Leaf morphological and physiological adjustments to the spectrally selective shade imposed by anthocyanins in Prunus cerasifera

Prunus domestica L. has green leaves, whereas Prunus cerasifera Ehrh. var. atropurpurea has red leaves due to the presence of mesophyll anthocyanins. We compared morphological and photosynthetic characteristics of leaves of these species, which were sampled from shoots grafted in pairs on P. domestica rootstocks, each pair comprising one shoot of each species. Two hypotheses were tested: (1) anthocyanins protect red leaves against photoinhibition; and (2) red leaves display shade characteristics because of light attenuation by anthocyanins. Parameters were measured seasonally, during a period of increasing water stress, which caused a similar drop in shoot water potential in each species. As judged by predawn measurements of maximum PSII yield, chronic photoinhibition did not develop in either species and, despite the anthocyanic screen, the red leaves of P. cerasifera displayed lower light-adapted PSII yields and higher non-photochemical quenching than the green leaves of P. domestica. Thus, it appears that, in this system, anthocyanins afford little photoprotection. As predicted by the shade acclimation hypothesis, red leaves were thinner and had a lower stomatal frequency, area- based CO2 assimilation rate, apparent carboxylation efficiency and chlorophyll a:b ratio than green leaves. However, red leaves were similar to green leaves in conductivity to water vapor diffusion, dry-mass-based chlorophyll concentrations and carotenoid:chlorophyll ratios. The data for red leaves indicate adaptations to a green-depleted, red-enriched shade, rather than a neutral or canopy-like shade. Thus, green light attenuation by anthocyanins may impose a limitation on leaf thickness. Moreover, the selective depletion of light at wavelengths that are preferentially absorbed by PSII and chlorophyll b may lead to adjustments in chlorophyll pigment ratios to compensate for the uneven spectral distribution of internal light. The apparent photosynthetic cost associated with lost photons and reduced leaf thickness, and the absence of a photoprotective advantage, suggest that there are other, yet to be identified, benefits for permanently anthocyanic leaves of P. cerasifera.     

Sprouts of shoot-clipped oak (Quercus alba and Q. robur) germinants show morphological and photosynthetic acclimation to contrasting light environments

New Forests - Sprouting by woody plants can increase species resilience to disturbance and foster regeneration during periods with little recruitment from seed. Though sprouting often plays a...     

Diversity of the endophytic filamentous fungal leaf community at different development stages of eucalyptus

Fungal endophytic species inhabiting the leaves of eucalypts are capable of utilising leaf sugars and can influence both plant growth and health. Endophytic fungal symbionts can use simple soluble sugars in leaves as their main carbon source. This study set out to determine the diversity and distribution of the endophytic filamentous fungal leaf community in the hybrid Eucalyptus urograndis due to its economic importance. The fungal leaf community was characterised using denaturing gradient electrophoresis (DGGE) and correlated with levels of leaf nutrients and sugars throughout plant development. Sequencing of DGGE bands revealed the presence of Basidiomycota and Ascomycota phyla. Fourteen species and three genera of filamentous fungi were identified, and the population structure was affected by the plant developmental stage. Levels of K, Cu, N and Mn influenced communities from the clonal garden, whereas leaves in the field had higher glucose, fructose and sucrose. Many fungi were found to be specific to a certain development stages: Diplomitoporus crustulinus, Podosphaera tridactyla and Aspergillus restrictus to the clonal garden stage;Chaetomella acutiseta and Ascotricha chartarum to the shading stage;Erratomyces patelii and Saxomyces sp. to the shading output stage;Lepidostroma sp. and Saxomyces sp. to the dispatch stage;and Mycosphaerella populicola to the field stage. Teratosphaeria toledana and Teratosphaeria acidotherma were found at more than one developmental stage. Cladosporium sp. and Rhodosporidium fluviale colonized and persisted in plants at the dispatch and field stages. This is the first report of P. tridactyla, A. restrictus, E. patelii, Saxomyces and Lepidostroma sp. as endophytes in eucalipt.     

不同经济发展阶段下我国的森林资源利用与保护

森林资源是经济发展过程中重要的投入要素,不同经济发展水平下的森林资源利用与保护具有明显的阶段性特征,反映了人类对森林资源的认识程度和发展林业的核心目标。依据经济发展阶段划分的相关理论,本文将我国的经济发展划分为4个阶段,研究了各发展阶段森林资源利用与保护的特点。分析认为:随着经济总量增加和经济增长方式的转变,森林利用的形式从单一趋向综合,对森林质量的要求不断提高,并决定着森林保护的形式和力度。     

三种园林植物叶形态生理指标及其环境指示作用

通过测定3种南方园林植物的叶面积、叶片含水量、比叶面积和叶绿素指数4项形态和生理指标,并对两种不同环境条件下各指标的差异进行分析,验证3种园林植物利用资源及对环境适应的能力。结果表明,高山榕(Ficus altissima)生长较快但不能较好地适应大气污染,白千层(Melaleuca quinquenervia)能抗大气污染,而尖叶杜英(Elaeocarpus apiculatus)更能适应资源丰富的环境条件。     

不同光照条件对有柄石韦的形态和生理特性的影响

为了解有柄石韦对光照条件的要求,以便将其更好地应用于园林绿化之中,分别设置了自然光强(CK组,9 000 lx)、重度强光(40 000 lx)、轻度强光(24 000 lx)、轻度弱光(4 000 lx)、弱光(800 lx)等5个胁迫处理,就其对有柄石韦的形态及光合生理特性的影响情况进行了试验,并采用DDS-11c型电导率仪、SPAD-502便携式叶绿素仪、美国产的LI-COR6400光合测定仪分别对不同光强胁迫处理后有柄石韦的相对电导率、叶绿素相对含量、相对含水量、光合荧光参数进行了测定。结果表明:在试验所设计的光照强度范围内,有柄石韦均可正常生长,而在光强为9 000 LUX的光照条件下其生长势最好;不同光强的胁迫处理对有柄石韦的相对电导率、叶绿素相对含量、相对含水量、光合荧光参数均有显著影响。     

薇菜加工各阶段的营养成份分析

薇菜采集后可加工制成干品包装出口，亦可加工制成各种罐头贮存销售。通过对完达山区薇菜的营养成份检测，获得部分基础数据可为这一资源的开发、加工和利用提供初步依据。     

桑天牛卵啮小蜂各发育阶段虫态的显微观察

为全面掌握桑天牛卵啮小蜂Aprostocetus prolixus各虫态的发育情况,显微镜下观察桑天牛卵啮小蜂的胚后发育,并采集图像。桑天牛卵啮小蜂卵期只有1 d,寄生桑天牛卵2 d时可见初孵幼虫,体小透明,卵圆形,淡黄色;寄生3~5 d时,幼虫逐渐变长呈梭状;寄生6~10 d时,体中部膨大尾部渐尖,分节明显,共13节;寄生15 d时,体色逐渐变白,体内已呈黑色;20 d时开始化蛹。雌蛹体长1.80~3.70 mm,雄蛹体长1.60~2.80 mm,预蛹乳黄色,近椭圆形。寄生30 d时,腹部、头部均变黑,触角展开,即将羽化成蜂。     

Pathogenicity of the pine wood nematode at different developmental stages

The ability of the pine wood nematode,Bursaphelenchus xylophilus, a pathogen that causes pine wilt disease, to kill cortical cells of Japanese black pine,Pinus thunbergii, during early development of the disease was conjectured to be a function of nematode developmental stage. A tangential segment of bark was removed from a 2-cm-long current-year stem. The cortex-exposed segments with cut cortical resin canals were designated as + RC-segments and those without them as − RC-segments. When a nematode population containing many older juveniles and adults (NL) was inoculated onto the cut surface, the − RC-segments were still alive 4 d after inoculation, as were non-inoculated control segments. When cortex-exposed segments were inoculated with either a nematode population containing many younger nematodes (NS) or with nematodes isolated from inoculated pine cuttings that also contained many younger juveniles, most tissue cells in − RC-segments died 4 d after inoculation, suggesting that younger juveniles killed pine cells directly, in contrast with older juveniles and adults. When nematodes were inoculated onto + RC-segments in which they could easily enter resin canals, both NL and NS killed the segment tissues. This suggests that NL is pathogenic to pine cells while living in resin canals. Such differences in the pathogenicity of NL and NS to pine parenchymatous cells were also demonstrated in a pathogenicity assay system using bark peelings, which allowed an estimate of direct attack on the cambial cells by nematodes. Based on these results, we hypothesize that younger juveniles are pathogenic to pine parenchymatous cells, while adults and older juveniles are not pathogenic. This work was supported in part by Grants-in-Aid for Scientific Research (No.01440012 and 06454088) and for Young Scientists (to K.I.) from Ministry of Education, Science, Culture, and Sports of Japan, and by a grant from PROBRAIN.     

The effects of sudden oak death on foliar moisture content and crown fire potential in tanoak

The introduction of non-native pathogens can have profound effects on forest ecosystems resulting in loss of species, changes in species composition, and altered fuel structure. The introduction of Phytophthora ramorum, the pathogen recognized as causing Sudden Oak Death (SOD), leads to rapid decline and mortality of tanoak (Lithocarpus densiflorus) in forests of coastal California, USA. We tracked foliar moisture content (FMC) of uninfected tanoaks, SOD-infected tanoaks, SOD-killed (dead) tanoaks, and surface litter for 12 months. We found that FMC values differed significantly among the three categories of infection. FMC of uninfected tanoaks averaged 82.3% for the year whereas FMC of infected tanoaks had a lower average of 77.8% (ANOVA, P = 0.04). Dead trees had a significantly lower FMC, averaging 12.3% (ANOVA, P < 0.01) for the year. During fire season (June–September), dead tanoak FMC reached a low of 5.8%, with no significant difference between dead canopy fuels and surface litter (ANOVA, P = 0.44). Application of low FMC values to a crown ignition model results in extremely high canopy base height values to escape crown ignition. Remote estimation of dead FMC using 10-h timelag fuel moisture shows a strong correlation between remote automated weather station (RAWS) 10-h timelag fuel moisture data and the FMC of dead leaves (R² = 0.78, P < 0.01). Results from this study will help refine the decision support tools for fire managers in SOD-affected areas as well as conditions in other forests where diseases and insect epidemics have altered forest canopy fuels.     

Linking morphological and ecophysiological leaf traits to canopy dieback in Persian oak trees from central Zagros

Intraspecific variability in morphological and ecophysiological leaf traits might be theorized to be present in declining populations,since they seem to be exposed to stress and plasticity could be advantageous.Here we focused on declining Persian oaks(Quercus brantii Lindl.var.persica(Jaub and Spach)Zohary)in the Zagros Mountains of western Iran,representing the most important tree species of this region.We selected trees with contrasting crown dieback,from healthy to severely defoliated,to investigate the relationships between canopy dieback and leaf morphology,water content and pigments.We also measured esterase and peroxidase,as enzymatic antioxidants and indicators of contrasting genotypes.Trees showing moderate to severe defoliation showed higher leaf mass area(LMA),reduced relative water content(RWC),and lower stomatal density(SD).Increasing LMA indicates a more sclerophyllic structure,according to drier conditions.We did not find significant differences in leaf pigments(chlorophyll a and b,and carotenoids)among crown dieback classes,suggesting that Persian oak trees are able to maintain accurate photochemical efficiency,while reduced RWC and SD suggest hydraulic limitations.Our results do not provide a consistent pattern as regards enzymatic antioxidant defense in Persian oak.Morphological leaf traits would be important drivers of future adaptive evolution in Persian oak,leading to smaller and thicker leaves,which have fitness benefits in dry environments.Nonetheless,drought responses may be critically affecting carbon uptake,as photosynthetic compounds are less effectively used in leaves with higher sclerophylly.     

The effect of defruiting at different stages of fruit development on leaf photosynthesis of "Golden Delicious" apple

Net photosynthetic rates (A) of leaves on 11-year-old, field-grown apple trees (Malus domestica Borkh. cv. Golden Delicious) were measured after removal of fruits at four different stages of development. Defruiting decreased A by 21, 42, 27 and 7% when fruits were growing at 311, 293, 229 and 113 mg(DW) day(-1), respectively. Photosynthesis was inhibited more in the afternoon than in the morning, but it was not affected during the first 8 h after fruit removal. Inhibition of A was positively correlated with crop sink strength, but it was not correlated with fruit relative growth rate or crop load. Defruiting decreased A at saturating irradiances (PPFD > 1000 micro mol m(-2) s(-1)), but did not modify the apparent quantum yield of single leaves. These results suggest that the overall effect of defruiting on carbon fixation is negligible in dense canopies, but it may be significant in sparse canopies and in single shoots.     

山区高等级公路不同设计阶段的地质勘察重点

论述山区高等级公路建设各阶段应重视的地质工作、提出勘察设计不同阶段的地质工作重点、分析目前在山区高等级公路勘察设计各阶段地质工作中存在的主要问题．并对山区高等级公路地质科技发展前景进行展望。     

Effects of enhanced nitrogen deposition on foliar chemistry and physiological processes of forest trees at the Bear Brook Watershed in Maine

Effects of enhanced nitrogen deposition on nutrient foliar concentrations and net photosynthesis of sugar maple (Acer saccharum Marsh.), American beech (Fagus grandifolia Ehrh) and red spruce (Picea rubens Sarg.) were evaluated at the Bear Brook Watershed in Maine (BBWM). The BBWM is a paired-watershed forest ecosystem study with one watershed treated since 1989 with bimonthly dry ammonium sulfate ((NH₄)₂SO₄) additions at a rate of 25.2 kg N ha⁻¹ year⁻¹, while the other watershed serves as a reference. The (NH₄)₂SO₄ treatment resulted in significant increases in foliar N concentrations for all three species and significant reductions in foliar Ca, Mg and Zn concentrations for American beech and red spruce. Treatment effects on foliar concentrations of other nutrients were not significant in any species. Despite higher N concentrations in all species, only treated sugar maple showed significantly higher photosynthetic rates. The non-response in net photosynthesis to higher foliar N in American beech and red spruce might be attributed to their low foliar Ca and/or Mg concentrations. Higher net photosynthetic rates in sugar maple might be explained by the higher foliar N and by the ability of this species to maintain an adequate Ca and Mg supply. Results suggested that nutrient imbalances due to inadequate supply of Ca and Mg might have counteracted a potential increase in net photosynthesis induced by higher N concentrations in American beech and red spruce.