Variation in leaf resin composition between parent tree and progeny in Hymenaea: Implications for herbivory in the humid tropics

Variation in the sesquiterpene hydrocarbon leaf resins in the tropical leguminous genus Hymenaea is compared between parent tree, seedling and sapling progeny. Relatively large discrete quantitative variation in the leaf resins, known experimentally to display little phenotypic plasticity, has been classified into Compositional Types. Differences in Compositional Types in the leaves between parent tree and their seedling and sapling progeny are more pronounced in rain forest and related eocystems than in savanna and dry forests. A model is presented in which it is suggested that this variation in leaf resin may play an important role in defence against lepidopteran herbivores and thus also in seedling establishment under Hymenaea parent trees in rain forest and related ecosystems.     

Relationship of light intensity to leaf resin composition and yield in the tropical leguminous genera Hymenaea and Copaifera

Hymenaea and Copaifera are closely related morphologically distinct tree genera whose leaf resins appear to be composed of the same sesquiterpene hydrocarbons which occur in similar quantitative compositional patterns. The seedlings of both genera grow in varying light intensities in the understories of different lowland tropical ecosystems from desert thorn forests to equatorial evergreen rain forests; all eventually grow into high light intensity. Previous controlled environment studies of the effects of photoperiod, temperature and moisture status have shown little phenotypic plasticity in the leaf resin composition of Hymenaea seedlings. In this study, focusing on light intensity, both control chamber experiments comparing seedlings of H. courbaril var. courbaril, H. courbaril var. subsessilis, C. officinalis and C. pubiflora, grown under low and high light treatments, and field data from saplings of C. multijuga, growing under shaded and unshaded conditions, also show lack of phenotypic plasticity in resin composition. The yield of resin (mg/g leaf tissue), however, varied considerably among individuals, and increased significantly from low to high light conditions in both control chamber and field conditions. The relationship of increased synthesis is discussed with regard to photosynthetic capacity, allocation of carbon and herbivory.     

Leaf age dependent changes in within-canopy variation in leaf functional traits: a meta-analysis

Within-canopy variation in leaf structural and photosynthetic characteristics is a major means by which whole canopy photosynthesis is maximized at given total canopy nitrogen. As key acclimatory modifications, leaf nitrogen content (N _A) and photosynthetic capacity (A _A) per unit area increase with increasing light availability in the canopy and these increases are associated with increases in leaf dry mass per unit area (M _A) and/or nitrogen content per dry mass and/or allocation. However, leaf functional characteristics change with increasing leaf age during leaf development and aging, but the importance of these alterations for within-canopy trait gradients is unknown. I conducted a meta-analysis based on 71 canopies that were sampled at different time periods or, in evergreens, included measurements for different-aged leaves to understand how within-canopy variations in leaf traits (trait plasticity) depend on leaf age. The analysis demonstrated that in evergreen woody species, M _A and N _A plasticity decreased with increasing leaf age, but the change in A _A plasticity was less suggesting a certain re-acclimation of A _A to altered light. In deciduous woody species, M _A and N _A gradients in flush-type species increased during leaf development and were almost invariable through the rest of the season, while in continuously leaf-forming species, the trait gradients increased constantly with increasing leaf age. In forbs, N _A plasticity increased, while in grasses, N _A plasticity decreased with increasing leaf age, reflecting life form differences in age-dependent changes in light availability and in nitrogen resorption for growth of generative organs. Although more work is needed to improve the coverage of age-dependent plasticity changes in some plant life forms, I argue that the age-dependent variation in trait plasticity uncovered in this study is large enough to warrant incorporation in simulations of canopy photosynthesis through the growing period.     

Sesquiterpene Deterrence of a Leaf-Tying Lepidopteran, Stenoma ferrocanella, on Hymenaea stigonocarpa in Central Brazil

Study of two populations of Hymenaea stigonocarpa in the central Brazilian cerrado (savanna/woodland) shows attack by a leaf-tying lepidopteran, Steoma ferrocanella, occurred after inferred peak concentration (% of leaf dry wt) of sesquiterpene leaf resins during leaf development. Also a highly statistically significant relationship existed between leaf-tier attack and level of caryophyllene in one population and γ-muurolene in the other population. The data from one population are consistent with laboratory experiments demonstrating highly significant dose-dependent effects of caryophyllene in Hymenaea leaf resin on mortaility of the lepidopteren Spodoptera exigua. Results from both populations support other evidence that changes in the amount of single terpenes in the mixture constituting the resin may have significant antiherbivore effects and, concomitantly, that herbivory may be a source of some of the leaf resin variation.     

Geographic and genetic variation in the leaf surface resin components of Mimulus aurantiacus from southern California

Nearly 30% of the dry weight of leaves of the chaparral subshrub Mimulus aurantiacus comprise leaf surface resins. This resin provides some defense against the insect herbivore, Euphydryas chalcedona and may also protect plants from desiccation and UV light injury. The resin is composed of several components and the different components may contribute differentially to the resin's multiple protective roles. The quantities of each of seven resin components from field-grown plants, from six southern California populations of M. aurantiacus spanning a range of water availability and differing in attack by E. chalcedona, and clones from these plants grown in a common garden, were determined. Two predictions were tested: (1) E. chalcedona will attack plant populations with relatively low quantities of total resins and/or concentrations of the ortho dihydroxy resins, and (2) plant populations in drier environments will produce resin that is relatively richer in the methoxylated components than plant populations in more mesic environments. Although resin composition differed genetically among plant populations, the pattern of variation was not as predicted. Insect attack was not associated with lower levels of ortho dihydroxy compounds, and populations with higher proportions of methoxylated flavonoids were not found in the drier sites. The pattern of genetic variation among populations in resin composition therefore was not explained by the differences in chemical structure that were predicted to influence the role of the components as herbivore protectants or antidesiccants.     

Elevated temperature is more effective than elevated [CO2] in exposing genotypic variation in Telopea speciosissima growth plasticity: implications for woody plant populations under climate change

Intraspecific variation in phenotypic plasticity is a critical determinant of plant species capacity to cope with climate change. A long‐standing hypothesis states that greater levels of environmental variability will select for genotypes with greater phenotypic plasticity. However, few studies have examined how genotypes of woody species originating from contrasting environments respond to multiple climate change factors. Here, we investigated the main and interactive effects of elevated [CO₂] (C_E) and elevated temperature (T_E) on growth and physiology of Coastal (warmer, less variable temperature environment) and Upland (cooler, more variable temperature environment) genotypes of an Australian woody species Telopea speciosissima. Both genotypes were positively responsive to C_E (35% and 29% increase in whole‐plant dry mass and leaf area, respectively), but only the Coastal genotype exhibited positive growth responses to T_E. We found that the Coastal genotype exhibited greater growth response to T_E (47% and 85% increase in whole‐plant dry mass and leaf area, respectively) when compared with the Upland genotype (no change in dry mass or leaf area). No intraspecific variation in physiological plasticity was detected under C_E or T_E, and the interactive effects of C_E and T_E on intraspecific variation in phenotypic plasticity were also largely absent. Overall, T_E was a more effective climate factor than C_E in exposing genotypic variation in our woody species. Our results contradict the paradigm that genotypes from more variable climates will exhibit greater phenotypic plasticity in future climate regimes.     

Temporal changes in the leaf monoterpenes of Sequoia sempervirens

Sequoia sempervirens leaf monotorpenes were analysed from bud burst through maturity. Significant changes occurred in both quantitative composition and total yield/dry wt during the first six months of leaf development. Composition then remained stable until initiation of twig abscission. Total yield also remained relatively stable except for a sharp increase at month 15, followed by a return to earlier levels and stability until initiation of abscission. The age of the shoot was important only for individuals less than 1 m high. Simulated herbivory by leaf removal showed only minor compositonal changes when plants were resampled one year later. Results support the concept that variation in individual compounds could provide an effective defensive strategy against herbivores and pathogens, and also establish a suitable time period for minimizing variation in sample collections.     

Genetic variation and plasticity of Plantago coronopus under saline conditions

Phenotypic plasticity may allow organisms to cope with variation in the environmental conditions they encounter in their natural habitats. Salt adaptation appears to be an excellent example of such a plastic response. Many plant species accumulate organic solutes in response to saline conditions. Comparative and molecular studies suggest that this is an adaptation to osmotic stress. However, evidence relating the physiological responses to fitness parameters is rare and requires assessing the potential costs and benefits of plasticity. We studied the response of thirty families derived from plants collected in three populations of Plantago coronopus in a greenhouse experiment under saline and non-saline conditions. We indeed found a positive selection gradient for the sorbitol percentage under saline conditions: plant families with a higher proportion of sorbitol produced more spikes. No effects of sorbitol on fitness parameters were found under non-saline conditions.Populations also differed genetically in leaf number, spike number, sorbitol concentration and percentages of different soluble sugars. Salt treatment led to a reduction of vegetative biomass and spike production but increased leaf dry matter percentage and leaf thickness. Both under saline and non-saline conditions there was a negative trade-off between vegetative growth and reproduction. Families with a high plasticity in leaf thickness had a lower total spike length under non-saline conditions. This would imply that natural selection under predominantly non-saline conditions would lead to a decrease in the ability to change leaf morphology in response to exposure to salt. All other tests revealed no indication for any costs of plasticity to saline conditions.     

Do the antiherbivore traits of expanding leaves in the Neotropical tree Inga paraensis (Fabaceae) vary with light availability?

Treefall gaps in tropical forests have a profound effect on plants growing in the understory, primarily due to increased light availability. In higher light, mature leaves typically have increased anti-herbivore defenses. However, since the majority of herbivory occurs while leaves are expanding, it is important to determine whether defense expression during the short period of leaf expansion is canalized (invariant) or plastic in response to variation in light. Therefore, we examined young leaves of Inga paraensis (Fabaceae) saplings growing along a light gradient in a terra-firme forest in Central Amazonia. We quantified leaf production and expansion time, dry mass of phenolics, saponins, and nitrogen, ants attracted to extrafloral nectaries, and leaf consumption. Over the entire light gradient, the number of leaves produced per flush increased by 50?% and the mass of phenolic compounds by 20?%, but no other traits changed. On average, 39?% of leaf area was consumed with no difference across the light gradient. Alone, none of the leaf traits was a significant predictor of leaf consumption, except for phenolics, which showed a positive relationship. Multiple regressions showed that leaf consumption was positively related to more leaves per flush and a higher concentration of phenolics in leaves. Unlike studies of mature leaves, young leaves of I. paraensis show low plasticity in defense traits across a light gradient, suggesting that leaf development is canalized.     

Variation in and adaptive plasticity of flower size and drought-coping traits

Although phenotypic plasticity of morphological and physiological traits in response to drought could be adaptive, there have been relatively few tests of plasticity variation or of adaptive plasticity in drought-coping traits across populations with different moisture availabilities. We measured floral size, vegetative size, and physiological traits in four field populations of Leptosiphon androsaceus (Polemoniaceae) that were distributed across a rainfall gradient in California, USA. Measurements were made over 5 years that varied in precipitation. We also conducted a growth chamber experiment in which half-sibs from three populations were divided equally among a well-watered and a drought treatment. We tested for selection on traits in each of the watering treatments, and evaluated whether traits exhibited plasticity. In the field, plant traits exhibited substantial variation across populations and years. Flower size, leaf size, and water-use efficiency (WUE) were generally higher for populations that received greater average rainfall. However, in dry years, we observed a decrease in flower and leaf size, but an increase in WUE across the populations. In the growth chamber experiment, leaf and physiological traits exhibited plasticity, with smaller leaves and higher WUE found in the drought, as compared to the well-watered treatment. Only specific leaf area exhibited differentiation in plasticity among populations. Although there was no observed plasticity in floral size, selection favored smaller flowers in the drought treatment and larger flowers in the well-watered treatment. Our results suggest that moisture availability has led to trait variation in L. androsaceus via a combination of selection and phenotypic plasticity.     

Source water, phenology and growth of two tropical dry forest tree species growing on shallow karst soils

Seasonally dry tropical forests are dominated by deciduous and evergreen tree species with a wide range of leaf phenology. We hypothesized that Piscidia piscipula is able to extend leaf senescence until later in the dry season due to deeper and more reliable water sources than Gymnopodium floribundum, which loses leaves earlier in the dry season. Physiological performance was assessed as timing of leaf production and loss, growth, leaf water potential, depth of water uptake determined by stable isotopes, and leaf stable isotopic composition of carbon (δ¹³C) and oxygen (δ¹⁸O). P. piscipula took water primarily from shallow sources, whereas G. floribundum took water from shallow and deep sources. The greatest variation in water sources occurred during the onset of the dry season, when G. floribundum was shedding old leaves and growing new leaves, but P. piscipula maintained its leaves from the previous wet season. P. piscipula showed greater relative growth rate, greater leaf expansion rates, and more negative predawn and midday water potentials than G. floribundum. P. piscipula also exhibited greater leaf organic δ¹³C and lower δ¹⁸O values, indicating that the decrease in photosynthetic carbon isotope discrimination was associated with greater stomatal conductance and greater photosynthesis. Our results indicate that the contrasting early and late dry season leaf loss phenology of these two species is not simply determined by rooting depth, but rather a more complicated suite of characteristics based on opportunistic use of dynamic water sources, maximizing carbon gain, and maintenance of water potential during the dry season.     

濒危种观光木小枝生物量分配与功能性状的纬度变异规律及其影响因素

为了探讨观光木当年生枝条生物量的分配规律和叶片功能性状的变化规律及其影响因素,该研究以濒危物种观光木(Michelia odora)为对象,测定了广西地区5个不同纬度上观光木当年生小枝及叶片功能性状.结果表明:(1)随着纬度的增加小枝总重和总叶重总体呈异速生长关系,其生物量更多趋于对小枝的构建.(2)观光木叶功能性状呈...     

Environmental conditions modulate plasticity in the physiological responses of three plant species of the Neotropical savannah

Plasticity in plants could be changed due to abiotic factors, tending to increase fitness across environments. In the Neotropical savannah, a strong water deficit during the dry season is one of the main factors limiting the plasticity in physiological responses of plants. The present study aims to assess the plasticity in physiological responses and vegetative phenology of three plant species of the Neotropical savannah (Cerrado in Brazil) during the dry and the rainy seasons. The three species, Byrsonima verbascifolia, Roupala montana, and Solanum lycocarpum, occur in Serra do Cipó in the state of Minas Gerais, Brazil. The development and vegetative phenology of individuals of these three species were evaluated over the course of 1 year. In February 2012 (rainy season) and August 2012 (dry season), stomatal conductance (g _s), water potential (Ψ), photosynthetic quantum yield, and concentration of leaf photosynthetic pigments were measured. The relative distance among the physiological parameters of all individuals within each season was measured using the relative distance plasticity index. B. verbascifolia has pronounced senescence in July and lost leaves completely by the early September, while R. montana and S. lycocarpum have green leaves throughout the year. The three studied species had greater control of stomatal opening during the dry season. S. lycocarpum and R. montana had negative water potential values in the dry season and in the middle of the day in both seasons. In the dry season, the three species exhibited a decrease in F _v/F _m, with values between 0.7 and 0.75. The relative distance plasticity index varied from 0 to 1. R. montana demonstrated the greatest plasticity and S. lycocarpum had lower plasticity. Then, a seasonal effect on physiological response was observed in all three model-species, with lower values for leaf water potential and stomatal conductance, and increased photoinhibition, in the dry season. Ecophysiological traits, such as stomatal conductance and leaf water potential, exhibited the greatest plasticity. In addition, there was a seasonal effect on the plasticity in physiological responses of the three plants species of the Neotropical savannah. The results are contradicting the idea that water restriction in the dry season would reduce the plasticity in most species of the Neotropical savannah.     

Sesquiterpenes in leaf pocket resins of Copaifera species

Four sesquiterpene leaf resin components were isolated and identified from Copaifera leaf resin. Additional GC and mass spectrometric evidence support the close similarity of Copaifera leaf pocket resin composition with that of the related genus, Hymenaea.     

The effect of moisture stress on monoterpenoid yield and composition in Satureja douglasii

The effect of moisture stress on monoterpenoid yield and composition of Satureja douglasii was studied under controlled conditions and in the field. Large differences in monoterpenoid yield observed among field populations were closely correlated with moisture stress. In greenhouse transplants grown under uniformly moist conditions these differences were significantly reduced. In all plants studied yield per leaf dry weight decreased with development. A growth chamber study using clones grown under different soil moisture regimes showed that high moisture stress reduced leaf weight and monoterpenoid yield per leaf, but had little effect on yield per leaf dry weight. Effects on monoterpenoid composition were less striking with high moisture stress causing a small decrease in the percentage of monoterpenoids with a p-menthane carbon skeleton and perhaps accelerating the rate of developmental conversions.     

Is seasonal variation in leaf traits adaptive for the annual plant Dicerandra linearifolia?

Empirical studies of phenotypic plasticity have often relied on the plausibility that a plastic response to the environment would increase fitness in order to diagnose the response as adaptive. I conducted a test of the hypothesis that seasonal variation in leaf traits is an adaptive response to seasonal variation in environmental conditions faced by the annual plant Dicerandralinearifolia. This species exhibits variation in leaf morphology and anatomy in response to temperature that is consistent with the expectations for adaptive plasticity. I examined variation in the size, thickness and density of stomata of leaves that develop in summer and winter and used analysis of phenotypic selection during winter and summer seasons to test the hypothesis that seasonal variation in these traits is adaptive. Regression analyses of estimated dry mass (as a proxy for fitness) on leaf traits revealed no evidence supporting the adaptive hypothesis. Selection favoured individuals with large and thick leaves in both winter and summer, and density of stomata had little or no effect on estimated relative fitness in any season. Correspondence between seasonal variation in leaf thickness and density of stomata and expectations for adaptive plasticity appears to be purely fortuitous. Seasonal variation in leaf traits may persist simply because there is no selection against individuals in which these traits vary. My results underscore the importance of definitive tests of the hypothesis of adaptation to distinguish adaptive plasticity from neutral or nonadaptive phenotypic plasticity.     

华南地区6种阔叶幼苗叶片形态特征的季节变化

对山杜英、米老排、樟树、海南红豆、红花油茶和红锥6种幼苗叶长和叶宽的相关性和叶片的比叶重变化进行了研究,结果表明：幼苗各月份的叶长和叶宽呈极显著正相关。根据相关系数把6种幼苗分为：a),叶长和叶宽的相关性随季节变化型,包括山杜英、红花油茶、海南红豆、红锥;b),叶长和叶宽的相关性稳定型,有樟树和米老排。6种幼苗叶片的比叶重随幼苗种类和季节而变化,新叶的比叶重上半年比下半年变化大,老叶全年变化较小,上半年新叶的比叶重比老叶低,下半年两者相近。红花油茶新叶和老叶的平均比叶重明显大于其余5种幼苗。     

Plant resource-use strategies: the importance of phenotypic plasticity in response to a productivity gradient for two subalpine species

Background and Aims

Functional traits are indicators of plant interactions with their environment and the resource-use strategies of species can be defined through some key functional traits. The importance of genetic variability and phenotypic plasticity in trait variations in response to a common environmental change was investigated in two subalpine species.

Methods

Two species with contrasted resource-use strategies, Dactylis glomerata and Festuca paniculata, were grown along a productivity gradient in a greenhouse experiment. Functional traits of different genotypes were measured to estimate the relative roles of phenotypic plasticity and genetic variability, and to compare their levels of phenotypic plasticity.

Key Results

Trait variability in the field for the two species is more likely to be the result of phenotypic plasticity rather than of genetic differentiation between populations. The exploitative species D. glomerata expressed an overall higher level of phenotypic plasticity compared with the conservative species F. paniculata. In addition to different amplitudes of phenotypic plasticity, the two species differed in their pattern of response for three functional traits relevant to resource use (specific leaf area, leaf dry matter content and leaf nitrogen content).

Conclusions

Functional trait variability was mainly the result of phenotypic plasticity, with the exploitative species showing greater variability. In addition to average trait values, two species with different resource-use strategies differed in their plastic responses to productivity.     

Influence of seasonal variation on the phenology and liriodenine content of Annona lutescens (Annonaceae)

Annona lutescens Saff. (Annonaceae) grows as a native tree in Chiapas, Mexico in Tropical Dry Forest habitat. Like most Annonaceae, it biosynthesizes benzylisoquinoline alkaloids, mostly liriodenine. To determine the influence of seasonal changes in the accumulation of liriodenine, the monthly variation of liriodenine content in roots, stems and leaves of mature and young trees was observed. These parts of young and mature A. lutescens trees were collected monthly over a 1 year period and the alkaloids were extracted; the liriodenine was quantified by high-resolution liquid chromatography. The phenological stages of the species were also assessed (leaf development, flowering and fruiting) using the Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie (BBCH) scale. The analysis of both young and mature trees showed a significant increase in the liriodenine concentration occurs within roots during the dry season, which coincides with leaf fall. A significant decrease also occurred at the beginning of the rainy season (the period of leaf growth); the liriodenine content for the next rainy season did not reach the levels of the previous dry season. The climatic variation induced phenological and physiological changes in this species.