Abstract:To understand the effect of atmospheric nitrogen deposition on seed germination and seedling growth of Ficus, the early regeneration process and growth conditions of four epiphytic and four terrestrial Ficus species treated with different nitrogen concentration (0, 5, 30, 60, 90, and 120 mmol/L) were analyzed. The results showed that at a low nitrogen concentration (5 mmol/L), compared with the control, there were no significant differences in the germination rate, emergence rate, survival rate, and germination and emergence speed of eight Ficus species seeds. However, the root complexity, main root length, bud length, and biomass all significantly increased (P<0.05). When the nitrogen concentration exceeded 5 mmol/L, the emergence and survival rates of seeds, the growth of roots and buds, and the biomass of all species significantly decreased. Under different nitrogen treatments, the survival rate and growth ability of epiphytic Ficus species were significantly higher than those of terrestrial Ficus species (P<0.05). When the nitrogen concentration was 30 mmol/L, the survival rate, root length, root complexity, seedling vigor index, and biomass of terrestrial Ficus species decreased by 43.8%, 85.6%, 82.3%, 57.4%, and 57.1%, respectively. Under the highest nitrogen treatment (120 mmol/L), all these indicators decreased by more than 87%, and the corresponding indicators of epiphytic Ficus species decreased by 44.9%, 90.4%, 58.1%, 60.2%, and 56.3%, respectively. Therefore, these indicate that in the context of increasing atmospheric nitrogen deposition, epiphytic Ficus species have stronger tolerance and competitiveness.

Abstract:Monsoon secondary forests are important ecosystems in tropical South China, but reports on their long- term response to nitrogen (N) and phosphorus (P) addition in terms of litter production and decomposition rates are scarce. This paper prbesents the results of a 12-year study on aboveground litter production and a 4-year study on decomposition rates in a long-term NP addition experiment in a tropical monsoon secondary forest in South China. The experiment employed a two-factor (N addition and P addition) and two-level (addition and no addition) design, including control, N-only addition, P-only addition, and combined NP addition treatments. The results showed that over 12 years, the total aboveground litter production for the four treatments was (11544±1115), (12649±1087), (13694±1456), and (11761±712) g/m², respectively. P addition significantly increased litter production, while N addition showed a trend of increasing litter production. There was a significant interaction between N and P addition, and the effects of NP addition did not vary with year or season. During the 4-year decomposition rate study, the decomposition rate constants for the four treatments were (1.44±0.07), (1.76±0.09), (2.10±0.10), and (1.81±0.08), respectively. P addition significantly affected litter decomposition rates, while N addition had no significant effect, and there was no significant interaction between N and P addition. Long-term P addition significantly increased aboveground litter production in this ecosystem, while long-term N addition had a weak effect. There was a significant interaction between N and P addition, and the effects of NP addition did not change with treatment duration or dry/wet seasons. Aboveground litter decomposition was mainly limited by P, with no response to increased N availability. Therefore, it was suggested that the effects of long-term NP addition on aboveground litter production and decomposition in tropical monsoon secondary forests, contributing to the understanding of long-term response mechanisms of this ecosystem to increased nutrient availability.

Abstract:Excentrodendron tonkinense, a national second-class key protected wild plant and one of the dominant species in the karst seasonal rainforest, still faces the threat of environmental disturbances. To explore the spatial distribution dynamics of its population, this study analyzed the relationship between population distribution dynamics and environmental factors based on the population and environmental survey data of a 15 hm² plot in the karst seasonal rainforest of Nonggang, Guangxi from 2011 to 2021, using spatial point pattern methods and zero-inflated models. The results showed that the number of individuals in the population decreased from 1851 to 1786 over 10 years. The proportion of small diameter classes (1–5 cm) was over 50% in all years, and the diameter class structure was inverted “J” shaped. The population was significantly aggregated at the 0–50 m scale in three years, and the overall aggregation intensity of the population was mainly driven by the aggregation degree of the spatial distribution pattern of small trees. The distribution range of the population was significantly affected by soil moisture content, total phosphorus and total potassium in the habitat, and its abundance changes were influenced by both biotic and abiotic factors. The spatial distribution of the population had strong habitat specificity. Adult trees preferred habitats with low concavity and low diversity, while small trees preferred habitats with high plant diversity. Under well-protected conditions, the population size of E. tonkinense still needs to be dynamically monitored. In specific conservation practices, it is necessary to focus on protecting slope habitats and reducing human disturbances.

Abstract:Merremia boisiana, a native vine with catastrophic characteristics, is rapidly spreading in Hainan Tropical Rainforest National Park in recent years, posing a serious threat to the stability of the local ecosystem. To analyze the influence of key environmental factors on the occurrence of M. boisiana, the spatial distribution pattern of M. boisiana in the Hainan Tropical Rainforest National Park was analyzed after a field investigation and established a predictive model of environmental driving factors and the occurrence probability of M. boisiana. The results showed that M. boisiana was most severely harmful in the Wuzhishan area, with an unevenly aggregated spatial kernel density and a positive spatial autocorrelation in the occurrence area (P<0.01). It mainly concentrated in areas with frequent human activities, such as the edges of artificial forests, secondary forests, and roads, and the most severely affected altitude range was 300–900 m. In addition, the random forest model indicated that the distance from roads and altitude were the main environmental factors affecting the occurrence of M. boisiana. The results of Logistic regression analysis showed that the distance from roads, altitude, the distance from artificial forests, and the distance from ecological recreation areas were important environmental factors affecting the occurrence of M. boisiana (P<0.01). The spread of M. boisiana is closely related to human activities, especially in areas with intensive production and tourism activities. It is recommended to strengthen monitoring and control measures in these areas to prevent further spread.

Abstract:To clarify the soil nutrient and fungal community characteristics under different vegetation restoration types (artificial restoration and natural restoration), and to reveal the differences in soil fertility between artificial and natural restoration, the soil chemical indicators, enzyme activities, and fungal community diversity and composition of 9-year-old pure stands of Eucalyptus urophylla×E. grandis (EU), Erythrophleum fordii (EF), and abandoned natural restoration shrubland (SH) with basically the same initial site conditions in the Nanning Eucalyptus Field Station were measured. The effects of different vegetation restoration types on soil chemical indicators, enzyme activities, and fungal communities were analyzed, and the correlations between fungal communities and soil chemical properties and enzyme activities were explored. The results showed that compared with SH, the total nitrogen (TN), available nitrogen (AN), and organic matter (OM) contents of EU and EF significantly increased, while the available phosphorus (AP) content of EU and EF significantly decreased. In addition, compared with SH, the catalase (CAT) and urease (UE) activities of EU and EF significantly increased, while the acid phosphatase (ACP) activity significantly decreased. The relative abundances of Basidiomycota and Glomeromycota in EU and EF were significantly higher than those in SH. However, there were no significant differences in these soil indicators between EU and EF (except for Glomeromycota). In addition, the relative abundances of Basidiomycota and Glomeromycota were significantly positively correlated with TN, AN, CAT, and OM, while the relative abundance of Ascomycota was significantly positively correlated with AP and ACP. Considering the soil nutrients and fungal community characteristics comprehensively, artificial restoration is suitable for vegetation restoration in this study area, but the differences between planting pure stands of EU and EFare relatively small.

Abstract:To explore the genetic diversity of Camellia sinensis ‘Tianshancaicha’ germplasm resources, the genetic background of 143 ‘Tianshancaicha’ germplasm resources and their genetic relationship were analyzed by using SSR molecular marker technology, with local tea tree germplasm resources from other production areas in Ningde City as references. The results showed that 6 pairs of primers amplified a total of 55 alleles, with an average of 9.166; the average observed heterozygosity, expected heterozygosity, Shannon index and PIC were 0.649, 0.779, 1.870 and 0.742, respectively. The 143 germplasm resources from different production areas could be divided into 5 groups by genetic cluster analysis. Among them, 112 ‘Tianshancaicha’ germplasm resources (including wild bitter tea trees in Jiaocheng) were scattered in different groups, indicating that they might share the same genetic background as ‘Mindencaicha’. The gene flow among different production areas was 2.225, suggesting that the gene exchange among ‘Mindencaicha’ was relatively strong. So, there was a phenomenon of cross-inheritance among the ‘Tianshancaicha’ germplasm resources, with significant genetic differences and rich genetic diversity, which can assist in the selection of core and excellent resources.

Abstract:Based on the transcriptome data of Diospyros morrisiana seedlings, 1620 pairs of polymorphic EST- SSR molecular markers were developed using CandiSSR software. The genetic diversity of 157 wild plants from 8 natural provenances was evaluated using 15 pairs of EST-SSR molecular markers randomly selected. The results showed that the transcriptome dataset contained 100 285 Unigene sequences with a total length of 98 738 602 bp; among them, 34 121 SSR loci were identified, with a frequency of 34.02%, approximately one SSR locus every 2.89 kb. The 15 pairs of EST-SSR primers with good polymorphism had a polymorphism information content (PIC) ranging from 0.244 to 0.877, with an average of 0.623, and 12 loci were highly polymorphic (PIC: 0.543-0.788). The observed heterozygosity of the 8 wild populations of D. morrisiana based on 15 pairs of EST-SSR primers ranged from 0.503 to 0.650, the expected heterozygosity ranged from 0.574 to 0.610, and the Shannon diversity index ranged from 1.072 to 1.245, indicating moderate genetic diversity. The majority of the genetic variation in the wild populations of D. morrisiana occurred within the populations (83.29%), and there was extensive gene flow among the populations, with a relatively close genetic relationship. These would provide technical support and scientific basis for the evaluation of germplasm resources, genetic diversity analysis, and molecular marker-assisted breeding of D. morrisiana.

Abstract:Tobacco is a warm-loving crop that is sensitive to low temperatures. During the floating seedling stage, it is vulnerable to adverse effects from cold spells such as “late spring cold” and low light. To address the issues of slow growth and reduced survival rate of tobacco seedlings caused by such cold spells, this study explored the colonization effect of the endophytic fungus Piriformospora indica in tobacco roots and its mechanism for enhancing tobacco cold resistance without altering the current floating seedling cultivation method. The results showed that the colonization of P. indica in the roots of tobacco seedlings significantly increased the activity of the antioxidant enzyme system, including SOD, CAT, POD, and APX, in tobacco, effectively curbing the excessive accumulation of reactive oxygen species (ROS). Additionally, P. indica promoted the accumulation of osmotic adjustment substances in tobacco, including soluble sugars, proline, and soluble proteins. Moreover, Piriformospora indica could further stimulate the expression of cold response genes and enhance the photosynthetic capacity of tobacco by promoting chlorophyll synthesis and the efficiency of photosystem II (PSII). This study clarified the multi-pathway mechanism by which P. indica enhances tobacco cold resistance and provided an effective strategy for promoting the growth of tobacco seedlings under low temperature.

Abstract:The strong seasonal rainfall in south China frequently subjects plants to water stress, making the selection and application of water-edge garden plants a key issue in the construction of sponge cities. To explore the morphological response strategies of tropical garden plants in water-edge areas, the leaf traits, root traits and biomass allocation of Senna alata seedlings under three water stress conditions, namely continuous flooding, continuous drought and alternate drought and flooding, were measured. The results showed that water stress had a significant impact on 15 indicators including leaf area, leaf thickness, specific root length, root tissue density, root biomass and leaf biomass of S. alata (P<0.05). Continuous flooding had a greater impact on leaf traits, while root traits were more sensitive to continuous drought. Alternate drought and flooding stress had a relatively small impact on the leaf traits, root traits and biomass of S. alata. The impact of water stress on roots with a diameter of 0.50 mm≤d<2.00 mm was the most significant. There was a certain correlation between the leaf and root traits of S. alata. Under water stress, the growth strategy of S. alata tended to be slow investment and return type. Therefore, Senna alata has better adaptability to alternate drought and flooding stress and is suitable for promotion and application in urban green spaces such as water-edge green spaces and rain gardens where alternate drought and flooding stress may occur.

Abstract:To determine the appropriate proportion of potassium silicate replacing potassium sulfate in the basal fertilizer for flue-cured tobacco, a gradient replacement of potassium silicate for potassium sulfate was designed based on the special basal fertilizer formula for flue-cured tobacco. The effects of this replacement on the agronomic traits, economic traits, quality traits and potassium fertilizer utilization characteristics of flue-cured tobacco were analyzed. The results showed that compared with the potassium sulfate treatment, when the replacement ratio of potassium silicate was 25%, the total scores of sensory quality evaluation of middle and upper leaves increased by 0.61 and 2.84 points respectively, and the potassium accumulation in leaves and potassium fertilizer utilization rate increased by 5.5% and 6.92% respectively. When the replacement ratio was 50%, only the total score of sensory quality evaluation of upper leaves increased by 1.21 points, and the other indicators showed no significant difference or decreased. When the replacement ratio was ≥75%, the maximum leaf area, the area of the third leaf from the top, output value, yield, chemical quality of middle leaves, sensory quality and potassium fertilizer utilization characteristics of flue-cured tobacco were all inferior to those with a 25% replacement ratio. That is, an excessively high replacement ratio was not conducive to the yield, quality and potassium fertilizer utilization of flue-cured tobacco. Combined with the curve fitting results, the appropriate replacement ratio of potassium silicate for potassium sulfate was 20.5% to 34.2%, which could improve the potassium fertilizer utilization efficiency, yield and sensory quality of flue-cured tobacco leaves.

Abstract:To explore the effects of plant growth regulators on growth and physiological metabolism of the rare economic tree species Cylocarya paliurus, foliar fertilizers of chlormequat chloride (C1: 500 mg/L, C2: 1000 mg/L, C3: 1500 mg/L, C4: 2000 mg/L), tridibenzyl (T1: 50 mg/L, T2: 100 mg/L, T3: 150 mg/L, T4: 200 mg/L), and brassinolide (B1: 0.05 mg/L, B2: 0.1 mg/L, B3: 0.15 mg/L, B4: 0.2 mg/L) were sprayed on one-year-old C. paliurus seedlings. The results showed that T1 treatment had the most significant inhibitory effect on the increase in seedling height and the most significant promoting effect on the increase in ground diameter. B4 treatment was the most effective in promoting the increase in the number of branches. All three plant growth regulators could promote the accumulation of seedling biomass, with the total biomass accumulation of seedlings being the highest under C2 treatment. The peroxidase (POD) activity in the leaves of seedlings was the highest under T2 treatment. All three plant growth regulator treatments could significantly increase the indoleacetic acid oxidase (IOD) activity in the leaves of seedlings, with the highest activity under C4 treatment. Seedling height was significantly negatively correlated with ground diameter, and seedling height was significantly negatively correlated with POD and IOD activities, while ground diameter was significantly positively correlated with the activities of the two enzymes, and POD activity was significantly positively correlated with IOD activity. All three plant growth regulators could effectively inhibit the increase in seedling height, among which tridibenzyl showed the strongest dwarfing effect, while brassinolide performed best in promoting branching. Moderate concentrations of growth regulators significantly promoted the accumulation of seedling biomass; the increase in POD and IOD enzyme activities could promote the accumulation of root biomass and inhibit the increase in seedling height. Therefore, choosing the appropriate concentration of growth regulators based on the cultivation purpose can effectively improve the structure and function of C. paliurus leaf-use forests.

Abstract:To explore the suitability of the new tea variety ‘Chunlü’ for different types of tea, the variety ‘Fuyun 6’ was used as a control, and the new variety was processed into green tea, white tea and black tea. The quality of the teas was compared and evaluated. The results showed that the total sensory quality score of the green tea made from the new variety ‘Chunlü’ was the highest, followed by white tea and black tea. The contents of tea polyphenols, water extract, phenol-amino acid ratio, theobromine, caffeine, epigallocatechin gallate (EGCG), gallocatechin gallate (GCG), catechin (C), gallic acid (GA), epicatechin gallate (ECG), epigallocatechin (EGC) and total catechins were the highest in green tea, and the contents of these components in the new variety ‘Chunlü’ were significantly higher than those in ‘Fuyun 6’. The content of gallocatechin (GC) was the highest in black tea, followed by white tea and green tea. The content of catechin gallate (CG) was the highest in white tea, followed by green tea and black tea. The contents of theanine and glutamic acid were the highest in green tea, followed by white tea and black tea, and the contents in the new variety ‘Chunlü’ were significantly higher than those in ‘Fuyun 6’. Therefore, the new variety ‘Chunlü’ is more suitable for green tea production, followed by white tea.

Abstract:This article reviews the outstanding achievements in cassava breeding and research made by the South China Institute of Botany, Chinese Academy of Sciences (now known as South China Botanical Garden, Chinese Academy of Sciences) from the beginning of China’s Reform and Opening-up in 1978 to its renaming in 2003. It highlights the significant contributions of Professor Guo Junyan and his team in areas such as cassava variety selection, tissue culture, genetic transformation, and the promotion of new cultivars. The research team introduced high-quality cassava germplasm resources from institutions such as the International Center for Tropical Agriculture (CIAT, Colombia), and, by integrating rapid propagation through tissue culture techniques, successfully developed high-yield and high-quality cassava cultivars ‘Nanzhi 188’ and ‘Nanzhi 199’. These varieties were rapidly promoted across southern China, effectively advancing the efficient utilization and industrial development of cassava germplasm resources. In addition, the team established an in vitro regeneration system for cassava based on somatic embryogenesis and shoot organogenesis, centered around the ‘Nanzhi 188’ cultivar. They also innovatively developed a genetic transformation system via Agrobacterium-mediated shoot organogenesis from cotyledons of somatic embryos. These groundbreaking studies not only propelled the advancement of basic and applied cassava research in China but also had a profound impact on international cassava breeding research. Furthermore, they nurtured a cohort of cassava research leaders with a global perspective, laying a solid foundation for the continued development of China’s cassava industry.