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.     

Leaf development in the tropical leguminous tree Copaifera in relation to microlepidopteran herbivory

Changes in sesquiterpene hydrocarbons, total phenolic compounds, astringency, total nitrogen, water content, leaf specific weight and toughness were monitored in five stages of leaf development in greenhouse-grown saplings of Copaifera pubiflora, C. officinalis and C. venezuelana var. laxa and six stages from adult trees of C. langsdorfii. In all species the phenolic content, astringency, nitrogen and water content decreased whereas the leaf specific weight and toughness increased as the leaf attained maturity. The pattern of sesquiterpene variation during leaf development, however, differed among the species. These analyses of changes in leaf development on adult trees of C. langsdorfii are related to preliminary field studies of microlepidopteran (oecophorid) herbivory in woodland sites in southeastern Brazil.     

Seasonal variation in standing crop,density and leaf growth rate of the seagrass, Heterozostera tasmanica, in western Port and Port Phillip Bay,Victoria, Australia

Standing crop, density and leaf growth rate of Heterozostera tasmanica (Martens ex Aschers.) den Hartog along with light, temperature, nutrient and sediment characteristics were determined monthly for fifteen months at three study sites in Western Port and one site in Port Phillip Bay, Victoria, Australia. Erect vegetative stems of H. tasmanica were frequently branched, were present throughout the year and accounted for 25–60% of the above-sediment biomass, with the stem proportion higher during winter than summer. At three of the four sites there was a unimodal seasonal pattern in which minimum leaf standing crop (27–61 g dry wt. m^?2), density (600–2000 leaf cluster m^?2) and leaf productivity (0.34–0.77 g dry wt. m^?2 day^?1) generally occurred during winter (June–August) and maximum leaf standing crop (105–173 g dry wt. m^?2), density (2700–5000 leaf cluster m^?2) and leaf productivity (2.6–4.2 g dry wt. m^?2 day^?1) occurred during summer (December–February). A bimodal seasonal pattern with minimum standing crop and density during midsummer occurred at one site. This anomalous seasonal pattern may be due to exposure and desiccation stress during spring low tides. At the site receiving the lowest irradiance, standing crop, density and annual leaf production also were lowest, but length and width of leaves, shoot height and leaf growth rate per leaf cluster were the highest of the four study sites. On average, each leaf cluster at any one of the study sites produced 30–31 leaves per year with mean leaf turnover rates of 1.3–1.7% day^?1. Annual leaf production of H. tasmanica ranged from 410 to 640 g dry wt.m^?2 at the four sites.     

Leaf traits variation in Sesleria nitida growing at different altitudes in the Central Apennines

Global climate change may act as a potent agent of natural selection within species with Mediterranean mountain ecosystems being particularly vulnerable. The aim of this research was to analyze whether the phenotypic plasticity of Sesleria nitida Ten. could be indicative of its future adaptive capability to global warming. Morphological, anatomical, and physiological leaf traits of two populations of S. nitida growing at different altitudes on Mount Terminillo (Italy) were analyzed. The results showed that leaf mass per unit leaf area, leaf tissue density, and total leaf thickness were 19, 3, and 31% higher in leaves from the population growing at 1,895 m a.s.l. (B site) than in leaves from the population growing at 1,100 m a.s.l. (A site), respectively. Net photosynthetic rate (P ^N) and respiration rate (R _D) peaked in June in both A and B leaves [9.4 ± 1.3 μmol(CO₂) m^?2 s^?1 and 2.9 ± 0.9 μmol(CO₂) m^?2 s^?1, respectively] when mean air temperature was 16 ± 2°C. R _D/P _N was higher in B than in A leaves (0.35 ± 0.07 and 0.21 ± 0.03, respectively, mean of the study period). The mean plasticity index (PI = 0.24, mean of morphological, anatomical, and physiological leaf traits) reflected S. nitida adaptability to the environmental stress conditions at different altitudes on Mount Terminillo. Moreover, the leaf key traits of the two populations can be used to monitor wild populations over a long term in response to global change.     

Feeding of large pine weevil on Scots pine stem triggers localised bark and systemic shoot emission of volatile organic compounds

Feeding by the large pine weevil (Hylobius abietis L.) causes severe damage to the bark of Scots pine (Pinus sylvestris L.) seedlings. We measured photosynthesis, the emission of volatile organic compounds from intact and weevil-damaged bark and systemic emissions from undamaged foliage. Feeding damage did not affect photosynthesis. Monoterpenes dominated the emissions from the feeding site, although some sesquiterpenes were also emitted. Weevil feeding increased bark emission of monoterpenes by nearly 4-fold and sesquiterpenes by 7-fold. The influence of weevil damage on systemic monoterpene emissions from shoots was more profound. Several compounds were substantially induced, including linalool, β-phellandrene, limonene and 1,8-cineole. Sesquiterpenes contributed only 1.2% of the total foliage emission, but comprised eight different compounds including (E,E)-α-farnesene, β-bourbonene and (E)-β-farnesene. The total emission of monoterpenes and sesquiterpenes from shoots was respectively 2.8-fold and 2.9-fold higher in the pine weevil damaged plants than the undamaged plants. As many of the induced compounds are highly reactive in the atmosphere and form organic aerosol particles, our results suggest that conifers damaged by insects could become a more important source of secondary organic aerosols than healthy trees.     

Leaf phenology, seasonal changes in leaf quality and herbivory pattern of Sanguisorba tenuifolia at different altitudes

Leaf demography, seasonal changes in leaf quality and leaf-beetle herbivory of a herbaceous perennial plant, Sanguisorba tenuifolia, were compared between low- and high-elevation sites. Leaf nitrogen concentration was higher and leaf mass per area (LMA) was lower at the higher site than at the lower one. At the lower site, with a long growth period, plants produced many leaf cohorts and leaves emerged throughout the growing season. At the higher site, with a short growth period, however, leaf emergence was concentrated early in the growing season. The improvement of leaf quality and acceleration of leaf emergence at higher altitude are seen as adaptations to a short growing season. Results of a feeding trial suggested that leaf quality for the leaf-beetle Galerucella grisescens was higher at the higher site, but plants at the higher site showed less damage. Oviposition of G. grisescens was seasonal and unimodal at both altitudes, but the period of oviposition was shorter and its density lower at the higher site. The low temperature and short growth period at the higher site appear to reduce the activity of the leaf-beetles, resulting in a decrease in damage by herbivory, despite better leaf quality. Received: 11 December 1997 / Accepted: 24 July 1998     

Essential oil yield,composition, bioactivity and leaf morphology of Juniperus oxycedrus L. from Bulgaria and Serbia

Juniperus oxycedrus L. (Cupressaceae Bartlett) is widely distributed in countries with a Mediterranean climate. All plant parts contain highly aromatic essential oil (EO) and recently there have been efforts to introduce it as a cultivated crop. The species is known for its large morphological and chemical variation and its debatable taxonomic status. This study aimed to (1) compare content, composition, and antimicrobial activity of J. oxycedrus EO samples from plants growing in Bulgaria and Serbia, and (2) quantify morphological variations of leaves. Тhe EO content (yield) in dried juniper leaves varied from 0.06% (Кopaonik, Serbia) to 0.24% (Markovo, Bulgaria). We identified 51 EO constituents, belonging to monoterpenes, sesquiterpenes, and diterpenes. The class monoterpenes (monoterpene hydrocarbons and oxygenated monoterpenes) were the predominant compounds, representing 38.6–65.4% of the total EO, consisting primarily of α-pinene, limonene, sabinene, β-pinene, and β-myrcene. In addition, α-pinene was the major oil constituent in plants from all locations. Sesquiterpenes (sesquiterpene hydrocarbons and oxygenated sesquiterpenes) were the second largest class of constituents, which represented 19.3% tо 33.6% of the total EO. γ-Elemene was found only in the EO of J. oxycedrus from Bulgaria, while a high concentration of α-curcumene was found only in samples from Serbia (7.5–7.8%). Significant differences in antimicrobial activity of the EO were found in bacterial strains Bacillus cereus and Streptococcus pneumoniae. There was no significant difference among the mean leaf width of the six combinations location x sex, and the overall leaf mean width was 1.24 mm. However, there was a significant difference between the mean leaf lengths. In this study, none of the studied populations had a higher concentration of limonene than of α-pinene, indicating that the flora of the two countries include J. oxycedrus and not the previously reported J. deltoides. The results revealed significant variation in EO profile that may contribute to the development of new cultivars of J. oxycedrus.     

Olfactory responses of adult Potato Tuber Moth,Phthorimaea operculella (Zeller) measured by attraction relative to the tomato leaf volatiles

The potato tuber moth (PTM) is an oligophagous herbivore and a severe pest of solanaceous crops in many countries of the world. Previously, we reported host expansion and damage potential of PTM on tomato, a congeneric crop of potato. Here we tested adult olfactory behaviour of PTM to leaves of five different cultivated tomato varieties including Moneymaker, Campari, Ailsa craig, LA3475 and E6203, and one wild species, Solanum pimpinellifolium. Tomato leaf hydro-distilled oils of Moneymaker, Campari, Ailsa craig, S. pimpinellifolium and E6203 showed strong attractiveness and LA3475 exhibited repulsiveness for adult PTM of both sexes in two-armed bioassays. Volatiles of Moneymaker, Campari, Ailsa Craig, S. pimpinellifolium and E6203 showed attractiveness for mated adult PTM of both sexes (> 70%). The extracted oil of all tomato leaves contains monoterpenes, sesquiterpenes, diterpenes and C₆ alcohols as well as other components. Phytol is one of the common and major compounds in all tomato varieties. Phytol showed weak attractiveness: 60.8–63.6% and 57.6–60.6% for male and female PTM, respectively when tested at concentrations of 0.1–10 mg/mL. Therefore, the attractiveness of tomato leaf volatiles might be due to synergistic effects of plant volatile mixtures. Identification PTM attractant volatile in tomato leaf is important in its control in environmentally friendly manner.     

Low Herbivory among Targeted Reforestation Sites in the Andean Highlands of Southern Ecuador

Insect herbivory constitutes an important constraint in the viability and management of targeted reforestation sites. Focusing on young experimental stands at about 2000 m elevation in southern Ecuador, we examined foliar damage over one season as a function of tree species and habitat. Native tree species (Successional hardwood: Cedrela montana and Tabebuia chrysantha; fast-growing pioneer: Heliocarpus americanus) have been planted among prevailing local landcover types (abandoned pasture, secondary shrub vegetation, and a Pinus patula plantation) in 2003/4. Plantation trees were compared to conspecifics in the spontaneous undergrowth of adjacent undisturbed rainforest matched for height and foliar volume. Specifically, we tested the hypotheses that H. americanus as a pioneer species suffers more herbivory compared to the two successional tree species, and that damage is inversely related to habitat complexity. Overall leaf damage caused by folivorous insects (excluding leafcutter ants) was low. Average leaf loss was highest among T. chrysantha (7.50% ± 0.19 SE of leaf area), followed by H. americanus (4.67% ± 0.18 SE) and C. montana (3.18% ± 0.15 SE). Contrary to expectations, leaf area loss was highest among trees in closed-canopy natural rainforest, followed by pine plantation, pasture, and secondary shrub sites. Harvesting activity of leafcutter ants (Acromyrmex sp.) was strongly biased towards T. chrysantha growing in open habitat (mean pasture: 2.5%; shrub: 10.5%) where it could result in considerable damage (> 90.0%). Insect folivory is unlikely to pose a barrier for reforestation in the tropical Andean mountain forest zone at present, but leafcutter ants may become problematic if local temperatures increase in the wake of global warming.     

Genotype × Herbivore Effect on Leaf Litter Decomposition in Betula Pendula Saplings: Ecological and Evolutionary Consequences and the Role of Secondary Metabolites

Plant genetic variation and herbivores can both influence ecosystem functioning by affecting the quantity and quality of leaf litter. Few studies have, however, investigated the effects of herbivore load on litter decomposition at plant genotype level. We reduced insect herbivory using an insecticide on one half of field-grown Betula Pendula saplings of 17 genotypes, representing random intrapopulation genetic variation, and allowed insects to naturally colonize the other half. We hypothesized that due to induced herbivore defence, saplings under natural herbivory produce litter of higher concentrations of secondary metabolites (terpenes and soluble phenolics) and have slower litter decomposition rate than saplings under reduced herbivory. We found that leaf damage was 89 and 53% lower in the insecticide treated saplings in the summer and autumn surveys, respectively, which led to 73% higher litter production. Litter decomposition rate was also affected by herbivore load, but the effect varied from positive to negative among genotypes and added up to an insignificant net effect at the population level. In contrast to our hypothesis, concentrations of terpenes and soluble phenolics were higher under reduced than natural herbivory. Those genotypes, whose leaves were most injured by herbivores, produced litter of lowest mass loss, but unlike we expected, the concentrations of terpenes and soluble phenolics were not linked to either leaf damage or litter decomposition. Our results show that (1) the genetic and herbivore effects on B. pendula litter decomposition are not mediated through variation in terpene or soluble phenolic concentrations and suggest that (2) the presumably higher insect herbivore pressure in the future warmer climate will not, at the ecological time scale, affect the mean decomposition rate in genetically diverse B. pendula populations. However, (3) due to the significant genetic variation in the response of decomposition to herbivory, evolutionary changes in mean decomposition rate are possible.     

Structural and functional traits of Quercus ilex in response to water availability

Water potential and morpho-anatomical parameters were measured, during the course of 1 year, on leaves of Quercus ilex trees growing in two coastal stands in Tuscany (Central Italy) with different conditions of water availability: Colognole (CL, mesic site) and Cala Violina (CV, xeric site). Morpho-anatomical measurements included: general leaf features and sclerophylly indices (surface area, thickness, mass per area and density), leaf moisture indices (water content, relative water content, succulence) and histochemical analysis (detection and localization of cutine and tannins in the leaves and starch reserves in the twigs). During the warmest and driest period (August) pre-dawn water potential (ψ_pd) in Holm-oak leaves reached −2.7 MPa at CV and −0.6 MPa at CL. Leaf surface was lower (−34%) and total leaf thickness (+10%), as well as spongy-palisade parenchyma ratio (+20%) were higher at CV. The sclerophylly parameters (leaf mass per area and leaf tissue density) were higher at CV than at CL (+24% leaf mass per area and +19% leaf tissue density). Among the moisture parameters, water content was higher at CL (+8%) and succulence was higher at CV (+13%). No differences in relative water content were observed between the two sites. All the parameters considered were substantially stable during the study period, with the exception of relative water content at CL, that fluctuated within the year. Histochemical analysis revealed a greater thickness of the upper cuticular layer at CV, whereas there were no differences in tannin distribution and content between the two sites. Differences in starch storage were detected in branchlets: it was abundant in CV but very scarce at CL. The strategies of Quercus ilex to cope with water stress were discussed at morpho-structural level.     

Insect herbivory on mangrove leaves in North Queensland*

Estimates of leaf damage by insect herbivores are presented for 25 species of mangrove plants, comprising canopy and understorey species. Leaf area loss was highly variable among the species sampled, with means ranging from 0.3 to 35.0% of expanded leaf area. There was also great variability amongst leaves within species, and the mean coefficient of variation for leaf loss from the 25 species was 266%. Of the 12 species sampled at more than one site in North Queensland, eight exhibited small, but significant, between-site differences in herbivory. In general, it did not appear that height in the canopy influenced herbivory. For the dominant mangrove forest community type at Missionary Bay, an estimated mean of 2.1% of leaf production, or 11 g m^-2 per year, entered the direct grazing pathway. This very low figure is compared with estimates from other studies on mangrove forests and estimates from a variety of Australian terrestrial forests.     

Sex-related differences in leaf traits in an androdioecious shrub under contrasting levels of soil salinity

This study explores whether male and hermaphrodite plants of Phillyrea angustifolia (Oleaceae) show physiological and structural differences at the leaf level under severe water stress driven by drought and soil salinity. Leaf traits were measured in summer, at the height of the summer drought period, in male and hermaphrodite plants from two adjacent sites under contrasting soil salinity levels. Male plants from the saline site had significantly higher leaf proline content compared to males from the nonsaline site. By contrast, leaf proline levels were similarly low in hermaphrodite plants from both sites. On the other hand, hermaphrodite plants from the saline site had higher leaf stomatal frequency than hermaphrodites from the nonsaline site, whereas this parameter did not differ for male plants across sites. Such differences could be interpreted as the result of two different solutions to the same selective pressure in the androdioecious shrub P. angustifolia.     

Combinatory effect of ethyl formate and phosphine fumigation on Pseudococcus longispinus and P. orchidicola (Hemiptera: Pseudococcidae) mortality and phytotoxicity to 13 foliage nursery plants

Combinatory effect of ethyl formate (EF) and phosphine (PH₃) fumigation against Pseudococcus longispinus and P. orchidicola was evaluated on 13 foliage nursery plants. Treatment with the combination of EF at 16 mg/L and PH₃ at 0.1 mg/L for 4 h resulted in 100% fumigant activity against both adults and nymphs of P. longispinus and P. orchidicola in a 12 L desiccator. The combination treatment showed higher efficacy towards adults than towards nymphs for both mealybug species, although it was reversed for P. orchidicola when EF was treated alone. The combination treatment showed higher fumigant activity than the single EF or PH₃ treatment. In larger fumigation chambers (0.65 m³ and 10 m³⁾, 100% fumigant activity was observed with the combination of EF at 20 g/m³ and PH₃ at 1 g/m³ against both mealybug species regardless of location inside chambers. The highest sorption rates for each fumigant were 24.4% for PH₃-treated Hoya carnosa and 75.4% for EF-treated Philodendron selloum. Except P. selloum, all other species tested exhibited significant leaf damage one week after the combination treatment. Two species, Echeveria 'Perle von Nürnberg' and Heteropanax fragrans showed 100% leaf damage and died 5 months later without any new leaf formation. However, other 10 species were able to recover the treatment damage after 5 months. Treatment of these two plants with EF seems unfeasible. This study suggests that the combination of EF and PH₃ can be used for controlling P. longispinus and P. orchidicola in some foliage nursery plants.     

Variation in Arundo donax stem and leaf strength: Implications for herbivory

We determined leaf and stem strength for Arundo donax from plants grown in different geographic areas and at different times within their growing cycle. Mean leaf strength for plants collected within California was 1.72 Newtons (N) and ranged from 0.36 to 6.32 N, based on 1170 individual determinations. For leaves collected from 30 plants within four states between July 11 and 20, 2007, mean leaf strength was 1.58 N based on 936 determinations. Values ranged from 0.24 to 4.90 N. Overall, leaf strength showed statistically significant changes depending on the sampling date, sampling location, type of leaf sampled, and position within the leaf where the measurement was taken. In general leaf strength was greater near the base of the leaf and decreased with distance away from the base; leaf strength changed as the growing season progressed; and first year leaves had leaf strength values about 25% greater than leaves produced on stems >1-year old. This represents two of the three age categories of leaves which may be present on giant reed at any one time. Stem strength and stem wall thickness were strongly correlated (Kendall's Tau b = 0.92, P < 0.0001, N = 26). Linear regression indicated that mean stem strength decreased by approximately 6.8% (95% confidence limits 5.8-7.7%) from one node to the successive node progressing from the stem base to the shoot tip. These results imply that the ability of biological control agents to damage A. donax leaves may not be the same across the locations this plant occurs or at all times during the growing season within a given location.     

Effects of leaf litter on woody seedlings in xeric successional communities

We investigated the effect of leaf litter on the establishment of Eucalyptus incrassata, a mallee eucalypt. It has been suggested that litter accumulation may hinder seedling establishment, and that the removal of litter may be one of the mechanisms through which fire enhances recruitment. We conducted factorial experiments testing the effects of three kinds of leaf litter on E. incrassata seeds and seedlings at three contiguous sites with different land use histories. One site was an uncleared E. incrassata open mallee woodland (Mallee site), one a cleared area that had been ungrazed for about five years (Pasture site) and the third an area of mallee rolled some 40 years ago and permitted to regenerate (Regrowth site). Litter had no effect on emergence of planted E. incrassata seeds, but emergence differed between sites. Overall, the percentage of seeds that germinated and emerged was substantial (mean 35.2% ± 25.9%). Seedling shoot biomass did not differ between sites or litter treatments. Although seedlings grown in Pasture litter suffered higher mortality rates, overall mortality rates were low (mean 13.2% ± 15.5%), suggesting that leaf litter has little effect on recruitment rates during winter and spring. We conclude that leaf litter does not affect emergence or growth in young E. incrassata seedlings during winter and spring, when most establishment occurs. Our results emphasize the difficulty in predicting litter effects on recruitment.     

Transcriptomic analysis reveals the significant effects of fertilization on the biosynthesis of sesquiterpenes in Phoebe bournei

Phoebe bournei is a potential medicinal plant. Its essential oils (Eos) are mainly composed of sesquiterpenes that has potential activities of anti-bacteria and anti-tumors. In this study, we evaluated the effects of compost and compound fertilizer on the total amount and main components of Eos in P. bournei, we also studied the molecular mechanism undergoing this process by deep sequencing the genes involved in the biosynthesis of sesquiterpenes. Fertilization enhanced the total amount of main components in Eos from both leaves and twigs. Bicyclogermacrene, the primary sesquiterpene in the leaf EO, was significantly increased under compost treatment, while bicyclogermacrene and δ-cadinene (the second most abundant sesquiterpene) were decreased under compound fertilizer treatment. The two fertilizers had no significant effect on the abundance of the primary (+) - δ-cadinene in the twig EO, but had a positive effect on the second most abundant sesquiterpene copaene. Significant differences were observed in the number of differentially expressed genes (DEGs) with the leaves showing greater number of DEGs as compared to the twigs after compost treatment. Terpenoid backbone biosynthesis (TBB) is a key pathway of sesquiterpenes synthesis. The expression of genes regulating several important enzymes in TBB was altered after fertilization. After the compost treatment, the expression of the leaf DXS gene (ACQ66107.1), being closely related to the sesquiterpene biosynthesis in P. bournei leaves, was decreased. Compost and compound fertilizer altered the expression of the two important branch-point enzymes (FPPS and GGPPS) genes (ART33314.1 and ATT59265.1), which contributed to the changes of the total amount and components of P. bournei sesquiterpenes. This study provides a new insight into the future use of P. bournei for Eos.     

Changes in Clonal Poplar Leaf Chemistry Caused by Stem Galls Alter Herbivory and Leaf Litter Decomposition

Gall-inducing insects are highly specialized herbivores that modify the phenotype of their host plants. Beyond the direct manipulation of plant morphology and physiology in the immediate environment of the gall, there is also evidence of plant-mediated effects of gall-inducing insects on other species of the assemblages and ecosystem processes associated with the host plant. We analysed the impact of gall infestation by the aphid Pemphigus spirothecae on chemical leaf traits of clonal Lombardy poplars (Populus nigra var. italica) and the subsequent effects on intensity of herbivory and decomposition of leaves across five sites. We measured the herbivory of two feeding guilds: leaf-chewing insects that feed on the blade (e.g. caterpillars and sawfly larvae) and skeletonising insects that feed on the mesophyll of the leaves (e.g. larvae of beetles). Galled leaves had higher phenol (35%) and lower nitrogen and cholorophyll contents (35% respectively 37%) than non-galled leaves, and these differences were stronger in August than in June. Total herbivory intensity was 27% higher on galled than on non-galled leaves; damage by leaf chewers was on average 61% higher on gall infested leaves, whereas damage by skeletonising insects was on average 39% higher on non-galled leaves. After nine months the decomposition rate of galled leaf litter was 15% lower than that of non-galled leaf litter presumably because of the lower nitrogen content of the galled leaf litter. This indicated after-life effects of gall infestation on the decomposers. We found no evidence for galling x environment interactions.     

Transpiration and stomatal control: a cross-species study of leaf traits in 39 evergreen and deciduous broadleaved subtropical tree species

Key message

Using an extensive dataset for 39 subtropical broadleaved tree species, we found traits of the leaf economics spectrum to be linked to mean stomatal conductance but not to stomatal regulation.

Abstract

The aim of our study was to establish links between stomatal control and functional leaf traits. We hypothesized that mean and maximum stomatal conductance (g _s) varies with the traits described by the leaf economics spectrum, such as specific leaf area and leaf dry matter content, and that high g _s values correspond to species with tender leaves and high photosynthetic capacity. In addition, we hypothesized that species with leaves of low stomata density have more limited stomatal closure than those with high stomata density. In order to account for confounding site condition effects, we made use of a common garden situation in which 39 deciduous and evergreen species of the same age were grown in a biodiversity ecosystem functioning experiment in Jiangxi (China). Daily courses of g _s were measured with porometry, and the species-specific g _s~vpd relationships were modeled. Our results show that mean stomatal conductance can be predicted from leaf traits that represent the leaf economics spectrum, with a positive relationship being related to leaf nitrogen content and a negative relationship with the leaf carbon: nitrogen ratio. In contrast, parameters of stomatal control were related to traits unassociated with the leaf economics spectrum. The maximum of the conductance~vpd curve was positively related to leaf carbon content and vein length. The vpd at the point of inflection of the conductance~vpd curve was lower for species with higher stomata density and higher for species with a high leaf carbon content. Overall, stomata size and density as well as vein length were more effective at explaining stomatal regulation than traits used in the leaf economics spectrum.     

First report of Avicennia germinans (Acanthaceae) as a larval host of Junonia litoralis (Nymphalidae) causing higher foliar damage in seedlings than trees

Herbivory is considered an important biotic interaction in mangroves. Nevertheless, detailed information on specific plant–herbivore interactions that might have considerable influence in ecological and evolutionary processes is still very poor and fragmented. Herbivory damage was quantified during December 2015 in seedlings and trees in monospecific stands of Avicennia germinans in Laguna Madre of Tamaulipas, Mexico. The use of this mangrove species as a larval host is well documented; however, this is the first report for Junonia litoralis. These lepidopteran larvae consumed, on average, 10.2% of the leaf area; but herbivory was higher on seedlings (mean 15%) than on trees (mean 2.3%). These values are comparable to estimations of 10% mean herbivory damage in other field studies. This indicates that herbivores cause greater damage in seedlings than in trees. Herbivore activity by J. litoralis only occurred in A. germinans and did not affect associated herbs or shrubs of other species. The close interaction between J. litoralis and A. germinans may have profound implications for ecological and evolutionary processes of mangroves and enables a better understanding of ecosystem function and its conservation. Further studies are needed to investigate such interactions and their implications including long-term monitoring of interstitial salinity and leaf chemistry at different stages of growth and maturity of the host species.