Abstract:In order to explore the adaptation strategies of plants to extreme environments such as drought, strong light, saline alkali and barren soil in tropical coral islands, leaf anatomical traits of 29 species grown in Wenchang, Hainan, and transplanted to tropical coral islands were measured and compared. The results showed that compared with the same species in Wenchang, Hainan, the herbaceous plants transplanted to the tropical coral island had no significant changes except for the increase of dry matter content; while the specific leaf area (SLA) of woody plants decreased significantly, the leaf thickness and dry matter content of leaves (LDMC) increased significantly, the spongy tissue was thicker and the palisade tissue was arranged more closely, but there was no significant difference in length, density and area index of stomata. Woody plants on the island adopt the resource acquisition strategy of slow investment income, put more resources into leaf construction to enhance adaptability under stress, and improve the potential of photosynthesis and water storage to resist stress through non stomatal regulation. In conclusion, the 29 plant species on tropical coral islands had stronger resource utilization ability, could adopt more conservative resource utilization strategies, better adapt to drought, strong light and other stress environments, and could be used for vegetation construction of tropical coral islands.

Abstract:Invasive plants pose a serious threat to the vegetation ecosystem on tropical coral islands. Studying the seed germination characteristics of invasive plants in tropical coral island habitats can provide scientific basis for predicting the expansion potential of invasive plants on tropical coral islands. The seed germination characteristics of invasive species Eupatorium odoratum, Sphagneticola trilobata, and coral island native species E. lindleyanum were compared under the simulated tropical coral island habitat via "3 ℃ warming + marine sand matrix + water". The results showed that the seed germination traits of E. odoratum were mainly affected by marine sand matrix and elevated temperature, while those of S. trilobata and E. lindleyanum were mainly affected by marine sand matrix. In tropical coral island habitats, the reproductive potential of the three plants was significantly lower than that in mainland habitats, in particular for E. odoratum and S. trilobata. The seed expansion potential of E. odoratum was similar to that of E. lindleyanum, but S. trilobata had higher seed expansion potential than E. lindleyanum. Although the reproductive potential of E. odoratum and S. trilobata decreased after being introduced into tropical coral island, the adaptability of their seed germination characteristics to the habitat and the expansion potential of invasive plants were higher than that of native species, indicating that the two invasive plants would pose a threat to the vegetation ecosystem of the tropical coral islands. In the future, it should be focused on the prevention and control of invasive plants in tropical coral islands.

Abstract:In order to explore the population status of Rhododendron xishuiense, an endemic plant in Xishui National Nature Reserve, Guizhou, reveal the dynamics and endangered causes of its population and strengthen its protection, the distribution of R. xishuiense was investigated along 13 transects in the reserve. The population structure of R. xishuiense distribution community was analyzed by using four diversity indexes and Raunkiear life form, the population age structure was obtained by replacing time with space. Thus, the static life table was compiled, and the survival curve and four survival function curves were drawn to analyze the dynamic characteristics of R. xishuiense population. The results showed that there were 65 species of vascular plants in 27 families, 42 genera, in which 62 species of seed plants in 24 families, 39 genera and 3 species of ferns in 3 families and 3 genera. The number of phanerophyte was the largest with 56 species in total, accounting for 86.15% to all species, followed by chamaephyte, hemicryptophyte, and geophyte. All of diversity indexes of the community was in the order of tree layer > shrub layer > herb layer, indicating that tree layer had an absolute dominant position. The age structure of the population was pyramidal, and the number of seedlings in population was large in whole population; the population survival curve was Deevey II type, and the number of individuals decreased along age, the population survival rate continued to decline, especially in the middle and late period of rapid decline, population decline. Therefore, with its narrow distribution range and high diversity, the number of seedlings showed an increasing pattern, but due to the suffering of intense competition, the R. xishuiense had a very small population of species. It was suggested to take appropriate measures to promote the growth of seedlings and young trees, so that middle-aged individuals can be effectively supplemented, so as to ensure the sustainable growth of the population.

Abstract:To explore the potential suitable distribution range of Dendrobium sinense, its current and future suitable habitat based on the distribution data of 25 field surveys, with climate variables and topographic variables as environmental predictors were predicted by using GIS technology and MaxEnt model. The results showed that the potential suitable habitat area of D. sinense in Hainan Island was approximately 403.4 km², accounting for 1.1% of the total area of Hainan Island. It was mainly distributed in the jurisdiction of Bawangling Branch, Yinggeling Branch, Jianfengling Branch, Diaoluoshan Branch and Wuzhishan Branch of Hainan Tropical Rainforest National Park, with scattered distribution in the jurisdiction of Limushan Branch, the southern part of Wuzhishan City, Qiongzhong County, Wanning City, Baoting County, and Sanya City. The suitable distribution area of D. sinense was extremely narrow, and the suitable habitat was patchy, showing more serious fragmentation. Altitude, coefficient of variation of precipitation seasonality, precipitation in the wettest quarter and maximum temperature in the warmest month were the main environment factors affecting the population distribution pattern of D. sinense. The most suitable habitat for D. sinense was at an altitude of 1 070-1 600 m, with the coefficient of variation of precipitation seasonality of 0.80-0.88, precipitation in the wettest quarter of 1 700-2 266 mm, and the maximum temperature of 18 ℃-25 ℃ in the warmest month. Compared with the current, the potential suitable habitat under RCP4.5 and RCP8.5 climate scenarios of D. sinense decreased by 19.1% and 19.5% in 2050, and 19.7% and 19.8% in 2070, respectively. From three evaluation indexes (AUC=0.997±0.003, Kappa coefficient= 0.990±0.03, TSS=0.990±0.03), the prediction model had good prediction ability. At present, Dendrobium sinense populations are mainly distributed in Hainan Tropical Rainforest National Park, so it is necessary to strengthen in situ conservation and epiphytic host tree protection. There are large areas of highly suitable habitat in the northeast and south of Mihouling, as well as south of Yinggeling, making them as focus region for investigating unknown D. sinense populations.

Abstract:Lingnan Duoji Fruit Forest Wetland is a semi-natural managed wetland in Pearl River Delta, which plays an important role in soil carbon sequestration. The soil organic carbon (SOC) components in surface layer (0-20 cm) under five planting types in Duoji Fruit Forest Wetland in Guangzhou were studied, including Clausena lansium (HP), Dimocarpus longan (LY), Averrhoa carambola (YT), D. longan and C. lansium interplanting (LH), A. carambola, D. longan and C. lansium interplanting (YLH). The results showed that the fruit-forest types significantly affected the contents of SOC, dissolved organic carbon (DOC), microbial biomass carbon (MBC), readily oxidizable carbon (ROC) and non-liable carbon (NLC). The SOC content of LY was the highest (22.6 g/kg), which was significantly higher than that of YLH (P < 0.05), and the NLC content was also significant higher than LH and YLH. The NLC was positively related with soil N and P, negatively related with soil bulk density. The content of MBC in YT was higher than that in LY, HP and LH, while the MBC/SOC was higher than that in HP and LY. The DOC content and DOC/SOC in YLH were significantly higher than that of other types (P < 0.05). The ROC/SOC of LH were significantly higher than that of HP and LY, while the NL/SOC were significantly lower than that of HP and LY (P < 0.05). Therefore, it was suggested that the stability of soil organic carbon was improved by planting C. lansium and D. longan alone, while the activity of soil organic carbon was the highest under mixed planting mode.

Abstract:The restoration and reconstruction of mangrove wetland ecosystems is one of the key research fields in ecological restoration in the coastal zones of South China. How to optimize the assembly of mangrove species is the priority to be concerned in the restoration and transformation of mangrove forest community. In order to reveal the ecophysiological strategies to light conditions of mangrove plant species and provide theoretical guidance for optimal assembly of mangrove community structure, the characteristics of leaf chlorophyll fluorescence parameters in seedlings of eight mangrove plant species, such as Sonneratia apetala, Kandelia candel, Bruguiera gymnorrhiza, Aegiceras corniculatum, Acanthus ilicifolius, Acrostichum aureum, Heritiera littoralis and Hibiscus tiliaceus, under different light intensities (100%, 45%, 30%, and 10% of natural sunlight) were studied using shading control experiment. The results showed that all of eight mangrove plant species appeared a significantly higher maximal photochemical efficiency of PSII (F_v/F_m) and actual photochemical efficiency of PSII (ΦPSII) in shading treatments, while the significant lower electron transport rate (ETR) was found in shading treatments in seedlings of eight mangrove species. Under 100% light intensity, S. apetala, K. candel, A. corniculatum, Heritiera littoralis and Hibiscus tiliaceus had higher F_v/F_m than the other three mangrove plant species, while A. corniculatum and Heritiera littoralis had higher ΦPSⅡ and ETR than B. gymnorrhiza, A. ilicifolius and A. aureum. Therefore, Sonneratia apetala, K. candel, A. corniculatum, Heritiera littoralis and Hibiscus tiliaceus had high light energy utilization, while A. corniculatum and Heritiera littoralis could make better use of high light and dissipate excess light energy to protect photosynthetic organs, thus these five mangrove species are suitable to be planted as upper layer tree species in mangrove forests. In contrast, the ΦPSII of B. gymnorrhiza, A. ilicifolius and A. aureum were lower than 0.2, and ETR was only 20%-33% of those of sun plant species like S. apetala, indicating that they are suitable to be used as understory species in dense mangrove forests.

Abstract:The niche and interspecific association of main shrub species in Acacia confusa community in Langqi Island of Fujian Province were analyzed to explore the interspecific relationship and succession dynamics of the community. The results showed that Sageretia thea had the largest importance value and niche breadth, and had the strongest competitive advantage and environmental adaptability. The niche similarity and niche overlap of the main species in the shrub layer were small, indicating that there were great differences in the utilization and requirements of environmental resources among the species, showing a relatively stable interspecific relationship. The overall association of the main species in the shrub layer was significant positive association, the positive and negative association ratio between species was 1.72, and the significant rate was 7.35%, indicating that the degree of association between species was weak, the independence was relatively strong, and the species competition was not fierce. The community was in a relatively late and stable succession state. There is vertical complementarity between Castanopsis hystrix and many other species, the niche overlap was small, and the interspecific association was positive. The alien species Lantana camara competed with Elaeagnus oldhamii to some extent, and the competition between Lantana camara and other main shrub plants was less intense, so its impact on the community was relatively small. The Acacia confusa community in Langqi Island had developed into a zonal climax community, the species competition is not intense, and the interspecific relationship is stable. The harsh environment and the spread of alien species on the island will lead to the shortage of plant habitat resources, forcing species to gather in the same habitat coexistence, so that the degree of plant utilization of the environment is weakened. Therefore, it was necessary to control the number of alien species and improve the ecological environment of islands in order to maintain the stable development of island communities.

Abstract:In order to understand the function of WRKY2 in zucchini (Cucurbita pepo), a length of 1 071 bp cDNA, named CpWRKY2 (GenBank accession No. XM_023676898.1), was isolated from leaves by using transcriptome sequencing technology (i.e. RNA-seq). The cDNA contains an 840 bp open reading frame (ORF) encoding 279 amino acids. The nucleotide sequence of ORF was sharing over 98.51% with that from Cucurbita moschata (GenBank accession No.: XM_023091218.1), indicating a highly conservative evolution. CpWRKY2 protein was located in the nucleus, containing a conserved WRKY domain (position 201-267), a WRKY DNA binding domain (position 206-266), a zinc finger domain (position 232-264) of the C₂H₂ type, and a conserved RTGHARFRRAP (positions 76-86) amino acid sequence, which belonged to the typical IId subclass WRKY family proteins. The upstream promoter region of CpWRKY2 gene (1 513 bp before ATG) contained possible stress response cis-acting elements, such as ARE, ABRE, MBS, TC-rich repeat, and W-box. CpWRKY2 expression had tissue specificity, which was the highest in flowers, followed by roots and stems, and the lowest in leaves and fruits. Moreover, the expression of CpWRKY2 was overall up-regulated under stresses, such as 5 ℃, 10% PEG 6000, 0.1 mmol/L ABA, 50 mmol/L ETH, 10 mmol/L SA, and 50 mmol/L MeJA, suggesting CpWRKY2 gene might be involved in defense response to different abiotic stresses of C. pepo.

Abstract:To elucidate the function in growth and development of expansins in Eucalyptus, two expansin genes EgrEXPA8 and EgrEXPA10 were cloned based on differential expression genes in the transcriptome of transition from primary growth to secondary growth of E. grandis. EgrEXPA8 and EgrEXPA10 encoded 249 and 244 amino acids, respectively. EgrEXPA8 and EgrEXPA10 were hydrophilic proteins. However, the stability of EgrEXPA8 was higher than that of EgrEXPA10. qRT-PCR analysis showed that the expression of EgrEXPA8 and EgrEXPA10 were high in young leaves and stem apex, and low in xylem and phloem. The expression of them was high in stem apex at primary growth stage, and low in internode at secondary growth stage, indicating that the two genes might be mainly involved in primary growth or negative regulation of secondary growth in E. grandis. The expressions of EgrEXPA8 and EgrEXPA10 were inhibited under salt stress and methyl jasmonate treatment, but significantly up-regulated treated with salicylic acid, under boron and phosphorus deficiency. Therefore, it was suggested that EgrEXPA8 and EgrEXPA10 genes in E. grandis would play an important role in response to stress.

Abstract:In order to reveal the response mechanism of Cunninghamia lanceolata to drought in subtropical region, the physiological characteristics of fine roots under precipitation exclusion were studied at the National Field Scientific Observation and Research Station of Forest Ecosystem in Sanming, Fujian. The results showed that soil moisture under precipitation exclusion decreased significantly (P < 0.05) compared with the control, but the contents of superoxide anion radical and malondialdehyde in fine roots had not significant differences (P > 0.05), indicating that the fine roots of Chinese fir maintained a low level of membrane lipid oxidation damage. The contents of proline, glutathione (GSH) and hydrogen peroxide (H₂O₂) increased significantly compared with the control (P < 0.05), indicating that Chinese fir was subjected to some degree of drought stress and self-regulation. GSH content significantly increased to some extent due to the accumulation of H₂O₂ caused by long-term precipitation exclusion, and there was a significant positive correlation between H₂O₂ and GSH (P < 0.01). Compared with the control, precipitation exclusion decreased the contents of endogenous hormones, such as cytokinin and indoleacetic acid, but they had not significantly correlated with the growth regulation of Chinese fir. In addition, the activity of superoxide dismutase under precipitation exclusion decreased by 21.5% (P < 0.05), and peroxidase activity increased by 16.7% (P < 0.05). However, the effect of antioxidant enzyme system on water deficit adaptation in fine roots of Chinese fir was weak. Therefore, Chinese fir could effectively adapt to the significant decrease of soil moisture under 50% precipitation exclusion through comprehensive regulation of non-enzymatic substances such as osmotic substances and endogenous hormones in fine roots.

Abstract:In order to explore the humidity and heat tolerance of Salvia species with high ornamental value, S. miltiorrhiza, S. daigui, S. cavaleriei, S. adiantifolia and 'Chendanyuebai' were planted in artificial climate chambers for simulating high temperature and high humidity environment. The morphological changes and physiological responses of Salvia were studied, and the humidity and heat tolerance of five Salvia species was comprehensively evaluated by membership function method. The results showed that the number of yellow leaves of 5 Salvia species increased significantly under stress, but the degree of damage by humidity and heat was not high, and all of them could be restored to normal growth after stress; under the complex stress, the chlorophyll content of these Salvia species decreased, relative conductivity and malondialdehyde content increased, indicating that the plants were damaged by moisture and heat to some extent. The superoxide dismutase activity and osmoregulatory substance content in Salvia species significantly increased after stress, showing an adaptive response. The moisture and heat tolerance of 5 Salvia species were in the order of S. daiguii ≈ S. adiantifolia > 'Chendanyuebai' ≈ S. miltiorrhiza > S. cavaleriei. Therefore, 'Chendanyuebai' showed strong resistance to humidity and heat, and could be introduced and cultivated.

Abstract:In order to reveal the characteristics of free amino acids (FAAs) profile in fresh leaves of oolong tea cultivars, young and mature shoots harvested from oolong tea cultivars in spring and autumn were detected by high performance liquid chromatography and classified by statistical pattern recognition, the young shoots (two or three leaves and a bud) and mature shoots (two to four leaves and a banjhi bud) of green tea cultivars in spring were used as controls. The results showed that all tea samples could be divided into two groups, oolong tea cultivars and green tea cultivars. The effect of shoots maturity on the FAAs profile in fresh leaves of oolong tea cultivars was second only to the difference of tea sample groups caused by tea tree variety characteristics. Furthermore, the objective group differences could be verified among young shoots (green tea cultivars vs oolong tea cultivars) in spring, mature shoots of (green tea cultivars vs oolong tea cultivars) in spring, (young shoots vs mature shoots) of oolong tea cultivars in spring, (young shoots vs mature shoots) of oolong tea cultivars in autumn, young shoots of oolong tea cultivars (spring vs autumn), and mature shoots of oolong tea cultivars (spring vs autumn). The different sources of fresh leaves (cultivars, shoots maturity and harvesting season) had significant or extremely significant effect on the total amount of FAAs and most of the components of FAAs. The higher contents of glycine, leucine and lysine and the lower content of γ-aminobutyric acid were the main difference components of fresh leaves in spring between oolong tea and green tea cultivars. The young shoots of oolong tea cultivars had higher content of arginine than mature shoots in the same harvesting season, and there were different characteristic components of fresh oolong tea leaves with different shoot maturity in spring and autumn. Therefore, it was suggested that the genetic characteristics of tea cultivars were dominant factors affecting the FAAs profile in fresh leaves. The specific chemical pattern of FAAs in fresh leaves of oolong tea provided a necessary material basis for the quality formation.

Abstract:Toxicodendron purpureum, a new species of Anacardiaceae from Shaowu County, Fujian Province of Eastern China, is described and illustrated here. The new species is similar to T. delavayi, but is distinguished from T. delavayi by leaves 25 cm (vs to 13 cm); leaflets papery, abaxially purplish red, rare green (vs abaxially glaucous, leaflet petiolule 1–2 mm); inflorescence as long as 1/3 pinnately compound leaf (vs as long as pinnately compound leaf); petals without brown featherlike venation pattern (vs petals with brown featherlike venation pattern). The comparison of morphological characteristics among four closely related species and phylogenetic analyses based on nuclear ITS and plastid sequences (trnL-F and ndhF) from 29 species both support the establishment of the new species.

Abstract:In order to reveal the floristic characteristics of plantws in Wuhuang Mountain area in southern Guangxi, the plant resources of Wuhuang Mountain National Geopark and its adjacent areas in Guangxi were studied through field investigation and literatures. The results showed that there were 1 002 species of wild plants in Wuhuang mountain area, belonging to 167 families and 581 genera, including 73 species of ferns in 20 families and 37 genera, 5 species of gymnosperms in 3 families and 4 genera, and 924 species of angiosperms in 144 families and 540 genera. Angiosperms were dominant. The geographical elements at family and genus levels were mainly tropical, and the genus was more tropical, in which the pantropical component was the most dominant, and the temperate component was mainly north temperate. There were 4 genera endemic to China and no endemic family to China. So, the flora of this area was characterized by high species richness, strong tropical and weak endemism.

Abstract:To understand the triterpenoids from Rosa laevigata var. leiocapus and their SARS-CoV-2 inhibitory activities, 15 compounds were isolated from the 95% EtOH extract by using chromatographic separation techniques, such as silica gel, Sephadex LH-20 and pre-HPLC. On the basis of spectral data, their structures were identified as laevigaterpene A (1), 2α, 23-dihydroxy oleanolic acid (2), 1β-hydroxyeuscaphic acid (3), 3β-(p-hydroxytranscin-namoyloxy)olean-12-en-28-oic acid (4), 3β-trans-p-coumaroyloxy-2α-hydroxy oleanolic acid (5), 2α, 3α-dihydroxyo-lean-12-en-28-oic acid (6), pomolic acid (7), lup-3β-ol-28-carboxylate (8), 2α, 3α, 19α, 23-tetrahydroxyurs-12-en-28-oic acid (9), acetyl-11α-methoxy-β-boswellic acid (10), arjunic acid (11), 2α, 3α, 19α-trihydroxy-28-norurs-12-ene (12), euscaphic acid (13), 2α, 19α-dihydroxy-3-oxo-12-ursen-28-oic acid (14), and oleanolic acid (15). Compounds 1-15 were obtained from this species at first time. Moreover, compounds4,10 and 12 were isolated from Rosa at first time. Compounds 8 and15 exhibited strong inhibitory effects on SARS-CoV-2 M^pro, with IC₅₀ of (6.74±0.33) and (5.19±0.25) μmol/L, respectively, showing potential anti-SARS-CoV-2 activity.

Abstract:Rubber trees (Hevea brasiliensis) are widespread in the tropics and are a major source of natural rubber for strategic materials. The study of their phenology is of great importance for the production management of rubber plantations and for assessing the response of tropical vegetation to global climate change. The early phenological research mainly served the production application, such as seedling breeding, rubber tapping planning, and stress-resistant cultivation. The use of remote sensing to monitor vegetation phenology has become increasingly mature and has been widely applied to rubber trees, becoming the mainstream method for phenological monitoring. Rubber tree phenology has obvious spatio-temporal heterogeneity and its response to climate change is complex, which temperature and precipitation are key influencing factors, and both internal factors (strain, gene, and tree age, etc.) and external factors (planting density, geographic location, and agricultural practices, etc.) also affect its phenology. In order to better serve the sustainable development of natural rubber industry and scientific research on climate change in tropics, future research on rubber tree phenology should focus on the collaborative reconstruction of multi-source remote sensing data, universalization of phenological index extraction algorithms, and precision of remote sensing prediction models. The monitoring methods, service values, spatio-temporal patterns of rubber tree phenology were systematic reviewed, and put forward the existing problems and future research directions.