Developmental process of sun and shade leaves in Chenopodium album L.

The authors’ previous study of Chenopodium album L. revealed that the light signal for anatomical differentiation of sun and shade leaves is sensed by mature leaves, not by developing leaves. They suggested that the two‐cell‐layered palisade tissue of the sun leaves would be formed without a change in the total palisade tissue cell number. To verify that suggestion, a detailed study was made of the developmental processes of the sun and shade leaves of C. album with respect to the division of palisade tissue cells (PCs) and the data was expressed against developmental time (leaf plastochron index, LPI). The total number of PCs per leaf did not differ between the sun and shade leaves throughout leaf development (from LPI ?1 to 10). In both sun and shade leaves, anticlinal cell division of PCs occurred most frequently from LPI ?1 to 2. In sun leaves, periclinal division of PCs occurred synchronously with anticlinal division. The constancy of the total number of PCs indicates that periclinal divisions occur at the expense of anticlinal divisions. These results support the above suggestion that two‐cell‐layered palisade tissue is formed by a change of cell division direction without a change in the total number of PCs. PCs would be able to recognize the polarity or axis that is perpendicular to the leaf plane and thereby change the direction of their cell divisions in response to the light signal from mature leaves.     

Phenotypic plasticity to light competition and herbivory in Chenopodium album (Chenopodiaceae)

Competition and herbivory are ubiquitous environmental challenges that affect most plants. We examined the influence of phenotypic responses to either competition or herbivory on the subsequent response of the plants to the other factor. The stem-elongation response of Chenopodium album to light competition attenuated its resistance to caterpillar herbivory in terms of herbivore mortality, but not in terms of growth of the survivors. Plant responses to herbivory did not affect subsequent responses to light competition. Thus, plants were largely able to express phenotypic plasticity (a proportional increase in the phenotype) following previous exposure to a different environmental factor. Although plants were able to express sequential plasticity, the final phenotype expressed was limited by exposure to previous environmental factors: induced resistance reduced plant height and stem elongation made plants more palatable to herbivores. Phenotypic plasticity in response to competition and herbivory may thus limit the subsequent expression of adaptive phenotypes.     

Effect of aqueous leaf extract of common lambsquarters (Chenopodium album L.) and NaCl on germination and seedling growth of rice

Aqucous leaf extract of common lambsquarters (Chenopodium album L.) was evaluated alone or in combination with NaCl for its effect on germination and rice seedling growth. The treatments have no effect on germination. However, growth of both shoot and root significantly decreased under NaCl alone and in combination with leaf extract. Root growth was affected more than the shoot and the effect of NaCl was accentuated in the presence of leaf extract.     

Specific leaf area, leaf nitrogen content, and photosynthetic acclimation of Trifolium repens L. seedlings grown at different irradiances and nitrogen concentrations

Clover seedlings were grown at different nitrogen concentrations (5, 10, 15, 20, 25 mM NO₃ ⁻, i.e. N₅ to N₂₅) and two irradiances, I (200 and 400 μmol m⁻² s⁻¹ of photon flux density, i.e. I ₂₀₀ and I ₄₀₀). Net photosynthetic rate (P _N), photosynthetic nitrogen use efficiency (PNUE), leaf chlorophyll (Chl) content, maximum photochemical efficiency (F_v/F_m), and actual photochemical efficiency of photosystem 2 (PS2) (Φ_PS2) increased from N₅ to N₁₅ and decreased with N₁₅ to N₂₅. P _N, PNUE, and Φ_PS2 were higher at I ₄₀₀ than at I ₂₀₀, but F_v/F_m and leaf Chl contents at I ₄₀₀ were lower than at I ₂₀₀. The effects of the N and I on specific leaf area (SLA) and N contents per unit dry mass (N_m) were similar, the SLA and N_m increased from N₅ to N₂₅ and they were higher at I ₂₀₀ than at I ₄₀₀. The nitrogen contents per unit area (N_a) increased from N₅ to N₂₀, but decreased from N₂₀ to N₂₅. The N_a was higher at I ₂₀₀ than at I ₄₀₀ when Trifolium repens grew at N₅ and N₁₀, but it was higher at I ₄₀₀ than at I ₂₀₀ at N₁₅ to N₂₅.     

Changes in leaf optical properties associated with light-dependent chloroplast movements

We surveyed 24 plant species to examine how leaf anatomy influenced chloroplast movement and how the optical properties of leaves change with chloroplast position. All species examined exhibited light-dependent chloroplast movements but the associated changes in leaf absorptance varied considerably in magnitude. Chloroplast movement-dependent changes in leaf absorptance were greatest in shade species, in which absorptance changes of >10% were observed between high- and low-light treatments. Using the Kubelka-Munk theory, we found that changes in the absorption (k) and chlorophyll a absorption efficiency (k*) associated with chloroplast movement correlated with cell diameter, such that the narrower, more columnar cells found in sun leaves restricted the ability of chloroplasts to move. The broader, more spherical cells of shade leaves allowed greater chloroplast rearrangements and in low-light conditions allowed efficient light capture. Across the species tested, light-dependent chloroplast movements modulated leaf optical properties and light absorption efficiency by manipulating the package (sieve or flattening) effect but not the detour (path lengthening) effect.     

Biotic and abiotic consequences of differences in leaf structure

Both within and between species, leaves of plants display wide ranges in structural features. These features include: gross investments of carbon and nitrogen substrates (e.g. leaf mass per unit area); stomatal density, distribution between adaxial and abaxial surfaces, and aperture; internal and external optical scattering structures; defensive structures, such as trichomes and spines; and defensive compounds, including UV screens, antifeedants, toxins, and silica abrasives. I offer a synthesis of selected publications, including some of my own. A unifying theme is the adaptive value of expressing certain structural features, posed as metabolic costs and benefits, for (1) competitive acquisition and use of abiotic resources (such as water, light and nitrogen) and (2) regulation of biotic interactions, particularly fungal attack and herbivory. Both acclimatory responses in one plant and adaptations over evolutionary time scales are covered where possible. The ubiquity of trade-offs in function is a recurrent theme; this helps to explain diversity in solutions to the same environmental challenges but poses problems for investigators to uncover numerous important trade-offs. I offer some suggestions for research, such as on the need for models that integrate biotic and abiotic effects (these must be highly focused), and some speculations, such as on the intensity of selection pressures for these structures.     

Morpho‐anatomical and physiological differences between sun and shade leaves in Abies alba Mill. (Pinaceae,Coniferales): a combined approach

Morphology, anatomy and physiology of sun and shade leaves of Abies alba were investigated and major differences were identified, such as sun leaves being larger, containing a hypodermis and palisade parenchyma as well as possessing more stomata, while shade leaves exhibit a distinct leaf dimorphism. The large size of sun leaves and their arrangement crowded on the upper side of a plagiotropic shoot leads to self‐shading which is explainable as protection from high solar radiation and to reduce the transpiration via the lamina. Sun leaves furthermore contain a higher xanthophyll cycle pigment amount and Non‐Photochemical Quenching (NPQ) capacity, a lower amount of chlorophyll b and a total lower chlorophyll amount per leaf, as well as an increased electron transport rate and an increased photosynthesis light saturation intensity. However, sun leaves switch on their NPQ capacity at rather low light intensities, as exemplified by several parameters newly measured for conifers. Our holistic approach extends previous findings about sun and shade leaves in conifers and demonstrates that both leaf types of A. alba show structural and physiological remarkable similarities to their respective counterparts in angiosperms, but also possess unique characteristics allowing them to cope efficiently with their environmental constraints.     

Variations in leaf morpho‐anatomy and photosynthetic traits between sun and shade populations of Eurya japonica (Pentaphylacaceae) whose seeds are dispersed by birds across habitats

Eurya japonica occurs in diverse light environments through seed dispersal by birds. As the seed size is extremely small, we hypothesized that newly germinated seedlings with restricted depth of roots and length of the hypocotyl would suffer high mortality due to increased transpiration in sunny habitats and low light in shady habitats. We also expected that surviving seedlings would differ in leaf traits between habitats as a result of selection. We aimed to determine how photosynthetic traits differ between habitats and how leaf structure is related to this difference. We examined photosynthesis and leaf morpho‐anatomy for plants cloned from cuttings collected from the forest understory (shade population) and neighboring roadsides and cut‐over areas (sun population) and then grown under two irradiances (18.5% and 100% sunlight) in an experimental garden. Under growth in 100% sunlight, cloned plants from the sun population exhibited significantly greater area‐based photosynthetic capacity compared to cloned plants from the shade population at a comparable stomatal conductance, which was attributable to a higher area‐based leaf nitrogen concentration. On the other hand, mean values of photosynthetic capacity did not significantly differ between the two populations. Cloned plants from the sun population had significantly thicker leaf laminas and spongy tissue and lower stomatal density compared to cloned plants from the shade population. Thickened leaf lamina might have increased leaf tolerance to physical stresses in open habitats. The variation in leaf morpho‐anatomy between the two populations can be explained in terms of the economy of leaf photosynthetic tissue.     

A model explaining genotypic and ontogenetic variation of leaf photosynthetic rate in rice (Oryza sativa) based on leaf nitrogen content and stomatal conductance

BACKGROUNDS AND AIMS: Identification of physiological traits associated with leaf photosynthetic rate (Pn) is important for improving potential productivity of rice (Oryza sativa). The objectives of this study were to develop a model which can explain genotypic variation and ontogenetic change of Pn in rice under optimal conditions as a function of leaf nitrogen content per unit area (N) and stomatal conductance (g(s)), and to quantify the effects of interaction between N and g(s) on the variation of Pn. METHODS: Pn, N and g(s) were measured at different developmental stages for the topmost fully expanded leaves in ten rice genotypes with diverse backgrounds grown in pots (2002) and in the field (2001 and 2002). A model of Pn that accounts for carboxylation and CO diffusion processes, and assumes that the ratio of internal conductance to g(s) is constant, was constructed, and its goodness of fit was examined. KEY RESULTS: Considerable genotypic differences in Pn were evident for rice throughout development in both the pot and field experiments. The genotypic variation of Pn was correlated with that of g(s) at a given stage, and the change of Pn with plant development was closely related to the change of N. The variation of g(s) among genotypes was independent of that of N. The model explained well the variation in Pn of the ten genotypes grown under different conditions at different developmental stages. Conclusions The response of Pn to increased N differs with g(s), and the increase in Pn of genotypes with low g(s) is smaller than that of genotypes with high g(s). Therefore, simultaneous improvements of these two traits are essential for an effective breeding of rice genotypes with increased Pn.     

Genetic variability in photosynthetic rate and leaf characters in Brassicaceae coenospecies

Thirty-nine Brassica coenospecies grown in pot cultures during 1993 and 1994 were screened for variability in photosynthetic rate (P _N ) and leaf characters. There were significant differences among the species in P _N per unit leaf area, chlorophyll (Chl) content, specific leaf mass (SLM), stomatal resistance (r _s ) and individual leaf size. The interactions species x year and species x date of measurement were small compared to the species effect. There was a significant negative correlation between P _N and r _s and a significant positive one between P _N and both Chl content and SLM. This revised version was published online in August 2006 with corrections to the Cover Date.     

水稻光合功能相关性状QTL分析

利用粳稻Kinmaze／籼稻DV85杂交后代单粒传衍生的81个F11家系所组成的重组自交系（Recombinant Inbred Lines,RILs）群体,研究水稻光合功能相关性状的数量性状基因座（QTL）。在水稻抽穗后7d测定叶片全氮含量（TLN）、叶绿素a／b比值（Chl．a：b）和叶绿素含量（Chl）。共检测到6个QTL,各QTL的LOD值为2．66～4．81,贡献率为11．2％-29．6％,其中,在第1、2和11染色体上检测到3个与全氮含量相关的QTL,相应贡献率为17．3％、15．3％、13．7％;在第3和4染色体检测到2个与叶绿素a／b比值相关的QTL,贡献率为13．8％和29．6％;在第1染色体检测到1个与叶绿素含量相关的QTL,贡献率为11．2％。4个QTL为本研究新检测的基因座。有趣的是,控制叶绿素含量的qCC-1位于第1染色体上RFLP标记C122附近,与已报道的NADH-谷氨酸合成酶基因位置一致,而叶绿素合成始于谷氨酸,暗示该基因座与水稻光合功能关系极为密切。然而,对抽穗后30d叶绿素含量进行QTL分析,结果未检测到与其相关的QTL,表明控制叶绿素含量qCC-1效应随水稻叶片的衰老而降低。     

Comparative leaf anatomy of Alpinia Roxb. species (Zingiberaceae) from China

The leaf anatomy of 20 Alpinia species from China was investigated. Results show that there is interspecific variation in the structure of the leaf midrib and petiole which can be used for species identification. Adaxial hypodermis is present in the lamina in all species of subgenus Catimbium and absent from all species of subgenera Dieramalpinia and Aobolocalyx and Alpinia , excepting A. conchigera, A. galanga and A. aquatica , which appear to be closely allied in having subepidermal fibres in midribs and petioles, which are absent from the rest of the species.     

Relationships between photosynthetic activity and silica accumulation with ages of leaf in Sasa veitchii (Poaceae, Bambusoideae)

BACKGROUND AND AIMS: Bamboos have long-lived, evergreen leaves that continue to accumulate silica throughout their life. Silica accumulation has been suggested to suppress their photosynthetic activity. However, nitrogen content per unit leaf area (N(area)), an important determinant of maximum photosynthetic capacity per unit leaf area (P(max)), decreases as leaves age and senescence. In many species, P(max) decreases in parallel with the leaf nitrogen content. It is hypothesized that if silica accumulation affects photosynthesis, then P(max) would decrease faster than N(area), leading to a decrease in photosynthetic rate per unit leaf nitrogen (photosynthetic nitrogen use efficiency, PNUE) with increasing silica content in leaves. METHODS: The hypothesis was tested in leaves of Sasa veitchii, which have a life span of 2 years and accumulate silica up to 41 % of dry mass. Seasonal changes in P(max), stomatal conductance, N(area) and silica content were measured for leaves of different ages. KEY RESULTS: Although P(max) and PNUE were negatively related with silica content across leaves of different ages, the relationship between PNUE and silica differed depending on leaf age. In second-year leaves, PNUE was almost constant although there was a large increase in silica content, suggesting that leaf nitrogen was a primary factor determining the variation in P(max) and that silica accumulation did not affect photosynthesis. PNUE was strongly and negatively correlated with silica content in third-year leaves, suggesting that silica accumulation affected photosynthesis of older leaves. CONCLUSIONS: Silica accumulation in long-lived leaves of bamboo did not affect photosynthesis when the silica concentration of a leaf was less than 25 % of dry mass. Silica may be actively transported to epidermal cells rather than chlorenchyma cells, avoiding inhibition of CO2 diffusion from the intercellular space to chloroplasts. However, in older leaves with a larger silica content, silica was also deposited in chlorenchyma cells, which may relate to the decrease in PNUE.     

Effects of leaf age,elevation and light conditions on photosynthesis and leaf traits in saplings of two evergreen conifers,Abies veitchii and A. mariesii

亚高山的针叶树物种分布在广泛的海拔范围内,因此它们必须具备抵抗严酷自然条件(如高海拔和长期的黑暗)的能力。 在日本中部的亚高山地带,两种常绿的针叶树冷杉(Abies veitchii)和马尾冷杉(Abies mariesii)分别在低海拔和高海拔地区占据优势。本研究的目的是探讨叶龄、海拔和光照条件对两个物种叶片形态和生理性状的影响。我们以两种针叶树的幼树为样本,分别在两种针叶树下部 (1600米)和上部(2300米)的林下层和冠层间隙中取样,并分析叶龄、海拔和光照条件对冷杉和马尾冷杉的光合作用和叶片性状的影响。研究结果表明,两种针叶树的光合作用和叶片性状对叶龄呈现相似的响应,但其对海拔和光照条件则表现出不同的响应。冷杉最大光合速率与单位叶面积质量和非结构性碳水化合物浓度呈负相关。两种树木的单位叶面积质量在高海拔处均增加,而非结构性碳水化合物浓度仅在冷杉中增加。因此,冷杉的最大光合速率在高海拔时降低。此外,两个物种的最大光合速率均与氮浓度呈正相关。在林下层,叶片氮浓度在冷杉中下降,而在马尾冷杉中上升。在林下条件下,只有马尾冷杉的单位叶面积质量下降、叶绿素-氮比增加,表明在黑暗条件下,马尾冷杉比冷杉有更高的捕光效率。本研究表明,与冷杉相比,马尾冷杉的光合和叶片特性具有更强的耐阴性,光合速率受海拔的影响较小,从而使马尾冷杉在林下植被中生存,并在高海拔地区占据优势。     

Corn (Zea mays L.) growth, leaf pigment concentration, photosynthesis and leaf hyperspectral reflectance properties as affected by nitrogen supply

Plant nitrogen (N)deficiency often limits crop productivity. Early detection of plant N deficiency is important for improving fertilizer N-use efficiency and crop yield. An experiment was conducted in sunlit, controlled environment chambers in the 2001 growing season to determine responses of corn (Zea mays L. cv. 33A14) growth and leaf hyperspectral reflectance properties to varying N supply. Four N treatments were: (1) half-strength Hoagland's nutrient solution applied throughout the experiment (control); (2) 20% of control N starting 15 days after emergence (DAE); (3) 0% N starting 15 DAE; and (4) 0% N starting 23 DAE (0% NL). Plant height, the number of leaves, and leaf lengths were examined for nine plants per treatment every 3–4 days. Leaf hyperspectral reflectance, concentrations of chlorophyll a, chlorophyll b,and carotenoids, leaf and canopy photosynthesis, leaf area, and leaf N concentration were also determined during the experiment. The various N treatments led to a wide range of N concentrations (11 – 48 g kg^–1 DW) in uppermost fully expanded leaves. Nitrogen deficiency suppressed plant growth rate and leaf photosynthesis. At final harvest (42 DAE), plant height, leaf area and shoot biomass were 64–66% of control values for the 20% N treatment, and 46-56% of control values for the 0% N treatment. Nitrogen deficit treatments of 20% N and 0% N (Treatment 3) could be distinguished by changes in leaf spectral reflectance in wavelengths of 552 and 710 nm 7 days after treatment. Leaf reflectance at these two wavebands was negatively correlated with either leaf N (r = –0.72 and –0.75^**) or chlorophyll (r = –0.60 and –0.72^**) concentrations. In addition, higher correlations were found between leaf N concentration and reflectance ratios. The identified N-specific spectral algorithms may be used for image interpretation and diagnosis of corn N status for site-specific N management.     

Effect of leaf structure and water status on carbon isotope discrimination in field-grown durum wheat

The relationships between leaf and kernel carbon isotope discriminations (Δ) and several leaf structural parameters that are indicators of photosynthetic capacity were studied in durum wheat grown in the field under three water regimens. A set of 144 genotypes were cultivated in two rain-fed trials, and 125 of these were grown under supplementary irrigation before heading. Total chlorophyll and nitrogen (N) contents, the dry mass per unit leaf area (LDM, the reciprocal of specific leaf area) and carbon isotope discrimination (Δ) were measured in penultimate leaves and Δ of mature kernels was also analysed. Both LDM and N per unit area showed significant (P≤ 0.001) negative correlation (r=–0.60 and r=–0.36, respectively) with leaf Δ in the wettest trial. Little or no correlation was found for any structural parameter and leaf Δ in the rain-fed trials. In contrast, in the two rain-fed trials LDM was the parameter with the strongest positive correlation (P≤ 0.001) with kernel Δ (r= 0.47 and 0.30) and grain yield (r= 0.43 and 0.29), whereas no correlation was found in the irrigation trial. These correlations, rather than representing a causal link between the amount of photosynthetic tissue and Δ, were probably indirect associations caused by a parallel effect of water status and phenology on leaf structure, grain Δ and yield. Correlations across trials (i.e. environments) between leaf structure and either Δ and yield were very high, although also spurious. Our results suggest that LDM should be used to cull segregating population differences in leaf Δ based on the internal photosynthetic capacity only in the absence of drought. Selecting for kernel Δ and grain yield on the basis of LDM is worthwhile for rain-fed trials.     

水龙骨亚科植物(水龙骨科)的形态解剖学研究

对水龙骨科水龙骨亚科5属16种植物的孢子形态、叶表皮结构、叶柄和根状茎的横切、根状茎上的鳞片以及叶脉特征进行了详细的观察和分析,探讨了该亚科植物的系统位置和亲缘关系。结果表明,在该亚科植物类群中,主要分布于亚洲亚热带地区的篦齿蕨属、拟水龙骨属和水龙骨属的亲缘关系较近,而主要分布于亚洲热带地区的棱脉蕨属和亚洲温带地区的多足蕨属的系统位置则分别较孤立。     

The relationship between phytochrome-photoequilibrium and Development in light grown Chenopodium album L.

Chenopodium album seedlings were grown in light environments in which supplementary far-red light was mixed with white fluorescent light during various parts of the photoperiod. Both the logarithmic rate constant of stem extension and the leaf dry weight: stem dry weight ratio were linearly related to estimated phytochrome photoequilibrium () in each treatment regime. These data are taken to be indicative of a functional link between phytochrome and development in the green plant. A layer of chlorophyllous tissue only affected the linearity between calculated and the logarithmic stem extension rate at high chlorophyll concentrations, whilst even low concentrations-equivalent to the levels found in stem tissue-caused a significant shift in measured . End-of-day supplementary far-red (FR) light induced between 0–35 per cent of the response elicited by all-day supplementary FR, whilst daytime supplementary FR (with a white fluorescent light end-of-day treatment) induced approximately 90 per cent. The ecological significance of this difference is discussed with respect to shade detection.Paper 7 in the series The function of phytochrome in the natural environment [for paper 6 see McLaren, J.S., Smith, H., Plant, Cell and Environment 1, 61–67, 1978]