草地群落类型对乳白香青种群特征和雌雄株形态及抗性的影响

为探究亚高山雌雄异株草本植物乳白香青对生境的适应方式,通过测定5个草地群落(A-老芒麦改良草地,B-虉草改良草地,C-天然草地,D-天然草甸,E-沙化草地)中乳白香青种群数、种群密度和面积、分布系数、性比组成,以及雌雄株构件性状、生物量配比、水分分配及抗性物质含量等参数,研究群落组成对乳白香青种群特征、雌雄株形态可塑性及抗性的影响。结果表明,5个草地群落的优势种、群落密度、基盖度、物种密度和优势种高度及土壤理化性状的显著差异(P<0.05),使不同群落中乳白香青种群特征显著不同,群落类型对种群特征参数影响顺序为种群面积>种群密度>性比>年龄结构>种群数>分布系数;D群落中乳白香青种群数和分布系数最高,C中乳白香青种群面积和密度最大,E中乳白香青种群数仅分别为D和C中的30.21%和35.11%,分布系数仅为C中的36.04%;群落类型对乳白香青种群年龄结构和性比有显著影响(P<0.05),雌株数为雄株的2.22~7.03倍;叶数和叶面积、株高和茎径、根长、小花数和苞片层数有显著的性别差异(P<0.05),群落类型对雌雄株的叶数和叶面积、株高、根数、花序数和小花数有显著影响,对雄株茎径和苞片层数有显著影响;雄株总生物量和花分配比显著高于雌株,而根分配比显著低于雌株(P<0.05),群落类型对乳白香青生物量配比有显著影响,雌株生物量配比受影响顺序为花>总生物量>叶>根>茎,雄株受影响顺序为花>茎>叶>总生物量>根;雄株茎、叶、花含水量显著高于雌株(P<0.05),根含水量在性别间和群落间差异较小,雌株构件含水量受群落类型影响顺序为花>茎>叶>根,雄株为叶>茎>花>根。雄株中MDA含量高于雌株,雌株中H₂O₂含量及T-AOC活性大于雄株(P<0.05),群落组成对雌、雄株中H₂O₂和MDA含量及T-AOC活性有极显著影响(P<0.01)。A和B中H₂O₂和MDA含量最低,E中H₂O₂和MDA达最大值,而T-AOC活性最低。雌、雄个体均能依据群落生境调整生长策略,通过构件性状、生物量配比、水分分配和抗性生理等适应性变化,使种群具有与生境匹配的种群特征,利于提高种群适合度和生活史完成。     

Major ascaroside pheromone component asc-C5 influences reproductive plasticity among isolates of the invasive species pinewood nematode

Pheromones are communication chemicals and regulatory signals used by animals and represent unique tools for organisms to mediate behaviors and make “decisions” to maximize their fitness. Phenotypic plasticity refers to the innate capacity of a species to tolerate a greater breadth of environmental conditions across which it adapts to improve its survival, reproduction, and fitness. The pinewood nematode, Bursaphelenchus xylophilus, an invasive nematode species, was accidentally introduced from North America into Japan, China, and Europe; however, few studies have investigated its pheromones and phenotypic plasticity as a natural model. Here, we demonstrated a novel phenomenon, in which nematodes under the condition of pheromone presence triggered increased reproduction in invasive strains (JP1, JP2, CN1, CN2, EU1, and EU2), while it simultaneously decreased reproduction in native strains (US1 and US2). The bidirectional effect on fecundity, mediated by presence/absence of pheromones, is henceforth termed pheromone-regulative reproductive plasticity (PRRP). We further found that synthetic ascaroside asc-C5 (ascr#9), the major pheromone component, plays a leading role in PRRP and identified 2 candidate receptor genes, Bxydaf-38 and Bxysrd-10, involved in perceiving asc-C5. These results suggest that plasticity of reproductive responses to pheromones in pinewood nematode may increase its fitness in novel environments following introduction. This opens up a new perspective for invasion biology and presents a novel strategy of invasion, suggesting that pheromones, in addition to their traditional roles in chemical signaling, can influence the reproductive phenotype among native and invasive isolates. In addition, this novel mechanism could broadly explain, through comparative studies of native and invasive populations of animals, a potential underlying factor behind of the success of other biological invasions.     

Living on the edge: morphological and behavioral adaptations to a marginal high-elevation habitat in an arboreal mammal

Habitats are characterized by different local environmental conditions that influence both behavior and morphology of species, which can result in habitat-dependent phenotypic differences among animals living in heterogeneous environments. We studied 3 alpine populations of Eurasian red squirrels (Sciurus vulgaris), 1 living in a marginal high-elevation habitat at the edge of the species’ altitudinal distribution, and 2 occurring in higher-quality habitats. Here, we investigated whether squirrels living in the marginal area differed in 2 morphological parameters (body size and body mass) and/or in the expression of 4 personality traits estimated with an open field test and a mirror image stimulation test (activity, exploration, activity-exploration, and social tendency). Furthermore, we tested whether within-individual variance of the traits (behavioral plasticity) was higher in the edge habitat. Male squirrels in the edge habitat were smaller and weighed less than in the other study areas, while among females, size–habitat relationships were less marked. These sex-specific patterns were explained by a strong association between body mass and reproductive success in female squirrels. Squirrels in the marginal habitat were more active, explorative, and had a more social personality than in the other habitats. However, in contrast to our predictions, behavioral plasticity was smaller in the marginal habitat, but only for the trait exploration. Our results suggest that animals choose the habitat that best fits their personality, and that habitat-related differences in selective pressures may shape animals’ morphology.     

Comparative performance of the highly invasive Mimosa invisa and its less invasive subspecies under different nutrient and light conditions

Invasive plants may be more plastic than non‐invasive plants and maintain high fitness under various environmental conditions. Previous studies mainly focused on the comparisons between invasive and native plants, and comparisons between highly invasive and less invasive exotic species are still relatively rare, especially for comparisons at the subspecies level. This study examined the effects of nutrient addition and shading on the performance of the highly invasive Mimosa invisa and its less invasive subspecies M. invisa var. inermis under either isolated or competitive conditions. Nutrient addition increased biomass and plant height and decreased root‐to‐shoot ratio (R/S). Shading decreased biomass and R/S and increased plant height. Under isolated conditions, the two invaders did not differ in R/S, plant height and plasticity of these traits in response to nutrient addition or shading, and the two invaders also did not differ in biomass production under each of the nutrient and light treatments. When the two invaders competed with each other, M. invisa outcompeted M. invisa var. inermis under high soil nutrient conditions, and the two invaders did not differ in performance under other growth conditions. Thus, only considering competition may we find out the difference between highly invasive species and their closely related, less invasive subspecies. Management of M. invisa should focus on habitats with high soil nutrient availability, in which M. invisa is more likely to dominate.     

Morphological sex change upon treatment by endocrine modulators in meiogynogenetic tench (Tinca tinca L.)

Exogenous steroids alter sex differentiation in fish substantially. In the present study we have evaluated the effects of 17α-methyltestosterone (MT) and oestrogen receptor antagonist Tamoxifen (TA) on gonadal development and skewness of the sex ratio in all-female tench juveniles. In the first two experiments, sexually undifferentiated juveniles were orally treated with three doses of MT and TA (50, 100 and 150 mg kg⁻¹). Both the treatments resulted in a moderate dose-dependent masculinization, with neomale production ranging from 17% (50 mg kg⁻¹) to 26% (150 mg kg⁻¹) for the MT only treatment, and from 0% (50 mg kg⁻¹) to 27% (100 mg kg⁻¹) only for the TA treatment respectively. In the third experiment treatment of sexually differentiated tench females with single steroid treatments or combinations of the two resulted in populations composed of females and intersex individuals. The significantly highest occurrence of intersex individuals (45.5%) was found in the group subjected to combine treatment of MT+TA (150+200 mg kg⁻¹). No masculinization effect of the single or the combined treatment occurred. It can be concluded that oral treatment with MT or TA only slightly modifies the normal process of sex differentiation in gynogenetic tench juvenile, but treatment with the above-mentioned combinations has a highly significant potential to skew the sex ratio in sexually differentiated tench females. However, from an applied point of view, the treatment procedure will need optimization before use at a commercial level.     

提高印尼20号标准橡胶塑性值的研究

研究了如何提高印尼20号标准天然橡胶塑性值,在印尼广垦橡胶(坤甸)有限公司进行,采用了喷洒草酸、水合联氨等试验方法。结果表明,使用3 %的水合联氨能得到较好的塑性值。     

Fertilizer location modifies root zone salinity,root morphology,and water‐stress resistance of tree seedlings according to the watering regime in a dryland reforestation

There is a direct relationship between soil nutrient concentration in localized zones and root proliferation and elongation under well‐watered conditions. However, in field studies under semiarid conditions this relationship can change due to higher salt accumulation and soil dryness that affect root growth, water stress resistance, and seedling survival. We assessed the effect of different locations of fertilizer placement in the soil profile and water availability on root zone salinity, root development and ecophysiological responses of Quillaja saponaria Mol. after outplanting. A single dose (6 g L^?1) of controlled‐release nitrogen fertilizer (CRF_N) was placed at 0 cm (top layer), 15 cm (middle layer), or 30 cm (bottom layer) depth in the containers in a greenhouse, in addition to an unfertilized treatment (control). After 6 months, seedlings were transplanted to the field and subjected to weekly watering regimes (2 L plant^?1 and unwatered). Morphological and ecophysiological parameters were periodically measured on seedlings, as well as soil electrical conductivity (EC). After 1 year, the shoot : root ratio of unwatered seedlings decreased as a function of CRF_N placement depth, which was attributed to lower shoot growth and not to greater root growth. The root morphology of the bottom layer treatment was negatively affected by high EC in unwatered seedlings. Greater total root length and root volume of the middle layer treatment was found only when well‐watered; however, this did not contribute to improve physiological responses against water stress. The lowest EC and the highest photochemical efficiency, net photosynthesis, and stomatal conductance were shown by unfertilized seedlings, independent of water availability. Our findings suggest that varying depth of CRF_N placement does not contribute significantly to improve root growth under water restriction. Water supplements, independently of the CRF_N location in the substrate, contribute to decrease root zone salinity, and consequently, improve root volume growth.     

Neuroprotective effect of novel Rho kinase inhibitor FSD-C10 on a mouse model of Alzheimer disease

AIM: To explore the neuroprotective effect of novel Rho kinase inhibitor FSD-C10 on Alzheimer disease (AD) model of APP/PS1 double transgenic (Tg) mice. METHODS: Male APP/PS1 Tg mice (n=20) at 8 months of age were randomly divided into 2 groups:model group and FSD-C10 treatment group. The mice were treated with normal saline or FSD-C10 (25 mg·kg^-1·d^-1) by intraperitoneal injection, once daily for 2 months. Age-and sex-matched wild-type (WT) mice without treatment were used as the control. The Morris water maze (MWM) test and SMART 3.0 behavioral record system were applied to examine and analyze the spatial cognitive function of the mice. The protein levels and distribution of Aβ, p-tau and synapse-associated proteins such as synaptophysin, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) and postsynaptic density protein 95 (PSD-95) were determined by immunofluorescence staining. The protein levels of phosphorylated amyloid precursor protein at Thr668[p-APP(Thr668)], beta-site APP-cleaving enzyme 1 (BACE1) and synapse-associated proteins in the brain were analyzed by Western blot. RESULTS: Compared with model group, FSD-C10 treatment significantly improved the cognitive function of the APP/PS1 Tg mice, accompanied by reduced Aβ deposition and p-tau level, increased protein level of p-APP (Thr668) in the central nervous system, decreased expression of BACE1, and increased expression of synapse-associated proteins in the brain of the mice (P<0.05). CONCLUSION: FSD-C10 has neuroprotective potential in the APP/PS1 Tg mice. The mechanism may be related to enhancing the non-amyloidogenic APP cleavage pathway, reducing the production of Aβ oligomers, the deposition of senile plaques and the amount of tau protein, up-regulating synapse-associated proteins, and increasing synaptic plasticity.     

Micro-scale heterogeneity in urban forest soils affects fine root foraging by ornamental seedlings of Buddhist pine and Northeast yew

Urban soils are frequently characterized by a strong heterogeneity caused by intense anthropogenic activity and land use changes. Soil heterogeneity is commonly known to affect tree root development, but little has been detected concerning root foraging by ornamental trees in heterogeneous urban soils at micro-scale. In this study, Buddhist pine [Podocarpus macrophyllus (Thunb.) D. Don] and Northeast yew (Taxus cuspidata S. et Z.) were selected as ornamental tree species for a two-year study. In the first-year, seedlings were cultured under contrasting photoperiods to generate different morphologies. In the second year, seedlings were transplanted to pots filled with soils collected from an urban forest. Controlled-release fertilizers (N-P₂O₅-K₂O, 14-13-13) were evenly broadcasted to a half patch of the pot (heterogeneity) or to both halves (homogeneity) on the surface 5 cm beneath the pot-top at the rate of 0.135 g N seedling⁻¹. In the fertilized heterogeneous patch, larger Buddhist pine seedlings had greater dry weight, length, surface area, volume, number of tips, and morphological foraging-precision in fine roots. Compared to Northeast yew seedlings under natural photoperiod in the first year, those under the extended photoperiod had larger size, greater fine root biomass, and length but lower foraging-precision in the second year. N and P concentrations in second-year fine roots mainly increased with the availability of patches generated by fertilization for both species. In conclusion, the ability to forage for nutrients by ornamental tree seedlings in heterogeneous urban forest soils was species-specific. Buddhist pine seedlings had higher foraging precision in heterogeneous urban soils than Northeast yew seedlings due to their response to the extended photoperiod during culture.