Geographic variation and plasticity to water and nutrients in Pelargonium australe

Here, patterns of phenotypic plasticity and trait integration of leaf characteristics in six geographically discrete populations of the perennial herb Pelargonium australe were compared. It was hypothesized that populations would show local adaptation in trait means, but similar patterns of plasticity and trait integration. Further, it was questioned whether phenotypic plasticity was positively correlated with environmental heterogeneity and whether plasticity for water-use traits in particular was adaptive. Seedlings were grown in a glasshouse at six combinations of water and nutrient availability. Leaf anatomical, morphological and gas exchange traits were measured. High amounts of plasticity in leaf traits were found in response to changes in growth conditions and there was evidence of local adaptation among the populations. While there were significant correlations between plasticity and environmental heterogeneity, not all were positive. Notably, patterns of plasticity and trait integration varied significantly among populations. Despite that variation, some of the observed plasticity was adaptive: fitness was correlated with conservative water use when water was limiting. Pelargonium arrived in Australia approximately 5 million yr ago. It is concluded here that high amounts of plasticity, in some cases adaptive, and weak integration among traits may be key to the spread and success of this species.     

氮素对不同品种烤烟叶片衰老、光合特性及产量和品质的影响

以豫烟5号、豫烟7号和NC89为材料,研究氮素对不同品种烤烟叶片衰老、光合特性及产量和品质的影响.结果表明：增施氮素可显著增强烤烟叶片超氧化物歧化酶(SOD)活性,降低丙二醛(MDA)含量,提高叶绿素含量,增强光合性能,从而延缓烤烟叶片衰老.与豫烟5号和NC89相比,豫烟7号叶片叶绿素含量较低,光合性能较弱,SOD活性低,MDA含量高,叶片衰老较快.与60和75 kg·hm^-2施N处理相比,45 kg·hm^-2 施N处理的烟叶均价、产值、上等烟比例均最高,且化学品质指标较好,符合优质烟叶要求.表明不同品种烤烟衰老生理特性有明显差异;氮素营养对烤烟叶片衰老、产量和品质有明显的调节作用;适量施氮可提高烟叶品质,获得较高的经济效益.     

小麦旗叶发育过程中光合效率的变化

作物的产量基本上取决于光合机构的大小和效率（Ｇａｒｄｎｅｒ等１９８５）。要不断提高作物的单位面积产量,除了尽可能满足水、肥供应以获得足够大的光合机构从而接受足够多的光能外,还必须提高叶片的光合效率。这是增加作物产量的一条必由之路。因此,很有必要深入开展光合效率调节控制机理的研究。关于叶片生长发育期间光合速率与叶片结构的变化,已经有大量的研究报告,并且有全面的综合评述（ˇＣａｔｓｋｙ和ˇＳｅｓｔàｋ１９９７）。然而,关于叶片生长发育期间光合效率特别是荧光参数如何变化的报告却很少。虽然ˇＣａｔｓｋｙ…     

A novel alkaline α-galactosidase gene is involved in rice leaf senescence

We previously isolated and identified numerous senescence-associated genes (SAGs) in rice leaves. Here we characterized the structure and function of an SAG-Osh69 encoding alkaline α-galactosidase that belongs to a novel family of glycosyl hydrolases. Osh69 is a single-copy gene composed of 13 exons located on rice chromosome 8. The expression level of Osh69 is not only up-regulated during natural leaf senescence but also induced rapidly by darkness, hormones (methyl jasmonic acid, salicylic acid), and stresses (H₂O₂ and wounding). The recombinant Osh69 protein over-expressed in Escherichia coli has displayed optimal α-galactosidase activity at pH 8.0. The enzyme showed good hydrolytic activities towards α-1,6-galactosyl oligosaccharides and galactolipid digalactosyl diacylglycerol. Immunoelectron microscopic analysis demonstrates that Osh69 is specifically localized in the chloroplasts of senescing leaves. These findings strongly suggest an important role for Osh69 in the degradation of chloroplast galactolipids during leaf senescence. The nucleotide sequence data reported will appear in the GenBank Nucleotide Sequence Database under the accession number AF251068.     

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.     

Influence of triacontanol on somatic embryogenesis in <Emphasis Type="Italic">Coffea arabica</Emphasis> L. and <Emphasis Type="Italic">Coffea canephora</Emphasis> P. ex Fr.

Summary A highly reproducible method for regeneration of Coffea arabica and C. canephora plants via direct somatic embryogenesis from cultured leaf and stem segments of regenerated plants was developed. Embryogenesis was influenced by the presence of triacontanol (TRIA) in the medium. TRIA incorporated at 4.55 and 11.38 μM in half-strength MS basal medium containing 1.1 μM 6-benzyladenine (BA) and 2.28 μM indole-3-acetic acid (IAA) induced direct somatic embryogenesis in both species. A maximum of 260±31.8 and 59.2±12.8 somatic embryos per culture were induced from in vitro leaf explants of C. arabica and C. canephora, respectively. TRIA also induced embryo formation from in vitro stem segment callus tissues along with multiplication of primary embryos into secondary embryos. By using TRIA, it was possible to obtain somatic embryogenesis in C. arabica and C. canephora.     

Effect of Rhizobium Sp. Inoculation on N2-Fixing and Photosynthetic Activities of Two Cowpea [Vigna unguiculata (L.) Walp.] Genotypes

Time course of symbiotic N₂-fixing and photosynthetic activities during vegetative growth from 30 d after plantation until pod set was measured in the CB5 and 7964 cowpea [Vigna unguiculata (L.) Walp.] genotypes of contrasting senescence traits. At emergence, seedlings were inoculated with a "non-cowpea miscellany" Rhizobium strain generally used to inoculate Cicer arietinum. Maximum N₂-fixing activity occurred in inoculated CB5 and 7964 plants about 54 and 68 d after plantation, respectively. A similar temporal shift of maximum was found for net photosynthetic rate (P _N), confirming a good coordination between the two processes. A higher P _N was found from the first measurements in inoculated plants of both genotypes as compared with uninoculated plants. Apparently, the maximum activity of both N₂-fixation and P _N was timed to occur at a particular stage of plant ontogeny correlating the high N supply with the high N demand by the plant. Rhizobium inoculation did not significantly affect partitioning coefficients of biomass to various plant organs but extended leaf longevity by about 10 d in the CB5 genotype, retarding thus the monocarpic senescence. This revised version was published online in June 2006 with corrections to the Cover Date.     

独叶草叶宏观形态性状的变异式样的初步研究

根据独叶草分布区内 8个居群的叶的 8个宏观性状在散点图上的表现 ,探讨了独叶草的形态变异式样。结果表明 ,独叶草在叶宏观性状上表现出了一定的变异性 ,这种变异性表现在不同居群间及由不同居群组成的区域上 ,但在居群间或由不同居群组成的区域间在性状上有不同程度的重叠。     

Global synthesis of the temperature sensitivity of leaf litter breakdown in streams and rivers

Streams and rivers are important conduits of terrestrially derived carbon (C) to atmospheric and marine reservoirs. Leaf litter breakdown rates are expected to increase as water temperatures rise in response to climate change. The magnitude of increase in breakdown rates is uncertain, given differences in litter quality and microbial and detritivore community responses to temperature, factors that can influence the apparent temperature sensitivity of breakdown and the relative proportion of C lost to the atmosphere vs. stored or transported downstream. Here, we synthesized 1025 records of litter breakdown in streams and rivers to quantify its temperature sensitivity, as measured by the activation energy (E_a, in eV). Temperature sensitivity of litter breakdown varied among twelve plant genera for which E_a could be calculated. Higher values of E_a were correlated with lower‐quality litter, but these correlations were influenced by a single, N‐fixing genus (Alnus). E_a values converged when genera were classified into three breakdown rate categories, potentially due to continual water availability in streams and rivers modulating the influence of leaf chemistry on breakdown. Across all data representing 85 plant genera, the E_a was 0.34 ± 0.04 eV, or approximately half the value (0.65 eV) predicted by metabolic theory. Our results indicate that average breakdown rates may increase by 5–21% with a 1–4 °C rise in water temperature, rather than a 10–45% increase expected, according to metabolic theory. Differential warming of tropical and temperate biomes could result in a similar proportional increase in breakdown rates, despite variation in E_a values for these regions (0.75 ± 0.13 eV and 0.27 ± 0.05 eV, respectively). The relative proportions of gaseous C loss and organic matter transport downstream should not change with rising temperature given that E_a values for breakdown mediated by microbes alone and microbes plus detritivores were similar at the global scale.