Spatial variation of plant species richness in a sand dune field of northeastern Inner Mongolia,China

Species richness is an important indicator of species diversity. Different sampling intensities will very likely produce different species richness values. Substantial efforts have already been made to explicitly quantify the spatial variability of soil properties in different ecosystems. However, concerns still remain on how to characterize the effect of different sampling intensities on plant species richness within a given region. This study characterized the spatial variability of plant species richness and the species distribution pattern in a 25-hm2 sand dune plot in northeastern Inner Mongolia, China by using an intense sampling method(n=10,000). We also evaluated the overall effect of information loss associated with the spatial variability and distribution patterns of species richness under various scenarios of sampling intensities(n=10,000 to 289). Our results showed that semi-variograms of species richness were best described by the spherical and exponential models. As indicated by the nugget/sill ratio, species richness was different in terms of the strength of the spatial relationship. The different spatial metrics of species richness with increasing sampling intensities can represent different responses of the spatial patterns when compared with the reference set(n=10,000). This study indicated that an appropriate sampling intensity should be taken into account in field samplings for evaluating species biodiversity properly. A sampling intensity of n>2,500 for species richness yielded satisfactory results to resemble the spatial pattern of the above-quantified reference set(n=10,000) in this sand dune region of China.     

Differences in flowering phenology and seed production of four morning glory (Ipomoea) species in Japan

The spread of morning glory (Ipomoea spp.) in soybean fields in Japan has severely decreased soybean yield. Yet, current control measures do not control the proliferation of Ipomoea spp. As little is known about the flowering period and seed production among the different invading Ipomoea spp., it is challenging to create targeted control measures based on ecological characteristics. This study aimed to reveal the characteristics of the flowering phenology and seed production of four morning glory species, namely, Ipomoea coccinea L. (red morning glory), Ipomoea lacunosa L. (pitted morning glory), Ipomoea hederacea L. Jacq. var. integriuscula A. Gray (entireleaf morning glory), and Ipomoea triloba L. (three-lobe morning glory). Between 2017 and 2019, the four selected study species were grown under similar conditions of soil quality, irrigation, and environmental influences and their flowering phenology and seed data were recorded. The flowering period ranged from 36 to 40 days, and the initial flowering of I. triloba was approximately 2 weeks later than the others. I. coccinea had the highest flowering number and seed production, followed by I. lacunosa, I. triloba, and I. hederacea var. integriuscula. The fruit setting rate of I. triloba decreased later in the reproductive stage but tended to increase as the daily mean temperature increased on each flowering day. Thus, we report that the flowering phenology and seed production differed greatly among the Ipomoea spp. These findings can provide crucial insights into designing targeted species-specific control measures against the spread of Ipomoea spp. in Japan.     

橘小实蝇不能在荔枝健果上成功产卵

根据在果园和室内测定，证实橘小蝇[Bactrocera dorsalis（Hendel）]不能在健康荔枝果实上成功产卵，但可在受损伤的果实上成功产卵。     

Induction of a viable but not culturable (VBNC) state in some Pseudomonas syringae pathovars upon exposure to oxidation of an apoplastic phenolic,acetosyringone

Acetosyringone is a phenolic metabolite often found in plant apoplasts. Its oxidation by hydrogen peroxide and peroxidase results in a prolonged increase in the redox potential of the reaction mixture, similar to redox increases observed in tobacco suspension cells upon treatment with incompatible bacteria. Since high redox potentials, being oxidative, are generally detrimental to bacteria, the effect of acetosyringone oxidation on bacterial viability was examined. Pseudomonas syringae pv. syringae was added to reaction mixtures containing acetosyringone, hydrogen peroxide and peroxidase and samples were removed to determine viability by dilution plating. Initial studies were done with low bacterial concentrations, 10⁵ CFU ml⁻¹, to ensure that scavenging of H₂O₂ was negligible and did not interfere with the reaction mixture. No colonies were formed by bacteria that had been added to reaction mixtures with acetosyringone ranging from 25 to 100 μΜ. Examination of the bacteria by microscopy and flow cytometry, using fluorescent stains that indicate bacterial membrane integrity, suggested that these bacteria had maintained their membrane integrity. In addition they were able to respire based on oxygen uptake. When bacteria were added to on-going reaction mixtures at a time point after the prolonged redox response, the CFU ml⁻¹ increased indicating that a stable reaction product was not responsible for the non-culturability bioactive effect. Other bacterial isolates, P. s. pv. tabaci and Pseudomonas fluorescens, were less susceptible to the bioactive effect of the acetosyringone oxidation. Other phenolics were tested and had lesser degrees of bioactivity and in some cases reduced the bioactivity of acetosyringone oxidation. The ‘viable but non-culturable’ (VBNC) state of the bacteria in this study is compared to that described for other medical and plant pathogens.