Leaf Mass Per Unit Area Research Articles

Gap effects on leaf traits of tropical rainforest trees differing in juvenile light requirement

The relationships of 16 leaf traits and their plasticity with the dependence of tree species on gaps for regeneration (gap association index; GAI) were examined in a Neotropical rainforest. Young saplings of 24 species with varying GAI were grown under a closed canopy, in a medium-sized and in a large gap, thus capturing the full range of plasticity with respect to canopy openness. Structural, biomechanical, chemical and photosynthetic traits were measured. At the chloroplast level, the chlorophyll a/b ratio and plasticity in this variable were not related to the GAI. However, plasticity in total carotenoids per unit chlorophyll was larger in shade-tolerant species. At the leaf level, leaf mass per unit area (LMA) decreased with the GAI under the closed canopy and in the medium gap, but did not significantly decrease with the GAI in the large gap. This was a reflection of the larger plasticity in LMA and leaf thickness of gap-dependent species. The well-known opposite trends in LMA for adaptation and acclimation to high irradiance in evergreen tropical trees were thus not invariably found. Although leaf strength was dependent on LMA and thickness, plasticity in this trait was not related to the GAI. Photosynthetic capacity expressed on each basis increased with the GAI, but the large plasticity in these traits was not clearly related to the GAI. Although gap-dependent species tended to have a greater plasticity overall, as evident from a principle component analysis, leaf traits of gap-dependent species are thus not invariably more phenotypically plastic.

When smaller is better: leaf hydraulic conductance and drought vulnerability correlate to leaf size and venation density across four Coffea arabica genotypes.

Leaf hydraulic conductance (Kleaf) and drought vulnerability in terms of leaf water potential inducing 50% loss of Kleaf (P50), were assessed in four genotypes of Coffea arabica L. We tested three hypotheses: (1) leaf P50 is lower in small leaves with higher vein densities; (2) lower P50 translates into lower Kleaf, limiting gas exchange rates and higher leaf mass per unit area (LMA); (3) P50 values are coordinated with symplastic drought tolerance. We found partial support for Hypotheses 1 and 3, but not for Hypothesis 2. Significant correlations existed among leaf size, vein network and drought resistance. Smaller leaves displayed higher major vein density, higher Kleaf and more negative P50. Kleaf was correlated with leaf gas exchange rates. A negative relationship was observed between Kleaf and LMA, whereas P50 was found to be positively correlated with LMA. Across coffee genotypes, reduced leaf surface area and increased vein density shifts P50 towards more negative values while not translating into higher LMA or lower Kleaf. Breeding crop varieties for both increased safety of the leaf hydraulic system towards drought-induced dysfunction and high gas exchange rates per unit of leaf area is probably a feasible target for future adaptation of crops to climate change scenarios.

Heterogeneity of anatomical structure in giant leaves of <italic>Musa balbisiana</italic>

Leaves are the site of photosynthesis in higher plants. Leaf size is one of the factors that determine energy capture and carbon acquisition; however, previous studies have considered leaves to be homogeneous in both structure and physiology. Consequently, little is known about how these parameters may vary in different parts of a leaf, especially in giant leaves. To test the hypothesis that very large leaves have a high level of within-leaf heterogeneity, we examined the anatomical structure of the giant leaves of Musa balbisiana Colla (Musaceae). We also calculated the stomatal pore area index (SPI) based on the anatomical data. We found that, from the leaf base to the tip along the midrib, vessel diameter in the midrib, leaf thickness, and guard cell length decreased sharply, while leaf mass per unit area (LMA) decreased in distal half of the leaf. Conversely, the ratio of palisade tissue to spongy tissue (P/S ratio), stomatal density, and SPI increased along this axis. However, neither chlorophyll content nor minor vein density varied from the basal to apical parts of the leaf. From the midrib to the lateral leaf margins, leaf thickness, LMA, chlorophyll content, guard cell length, stomatal density, and SPI decreased, while the P/S ratio and minor vein density increased. Our results indicated a remarkable level of structural heterogeneity within the giant leaves of M. balbisiana . The apical region of its leaves is likely limited by water supply, while the leaf lateral margins probably suffer mainly from heat stress due to reduced transpirational cooling. These constraints at the edges of the leaves could restrict size in large leaves.

Functional relationships between leaf hydraulics and leaf economic traits in response to nutrient addition in subtropical tree species

Leaves can be both a hydraulic bottleneck and a safety valve against hydraulic catastrophic dysfunctions, and thus changes in traits related to water movement in leaves and associated costs may be critical for the success of plant growth. A 4-year fertilization experiment with nitrogen (N) and phosphorus (P) addition was done in a semideciduous Atlantic forest in northeastern Argentina. Saplings of five dominant canopy species were grown in similar gaps inside the forests (five control and five N + P addition plots). Leaf lifespan (LL), leaf mass per unit area (LMA), leaf and stem vulnerability to cavitation, leaf hydraulic conductance (K(leaf_area) and K(leaf_mass)) and leaf turgor loss point (TLP) were measured in the five species and in both treatments. Leaf lifespan tended to decrease with the addition of fertilizers, and LMA was significantly higher in plants with nutrient addition compared with individuals in control plots. The vulnerability to cavitation of leaves (P50(leaf)) either increased or decreased with the nutrient treatment depending on the species, but the average P50(leaf) did not change with nutrient addition. The P50(leaf) decreased linearly with increasing LMA and LL across species and treatments. These trade-offs have an important functional significance because more expensive (higher LMA) and less vulnerable leaves (lower P50(leaf)) are retained for a longer period of time. Osmotic potentials at TLP and at full turgor became more negative with decreasing P50(leaf) regardless of nutrient treatment. The K(leaf) on a mass basis was negatively correlated with LMA and LL, indicating that there is a carbon cost associated with increased water transport that is compensated by a longer LL. The vulnerability to cavitation of stems and leaves were similar, particularly in fertilized plants. Leaves in the species studied may not function as safety valves at low water potentials to protect the hydraulic pathway from water stress-induced cavitation. The lack of rainfall seasonality in the subtropical forest studied probably does not act as a selective pressure to enhance hydraulic segmentation between leaves and stems.

Comparative Leaf Characteristics of Quercus Mongolica and Rhododendron Schilippenbachii Plants Inhabiting at South- and North- Facing Slopes around Mountain Ridge

Leaf characteristics of two representative deciduous-tree species in Korean peninsula were compared to assess directional ridge effect on leaf traits of both species. Leaf mass per unit area (LMA) of Rhododendron schilippenbachii in south-facing ridge slope was significantly higher than that in north-facing ridge slope, while Quercus mongolica did not change LMA. Leaf mass of Q. mongolica was increased depending on leaf size irrespective of slope. However, leaf mass of R. schilippenbachii changed differently in responding to expansion of leaf area between both slopes resulting from retardation of leaf expansion in south-facing slope. R. schilippenbachii showed higher leaf nitrogen concentration per unit area (LNCA) in south-facing slope than that in north-facing slope, while Q. mongolica indicated no difference in LNCA between southand north-facing slopes. However, both species revealed no significant difference in leaf nitrogen concentration per unit mass (LNCM) between south- and north-facing slopes. LNCA of Q. mongolica was about two times higher than that of R. schilippenbachii. These results indicate that there is a difference in leaf characteristics including leaf thickness and nitrogen allocation between Q. mongolica and R. schilippenbachii, suggesting the difference of plasticity.

Diversity of phenolic compounds and plant traits in coexisting Patagonian desert shrub species of Argentina

Desert shrubs often accumulate different types of phenolic compounds but what determines the amount and diversity of these compounds is an issue scarcely explored. The aim of this study was to assess differences in the amount and diversity of phenolic compounds in leaves among coexisting shrub species differing in rooting depth and leaf turnover. We hypothesized that the diversity and amount of phenolic compounds in leaves of desert shrubs are related to access to soil water through rooting depth, and to leaf turnover. The study was carried out in the Patagonian Monte of Argentina. We collected green leaves of six species representing the dominant shrub morphotypes (tall evergreen, tall deciduous, and medium evergreen shrubs) and assessed lignin concentration and groups of soluble phenols obtained by sequential extraction with ethyl ether, ethyl acetate, and amyl alcohol. We also assessed nitrogen concentration in leaves and leaf mass per unit area (LMA) as traits related to leaf lifespan. The diversity of phenolic compounds was higher in green leaves of tall shrubs with deep rooting depth than in those of medium evergreen shrubs with shallow rooting depth. Diversity of phenolic compounds in green leaves was negatively related to lignin concentration. Evergreen shrubs had higher amount of phenolic compounds in green leaves than deciduous ones and the total amount of phenolic compounds in green leaves was positively related to LMA. We concluded that access to soil water sources and leaf turnover were related to the amount and diversity of phenolic compounds in green leaves of desert shrub species and these results are consistent with those predicted by the resource availability theory for plants from resource-rich and resource-poor habitats.

Different mechanisms explain feeding type-specific patterns of latitudinal variation in herbivore damage among diverse feeding types of herbivorous insects

To determine whether latitudinal variation in herbivore impact exists, we examined three major herbivorous insect feeding types (chewers, gallers, and miners) on/in leaves of Japanese beech. Herbivores were collected with litter traps deployed in forests across a latitudinal gradient of 10°. Leaf litter analyses demonstrated that chewing herbivory increased with increasing latitude of collection site. However, the densities of miners and gallers decreased with latitude. To test whether latitudinal variation in herbivore damage occurs in the absence of geographically differentiated environmental cueing (e.g., physical stresses or herbivore damage), we measured both genetically determined constitutive leaf traits and herbivore damage in a common-garden experiment. In this experiment, miner density decreased with latitude, but chewing herbivory did not vary latitudinally. Galler density was higher on trees from native provenances than on trees from unrelated provenances likely because of local adaptations. Leaf mass per unit area (LMA), tannin, and phenolics all decreased with latitude of provenance. The latitudinal variation in one constitutive leaf trait (LMA) best explained latitudinal variation in chewing herbivory. Thus, different mechanisms account for feeding type-specific patterns of latitudinal variation in herbivore damage among different herbivore feeding types.

Variation in leaf and twig CO2 flux as a function of plant size: a comparison of seedlings, saplings and trees

Rates of tissue-level function have been hypothesized to decline as trees grow older and larger, but relevant evidence to assess such changes remains limited, especially across a wide range of sizes from saplings to large trees. We measured functional traits of leaves and twigs of three cold-temperate deciduous tree species in Minnesota, USA, to assess how these vary with tree height. Individuals ranging from 0.13 to 20 m in height were sampled in both relatively open and closed canopy environments to minimize light differences as a potential driver of size-related differences in leaf and twig properties. We hypothesized that (H1) gas-exchange rates, tissue N concentration and leaf mass per unit area (LMA) would vary with tree size in a pattern reflecting declining function in taller trees, yet maintaining (H2) bivariate trait relations, common among species as characterized by the leaf economics spectrum. Taking these two ideas together yielded a third, integrated hypothesis that (H3) nitrogen (N) content and gas-exchange rates should decrease monotonically with tree size and LMA should increase. We observed increasing LMA and decreasing leaf and twig Rd with increasing size, which matched predictions from H1 and H3. However, opposite to our predictions, leaf and twig N generally increased with size, and thus had inverse relations with respiration, rather than the predicted positive relations. Two exceptions were area-based leaf N of Prunus serotina Ehrh. in gaps and mass-based leaf N of Quercus ellipsoidalis E. J. Hill in gaps, both of which showed qualitatively hump-shaped patterns. Finally, we observed hump-shaped relationships between photosynthetic capacity and tree height, not mirroring any of the other traits, except in the two cases highlighted above. Bivariate trait relations were weak intra-specifically, but were generally significant and positive for area-based traits using the pooled dataset. Results suggest that different traits vary with tree size in different ways that are not consistent with a universal shift towards a lower 'return on investment' strategy. Instead, species traits vary with size in patterns that likely reflect complex variation in water, light, nitrogen and carbon availability, storage and use.

Seedling growth of five tropical dry forest tree species in relation to light and nitrogen gradients

Aims Increasing anthropogenic nitrogen (N) deposition has been claimed to induce changes in species composition and community dynamics. A greenhouse experiment was conducted to examine the effect of increased N availability on growth and functional attributes of seedlings of five tree species with different life history characteristics under varying irradiances. The following questions have been addressed: (i) how do the pioneer and non-pioneer species respond in absolute growth and relative growth rate (RGR) to the interaction of light and nitrogen? (ii) how does the interaction between irradiance and nitrogen availability modulate growth attributes (i.e. functional attributes)? (iii) is there any variation in growth responses between leguminous and non-leguminous species along the light and nitrogen gradients? Methods Seedlings of five tree species (Acacia catechu, Bridelia retusa, Dalbergia sissoo, Lagerstroemia parviflora and Terminalia arjuna) were subjected to twelve combinations of irradiance and N levels. Various growth traits, including height (HT), basal area (BA), whole plant dry biomass (MD), leaf mass per unit area (LMA), leaf area ratio (LAR), net assimilation rate (NAR), RGR, biomass fractions, root-toshoot ratio (R:S) and leaf nitrogen content, were studied to analyse intra- and inter-specific responses to interacting light and N gradients.

갯메꽃의 수분스트레스에 대한 물질분배 특성

Dry matter allocation characteristics of Calystegia soldanella, grown in pots, was analysed to assess its plasticity in response to water-stressed conditions. As water was withheld leaf water potential between the two watering treatments was similar during the first 6 days, followed by a rapid decrease in water-stressed plants. The minimum leaf water potential was -1.50 MPa on day 15 and the maximum leaf water potential was about -0.5 MPa on day 0 in water-stressed plants. In well-watered plants leaf water potential was maintained almost consistently throughout the experiment. There was no significant difference in plant dry weight between the two watering treatments for 9 days after the start of experiment and that was remarkably increased thereafter, compared with that remained without any increase in water-stressed plants. In dry mass partitioning, however, the water-stressed plants showed a great plasticity, showing that there were 1.81, 1.35 and 0.81 times increase in root, stem and leaf, respectively. Dry mass partitioning in well-watered plants varied from 2% to 5%. The difference of dry mass partitioning between the two watering treatments was reflected in leaf mass per unit area (LMA) and root/shoot (R/S) ratio. LMA in water-stressed plants was lower than that in well-watered plants, while R/S ratio in water-stressed plants was higher in well-watered plants. This means that the water-stressed plants reduced its leaf area and increased dry mass partitioning into root and stem during the progress of soil drying. These results indicate that Calystegia soldanella inhabiting in sand dune cope with water stress with high plasticity which can adjust its dry mass partitioning according to soil water conditions.

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.

Assessing leaf nitrogen content and leaf mass per unit area of wheat in the field throughout plant cycle with a portable spectrometer

Leaf nitrogen content (LNC) and leaf mass per unit area (LMA) were assessed by near-infrared spectroscopy (NIRS) on fresh and dried plants of durum wheat (Triticum turgidum ssp). Individual leaves were scanned with a portable spectrometer and reference analyses of LNC and LMA were then carried out. Partial least squares (PLS) regression was used for calibration and cross-validation. LNC was accurately predicted for both fresh and dry leaves whatever the phenologic stage (correlation coefficient of calibration R2cal ranging from 0.932 to 0.958, standard error of cross-validation SECV ranging from 0.215 to 0.320% (dry matter)). LMA was predicted with R2cal=0.942 and SECV=4.84gm−2. The combination of these two calibrations made it possible to predict leaf nitrogen per unit area (R2cross-validation=0.94, SECV=0.248gNm−2) and provides a relevant and non-destructive tool for following the dynamics of three major leaf parameters.

Intraspecific variation in growth and yield response to elevated CO2 in wheat depends on the differences of leaf mass per unit area.

In order to investigate the underlying physiological mechanism of intraspecific variation in plant growth and yield response to elevated CO2 concentration [CO2], seven cultivars of spring wheat (Triticum aestivum L.) were grown at either ambient [CO2] (~384μmolmol-1) or elevated [CO2] (700μmolmol-1) in temperature controlled glasshouses. Grain yield increased under elevated [CO2] by an average of 38% across all seven cultivars, and this was correlated with increases in both spike number (productive tillers) (r=0.868) and aboveground biomass (r=0.942). Across all the cultivars, flag leaf photosynthesis rate (A) increased by an average of 57% at elevated [CO2]. The response of A to elevated [CO2] ranged from 31% (in cv. H45) to 75% (in cv. Silverstar). Only H45 showed A acclimation to elevated [CO2], which was characterised by lower maximum Rubisco carboxylation efficiency, maximum electron transport rate and leaf N concentration. Leaf level traits responsible for plant growth, such as leaf mass per unit area (LMA), carbon (C), N content on an area basis ([N]LA) and the C:N increased at elevated [CO2]. LMA stimulation ranged from 0% to 85% and was clearly associated with increased [N]LA. Both of these traits were positively correlated with grain yield, suggesting that differences in LMA play an important role in determining the grain yield response to elevated [CO2]. Thus increased LMA can be used as a new trait to select cultivars for a future [CO2]-rich atmosphere.

Trade‐offs between leaf hydraulic capacity and drought vulnerability: morpho‐anatomical bases, carbon costs and ecological consequences

Leaf hydraulic conductance (K(leaf) ) and vulnerability constrain plant productivity, but no clear trade-off between these fundamental functional traits has emerged in previous studies. We measured K(leaf) on a leaf area (K(leaf_area)) and mass basis (K(leaf_mass)) in six woody angiosperms, and compared these values with species' distribution and leaf tolerance to dehydration in terms of P(50), that is, the leaf water potential inducing 50% loss of K(leaf) . We also measured several morphological and anatomical traits associated with carbon investment in leaf construction and water transport efficiency. Clear relationships emerged between K(leaf_mass), P(50), and leaf mass per unit area (LMA), suggesting that increased tolerance to hydraulic dysfunction implies increased carbon costs for leaf construction and water use. Low P(50) values were associated with narrower and denser vein conduits, increased thickness of conduit walls, and increased vein density. This, in turn, was associated with reduced leaf surface area. Leaf P(50) was closely associated with plants' distribution over a narrow geographical range, suggesting that this parameter contributes to shaping vegetation features. Our data also highlight the carbon costs likely to be associated with increased leaf tolerance to hydraulic dysfunction, which confers on some species the ability to thrive under reduced water availability but decreases their competitiveness in high-resource habitats.

No globally consistent effect of ectomycorrhizal status on foliar traits

The concept that ectomycorrhizal plants have a particular foliar trait suite characterized by low foliar nutrients and high leaf mass per unit area (LMA) is widely accepted, but whether this trait suite can be generalized to all ectomycorrhizal clades is unclear. We identified 19 evolutionary clades of ectomycorrhizal plants and used a global leaf traits dataset comprising 11,466 samples across c. 3000 species to test whether there were consistent shifts in leaf nutrients or LMA with the evolution of ectomycorrhiza. There were no consistent effects of ectomycorrhizal status on foliar nutrients or LMA in the 17 ectomycorrhizal/non-ectomycorrhizal pairs for which we had sufficient data, with some ectomycorrhizal groups having higher and other groups lower nutrient status than non-ectomycorrhizal contrasts. Controlling for the woodiness of host species did not alter the results. Our findings suggest that the concepts of ectomycorrhizal plant trait suites should be re-examined to ensure that they are broadly reflective of mycorrhizal status across all evolutionary clades, rather than reflecting the traits of a few commonly studied groups, such as the Pinaceae and Fagales.

Leaf Physiological and Morphological Responses to Shade in Grass-Stage Seedlings and Young Trees of Longleaf Pine

Longleaf pine has been classified as very shade intolerant but leaf physiological plasticity to light is not well understood, especially given longleaf pine’s persistent seedling grass stage. We examined leaf morphological and physiological responses to light in one-year-old grass-stage seedlings and young trees ranging in height from 4.6 m to 6.3 m to test the hypothesis that young longleaf pine would demonstrate leaf phenotypic plasticity to light environment. Seedlings were grown in a greenhouse under ambient levels of photosynthetically active radiation (PAR) or a 50% reduction in ambient PAR and whole branches of trees were shaded to provide a 50% reduction in ambient PAR. In seedlings, shading reduced leaf mass per unit area (LMA), the light compensation point, and leaf dark respiration (RD), and increased the ratio of light-saturated photosynthesis to RD and chlorophyll b and total chlorophyll expressed per unit leaf dry weight. In trees, shading reduced LMA, increased chlorophyll a, chlorophyll b and total chlorophyll on a leaf dry weight basis, and increased allocation of total foliar nitrogen to chlorophyll nitrogen. Changes in leaf morphological and physiological traits indicate a degree of shade tolerance that may have implications for even and uneven-aged management of longleaf pine.

Photosynthetic thermotolerance of woody savanna species in China is correlated with leaf life span.

Photosynthetic thermotolerance (PT) is important for plant survival in tropical and sub-tropical savannas. However, little is known about thermotolerance of tropical and sub-tropical wild plants and its association with leaf phenology and persistence. Longer-lived leaves of savanna plants may experience a higher risk of heat stress. Foliar Ca is related to cell integrity of leaves under stresses. In this study it is hypothesized that (1) species with leaf flushing in the hot-dry season have greater PT than those with leaf flushing in the rainy season; and (2) PT correlates positively with leaf life span, leaf mass per unit area (LMA) and foliar Ca concentration ([Ca]) across woody savanna species. The temperature-dependent increase in minimum fluorescence was measured to assess PT, together with leaf dynamics, LMA and [Ca] for a total of 24 woody species differing in leaf flushing time in a valley-type savanna in south-west China. The PT of the woody savanna species with leaf flushing in the hot-dry season was greater than that of those with leaf flushing in the rainy season. Thermotolerance was positively associated with leaf life span and [Ca] for all species irrespective of the time of flushing. The associations of PT with leaf life span and [Ca] were evolutionarily correlated. Thermotolerance was, however, independent of LMA. Chinese savanna woody species are adapted to hot-dry habitats. However, the current maximum leaf temperature during extreme heat stress (44·3 °C) is close to the critical temperature of photosystem II (45·2 °C); future global warming may increase the risk of heat damage to the photosynthetic apparatus of Chinese savanna species.

Hydraulic conductance of leaves correlates with leaf lifespan: implications for lifetime carbon gain

Previous research suggests that the lifetime carbon gain of a leaf is constrained by a tradeoff between metabolism and longevity. The biophysical reasons underlying this tradeoff are not fully understood. We used a photosynthesis-leaf water balance model to evaluate biophysical constraints on carbon gain. Leaf hydraulic conductance (K(Leaf)), carbon isotope discrimination (Δ(13)C), leaf mass per unit area (LMA) and the driving force for water transport from stem to leaf (ΔΨ(Stem-Leaf)) were characterized for leaves spanning three orders of magnitude in surface area and two orders of magnitude in lifespan. We observed positive isometric scaling between K(Leaf) and leaf area but no relationship between Δ(13)C and leaf area. Leaf lifespan and LMA had minimal effect on K(Leaf) per unit leaf area, but a negative correlation exists among LMA, lifespan, and K(Leaf) per unit dry mass. During periods of leaf water loss, ΔΨ(Stem-Leaf) was relatively constant. We show for the first time that K(Leaf, mass), an index of the carbon cost associated with water use, is negatively correlated with lifespan. This highlights the importance of characterizing K(Leaf, mass) and suggests a tradeoff between resource investment in liquid phase processes and structural rigidity.

Leaf traits and persistence of relict and endangered tree species in a rare plant community.

The rare plant communities, located in Houhe Nature Reserve, Hubei, China, are remnant evergreen and deciduous mixed broadleaved forest where many tree species have been identified as Tertiary relict and endangered plants and environmental conditions are typically characterised by low light and high rainfall. Knowledge of their patterns of leaf traits would contribute to our understanding of persistence of relict and endangered species. Here, we measured leaf mass per unit area (LMA), mass-based photosynthetic capacity (Amass), nitrogen content (Nmass), construction cost (CCmass) and photosynthetic nitrogen-use efficiency (PNUE) of 20 major tree species in a typical rare plant community. Correlations among leaf traits in the community were consistent with those from the global dataset, but they had lower Amass at any given Nmass and lower Amass and PNUE at any given LMA. Such results suggested the capacity and efficiency of photosynthetic gain from a unit investment in leaf tissue tend to be lower in the community. Moreover, they had lower LMA, CCmass and PNUE but higher Nmass than global broadleaved tree species. For relict and endangered species, the common limited factors (such as low light and high rainfall), similar leaf traits as coexisting deciduous non-endangered species and significant leaf trait relationships may allow them to persist in the community.

Temporal variations of starch and mass in greenhouse tomato leaves under CO2 enrichment

Edwards, D., Ehret, D. and Jolliffe, P. 2011. Temporal variations of starch and mass in greenhouse tomato leaves under CO2enrichment. Can. J. Plant Sci. 91: 167–177. A plant-based method of guiding CO2 dosing may improve the effectiveness of CO2 enrichment in commercial greenhouse tomato (Lycopersicon esculentum Mill) production. The temporal dynamics of two plant response indicators, leaf starch and leaf mass per unit area (LMA) were investigated in commercial and research greenhouses throughout day/night periods, as well as after the onset of CO2 enrichment. Both leaf starch and LMA tended to follow the diurnal profile of light but with 3 to 4 h of lag. The magnitude of the response, especially for starch, was affected by leaf position, CO2 enrichment and light. The highest starch contents were measured between 1400 and 1600 and the lowest levels occurred in the morning between sunrise and 1100. In many cases plants carried over substantial starch in upper leaves from one day to the next, indicating a carbon-surplus state. In the onset experiment leaf starch and LMA increased with 4 d of exposure to CO2 enrichment for mid and upper canopy leaves and continued to increase to the end of the monitoring period (7 d). Leaf starch contents and LMA are indicators of plant carbon status that show potential for guiding CO2 dosing.