Bioactive benzoquinones content variability in red-berry and white-berry varieties of Ardisia crenata Sims. and assessment of cytotoxic activity.

Ardisia crenata Sims (Myrsinaceae) occurs in two varieties differing in the fruit color, the red berries being common while the white ones are rare. The roots of red-berried A. crenata are a valued TCM product which contains bioactive benzoquinones such as embelin and rapanone. In this study we compared their profiles in different organs of the plant to provide an insight in the pattern of their accumulation within the two varieties. Moreover, cytotoxic activity against human melanoma and prostate cancer cells was evaluated. Quantitative HPLC revealed that the white-berried variety differs profoundly in the content of rapanone, with its total level of 606.5 mg/100 g d.w., as compared to 16.2 mg/100 g d.w. in A. crenata 'red'. Embelin was less distributed and found in minor amounts in both varieties. This is the first report on rapanone content in various parts of Ardisia crenata and on benzoquinones in the white-berried variety.

Diversity of epicotyl dormancy among tropical montane forest species in Sri Lanka.

Fruiting season of many Sri Lankan tropical montane species is not synchronised and may not occur when conditions are favourable for seedling establishment. We hypothesised that species with different fruiting seasons have different seed dormancy mechanisms to synchronise timing of germination with a favourable season for establishment. Using six species with different fruiting seasons, we tested this hypothesis. Germination and imbibition of intact and manually scarified seeds were studied. Effect of GA3 on germination was examined. Embryo length:seed length (E:S) ratio of freshly matured seeds and of those with a split seed coat was determined. Time taken for radicle and plumule emergence and morphological changes of the embryos were recorded. The radicle emerged from Ardisia missionis, Bheza nitidissima and Gaetnera walkeri seeds within 30 days, whereas it took >30 days in other species. Embryos grew in seeds of B. nitidissima and G. walkeri prior to radicle emergence but not in Microtropis wallichiana, Nothapodytes nimmoniana and Symplocos cochinchinensis. A considerable delay was observed between radicle and plumule emergence in all six species. Warm stratification and/or GA3 promoted germination of all species. All the tested species have epicotyl dormancy. Seeds of B. nitidissima and G. walkeri have non-deep simple morphophysiological epicotyl dormancy, and the other four species have non-deep physiological epicotyl dormancy. Differences in radicle and epicotyl dormancy promote synchronisation of germination to a favourable time for seedling development. Therefore, information on dormancy-breaking and germination requirements of both radicle and epicotyl are needed to determine the kind of dormancy of a particular species.

[Effects of shade on photosynthetic characteristics and chlorophyll fluorescence of Ardisia violacea].

Ardisia violacea is one of the rare and endangered species, and distributes only in Zhejiang and Taiwan Provinces in China. In order to understand the light requirement and adaptability of A. violacea, the effects of different light intensities (shading rate of 90%, 60%, 25%, and the full light) on leaf photosynthetic characteristics and chlorophyll fluorescence of A. violacea were studied. The photosynthetic rate (Pn) and stomatal conductance (g(s)) of A. violacea varied as a bimodal curve with a 'midday depression' phenomenon in full bright light, and as a unimodal curve in the shading treatments. With the increasing shading rate, the Pn and apparent quantum efficiency (AQY) first increased, and then decreased, the light compensation point (LCP) and light saturation point (LSP) decreased, and the g(s), transpiration rate (Tr), original light energy conversion (Fv/Fm) and potential activity of PS II (Fv/Fo) increased. The total quantity of chlorophyll and the carotenoid (Car) content increased, and Chl a/b decreased under shading conditions. When the shading rate was 25%, the specific leaf mass (LMA) and root to shoot (R/T) ratio of A. violacea reached the maximum. A. violacea possessed a strong flexibility to different light environments, suggesting that light could not be the main limiting factor for natural regeneration of A. violacea populations.

[Growth and photosynthetic characteristics of Ardisia corymbifera var. tuberifera in bionic wild cultivation].

OBJECTIVE: To explore the growth dynamic and photosynthetic characteristics of Ardisia corymbifera var. tuberifera in bionic wild cultivation. METHODS: The test of bionic wild cultivation was conducted with two-year-old seedlings as well as three-year-old cuttings of Ardisia corymbifera var. tuberifera, and their growth dynamic and photosynthetic characteristics were studied. RESULTS: Both seedlings and cuttings of Ardisia corymbifera var. tuberifera maintained good growth in imitation of the wild, the height were increased by 9.2 cm and 12 cm, base diameter were increased by 2.48 mm and 2.39 mm,and crown width were increased by 10.6 cm and 17 cm, respectively. Two-year-old seedlings branched only once a year, and three-year-old cuttings branched thrice a year. There were no significant differences in all photosynthetic parameters of the two kinds of seedlings, and the range of growth light intensity of Ardisia corymbifera var. tuberifera was wider. Owing to the weaker light quantum efficiency under lower light and relatively lower light photosynthetic capacity under higher light, its competition ability was lower in the field. CONCLUSION: The increases of height and crown width were greater in cuttings than those in seedlings, and the transplanting survival rate of the former was larger.

Bacterial leaf symbiosis in Ardisia (Myrsinoideae, Primulaceae): molecular evidence for host specificity.

The association between bacteria and leaves in Ardisia has been described as a cyclic and obligate symbiosis in which bacteria are maintained throughout all stages of the plant's life cycle to guarantee normal growth and survival of the host. This intimate interaction suggests that both partners have co-diversified together. To test this co-speciation hypothesis, we constructed an endosymbiont (16S rDNA and gyrB) and host (rps16, trnL, matK and ITS) phylogeny. Phylogenetic analyses of the endosymbionts revealed a pattern of strict host specificity and recovered a single clade in the genus Burkholderia (ß-proteobacteria), which was closely related to the endosymbionts of leaf-nodulated Rubiaceae. Comparison of symbiont and host phylogenies suggests a single origin of bacterial leaf symbiosis in the nodulated ancestor of Ardisia and does not reject the co-speciation hypothesis.

[Tissue culture and plant regeneration of Ardisia crenata].

OBJECTIVE: Our research studied the fast-breeding technology of Ardisia crenata sims by using tissue culture and provided the scientific foundation for industry production. METHOD: The effects of axillary buds and plant regeneration of different basic medium, hormones and additives on induction and multiplication were studied. RESULT: The best culture medium for the induction of axillary buds, which took the stems of A. crenate were as explants, was MS + 6-BA 0.5 mg x L(-1) + NAA 0.1 mg x L(-1), and the best medium for multiplication was MS + 6-BA 2.0 mg x L(-1) + NAA 0.1 mg x L(-1) + KT 0.5 mg x L(-1), the best medium for roots generation was 1/2MS + IBA 0.2 mg x L(-1). We also found that the roots'generation, roots rate and mean number of roots can be promoted by adding 0.2% Ac, and the most suitable ground substance was river sand-perlite-vermiculite (1:1:1) or perlite-vermiculite (1:1). With axillary buds and plant regeneration methode, more than 80% A. crenata sims could be regenerated integratedly. CONCLUSION: A. crenata sims can be regenerated integratedly and breeded fast by using axillary bud proliferation technology.

The many growth rates and elasticities of populations in random environments.

Despite considerable interest in the dynamics of populations subject to temporally varying environments, alternate population growth rates and their sensitivities remain incompletely understood. For a Markovian environment, we compare and contrast the meanings of the stochastic growth rate (lambdaS), the growth rate of average population (lambdaM), the growth rate for average transition rates (lambdaA), and the growth rate of an aggregate represented by a megamatrix (shown here to equal lambdaM). We distinguish these growth rates by the averages that define them. We illustrate our results using data on an understory shrub in a hurricane-disturbed landscape, employing a range of hurricane frequencies. We demonstrate important differences among growth rates: lambdaS lambdaM. We show that stochastic elasticity, ESij, and megamatrix elasticity, EMij, describe a complex perturbation of both means and variances of rates by the same proportion. Megamatrix elasticities respond slightly and stochastic elasticities respond strongly to changing the frequency of disturbance in the habitat (in our example, the frequency of hurricanes). The elasticity EAij of lambdaA does not predict changes in the other elasticities. Because ES, although commonly utilized, is difficult to interpret, we introduce elasticities with a more direct interpretation: ESmu for perturbations of means and ESsigma for variances. We argue that a fundamental tool for studying selection pressures in varying environments is the response of growth rate to vital rates in all habitat states.