Comparative Study of the Genetic and Biochemical Variability of Polyscias filicifolia (Araliaceae) Regenerants Obtained by Indirect and Direct Somatic Embryogenesis as a Source of Triterpenes.

Polyscias filicifolia (Araliaceae) is broadly used in traditional medicine in Southeast Asia due to its antimicrobial, immunomodulating and cytotoxic activities. The main groups of compounds responsible for pharmacological effects are believed to be oleanolic triterpene saponins. However, Polyscias plants demonstrate relatively slow growth in natural conditions, which led to applying a developing sustainable source of plant material via primary (PSE), secondary (DSE) and direct somatic embryogenesis from DSE (TSE). The AFLP and metAFLP genotyping resulted in 1277 markers, amplified by a total of 24 pairs of selective primers. Only 3.13% of the markers were polymorphic. The analysis of variance showed that the PSE and TSE regenerants differed only in terms of root number, while the DSE plantlets differed for all studied morphological characteristics. Further, the chemical analysis revealed that oleanolic acid (439.72 µg/g DW), ursolic acid (111.85 µg/g DW) and hederagenin (19.07 µg/g DW) were determined in TSE regenerants. Our results indicate that direct somatic embryogenesis ensures the production of homogeneous plant material, which can serve as a potential source of triterpene compounds. Plants obtained via somatic embryogenesis could also be reintroduced into the natural environment to protect and preserve its biodiversity.

A multi-species comparison of selective placement patterns of ramets in invasive alien and native clonal plants to light, soil nutrient and water heterogeneity.

A worth noticing pattern in current invasive biology is the clonal ability of many of the world's worst invasive plants. Selective placement of ramets (i.e. foraging behavior) can intensify ramet performance and allocation, and place more ramets in the more favorable microhabitats, which can maximum utilize resource and share risk in heterogeneous environments. Still little is known about whether invasive alien and native clonal plants differ in the selective placement patterns of ramets in invasive clonal plants or not. We used five congeneric pairs of naturally co-occurring invasive alien and native clonal plant species in China. In a glasshouse, we grew all species in pots under a homogeneous and three heterogeneous conditions (i.e. light, soil nutrients or water) subjected to resource-high or -low patches. All biomass parameters and number of ramets significantly increased in resource-high patches in all three types of heterogeneous environments. Interestingly, growth of invasive alien plants benefited significantly more from resource-high patches than native plants in all heterogeneous environments. Overall, invasive had higher biomass parameters per ramet than natives. Ramet parameters of invasive plants also benefited more from resource-low patches than natives. Three different selective placement patterns of ramets in resource-low patches were exhibited in invasive plants: ramet increasing shoot investment (above pattern), increasing root investment (below pattern) and increasing both investments (complete pattern) in the light, soil water and nutrient heterogeneity, respectively. Investment on less, larger ramet was the adaptive strategy of invasive plants in resource-poor patches. The results suggest that adaptively selective placement patterns of ramets promote a higher morphology plasticity and performance in invasive clonal plants over natives. When alien clonal plants spread new areas with light, soil nutrients or water heterogeneity, selective placement patterns of ramets might play an important role in plant performance and competitive superior by capitalizing more on additional resources.

[Cold resistance of four evergreen broad-leaved tree species]. / å››ç§å¸¸ç»¿é˜”å¶æ ‘ç§çš„æŠ—å¯’æ€§.

The leaves of four evergreen plants, i.e., Fatsia japonica, Nerium indicum, Mahonia bealei and Acer cinnamomifolium were used as the experimental materials. By measuring the changes of in vitro leaf in soluble sugar, soluble protein, free proline, POD activity, chlorophyll content and relative electrolytic conductivity under aritificial simulated low temperature, combining the measurements of SPAD, leaf surface features and anatomical changes in organizational structure in the process of natural wintering, the cold resistance of four evergreen tree species was evaluated comprehensively. The results showed that in the process of artificial low temperature stress, the chlorophyll content of the leaves of four evergreen species decreased, the content of soluble protein pea-ked at -20 ℃, and the soluble sugar, free proline, POD activity and relative electrolytic conductivity showed an overall upward trend. The semilethal temperatures of four species were -8.0, -13.4, -19.4 and -14.8 ℃, respectively. During the winter, the leaf SPAD of the four species changed markedly, reflecting that the change of relative chlorophyll content was related to the change of temperature. Meanwhile, the leaf thickness, cutin layer thickness, stockade tissue thickness and tightness of four species increased and the plasmolysis occurred thereafter. Also the content of starch grains and calcium oxalate cluster crystal increased. The typical stomatal pits and the intensive non-glandular trichome within the pits of N. indicum and the sclerenchyma of M. Bealei could improve the cold resistance of plants to some extent. In addition, the phenomena like the breakage of wax layer in leaf surface, the fracture of epidermal hair and the deformation of palisade tissue indicated that plants were damaged to a certain extent by low temperature.

Distinct invasion strategies operating within a natural annual plant system.

Alien plant species are known to have a wide range of impacts on recipient communities, from resident species' exclusions to coexistence with resident species. It remains unclear; however, if this variety of impacts is due to different invader strategies, features of recipient communities or both. To test this, we examined multiple plant invasions of a single ecosystem in southwestern Australia. We used extensive community data to calculate pairwise segregation between target alien species and many co-occurring species. We related segregation to species' positions along community trait hierarchies and identified at least two distinct invasion strategies: 'exploiters' which occupy high positions along key trait hierarchies and reduce local native species diversity (particularly in nutrient-enriched situations), and 'coexisters' who occupy intermediate trait positions and have no discernable impact on native diversity. We conclude that trait hierarchies, linked to measures of competition, can provide valuable insights about the processes driving different invasion outcomes.

Interaction between Mutualisms: Ant-tended butterflies exploit enemy-free space provided by ant-treehopper associations.

Although mutualisms have been intensively investigated, demonstration of indirect effects between co-occurring mutualistic systems is rare. For instance, the ecological consequences of co-occurrence of ant-tended insects on a plant have never been examined for survival effects on either trophobiont species. Here, we assess the selective pressures mediating co-occurrence of a facultative ant-tended butterfly (Parrhasius polibetes) with ant-tended treehoppers (Guayaquila xiphias) on Schefflera vinosa shrubs. We evaluated host plant selection and caterpillar survival in P. polibetes in the presence and absence of ant-treehopper associations. Paired trials revealed that butterflies preferably oviposit on branches hosting ant-tended treehoppers when they had a choice between those and branches without this interaction. Presence of ant-tended treehoppers on a branch reduced the abundance of P. polibetes' natural enemies and improved caterpillar survival in both premyrmecophylic and ant-tended phases. Thus ant-tended treehoppers create an enemy-free space on foliage that butterflies exploit to protect larval offspring. These findings connect two widely documented ant-trophobiont mutualisms and highlight the importance of considering multiple interactions for a proper understanding of ant-plant-herbivore systems. Detection of other ant-based mutualisms on oviposition to improve offspring survival may have represented an important evolutionary step in the process of host plant selection in facultative myrmecophilous butterflies.

Ontogenetic colour changes in an insular tree species: signalling to extinct browsing birds?

* Animals often use colours to hide from predators (crypsis) or advertise defences (aposematism), but there is little evidence for colour-based defence in plants. * Here, we test whether ontogenetic changes in leaf colour of lancewood (Pseudopanax crassifolius) may have been part of a defensive strategy against flightless browsing birds called moa, which were once the only large herbivores in New Zealand. We tested this hypothesis by conducting spectrographic measurements on different-sized plants grown in a common garden. We also compared these results with observations on a closely related, derived species that evolved in the absence of moa on the Chatham Islands. * Spectrographic analyses showed that birds would have difficulty distinguishing seedling leaves against a background of leaf litter. Conversely, brightly coloured tissues flanking spines on sapling leaves are highly conspicuous to birds. Once above the reach of the tallest known moa, adults produce leaves that are typical in appearance to adult leaves. The Chatham Island species lacks ontogenetic colour changes entirely. * Overall, the results indicate that P. crassifolius goes through a remarkable series of colour changes during development, from cryptically coloured seedlings to aposematically coloured saplings, which may have formed a defensive strategy to protect against giant browsing birds.

Photoinhibition, carotenoid composition and the co-regulation of photochemical and non-photochemical quenching in neotropical savanna trees.

Plants in the neotropical savannas of central Brazil are exposed to high irradiances, high air temperatures and low relative humidities. These conditions impose a selection pressure on plants for strong stomatal regulation of transpiration to maintain water balance. Diurnal adjustments of non-photochemical energy dissipation in photosystem II (PSII) provide a dynamic mechanism to reduce the risk of photoinhibitory damage during the middle of the day when irradiances and leaf temperatures are high and partial closure of the stomata results in considerable reductions in internal CO(2) concentration. At the end of the dry season, we measured diurnal changes in gas exchange, chlorophyll fluorescence parameters and carotenoid composition in two savanna tree species differing in photosynthetic capacity and in the duration and extent of the midday depression of photosynthesis. Non-photochemical quenching and its quantum yield were tightly correlated with zeaxanthin concentrations on a total chlorophyll basis, indicating that the reversible de-epoxidation of violaxanthin to antheraxanthin and zeaxanthin within the xanthophyll cycle plays a key role in the regulation of thermal energy dissipation. In both cases, a single linear relationship fitted both species. Although efficient regulation of photochemical and non-photochemical quenching and adjustments in the partitioning of electron flow between assimilative and non-assimilative processes were operating, these trees could not fully cope with the rapid increase in irradiance after sunrise, suggesting high vulnerability to photoinhibitory damage in the morning. However, both species were able to recover quickly. The effects of photoinhibitory quenching were largely reversed by midday, and zeaxanthin rapidly converted back to violaxanthin as irradiance decreased in late afternoon, resulting in the maximal quantum yield of PSII of around 0.8 just before sunrise.

In vitro regeneration of Didymopanax morototoni.

The present study aimed at establishing a complete plant regeneration protocol for Didymopanax morototoni (matchwood), a native Brazilian forest species. Four types of explants (root, shoot, node, and cotyledonary leaves) were obtained from in vitro germinated seeds. In the first step, woody plant medium (WPM) with casein hydrolysate (250 mgL-1 ) and 2,4-D (1.0 and 5.0 mgL-1) were used combined with kinetin (0.1 and 1.0 mgL-1). Twenty days after inoculation, the material was evaluated. Embryogenic calli were split, transferred to expression medium with several combinations of NAA and KIN, and moved to fresh medium after 60 days. Light did not interfere in embryo expression. Somatic embryos were formed either from individual cells or cell clusters. Plantlets were obtained in WPM medium and 10 gL-1 of sucrose with no plant regulator, or using 0.1 mgL-1 BAP and 0.5 mgL-1GA. Plantlets from somatic embryos of D. morototoni developed in 33% of the cases.

In vitro regeneration of Didymopanax morototoni

O presente estudo visou o estabelecimento de um completo protocolo de regeneração para Didymopanax morototoni (morototó, caixeta) uma espécie florestal nativa do Brasil. Quatro tipos de explantes (raiz, caule, nódulo foliar e folha cotiledonar) foram obtidos a partir de sementes germinadas. Na primeira etapa, meio WPM com caseína hidrolisada (250 mgL-1) e 2,4D (1,0 e 5,0 mgL-1) foram usados em combinação com cinetina (0,1 ou 1,0 mg L-1). Vinte dias depois de inoculado, o material foi avaliado. Calos embriogênicos foram divididos e transferidos para meio de expressão com várias combinações de ácido naftaleno-acético e cinetina, e repicados a cada 60 dias para meio novo. A luz não interferiu na expressão embriogênica. Embriões somáticos foram formados ou de células individuais ou de agregados de células. As plântulas foram obtidas no meio WPM com 10 g L-1 de sacarose e sem reguladores de crescimento ou com 0,1 mg L-1 de Benzil-adenina e 0,5 mg L-1 de giberelina. O desenvolvimento das plântulas a partir de embriões somáticos de D. morototoni foi alcançada em 33% dos casos.

Spatial and temporal variations in leaf area index, specific leaf area and leaf nitrogen of two co-occurring savanna tree species.

Foliage growth, mass- and area-based leaf nitrogen concentrations (Nm and N a) and specific leaf area (SLA) were surveyed during a complete vegetation cycle for two co-occurring savanna tree species: Crossopteryx febrifuga (Afzel. ex G. Don) Benth. and Cussonia arborea A. Rich. The study was conducted in the natural reserve of Lamto, Ivory Coast, on isolated and clumped trees. Leaf flush occurred before the beginning of the rainy season. Maximum leaf area index (LAI), computed on a projected canopy basis for individual trees, was similar (mean of about 4) for both species. Seasonal courses of the ratio of actual to maximum LAI were similar for individuals of the same species, but differed between species. For C. febrifuga, clumped trees reached their maximum LAI before isolated trees. The LAI of C. arborea trees did not differ between clumped and isolated individuals, but maximum LAI was reached about 2 months later than for C. febrifuga. Leaf fall was associated with decreasing soil water content for C. arborea. For C. febrifuga, leaf fall started before the end of the rainy period and was independent of changes in soil water content. These features lead to a partial niche separation in time for light resource acquisition between the two species. Although Nm, N a and SLA decreased with time, SLA and N a decreased later in the vegetation cycle for C. arborea than for C. febrifuga. For both species, N a decreased and SLA increased with decreasing leaf irradiance within the canopy, although effects of light on leaf characteristics did not differ between isolated and clumped trees. Given relationships between N a and photosynthetic capacities previously reported for these species, our results show that C. arborea exhibits higher photosynthetic capacity than C. febrifuga during most of the vegetation cycle and at all irradiances.

Heat dissipation sensors of variable length for the measurement of sap flow in trees with deep sapwood.

Robust thermal dissipation sensors of variable length (3 to 30 cm) were developed to overcome limitations to the measurement of radial profiles of sap flow in large-diameter tropical trees with deep sapwood. The effective measuring length of the custom-made sensors was reduced to 1 cm at the tip of a thermally nonconducting shaft, thereby minimizing the influence of nonuniform sap flux density profiles across the sapwood. Sap flow was measured at different depths and circumferential positions in the trunks of four trees at the Parque Natural Metropolitano canopy crane site, Panama City, Republic of Panama. Sap flow was detected to a depth of 24 cm in the trunks of a 1-m-diameter Anacardium excelsum (Bertero & Balb. ex Kunth) Skeels tree and a 0.65-m-diameter Ficus insipida Willd. tree, and to depths of 7 cm in a 0.34-m-diameter Cordia alliodora (Ruiz & Pav.) Cham. trunk, and 17 cm in a 0.47-m-diameter Schefflera morototoni (Aubl.) Maguire, Steyerm. & Frodin trunk. Sap flux density was maximal in the outermost 4 cm of sapwood and declined with increasing sapwood depth. Considerable variation in sap flux density profiles was observed both within and among the trees. In S. morototoni, radial variation in sap flux density was associated with radial variation in wood properties, particularly vessel lumen area and distribution. High variability in radial and circumferential sap flux density resulted in large errors when measurements of sap flow at a single depth, or a single radial profile, were used to estimate whole-plant water use. Diurnal water use ranged from 750 kg H2O day-1 for A. excelsum to 37 kg H2O day-1 for C. alliodora.