Specific Leaf Area Values Research Articles

Outbreeding Depression Caused by Intraspecific Hybridization Between Local and Nonlocal Genotypes in Abies sachalinensis

To evaluate the effects of intraspecific hybridization of local and nonlocal genotypes on growth traits of progeny in Abies sachalinensis, we performed reciprocal crossing between nonlocal trees in a high‐elevation zone (1,100–1,200 m asl) and local trees in a low‐elevation zone (530 m asl) in Hokkaido, northern Japan, in 1979 and established a common garden experiment using local × local (female × male ), local × nonlocal , nonlocal × local , and nonlocal × nonlocal progeny in the low‐elevation zone in 1986. Survival, height, diameter at breast height (dbh), needle nitrogen content, specific leaf area (SLA), and needle area per shoot diameter (NA) of 25‐year‐old progeny were measured in 2005. The survival rate was consistently high (>85% on average). Reductions in height and dbh were apparent in F1 hybrids compared with local × local progeny. Furthermore, outbreeding depression was significant in height growth of nonlocal × local F1 hybrids and in dbh of both F1 hybrids. Reductions in growth traits may be related to morphological needle traits, such as the low values of SLA and NA. Elevation guidelines for A. sachalinensis seed zones are discussed to ensure the long‐term viability of both restored and native populations.

Leaf-level responses to light in two co-occurring Quercus (Quercus ilex and Quercus suber): leaf structure, chemical composition and photosynthesis

We studied morphological, biochemical and physiological leaf acclimation to incident Photon-Photosynthetic-Flux-Density (PPFD) in Quercus ilex (holm oak) and Quercus suber (cork oak) at Mediterranean evergreen oak woodlands of southern Portugal. Specific leaf area (SLA) decreased exponentially with increasing PPFD in both species. Q. ilex had lower SLA values than Q. suber. Leaf nitrogen, cellulose and lignin concentration (leaf area-based) scaled positively with PPFD. Maximum rate of carboxylation (Vcmax), capacity for maximum photosynthetic electron transport (Jmax), rate of triose-P utilization (VTPU) and the rate of nonphotorespiratory light respiration (Rd) were also positively correlated with PPFD in both Quercus species, when expressed in leaf area but not on leaf mass basis. Q suber showed to have higher photosynthetic potential (Vcmax, J max m and V TPU m ) and a higher nitrogen efficient nitrogen use than Q.ilex. Leaf chlorophyll concentration increased with decreasing PPFD, improving apparent quantum use efficiency (Φ) in both Quercus species. We concluded that, in Q.ilex and Q.suber, leaf structural plasticity is a stronger determinant for leaf acclimation to PPFD than biochemical and physiological plasticity.

Genotypic and environmental variation in specific leaf area in a widespread Alpine plant after transplantation to different altitudes

Specific leaf area (SLA) is an important plant functional trait as it is an indicator of ecophysiological characteristics like relative growth rate, stress tolerance and leaf longevity. Substantial intraspecific variation in SLA is common and usually correlates with environmental conditions. For instance, SLA decreases with increasing altitude, which is understood as adjustment to temperature. It is generally assumed that intraspecific variation is mostly the result of environmentally induced phenotypic plasticity, but genetic effects may also be present, due to local adaptation or genetic drift. In this study, genotypic and environmental effects on SLA were experimentally separated for the widespread Alpine bell flower Campanula thyrsoides by transplanting plants to three common gardens at contrasting altitudes (600, 1,235 and 1,850 m a.s.l.). Seeds were sampled from 18 populations in four phylogeographic regions within the European Alps. A strong plastic response was observed: SLA decreased with increasing altitude of the common gardens (22.0% of variation). The phylogeographic regions were differentiated in SLA in the common gardens (10.1% of variation), indicating that SLA is at least partly genetically determined. Plants from the six easternmost populations experienced a submediterranean climate and showed decreased SLA values in the three common gardens compared to populations to the west, which may be explained as adaptation to drought. Within these submediterranean populations, SLA decreased with altitude of origin in two out of three common gardens. Concluding, SLA shows strong phenotypic plasticity as well as substantial genetic effects, the latter probably being the result of adaptation to local conditions rather than genetic drift.

Growth rhythms in sunflower (Helianthus annuus L.) in response to environmental disparity.

Sunflower hybrids maintain high level of stability in a variety of environments. Environmental variations affect and modify plant attributes like growth, development and assimilation through physio-morphic functions, thus modifying plant phenology. Field experiments, one each in spring and autumn, were conducted at Pir Mehr Ali Shah, Arid Agriculture University, Rawalpindi, Pakistan for two years (2007 and 2008) to document the effect of environmental variations on growth rhythms of sunflower hybrids. Four Sunflower hybrids, Alisson-RM, Parasio-24, MG-2 and S-278 were planted in randomized complete block design with four replications. The data based on physiological attributes like leaf area (LA), specific leaf area (SLA), crop growth rate (CGR) and net assimilation rate (NAR) at 10 days interval after complete emergence to 60 days after emergence (DAE) were recorded. Overall higher values of LA, SLA, CGR and NAR were recorded during spring as compared to autumn for both years. LA, CGR and NAR of all the hybrids followed a sigmoid curve pattern during both seasons; however, at the start of the season lesser values were observed during spring as compared to autumn. SLA exhibited an opposite trend and continuously decreased till the end. Sigmoid curve pattern of LA, CGR and NAR may be related to environmental variables like temperature and sunshine hours. The decrease after a peak may be due to senescence of older leaves and shifting of crop from vegetative to reproductive phase.

Phenotypic plasticity and local adaptation in leaf ecophysiological traits of 13 contrasting cork oak populations under different water availabilities

Plants distributed across a wide range of environmental conditions are submitted to differential selective pressures. Long-term selection can lead to the development of adaptations to the local environment, generating ecotypic differentiation. Additionally, plant species can cope with this environmental variability by phenotypic plasticity. In this study, we examine the importance of both processes in coping with environmental heterogeneity in the Mediterranean sclerophyllous cork oak Quercus suber. For this purpose, we measured growth and key functional traits at the leaf level in 9-year-old plants across 2 years of contrasting precipitation (2005 and 2006) in a common garden. Plants were grown from acorns originated from 13 populations spanning a wide range of climates along the distribution range of the species. The traits measured were: leaf size (LS), specific leaf area (SLA), carbon isotope discrimination (Delta(13)C) and leaf nitrogen content per unit mass (N(mass)). Inter-population differences in LS, SLA and Delta(13)C were found. These differences were associated with rainfall and temperature at the sites of origin, suggesting local adaptation in response to diverging climates. Additionally, SLA and LS exhibited positive responses to the increase in annual rainfall. Year effect explained 28% of the total phenotypic variance in LS and 2.7% in SLA. There was a significant genotype x environment interaction for shoot growth and a phenotypic correlation between the difference in shoot growth among years and the annual mean temperature at origin. This suggests that populations originating from warm sites can benefit more from wet conditions than populations from cool sites. Finally, we investigated the relationships between functional traits and aboveground growth by several regression models. Our results showed that plants with lower SLA presented larger aboveground growth in a dry year and plants with larger leaf sizes displayed larger growth rates in both years. Overall, the study supports the adaptive value of SLA and LS for cork oak under a Mediterranean climate and their potentially important role for dealing with varying temperature and rainfall regimes through both local adaptation and phenotypic plasticity.

Evaluation of sugarcane genotypes for high water use efficiency and thermostability tolerance under imposed moisture stress at formative stage

Fourteen sugarcane genotypes were screened for traits contributing to high water use efficiency (WUE) and temperature tolerance in a field experiment by imposing moisture stress at formative phase i.e. 40 DAP to 120 DAP (days after planting). WUE was measured using surrogate methods viz., SPAD chlorophyll meter readings (SCMR), specific leaf area (SLA) and thermostability was quantified by measuring membrane relative injury percentage on 20 days (60 DAP) and 80 days (120 DAP) after imposing moisture stress (DAIS). Among the fourteen genotypes, four genotypes viz., 97 R 129, 92 V 104, CO (O) 061 and CO 6907 showed low SLA and higher SCMR values, which indicates higher water use efficiency. However, higher thermostability was recorded in 92 V 104 and CO 6907 genotypes only. Hence, the 92 V 104 and CO 6907 genotypes having both WUE and temperature tolerance traits can be used as donar parents in breeding programmes. SCMR, SLA, relarive injury per cent can be used as surrogate methods for measurement of WUE and temperature tolerance in sugarcane and can be used as selection traits in breeding programme for developing drought tolerant genotypes.

Effects of coloured shade netting on the vegetative development and leaf structure of Ocimum selloi

The objective of this work was to investigate the effects of shading on the growth and development of the medicinal plant Ocimum selloi after 90 days. Seedlings were maintained under three different light treatments, namely, full sunlight vs coloured shade treatments provided by red and blue ChromatiNet® 50% coloured netting. After 90 days of cultivation, height, stem diameter, petiole length, total leaf area (TLA), specific leaf area (SLA), leaf area ratio (LAR) and leaf weight ratio (LWR) of each plant hare measured. Microscopic examination of leaf sections were conducted in order to determine the leaf blade thicknesses, together with the size and density of the stomata, the number and area of chloroplasts, and chloroplast starch grains present in the palisade parenchyma cells. Although coloured shade-grown plants were taller in comparison with those grown in full sunlight, total dry biomass together with root, stem and leaf tissue biomasses were lower. Plants exhibited phenotypic plasticity, as demonstrated by the different TLA, SLA, LAR and LWR values that were recorded under the various light treatments. Stomatal density and leaf thickness was increased in plants maintained in full sunlight owing to the expansion of the abaxial epidermis and the spongy parenchyma. Chloroplasts were more numerous and larger in plants grown under shading, whilst the accumulation of chloroplastic starch grains was greater in plants grown under red shading or in full sunlight.

Relationships among Water Use Efficiency, Carbon Isotope Discrimination, and Specific Leaf Area in Maize

Plant fractionates heavy carbon isotopes during photosynthesis, which usually occurs when CO2 diffuses to the car- boxylation site, and during carboxylation reaction. On account of CO2 fixation process is coupled with water transpiration during the photosynthesis, it is possible to apply stable carbon isotope to study crop water use efficiency (WUE). At present, stable car- bon isotope techniques have been widely studied and applied in C3 plants, however, the relative studies are less reported in C4 plants. In this way, a pot experiment was conducted from June 9 to September 25 in 2007 to study the variation of leaf area (LA), specific leaf area (SLA), water use efficiency (WUE), and carbon isotope discrimination (Δ13C) in maize (Zea mays L.) under different water deficit conditions. The objective was to understand the relationship among WUE, Δ13C, and SLA. Maize were subjected to four water treatments, i.e.: 75–100% (W1), 50–75% (W2), 30–50% (W3), and 0–30% (W4) of field water-holding capacity of the soil. The WUE, SLA, and Δ13C values were measured at seedling, jointing, booting, tasseling, filling, and mature stages. The dry matter accumulation at jointing was obviously affected by W2 and W3 treatments, and decreased significantly in W4 treatment after booting. WUE increased with water stress during all growth stages in W2 and W3 treatments, but decreased significantly in W4 treatment after booting. SLA reached maximal value at booting. Leaf Δ13C decreased in W1, W2, and W3 treatments from jointing to mature, whereas leaf Δ13C value was greater in W4 treatment than in W2 and W3 treatments. Stem Δ13C significantly and positively correlated and presented no significant difference with leaf Δ13C, which indicated that carbon isotope was not fractionated during photosynthate transport from leaves to stems. Maize Δ13C was negatively correlated with WUE; SLA and Δ13C presented positive correlation and both negatively correlated with WUE.

Central composite design-based analysis of specific leaf area and related agronomic factors in cultivars of rapeseed ( Brassica napus L .)

Specific leaf area (SLA) is an important parameter in evaluating leaf function, yield potential, and ecological adaptability. Data from our field experiments from 2000 to 2005 were used to evaluate the values of SLA and related agronomic factors. SLA remained stable during winter, differed significantly among the dates of observation, and declined from seedlings to maturation in all the cultivars tested. ANOVA analysis showed that SLA differed significantly with sowing date but not with the cultivar, and was correlated positively with population density but negatively with the weight of leaves, roots, and the stem and with potassium application. A parabolic relationship was found between SLA and application of phosphorus. SLA at different observation dates before anthesis was negatively correlated with shoot weight at anthesis. An appropriate combination of population density and application of phosphorus and potassium could be helpful in securing desirable values of SLA (high at the seedling stage and low from the middle growth stage to maturity) and optimal population morphogenesis and, in turn, high yields.

Modulation of leaf attributes and water use efficiency in Quercus suber along a rainfall gradient

The aim of our study was to assess the intraspecific variation of a range of leaf attributes and carbon isotope discrimination (Δ), in Quercus suber, along an 800 mm rainfall gradient in Portugal. We measured specific leaf area (SLA), leaf thickness (LT) and density, and used leaf carbon isotope content as an integrated record of water use efficiency. The values of SLA of Q. suber were strongly, positively correlated with rainfall, decreasing as rainfall decreased. This reduction was mainly driven by LT, which was tightly correlated with SLA (R = −0.80, P < 0.001), and steadily increased with declining rainfall. The significant increase in carbon isotope discrimination towards the wetter end of the gradient, with a difference of 4.2‰ in Δ between the two extremes, suggests a strong adjustment of leaf gas exchange to water availability. Leaf changes associated with precipitation in Q. suber thus seem to influence water economy, since reduction of SLA with the increase of LT with aridity improves water use efficiency. These data suggest that this evergreen tree species relies on its foliage plasticity and physiology to overcome water shortage.

Can we predict dispersal guilds based on the leaf-height-seed scheme in a disjunct cerrado woodland?

Although there have been advances in methods for extracting information about dispersal processes, it is still very difficult to measure them. Predicting dispersal groups using single readily-measured traits would facilitate the emergence of instructive comparisons among ecological strategies of plants and offer a path towards improved synthesis across field experiments. The leaf-height-seed scheme consists of three functional traits: specific leaf area, plant canopy height, and seed mass. We tested, applying logistic regression analysis, whether these traits are potential predictors of dispersal guilds in a disjoint cerrado woodland site in southeastern Brazil. According to our results, none of the plant traits studied could predict dispersal guild; this means that abiotically and biotically dispersed species showed similar values of specific leaf area, height, and seed mass. The species of both guilds exhibited sclerophylly, probably a result of the typical soil nutrient deficiency of cerrado, which also may have placed constraints upon plant canopy height regardless of the dispersal mode. In the cerrado, some abiotically dispersed trees might present higher than expected seed mass as support to the investment in high root-to-shoot ratio at the seedling stage. Seeds of bird-dispersed species are limited in size and mass because of the small size of most frugivorous birds. Since soil nutrient quality might contribute to the similarity between the dispersal guilds regarding the three traits of the scheme, other plant traits (e.g., root depth distribution and nutrient uptake strategy) that detail the former should be considered in future predictive studies.

Annual rainfall does not directly determine the carbon isotope ratio of leaves of Eucalyptus species

Leaf carbon isotope discrimination (delta13C) was widely considered to directly reflect the rainfall environment in which the leaf developed, but recent observations have queried this. The relationship between delta13C and rainfall was explored in Eucalyptus species growing along a rainfall gradient in Australia. The leaves of 43 species of Eucalyptus and the closely related Corymbia species produced in 2003 were sampled in September 2004 at 50 sites and grouped into 15 locations along a rainfall gradient in southwest Western Australia. At 24 sites, the same species and same trees were sampled as in a study in September 2003 when leaves produced in 2002 were sampled. The rainfall in 2004 was on average 190 mm (range 135-270 mm) higher at all locations than in 2003. In the leaves sampled in 2004, the mean carbon isotope discrimination (delta13C) across the 15 locations decreased 2.9 per thousand per 1000 mm of rainfall, the specific leaf area (SLA) increased by 2.9 m2 kg(-1) per 1000 mm of rainfall and the nitrogen (N) content decreased by 1.56 g m(-2) per 1000 mm of rainfall. In contrast, a comparison between the leaves produced in the drier 2002 year compared with the wetter 2003 year showed that there was a strong correlation (r2= 0.85) between the SLA values between years and a trend for higher values with increasing SLA, but the values of delta(13)C were on average only 0.38 per thousand lower (more negative) at all locations in the wetter year, equivalent to a decrease of 2.0 per thousand per 1000 mm of rainfall. The results suggest that while there may be constitutive differences in leaf morphology, SLA and N content per unit area, increasing rainfall or cloudiness associated with higher rainfall increases SLA and decreases N content per unit area. We conclude that rainfall does not directly influence delta13C, but induces leaf morphological and physiological changes that affect the resultant delta13C.

Invasive trees show only weak potential to impact nutrient dynamics in phosphorus‐poor tropical forests in the Seychelles

Summary 1. Some invasive alien plants accelerate nutrient turnover in the ecosystem because the litter they produce has a high specific leaf area (SLA), high concentrations of nutrients and low concentrations of lignin and polyphenolics, and therefore decomposes rapidly. These litter properties are typical of plants from nutrient-rich but not nutrient-poor ecosystems, and we therefore hypothesize that species that successfully invade nutrient-poor ecosystems might not exhibit them. We tested our hypothesis in a nutrient-poor tropical forest on a granitic island in the Seychelles. 2. Leaf litter properties and annual decomposition rates of six native and six invasive woody species were compared in a field experiment. Each species group included two pioneer, two understorey and two canopy species. We also compared soil fertility under trees of Cinnamomum verum (dominant alien canopy tree), Falcataria moluccana (alien pioneer N-fixing tree) and Northea hornei (dominant native canopy tree), measuring total nutrient concentrations and nutrient absorption by ion exchange resins. 3. Within the ecological groups of pioneer and canopy species, litter of invasive species had higher mean values of SLA (120% higher) and leaf N concentration (80% higher), and litter decomposition was 40%‐80% faster (rate k ) than for native species; however, there were no such differences in the group of understorey species. Soils sampled under the three tree species differed little in nutrient concentrations. 4. The results indicate that even on the very nutrient-poor soils of the granitic Seychelles, some pioneer invasive species produce more decomposable litter and therefore have the potential to alter rates of nutrient cycling. However, the small differences in soil fertility beneath native and invasive trees suggest that impacts of invasive species on nutrient cycling are more complex and less predictable in nutrient-poor ecosystems, where several nutrients may be co-limiting, and native and alien species coexist.

Stability of soil plant analytical development (SPAD) chlorophyll meter reading (SCMR) and specific leaf area (SLA) and their association across varying soil moisture stress conditions in groundnut (Arachis hypogaea L.)

The complex nature of physiological traits associated with drought tolerance and the difficulties associated with their measurements in segregating populations and large number of genotypes inhibited their use in the past in developing water-use efficient genotypes in breeding programmes. With new knowledge of easily measurable surrogates of transpiration efficiency (TE), a trait associated with drought tolerance—specific leaf area (SLA) and soil plant analytical development (SPAD) chlorophyll meter reading (SCMR), it is now possible to integrate TE through the surrogates in breeding and selection schemes in groundnut (Arachis hypogaea L.). As a noninvasive surrogate of TE, SCMR is easy to operate, reliable, fairly stable and low cost. However, in a large-scale breeding program, it is difficult to complete SCMR observations within a specified time. The present study addressed the issue as to what extent the SCMR measurements can be spread over time by evaluating 18 diverse groundnut genotypes for two physiological traits, SCMR and SLA in two postrainy (Nov–Apr) seasons (2002/2003 and 2003/2004) in India. Observations were recorded at different times during and after the release of moisture deficit stress. There was general agreement in genotype and trait performance in both the seasons. Interaction between SCMR and time of observation was significant in only one season (2002/2003) but its variance relative to genotypes and time of observation was very small. ICGV 99029 and ICR 48, which recorded higher SCMR and lower SLA values in both the seasons, will make good parents for water-use efficiency trait in breeding programmes. Other good parents include ICGS 76, TCGS 647 and TCGP 6. SCMR recorded at three different times under differing soil moisture deficit in each season showed highly significant correlation with each other. Similarly, SLA at different times also correlated significantly with each other. SCMR and SLA were significantly negatively correlated with each other and the relationship was insensitive to time of observation. The results of the present study indicated that SCMR/SLA observations can be recorded at any time after 60 days of crop growth, preferably under moisture deficit conditions. This gives groundnut breeders a large flexibility to record these observations in a large number of segregating populations and breeding lines in the field. Thus, making it easy to incorporate these physiological traits associated with drought tolerance in breeding and selection scheme in groundnut.

Variation in transpiration efficiency and its related traits in a groundnut ( Arachis hypogaea L.) mapping population

Transpiration efficiency (TE) has been recognized as an important source of yield variation under drought stress in groundnut. Here the variation for TE is evaluated in a set of 318 recombinant inbred lines (RILs) of groundnut at F 8 generation, derived from a cross between a high TE (ICGV 86031) and a low TE (TAG 24) parent, and the value of specific leaf area (SLA), SPAD chlorophyll meter readings (SCMR) and carbon isotope discrimination (Δ 13C) as surrogates of TE are measured. Transpiration efficiency was measured gravimetrically in the 318 RILs and parents under progressive soil drying in a pot culture in two post-rainy seasons. Large and consistent variation for TE existed among the RILs across years. The overall distribution of TE among the RILs indicated that TE was governed by dominant and additive genes. Surrogates SLA and SCMR, were measured prior, during and after completion of the drought period, whereas Δ 13C was measured on the dried tissue after harvest. Transpiration efficiency was negatively associated with SLA after the completion of stress treatment ( r 2 = 0.15) and Δ 13C in leaves ( r 2 = 0.13) and positively associated with SCMR during stress ( r 2 = 0.17). These associations, all fairly weak, were significant only in 2004. None of these relationships was found in 2005. Although the heritability of SCMR during 2005 was relatively higher than that of TE, and although SCMR has previously been used to identify contrasting germplasm for TE, the stress-dependence of the relationship with TE, and the poor regression coefficients ( r 2) with that RIL population, do not confer that these surrogates are adequately robust enough in that population. Though more time consuming, a direct gravimetric evaluation for TE appeared to be more reliable.

Evaluation of genus Cenchrus based on malondialdehyde, proline content, specific leaf area and carbon isotope discrimination for drought tolerance and divergence of species at DNA level

Cenchrus (family Poaceae) is an important component of major grass covers of the world. Largely it is apomictic and both annual and perennial species exist in nature. Variations in contents of malondialdehyde, proline, specific leaf area and carbon isotope discrimination for drought tolerance were estimated among eight prominent species of Cenchrus. Simultaneously, genetic variations were also estimated by employing 187 RAPD primers. Of these, 23 primers did not react, 2 performed poorly and 7 produced many non-scorable bands and one primer yielded a single monomorphic band. Rest of the 154 primers generated one or more unambiguously scorable fragments. Twelve hundred and four of the 1,296 putative loci were polymorphic (93%) between at least one pair-wise comparisons among eight species. Dice coefficient and neighbor-joining algorithm analyses showed clustering patterns that fit with the known habitat of the species except perennial, C. myosuroides which formed a node between two annuals species. When these species were subjected to water stress tolerance test, a correlation (r = 0.612) between specific leaf area (SLA) and carbon isotope discrimination (CID) and difference in levels of drought tolerance based parameters among eight species were observed. Of the eight species investigated two annuals viz., C. biflorus and C. echinatus showed highest level of genetic similarity which was also evident from the similar levels of SLA, MDA, proline contents and carbon isotope discrimination values observed in these two species.

Determination of specific leaf area of some commercially useful sub-tropical hardwood species

Summary Variability of specific leaf area (SLA) across taxa, sites and crown zones was determined for four sub-tropical hardwood species, Eucalyptus grandis, E. cloeziana, E. argophloia and Corymbia citriodora ssp. variegata, growing in south-eastern Queensland. Mean SLA values were stable amongst those taxa sampled on dry sites but varied markedly between provenances of E. grandis on a moist site. Mean SLA did not vary significantly with crown zone in any of these four sub-tropical eucalypts, which is in contrast to that observed in temperate species, both in Australia and overseas. A provenance of E. cloeziana from a moist coastal site exhibited the largest SLA of all taxa studied.

Relative Growth Rate and Biomass Allocation in Ten Woody Species with Different Leaf Longevity Using Phylogenetic Independent Contrasts (PICs)

In this study, we compare the relative growth rate (RGR) and biomass allocation of 10 woody species (5 deciduous and 5 evergreen) from the Mediterranean region using phylogenetic independent contrasts (PICs) to test if these two functional groups differ in these traits. In general, the results were similar when using PICs or without taking into account phylogenetic relations. Deciduous species had a higher RGR than evergreen species, due to the higher net assimilation rate (NAR). Deciduous species had a higher specific leaf area (SLA) but a lower leaf mass ratio (LMR), resulting in a similar LAR for deciduous and evergreen species (LAR = SLA x LMR). In some cases, the use of PICs revealed patterns that would not have appeared if phylogeny had been overlooked. For example, there was no significant correlation between RGR and final dry mass (after 4 months of growth) but PICs revealed that there was a positive relation between these two variables in all deciduous-evergreen pairs. In general, RGR decreased with time and this temporal variation was due primarily to NAR variations (r = 0.79, p < 0.01), and also to variations in LAR (r = 0.69, p < 0.05). Considering the phylogeny, the only variable constantly different for all deciduous-evergreen pairs was SLA. This result, and the fact that SLA was the best correlated variable with RGR (r = 0.81, p < 0.01), reinforce the value of SLA as a variable closely associated to growth and to the functional groups (deciduous vs. evergreen).

Variability for Drought Resistance Related Traits in the Mini Core Collection of Peanut

Peanut (Arachis hypogaea L.) productivity is low in the semiarid tropics mainly because of drought caused by low and erratic rainfall. Identification of genotypes that have a greater ability to use limited available water is important to enhance productivity of the crop. Water‐use efficiency (WUE) is correlated with specific leaf area (SLA) and soil plant analysis development (SPAD) chlorophyll meter reading (SCMR) and both have been suggested as surrogate traits for selecting for WUE in peanut. The present study was conducted to: (i) identify genotypes with high WUE using SLA or SCMR and (ii) evaluate relationship between and relative stability of SCMR and SLA in these genotypes. The 184 mini core entries, consisting of 37 fastigiata, 58 vulgaris, 85 hypogaea, two peruviana, and one each of aequitoriana and hirsuta and four control cultivars, M 13, Gangapuri, ICGS 44 and ICGS 76 were evaluated for SLA, SCMR, and 19 vegetative, reproductive, and quality traits in the 2001 rainy and 2001–2002 postrainy seasons at ICRISAT Center. Data were analyzed by REML analysis. Seasons were significant for all traits. Variances due to genotypes were significant for SCMR and SLA at 60 and 80 d after sowing (DAS) and other traits except pods per plant, yield per plant, haulm yield per plot, and protein and oil contents. The genotype × season interactions were significant for both SCMR and SLA at 80 DAS only and for all other quantitative traits except number of primary branches, and pod width. The SCMR values at different stages and seasons were more positively correlated with each other than the correlation of SLA values together. SCMR and SLA were negatively correlated. SCMR values were more strongly correlated with pod yield and other economic traits such as 100‐seed weight at both 60 and 80 DAS than SLA. On the basis of higher heritability and lower proportion of genotype × season interaction variance to phenotypic variance, SCMR appeared to be more stable than SLA. On the basis of SLA and SCMR values compared with the control cultivar, five vulgaris and 13 hypogaea accessions were selected. These accessions and control cultivars were grouped by scores of the first 15 principal components (PCs). The clustering by UPGMA method indicated that the selected accessions were diverse from the control cultivars and can be used in the peanut improvement programs to develop cultivars with a broad genetic base.

Using plant traits to compare sward structure and composition of grass species across environmental gradients

Abstract. Plant traits which may give an indication of a plant's strategy for nutrient acquisition and regeneration are known for numerous grassland species. This study aimed to establish whether there is any relationship between two plant traits: specific leaf area (SLA) and number of reproductive tillers, and sward structural characteristics which influence herbage intake by grazers (bulk density and digestibility, leaf:stem ratio). Comparison is made for nutrient‐rich (Dactylis glomerata) and nutrient‐poor (Festuca rubra) grass species. We hypothesized that these traits are responsive to environmental gradients and also act on the processes of the ecosystem. Both grasses were compared with two P‐fertilizer rates in two localities (200 and 1300 m a.s.l.) which differed in their temperature:radiation ratios. For the vegetative phase SLA was well correlated with sward characteristics: D. glomerata, which has the higher SLA, has the lower bulk density and higher digestibility. The values of SLA and vegetation bulk density varied according to growing conditions (P‐rate and temperature:radiation ratio), but the ranking of the species remained the same because the phenotypic plasticity that exists for plant traits was also observed for sward structure and composition. That suggested the possibility of grouping natural grassland species for their relevant characteristics for grazers according to SLA values. Over the reproductive phase, the proportion of stems was well correlated to the percentage of reproductive tillers. However, the percentage of reproductive tillers was a very plastic trait for both species, depending on the growing conditions, and resulting in a density‐dependent effect, particularly for F. rubra. The species studied were too plastic and too similar in their regenerative strategy so that there is no unique relationship between percentage of reproductive tillers and stem proportion, regardless of the species and the growing conditions. The number of reproductive tillers is not a suitable plant trait which could be used to rank species for leaf and stem proportions in the sward.