal frequency decreases with lower light intensities. The gradients of stomatal frequency of successive leaves show an increase up to the third or fourth leaf with a subsequent decrease of values up to the highest leaf. The total number of stomata per leaf is not constant; differences exist in successive leaves of a shoot as well as among the leaves of plants growing under various light intensities. The character of gradients was changed at lower light intensities. The largest reaction to the light intensity appeared in leaves with higher stomatal frequency. The gradients in individual leaves depend on the insertion of the leaf. Both the shape and the slope of these gradients are influenced by the light intensity.     

Anatomical and morphological parameters of leaves and leaf petioles of Actinidia deliciosa

Differences in anatomy and morphology of the kiwifruit leaves and leaf petioles might play a considerable role in the sex-determination. Three months after bud break (June), the kiwifruit leaves of both male and female plants, grown on the vegetative and generative shoots showed different leaf area (128.6 ± 13.45 cm2 in male and 104.5 ± 4.02 cm2 in female plants) and shape. The most frequently leaf shape was determined as "folium cordatum" and "folium rotundato-cordatum". Higher values of total leaf thickness of the female leaves (190 ± 3.84 μm) in comparison to male leaves (174 ± 3.52 μm) were estimated, resulting in the thicker adaxial leaf epidermis and especially in thicker palisade parenchyma in female leaves (136 ± 2.76 μm in comparison to 104 ± 1.61 μm in male leaves). Typically bifacial leaves were observed in both male and female leaves. Anomocytic stomata in hypostomatic leaves were found. The reticulate venation appears to be the main type of leaf venation. Stalked stellate multicellular trichomes on the abaxial leaf side were frequently observed in the leaves of both sexes. No important differences between male and female plants were found in the structures of vascular system in leaves and leaf petioles. Thus leaf thickness and surface morphology of adaxial leaf epidermis can be considered as important structural parameters in the sex determination. This revised version was published online in July 2006 with corrections to the Cover Date.     

Contribution of osmotic adjustment to the dehydration tolerance of water-stressed pigeon pea (Cajanus cajan (L.) millsp.) leaves

Abstract Water-stressed pigeonpea leaves have high levels of osmotic adjustment at low leaf water potentials. The possible contribution of this adjustment of dehydration tolerance of leaves was examined in plants grown in a controlled environment. Osmotic adjustment was varied by withholding water from plants growing in differing amounts of soil, which resulted in different rates of decline of leaf water potential. The level of osmotic adjustment was inversely related to leaf water potential in all treatments. In addition, at any particular water potential, plants that had experienced a rapid development of stress exhibited less osmotic adjustment than plants that experienced a slower development of stress. Leaves with different levels of osmotic adjustment died at water potentials between –3.4 and –6.3 MPa, but all leaves died at a similar relative water content (32%). Consequently, leaves died when relative water content reached a lethal value, rather than when a lethal leaf water potential was reached. Osmotic adjustment delayed the time and lowered the leaf water potential when the lethal relative water content occurred, because it helped maintain higher relative water contents at low leaf water potentials. The consequences of osmotic adjustment for leaf survival in water-stressed pigeonpea are discussed.