Individual Leaf Area Research Articles

Simple and accurate allometric model for leaf area estimation in Vitis vinifera L. genotypes

The aim of the present experiment was to evaluate the currently used allometric models for Vitis vinifera L., as well as to develop a simple and accurate model using linear measurements [leaf length (L) and leaf width (W)], for estimating the individual leaf area (LA) of nine grapevine genotypes. For model construction, a total of 1,630 leaves coming from eight genotypes in 2010 was sampled during different leaf developmental stages and encompassed the full spectrum of leaf sizes. The model with single measurement of L could be considered an interesting option because it requires measurement of only one variable, but at the expense of accuracy. To find a model to estimate individual LA accurately for grapevine plants of all genotypes, both measurements of L and W should be involved. The proposed linear model [LA = −0.465 + 0.914 (L × W)] was adopted for its accuracy: the highest coefficient of determination (> 0.98), the smallest mean square error, the smallest prediction sum of squares, and the reasonably close prediction sum of squares value to error sum of squares. To validate the LW model, an independent data set of 200 leaves coming from another genotype in 2011 was used. Correlation coefficients showed that there was a highly reliable relationships between predicted leaf area and the observed leaf area, giving an overestimation of 0.8% in the prediction.

Growth synchrony between leaves and stems during twig development differs among plant functional types of subtropical rainforest woody species.

During the development of woody twigs, the growth in leaf may or may not be proportional to the growth in stem. The presence or absence of a synchronicity between these two phenologies may reflect differences in life history adaptive strategies concerning carbon gain. We hypothesized that sun-adapted species are more likely to be less synchronous between growths in total leaf area (TLA) and stem length compared with shade-adapted species, with a bias in growth in stem length, and that shade-adapted species are more likely to be more synchronous between increases in individual leaf area (ILA) (leaf size) and leaf number (LN) during twig development compared with sun-adapted species, giving priority to growth of leaf size. We tested these two hypotheses by recording the phenologies of leaf emergence, leaf expansion and stem elongation during twig development for 19 evergreen woody species (including five shade-adapted understory species, six sun-adapted understory species and eight sun-adapted canopy species) in a subtropical evergreen broad-leaved forest in eastern China. We constructed indices to characterize the synchronicity between TLA and stem length (αLS) and between leaf size and leaf number (αSN) and we derived the α values from logistic functions taking the general form of A = A(max)/[1 + exp(β - αB)] (where A is the TLA or average ILA, B is the corresponding stem length or LN at a specific time, and A(max) is the maximum TLA or the maximum ILA of a twig; the higher the numerical value of α, the less synchronous the corresponding phenologies). Consistent with our hypotheses, sun-adapted species were higher both in α(LS) and α(SN), showing less synchronous patterns in the growths of TLA vs stem length and leaf size vs LN during twig development. Moreover, α(LS) and α(SN) were significantly positively correlated with relative growth rates of LN and leaf size across species, as indicated by both analyses of ordinary regression and phylogenetic generalized least squares. The across-species synchronies during twig development show that the temporal dynamics of the leaf size-twig size spectrum is of adaptive significance in plants. We suggest that temporal dynamics of plant functional traits should be extensively studied to characterize plant life history.

Plant functional traits predict green roof ecosystem services.

Plants make important contributions to the services provided by engineered ecosystems such as green roofs. Ecologists use plant species traits as generic predictors of geographical distribution, interactions with other species, and ecosystem functioning, but this approach has been little used to optimize engineered ecosystems. Four plant species traits (height, individual leaf area, specific leaf area, and leaf dry matter content) were evaluated as predictors of ecosystem properties and services in a modular green roof system planted with 21 species. Six indicators of ecosystem services, incorporating thermal, hydrological, water quality, and carbon sequestration functions, were predicted by the four plant traits directly or indirectly via their effects on aggregate ecosystem properties, including canopy density and albedo. Species average height and specific leaf area were the most useful traits, predicting several services via effects on canopy density or growth rate. This study demonstrates that easily measured plant traits can be used to select species to optimize green roof performance across multiple key services.

Slope-related variations in twig and leaf traits of Robinia pseudoacacia in the northern mountains of Lanzhou

Aims The growth relationship between twigs and leaves is a strategy that plants enhance the ability to use space resources under environmental stresses, and elucidation of this characteristics is important for understanding the phenotypic plasticity of plants in coping with environmental heterogeneity. Our objective was to examine how Robinia pseudoacacia would vary in twig and leaf configuration in response to changes in slope aspect. Methods In the northern mountains of Lanzhou in Gansu Province, China, 20 transects were laid out horizontally along the contour at intervals of 50 m from an elevation of 1 550 m upward in four different slope aspects, and 12 plots were set up along each transect at intervals of 5 m. A handheld GPS was used to measure latitude, longitude and altitude of each plot. Community traits were investigated and all individuals of R. pseudoacacia were used for measurements of the cross-sectional area of twigs, total leaf area, leafing intensity, and average area of a single leaf on each twig. Arc GIS was used to construct the digital elevation model(DEM). The 240 plots were categorized into groups of northern, eastern, western and southern aspects, and the standardized major axis(SMA) estimation method was then used to examine the allometric relationship between the cross-sectional area of twigs, total leaf area, leafing intensity and average area of a single leaf. Important findings With changes in the slope aspect from north to east, south and west, the crown density, average tree height and soil moisture of the plant community displayed a pattern of decrease—increase, and the cross-sectional area of twigs, total leaf area and average area of a single leaf of R. pseudoacacia displayed a pattern of decrease—increase and the leafing intensity displayed a pattern of increase—decrease. Significant positive relationships between the cross-sectional area of twigs and total leaf area were found in R. pseudoacacia in all slope aspects(p 0.05), and the common slope of the regressions was significantly greater than 1; significant negative relationships between leafing intensity and average area of a single leaf were found in all slope aspects(p 0.05), and the common slope of the regressions was significantly close to –1. In addition, when the slope aspect changed from north to east, south and west, the y-intercepts in the scaling relationships of the cross-sectional area of twigs vs. total leaf area and the leafing intensity vs. individual leaf area both displayed a pattern of decrease—increase. The allometric relationship between twig and leaf with changes in slope aspect of the habitat reflected the response and adaption of plant functional traits to their biotic and abiotic environments and the investment balance mechanism of plant architecture construction.

Relationships between biomass allocation, axis organogenesis and organ expansion under shading and water deficit conditions in grapevine.

The relationships between whole-plant growth and morphogenetic processes under abiotic stresses are still partly unknown. Whole-plant biomass growth can be decreased by many abiotic stresses, including water deficit and shading. Two experiments were performed on potted plants of one grapevine cultivar (Vitis vinifera L. cv. Syrah) subjected to watering and shading treatments. Under water stress, plants reduced their primary and secondary axis leaf production rate, whereas secondary axis budburst was relatively unaffected. Individual leaf area was reduced and a strong decrease in leaf expansion rate was observed. Under shading, primary axis organogenesis was maintained, both secondary axis budburst rate and phytomer appearance rate were decreased, and individual leaf area slightly increased. Specific leaf area did not change under soil water deficit, whereas it increased under shading. These results confirm the existence of dynamic changes in organ sink strength and biomass allocation patterns to favour plant leaf area growth under shading, and to reduce plant leaf area and water losses by transpiration under water stress. From a modelling point of view, this study shows that functional structural models based on a C balance are not fully relevant for simulating plant growth under abiotic constraints if they do not include non-trophic relationships (hormonal signalling or plant hydraulic properties) that modify organ sink strength according to abiotic constraints.

Individual Leaf Area of Early Flowering Arabidopsis Genotypes Is More Affected by Drought than Late Flowering Ones: A Multi-Scale Analysis in 35 Genetically Modified Lines

Plants acclimate to drought optimizing the trade-off between biomass production and water loss while ensuring their survival and reproduction. Plants also modify their growth or phenology as complementary strategies in response to stress. Despite evidence of an interaction between flowering time and plant growth response to environmental stresses, this interaction in response to drought is under debate. To contribute to the analysis of this interaction, leaf growth of 35 genetically modified lines of Arabidopsis thaliana and their common wild-type, Col-0 was analyzed by a quantitative multi-scale phenotyping approach from cellular to whole plant scale both in wellwatered and soil moderate water deficit conditions. These genotypes were selected for the various physiological functions potentially altered by their genetic modification and that could interact with plant growth and/or their drought responses. In all genotypes, leaf expansion decreased in response to drought both at the whole rosette and the individual leaf levels. Additionally, epidermal cell area and/or epidermal cell number decreased in response to the drought treatment. In contrast, the number of rosette leaves was reduced in only half of the genotypes and leaf growth duration was only modified in 4 of them. Despite long photoperiod conditions, the duration of the vegetative phase, i.e. the time elapsed between germination and flowering stage, varied from 12 to 27 days among genotypes under well watered conditions. Our analyses revealed that the differences of flowering time observed in well-watered condition impacted the leaf area response to drought. Early-flowering genotypes slightly decreased their final leaf number, but strongly reduced their

Family-specific responses in survivorship and phenotypic traits to different light environments in a seedling population of Fagus crenata in a cool-temperate forest

Natural plant populations consist of individuals that exhibit variation in their phenotypic traits and demographic parameters. Here we report a study on maternal effects and the effects of different light environments on intra-specific variation in survivorship and ecologically relevant phenotypic traits of Fagus crenata seedlings in a cool-temperate forest community. We collected 901 seedlings from the ground beneath five maternal trees and used microsatellite DNA markers to identify maternal siblings that germinated naturally in the forest community. Selected seedlings were planted at three sites––one under a closed canopy with low light availability, one under a canopy gap in the natural forest community with moderate light availability, and one in a common garden with high light availability. The proportion of seedlings that were correctly assigned to their putative mother ranged from 60.0 to 82.7 % per maternal family, and 655 (72.7 %) seedlings in total were used for the analysis of survivorship and phenotypic traits. Among-family differences in survivorship remained after correcting for the effects of initial stem size during the first year after planting. However, this difference in survivorship became less pronounced in subsequent years. Seedlings grown under the canopy gap and/or in the common garden exhibited better performance in terms of phenotypic traits such as stem, leaf, and root morphology. In addition, seedlings of different maternal origins grown in the same environments had different individual leaf areas. These findings suggest that phenotypic variation due to maternal effects was a significant source of intra-specific variation within the local population.

Microclimate and development of 'Conilon' coffee intercropped with rubber trees

The objective of this work was to evaluate the influence of intercropping 'Conilon' coffee (Coffea canephora) with rubber trees on coffee tree microclimate, nutrition, growth, and yield. Rubber trees were planted in two double rows 33 m apart, with 4x2.3 m spacing between plants. Treatments consisted of the distances from the coffee plants to the rubber trees: 3, 6, 9, 12, and 15 m. Measurements of atmospheric variables (temperature, irradiance, and relative humidity), leaf nutrient concentration, internode length of plagiotropic and orthotropic branches, individual leaf area, chlorophyll content, and yield were performed. Intercropping promotes changes in the microclimatic conditions of coffee plants close to rubber trees, with reduction of temperature and irradiance level and increase in air relative humidity. The proximity of the coffee tree to the rubber trees promotes the elongation of the plagiotropic and orthotropic branches and increases the individual leaf area; however, it does not affect leaf concentrations of N, K, Mg, Fe, Zn, and B in 'Conilon' coffee and does not have a negative impact on yield.

Are leaf functional traits ‘invariant’ with plant size and what is ‘invariance’ anyway?

Summary Studies of size‐related plant traits have established a suite of mathematical functions describing whole plant investment and allocation. In parallel, studies of plant ‘economic spectra’ have measured the scaling and variance composition of traits related to the major dimensions of both structure and function. Here, we explore the intersection of these two broad areas by exploring the notion that many leaf economic traits are invariant with species differences in adult plant size. Invariant traits are those that do not change with plant size and are invoked as a key simplifying assumption of prominent models that purport to explain the scaling of plant size and metabolism. Unfortunately, leaf trait invariance is neither well defined nor understood and has never been critically evaluated. Using a global plant trait data set, we evaluated whether nine key traits can be considered as effectively invariant as a function of the maximum height of plant species, within and across plant growth forms and within and across broad taxonomic groups. We also examine the influence of habitat, biome and global spatial scales on the size‐relative variance in plant functional traits. We suggest that while invariance is an intuitive concept, an objective statistical definition is elusive. Expanding on ideas drawn from the study of life‐history invariants, we propose five criteria to identify traits that are effectively invariant, depending on the research question. We show that all studied ‘leaf economic spectrum’ (LES) traits approach invariance within and between herbaceous and woody plant groups, angiosperms and gymnosperms, and within most biome and habitat types. Individual leaf area, however, shows a modest increase with plant size, and there are significant shifts in the average LES trait values at a given plant maximum height, among the plant growth forms and taxonomic groups. Our results demonstrate that generally, LES traits show little interspecific variation with maximum plant height, which provides some support for attempts to model plants with ‘average’ leaf properties. Our work also highlights the need for a better understanding of the drivers of leaf size variation within and across individuals, functional groups, clades, biomes and habitats.

Morphological changes in response to drought stress in cultivated and wild almond species.

This study was undertaken to identify morphological changes in young seedlings of 5 Iranian almond species (Prunus dulcis, P. eburnea, P. eleagnifolia, P. haussknechti, and P. scoparia) under polyethylene glycol-induced drought stress. Drought stress caused a significant reduction in plant growth parameters such as fresh and dry weights of plant organs, leaf number, total leaf area, and leaf relative water content in all almond species. Specific leaf weight also increased significantly in drought-treated plants compared to control. No significant changes in shoot length, individual leaf area, leaf dimension (length and width), or stomatal size and frequency were observed in response to drought treatments. P. eburnea had the highest relative water content among the species and showed the smallest decrease in fresh and dry weights of organs and greatest decrease in leaf number and total leaf area (the most reduction in transpiration area) as an adaptive mechanism to drought stress.

The grass-free lawn: Management and species choice for optimum ground cover and plant diversity

In Britain, managed grass lawns provide the most traditional and widespread of garden and landscape practices in use today. Grass lawns are coming under increasing challenge as they tend to support a low level of biodiversity and can require substantial additional inputs to maintain. Here we apply a novel approach to the traditional monocultural lawnscape by replacing grasses entirely with clonal perennial forbs. We monitored changes in plant coverage and species composition over a two year period and here we report the results of a study comparing plant origin (native, non-native and mixed) and mowing regime. This allows us to assess the viability of this construct as an alternative to traditional grass lawns. Grass-free lawns provided a similar level of plant cover to grass lawns. Both the mowing regime and the combination of species used affected this outcome, with native plant species seen to have the highest survival rates, and mowing at 4cm to produce the greatest amount of ground coverage and plant species diversity within grass-free lawns. Grass-free lawns required over 50 percent less mowing than a traditionally managed grass lawn. Observations suggest that plant forms that exhibited: (a) a relatively fast growth rate, (b) a relatively large individual leaf area, and (c) an average leaf height substantially above the cut to be applied, were unsuitable for use in grass-free lawns. With an equivalent level of ground coverage to grass lawns, increased plant diversity and a reduced need for mowing, the grass-free lawn can be seen as a species diverse, lower input and potentially highly ornamental alternative to the traditional lawn format.

First and second sets of shoots in five evergreen woody species from Tiantong National Forest Park of Zhejiang, China

Aims Some woody species of subtropical evergreen broad-leaved forests in Eastern China form a second set of shoots in late summer or autumn after a first set in spring. Our objective is to elucidate features of this second set of shoots, including their adaptive significance. Methods We investigated differences between the first and second sets of shoots for five evergreen woody species (Symplocos lancifolia, Loropetalum chinense, Eurya rubiginosa var. attenuata, Myrica rubra, and Castanopsis fargesii) from an evergreen broad-leaved forest in Tiantong National Forest Park of Zhejiang, China. Herbivore damage of leaves was estimated, leaf emergence rate, leaf expansion rate and duration were calculated, and twig investment (leaf number and individual leaf area within twigs, twig stem length and diameter) was measured for both sets of shoots. Important findings Leaves of M. rubra and C. fargesii suffered greater herbivore damage to the second shoots compared with the first, and no significant difference was found in damage between the two sets of shoots for S. lancifolia, L. chinense and E. rubiginosa var. attenuata. The first and second sets of shoots shared the same leaf emergence pattern. Symplocos lancifolia, L. chinense, E. rubiginosa var. attenuata, and M. rubra showed a succeeding type of leaf emergence, and C. fargesii showed a flushing type of leaf emergence. However, duration of leaf emergence was much shorter in the second set of shoots for S. lancifolia, E. rubiginosa var. attenuata and M. rubra than in the first but not for the other two species. Leaf expansion rate was significantly higher for the second set of shoots for S. lancifolia, L. chinense and E. rubiginosa var. attenuata and was indistinguishable for M. rubra, C. fargesii leafed out late in the first set of shoots. Moreover, leaf number (except for L. chinense), individual leaf area, twig stem length (except for L. chinense) and diameter were significantly smaller in the second than in the first set of shoots for four species, indicating lower twig investment in the second shoots for all the sampled species. In general, leaf herbivory damage, rates of leaf emergence and expansion were not smaller (sometimes significantly greater), but the total investment on twigs was significantly lower in the second shoots compared to the first. We speculate that these differences might result from the selective force of heavy herbivory pressure and adverse climate conditions of coming winter for the leaves produced during the second set of shoots.

Reduction of stand density increases drought resistance in xeric Scots pine forests

In Valais, a dry Inner-Alpine valley in Switzerland, increasing tree mortality has been related to drought and reduced forest management, which have led to increased competition between trees. Since increasing drought and reduced forest management were co-occurring during the last decades, it is not clear if forest management alone could increase tree resistance to drought. To test whether thinning of Scots pine (Pinus sylvestris L.) stands could be used to mitigate the effects of drought, we analyzed a long-term thinning trial set up in xeric Pfynwald forest in 1965. The trial featured one control (unmanaged plots; basal area 40m2ha−1) and three thinning intensities; light (33m2ha−1), medium (22m2ha−1) and heavy (11m2ha−1). Thinning was repeated in 1971, 1978 and 2010. Individual tree radial growth responses and tree leaf area to sapwood area ratio were assessed and compared among treatment. Additionally, stand-level growth, tree mortality and the relationship between stand density and tree diameter (allometric slope r) were analyzed and compared between two periods (1978–1990; 1991–2009) where the last period was drier. Individual tree basal area increment increased significantly for up to three decades after heavy thinning and mortality rates decreased with decreasing basal area while stand-level growth did not significantly differ. The higher mortality rate and the more negative allometric slope r in the second period suggests that site conditions have become hotter and drier and can partially explain a decrease in the basal area in the control plots and in the light thinning treatment. Leaf area to sapwood area ratio increased with lower basal area and suggests that competition for water was reduced. Taken together, our results suggest that a reduction in basal area of 40–60% to ca. 15–25m2ha−1 could mitigate drought effects on Scots pine on xeric sites for the coming decades prolonging the provision of important ecosystem services. After this time, sustainability of Scots pine forests at xeric sites will depend on the intensity of anticipated climate change, so that in the worst case, thinning might be applied to convert Scots pine forests to mixed forests with more drought-resistant species.

Modifications in development and growth of a dual-adapted tropical rice variety grown as either a flooded or an aerobic crop

As the human population continues to grow and competition for natural resources increases, there is a consequent need to produce more food with fewer resources. Flooded rice crops use large quantities of water, which becomes scarcer for farmers. New methods of saving irrigation water have been tested and released but they often suffer from a yield trade-off. A comparative study was carried out with a recent dual-adapted variety cultivated as either a flooded transplanted crop or a direct-seeded and soil water-saturated crop, referred to as an aerobic crop, to dissect the crop physiological differences induced by crop management. Experiments were conducted at IRRI's experiment station in Los Baños, Philippines, in the dry seasons of 2011 and 2012. Grain yields were 2tons/ha or 25% lower in the aerobic crop as a result of a complex series of modifications and adjustments in plant architecture and yield components. Four main changes — higher plant density, slower rate of leaf appearance, lower nitrogen content, and reduced size of all organs — induced by the aerobic crop environment were responsible for three chains of modifications that resulted in lower biomass accumulation and finally lower grain yield. Leaf appearance rates were bilinear in both environments, initially similar in both environments and slower after an inflection point that occurred at the appearance of the 8th leaf in aerobic crops instead of the 11th leaf in flooded crops. As a consequence, two fewer leaves were produced by main tillers in aerobic crops, whose individual leaf area thus was much lower. In 2012, plant nitrogen content was about 1% lower in the aerobic crop than in the flooded crop during the entire crop duration. Biomass accumulation of the variety used was biphasic in both environments, with high radiation use efficiency during the two phases of effective biomass accumulation in flooded crops, and the standard radiation use efficiency expected with C3 species in aerobic crops during the same phases.

Scaling relationships among twig size, leaf size and leafing intensity in a successional series of subtropical forests

Scaling relationships among twig size, leaf size and leafing intensity fundamentally influence the twig-leaf deployment pattern, a property that affects the architecture and functioning of plants. However, our understanding of how these relationships change within a species or between species as a function of forest succession is unclear. We determined log-log scaling relationships between twig cross-sectional area (twig size) and each of total and individual leaf area, and leafing intensity (the number of leaves per twig volume) for 78 woody species along a successional series in subtropical evergreen forests in eastern China. The series included four stages: secondary shrub (S1), young (S2), sub-climax (S3) and climax evergreen broadleaved forests (S4). The scaling slopes in each of the three relationships did not differ among the four stages. The y-intercept did not shift among the successional stages in the relationship between twig cross-sectional area and total leaf area; however, the y-intercept was greatest in S4, intermediate in S3 and lowest in S2 and S1 for the relationship between twig size and individual leaf area, while the opposite pattern was found for the twig size-leafing intensity relationship. This indicates that late successional trees have few but large leaves while early successional trees have more small leaves per unit twig size. For the relationship between twig cross-sectional area and total leaf area, there was no difference in the regression slope between recurrent (appear in more than one stages) and non-recurrent species (appear in only one stage) for each of the S1-S2, S2-S3 and S3-S4 pairs. A significant difference in the y-intercept was found in the S2-S3 pair only. In the relationship between twig cross-sectional area and individual leaf area, the regression slope between recurrent and non-recurrent species was homogeneous in the S1-S2 and S3-S4 pairs, but heterogeneous in the S2-S3 pair. We conclude that forest succession caused the shift in the intercept, but did not affect scaling slopes for relationships among twig size, leaf size and leaf intensity. For recurrent species, the invariant scaling slope in the twig-leaf size relationship between adjacent pairs of successional stages may be related to their phenotypic plasticity by adjusting their twig and leaf deployment strategy to similar to what the non-recurrent species display.

Simulation and validation of leaf area prediction model for Picrorhiza kurroa - An endangered medicinal plant of Western Himalaya

The study was aimed at modeling of individual leaf area of Picrorhiza kurroa using linear measurements of leaf length (L) and maximum width (W). Leaves were collected from the greenhouse at different time intervals during 2009 and 2011. The actual leaf area (LA) and leaf dimensions were measured with a laser area meter. Different combinations of prediction equations were obtained from length (L), width (W), product of LW to build linear (y = a + bx), quadratic (y = a+bx+cx2), exponential (y = aebx), logrithmatic (y = a+bLnx) and power models (y = axb) for different samples and pooled data compared with earlier models by graphical procedures and statistical criteria root mean square error (RMSE). A linear model having LW as the independent variables (y = 0.333 + 0.603LW) provided the most accurate estimate (R2 = 0.955, RMSE = 0.573, coefficient of variation (CV) = 7.46%) of P. kurroa leaf area. Validation of the regression model having LW of leaves measured in two different experiments during September, 2011 showed that the correlation between measured and predicted values by the use of this equation was very high (R2 = 0.9053), with low RMSE (0.39) and CV (5.44%). Key words: Picrorhiza kurroa, leaf area model, non destructive, validation.

Influence of shrub canopy morphology and rainfall characteristics on stemflow within a revegetated sand dune in the Tengger Desert, NW China

AbstractStemflow of xerophytic shrubs was monitored on event basis within a revegetated sand dune. Quantity of stemflow showed a clear species‐specific dependence in combination with the rainfall characteristics. Results obtained revealed that for ovate‐leaved C. korshinskii with an inverted cone‐shaped canopy and smooth bark, the quantity of stemflow in depth accounted for 7.2% of the individual gross rainfall, while it was 2.0% for needle‐leaved A. ordosica with a cone‐shaped canopy and coarse bark. There were significant positive linear relationships between stemflow and individual gross rainfall and rainfall intensity for the two shrubs. An individual gross rainfall of 1.4 and 1.8 mm was necessary for stemflow generation for C. korshinskii and A. ordosica, respectively. Multiple regression analysis showed that the abiotic and biotic variables including the individual gross rainfall, mean windspeed (WS), canopy height, branch length, and canopy volume have significant influence on stemflow for C. korshinskii, whereas for A. ordosica, the notable influencing variables were individual gross rainfall, stem diameter, and leaf area index. Generally, WS has less effect on stemflow than that of rainfall for A. ordosica. The correlation relationship between individual gross rainfall and funneling ratio showed that the funneling ratio attains its peak when the gross rainfall is 13 and 16 mm for C. korshinskii and A. ordosica, respectively, implying that the canopy morphology emerged as determining factors on funneling ratio decrease when the individual gross rainfall exceeds these values. In comparison, higher WS increased the funneling ratio remarkably for C. korshinskii than A. ordosica due partly to the greater branch length and canopy projection area in C. korshinskii. Funneling ratio can be used as an integrated variable for the effects of canopy morphology and rainfall characteristics on stemflow. The implication of stemflow on water balance and its contribution to sustain the shrubs and the revegetation efforts was discussed. Copyright © 2013 John Wiley & Sons, Ltd.

Distribution of leaf characteristics in relation to orientation within the canopy of woody species

Over the last few decades considerable effort has been devoted to research of leaf adaptations to environmental conditions. Many studies have reported strong differences in leaf mass per unit area (LMA) within a single tree depending on the photosynthetic photon flux density (PPFD) incident on different locations in the crown. There are fewer studies, however, of the effects of differences in the timing of light incidence during the day on different crown orientations.Leaves from isolated trees of Quercus suber and Quercus ilex in a cold Mediterranean climate were sampled to analyze differences in LMA and other leaf traits among different crown orientations. Gas-exchange rates, leaf water potentials, leaf temperatures and PPFD incident on leaf surfaces in different crown orientations were also measured throughout one entire summer day for each species.Mean daily PPFD values were similar for the leaves from the eastern and western sides of the canopy. On the western side, PPFD reached maximum values during the afternoon. Maximum leaf temperatures were approximately 10–20% higher on the west side, whereas minimum leaf water potentials were between 10 and 24% higher on the east side. Maximum transpiration rates were approximately 22% greater on the west, because of the greater leaf-to-air vapor pressure deficits (LAVPD). Mean individual leaf area was around 10% larger on the east than on the west side of the trees. In contrast, there were no significant differences in LMA between east and west sides of the crown.Contrary to our expectations, more severe water stress on the west side did not result in increases in LMA, although it was associated with lower individual leaf area. We conclude that increases in LMA measured by other authors along gradients of water stress would be due to differences in light intensity between dry and humid sites.

Bell Pepper (Capsicum annum L.) Crop as Affected by Shade Level: Microenvironment, Plant Growth, Leaf Gas Exchange, and Leaf Mineral Nutrient Concentration

Use of shading nets helps ameliorate heat stress of vegetable crops. This study evaluated the effects of shade level on microenvironment, plant growth, leaf gas exchange, and mineral nutrient content of field-grown bell pepper crop. Bell pepper cultivars Camelot, Lafayette, Sirius, and Stiletto were grown at 0%, 30%, 47%, 62%, and 80% shade levels. Photosynthetically active radiation and air, leaf, and root zone temperatures decreased as shade level increased. Despite having increased plant leaf area, there was increased soil water content with increased shade level, indicating reduced soil water use. With increased shade level, the total plant leaf area, individual leaf area, and individual leaf weight increased, whereas leaf number per plant and specific leaf weight decreased. In contrast to non-normalized chlorophyll index (CI) values, CI normalized by specific leaf weight were related to leaf nitrogen (N) and increased with increased shade level. Net photosynthesis and stomatal conductance (gS) decreased and leaf transpiration increased with increased shade level, particularly above 47% shade level. Leaf concentrations of N, potassium (K), calcium (Ca), magnesium (Mg), manganese (Mn), sulfur (S), aluminum (Al), and boron (B) increased with increased shade level. Relatively few differences in plant growth, leaf gas exchange, and leaf mineral nutrient concentrations were observed among cultivars. In conclusion, morphological changes such as taller plants and thinner and larger leaves likely enhanced light capture under shaded conditions compared with unshaded plants. High shade levels reduced leaf temperature and excessive leaf transpiration but resulted in reduced leaf photosynthesis. Thus, moderate shade levels (30% and 47%) were the most favorable for bell pepper plant growth and function.

Comparative Morpho-Biochemical Responses of Sunflower Lines Sensitive and Tolerant to Water Stress

Water stress is likely the most important factor that adversely affects plant growth and development. In our study two inbred lines of sunflower (Helianthus annuus L.) with contrasting behavior to water deficit, the inbred lines B59, sensitive, and B71, tolerant, were subjected to water stress and compared in terms of growth parameters, relative water content, photosynthetic pigments and osmo-compatibles contents. Mannitol treatment generated a moderate water stress which resulted in a relative water content decline in both lines. In aerial part of B59 and B71 stressed-seedlings, a dramatic reduction of osmotic potential was observed, although in B71 the osmotic potential was 1.8-fold lower than in B59. The B71 line recovered the osmotic potential to control values after 8 d of re-watering. Several morphological parameters were altered by the water stress. Shoot and root relative fresh weight decreased in both lines under water stress, although B71 showed a minor drop. However, the root was less affected than the shoot in stress condition and recovery period. Water stress was affected in a greater proportion shoot dry weight (DW) than root DW in B59 and B71 lines. Nevertheless, a significant increase in root DW/shoot DW ratio was observed in stressed seedlings. A higher reduction in the individual leaf area was observed in B71 line under stress. The basal chlorophyll content was higher in the tolerant line B71 than in the sensitive B59, and carotenoids showed a high content in B71 control and stressed seedlings. Under water stress, the aerial and root proline content increased in the tolerant B71 line. Glycinebetaine decreased significantly in the aerial part of both lines in response to water stress indicating that this compound is not the main osmo-regulator. In conclusion, B71 has suitable mechanisms to enable it to respond more effectively to moderate water stress.