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2022  Vol. 40  No. 4

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Ecology and Biogeography
Abstract:
To study intra-annual variations in leaf traits of long-term submerged plants in the riparian zone of the Three Gorges Reservoir Area (TGA) during the dry period of the flood-dry-flood cycle, we investigated eight leaf functional traits (maximum net photosynthesis rate (Aarea, Amass), stomatal conductance (Gs), specific leaf area (SLA), leaf nitrogen concentration (Narea, Nmass), and leaf phosphorus concentration (Parea, Pmass)) of Cynodon dactylon ( L.) Pers. at four elevations (176, 170, 164, and 158 m) in June and August 2014. Results showed that: (1) Exposed period significantly contributed to variations in Aarea, Amass, Gs, SLA, and Pmass (more than 26% of total variation), similar to or even higher than submergence intensity. However, exposed days contributed little to variations in Narea, Nmass, and Parea (less than 15%). (2) Five bivariate relationships between leaf traits (Aarea vs. Gs, Amass vs. Gs, SLA vs. Gs, Aarea vs. Narea, Pmass vs. Nmass) showed significant changes between two exposed periods. The intercept of Amass vs. Gs changed significantly between June and August. (3) Amass, Nmass, and Pmass showed no obvious trends in submergence intensity between June and August; Aarea was significantly higher at 158 m than at 176 m regardless of month; SLA and Parea were significantly lower in the riparian zone (170, 164, and 158 m) than at 176 m; variation in Narea was in the order: 158 m > 164 m > 176 m > 170 m. These results suggest that annual exposed period can lead to significant variations in C. dactylon leaf traits, as well as the relationships between them. As Narea and Parea were stable traits (less affected by exposed days and submergence intensity), they may be candidate predictors for the structure and function of the TGA riparian ecosystem.
Abstract:
Studying the response of biodiversity to seasonal changes is important for maintaining ecosystem stability, protecting biodiversity, and analyzing community construction mechanisms. Here, we explored changes in species and functional diversity of plant communities in the Bosten Lake wetlands in different seasons. Results showed that: (1) the species diversity index did not change significantly with season. For the functional diversity index, functional richness gradually decreased from spring to summer, functional dispersion gradually increased, and functional uniformity showed no significant difference in different seasons. (2) Significant differences were found in plant functional traits in different seasons. Chlorophyll content was significantly lower in spring than in summer; specific leaf area and dry matter content were significantly higher in summer than in autumn; and water content and thickness of leaves increased from spring to autumn. (3) The main environmental factors affecting the Pielou index and functional richness were soil ammonium nitrogen and available phosphorus, respectively; the main environmental factor affecting the Shannon-Wiener index, Simpson index, and functional uniformity was soil organic matter; and the main environmental factor affecting functional dispersion was soil water content. (4) The main environmental factors affecting maximum plant height and leaf dry matter content were soil pH and available potassium, respectively; the main environmental factor affecting leaf dry matter content was soil available potassium; the main environmental factor affecting leaf thickness and specific leaf area was soil total phosphorus; the main environmental factor affecting leaf water content was soil nitrate nitrogen; and chlorophyll content and soil factors showed no significant correlation.
Abstract:
Changes in wetland ecosystem structure and function are closely related to wetland ecological vulnerability and high-level ecological services. At present, however, few studies have explored the ecological losses caused by changes in wetland ecosystem structure and function. Based on the accurate registration and interpretation of a topographic map of Haikou from 1959 and image data from year of 1976, 1985, 1995, 2005, and 2018, we developed an ecosystem service value (ESV) method based on the equivalent factor, constructed an assessment model of the impact of changes in wetland ecosystem structure and function on ESV, and analyzed dynamic changes in wetland ESV. Results showed that: (1) from 1959 to 2018, ESV decreased by 1.073 billion yuan. From 1959 to 2018, only the ESV supply service increased by 58 million yuan, whereas the adjustment, support, and culture services decreased by 509, 187, and 47 million yuan, respectively. (2) Based on the revised ESV equivalent of the dynamic ESV model, only shallow waters, silty beaches, and mariculture farms showed an increase in ESV; wetlands/inland tidal flats, freshwater lakes, rivers, and reservoirs showed considerable losses in the ESV equivalent; freshwater farms, agricultural ponds/pit ponds, paddy fields, and other land types showed relatively light losses in the ESV equivalent; construction land showed a continuous decrease in the ESV equivalent. (3) Spatial scale differences were found in the assessment of wetland ESV, indicating that the self-regulation and restoration ability of a wetland cannot be ignored, and the threshold value of wetland ecosystem service function change under external disturbance needs to be further studied.
Abstract:
Sonneratia is the most endangered genus of mangrove plants in China. Among the six existing mangrove species in Sonneratia, S. ovata Backer, S. × hainanensis W.C. Ko, E.Y. Chen & W.Y. Chen, and S. × gulngai N.C. Duke & B.R. Jackes are all critically endangered. In this paper, we explored the distribution and status of these three Sonneratia mangrove plants based on literature review and field investigation. Results identified two natural and three artificial populations of S. ovata, with 231 and 38 individuals, respectively; four natural and two artificial populations of S. × hainanensis, with 139 and 11 individuals, respectively; and four natural and three artificial populations of S. × gulngai, with 345 and 12 individuals, respectively. The natural regeneration ability of the populations was extremely poor, with no new individuals in the artificial populations. Climate change and human disturbance are the main reasons for the decrease in Sonneratia species, and poor self-regeneration is a limiting factor for population size recovery. To strengthen in situ protection, ex situ conservation strategies should be optimized, artificial breeding research should be strengthened, breakthroughs in breeding difficulties should be accelerated, and returning populations should be scientifically cultivated to ensure normal population development.
Abstract:
Two dominant ephemeral plants, i.e., Erodium oxyrhinchum M. Bieb. and Eremopyrum orientale (L.) Jaubert & Spach, from the Gurbantünggüt Desert were used for potted plant experiments under controlled conditions. We set two temperature gradients and three moisture gradients to analyze variation characteristics in carbon (C), nitrogen (N), and phosphorus (P) contents and their stoichiometric ratios under different temperature and humidity treatments. Results show that: (1) Temperature significantly affected N, P contents, C∶P, and N∶P in Erodium oxyrhinchum, and C, N, P, C∶N, and N∶P in Eremopyrum orientale. Water significantly affected N, P, C∶N, and C∶P in both plants and N∶P in Eremopyrum orientale. The changes in N content with temperature conformed to the temperature-biogeochemical hypothesis, while the changes in P content with temperature conformed to the temperature-plant physiology hypothesis. (2) Interactions between temperature and water also affected the plants. Under high temperature treatment, as the water gradient increased, N and P contents in both plants first increased and then decreased, while C∶N, C∶P, and N∶P first decreased and then increased. Under low temperature treatment, changes in N and P contents in Erodium oxyrhinchum were inversely proportional to the water gradient, while changes in C∶P were directly proportional to the water gradient. However, the stoichiometric changes in Eremopyrum orientale were not significant. (3) Correlation analysis showed that temperature and water significantly affected element correlations in both plants, and the growth rates and nutrient limitations of the plants were also subject to dominant regulation of the nutrient elements.
Genetics and Breeding
Abstract:
Genetic analysis of fruit traits in hybrid populations of kiwifruit (Actinidia) can provide a theoretical basis for hybridization breeding. Here, we measured nine traits of fruit quality and shape characteristics of an F1 population generated through hybridization between a female A. rufa '63101’ parent and male A. chinensis 'Moshan male No. 7’ parent. Results showed that average fruit mass of the F1 population was lower than that of their parents, indicating a genetic tendency of regressing to small fruit. Average content of soluble solids was higher than the median content in parents, showing a genetic tendency to a higher level. The fruit shape of F1 showed five segregated traits, 82% of which were the same as the female parent (cylinder). Fruit hairiness of F1 showed a genetic tendency toward the male parent, with 60% and 40% being piliferous and glabrous, respectively. Skin color was characterized as green, greenish brown, or brown, at a ratio of 1.0∶1.5∶1.0. Shoulder shape at the stalk end was mainly square and outer pericarp color was mainly green, showing genetic tendencies toward the female parent (63% and 86%, respectively). For fruit flavors of the F1 population, 64% were identical to the parents, 1% were extremely sour, and 9% were highly sweet. These results indicated that the hybrids showed a genetic tendency toward smaller fruit mass and higher soluble solid content. Fruit shape, shoulder shape at stalk, and color of outer pericarp showed genetic tendencies toward the female parent, but fruit hair showed a genetic deviation from the female parent. Fruit flavors showed wide separation, with some strains exceeding the parents. Thus, these progenies exhibit potential superiority.
Abstract:
The WRKY transcription factor gene family is a class of plant-specific genes that play important regulatory roles in plant secondary metabolism and biotic and abiotic stresses. Through bioinformatic analysis, 60 WRKY genes were identified in the whole genome of Cinnamomum camphora (L.) Presl., which were divided into Groups Ⅰ,Ⅱ, and Ⅲ. Genes in Group Ⅰ and Group Ⅲ were contracted, while segment duplication was the main cause of CcWRKY gene expansion. The C terminus and N terminus of Group Ⅰ contained a complete WRKY domain and zinc finger motif, however there is loss and variation of the domain and zinc finger motif in members of Group Ⅱ and Group Ⅲ. There were many hormone- and stress-responsive cis-acting elements on the promoter of CcWRKYs, such as ABA, MeJA, SA, drought induction, and anaerobic-related stress response. Expression analysis showed that most CcWRKY genes were highly expressed in various tissues in barren environment (without fertilization), while under suitable environmental (fertilization) conditions, the level of gene expression decreased. This study analyzed the expression patterns of CcWRKY genes in response to abiotic stress and provided a theoretical basis for the subsequent functional verification of the C. camphora WRKY gene.
Abstract:
We cloned the QaGDU3 gene from Quercus aquifolioides Rehd. et Wils. and obtained transgenic Arabidopsis thaliana (L.) Heynh. using ligation-independent cloning (LIC) and floral dipping transformation. We evaluated QaGDU3 expression and analyzed phenotypic changes in transgenic plants using quantitative real-time polymerase chain reaction (qRT-PCR) and image analysis, respectively. We investigated the structure, sequence divergence, and evolutionary relationship of QaGDU3 with related species. Structural analysis showed that QaGDU3 is an acidic and unstable hydrophilic transmembrane protein. Phylogenetic analysis indicated that GDU3 may only be present in seed plants. The qRT-PCR results showed that overexpression of the QaGDU3 gene in transgenic plants activated the expression of the AtPR1 (PATHOGENESIS-RELATED GENE 1), AtACD6 (ACCELERATED CELL DEATH 6), AtCBP60g (CAM-BINDING PROTEIN 60-LIKE g), and AtPAD4 (PHYTOALEXIN DEFICIENT 4) genes involved in the salicylic acid (SA) pathway. Furthermore, the rosette size of transgenic A. thaliana decreased with the increase in QaGDU3 expression. These data suggest that GDU3 may be a seed plant-specific amino acid transporter and that overexpression of QaGDU3 can affect plant growth and development.
Abstract:
Many species of the genus Polygonatum have important medicinal value, but there is currently a lack of DNA barcodes that can effectively identify medicinal plants within Polygonatum. In the present study, based on the amplification and sequencing of ITS, trnK-matK, rbcL, psbA-trnH, and psbK-psbI, and the extraction of the ITS2 sequences, 138 sequences were obtained from 23 samples of seven Polygonatum medicinal species. Similarity search algorithm (BLAST) and neighbor-joining (NJ) analysis were used to compare the efficacy of sequences for identifying medicinal species and analysis of molecular variance (AMOVA) was applied to verify the reliability of the screened barcodes. Results demonstrated that the intra- and inter-specific genetic variation of trnK-matK showed less overlap and an obvious barcoding gap, while the other five sequences showed considerable overlap and no barcoding gaps. The BLAST search results showed that trnK-matK had the highest identification efficiency (85.7%). The phylogenetic trees also showed that trnK-matK had the most efficient identification ability, clustering all 12 samples of P. cyrtonema together and distinguishing P. sibiricum, P. kingianum, P. odoratum, P. punctatum, and P. zanlanscianense. AMOVA revealed that trnK-matK had the highest population genetic differentiation index (Fst) and was the most suitable for distinguishing differences between Polygonatum species. Therefore, among the six candidate barcodes, trnK-matK is the most suitable for molecular identification of medicinal plants of Polygonatum.
Physiology and Development
Abstract:
Six heteroblastic aquatic plants, i.e., Nymphaea tetragona Georgi, Nuphar pumila (Timm) de Candolle, Nuphar sagittifolia Pursh, Potamogeton distinctus A. Bennett, Potamogeton octandrus Poir, and Alisma plantago-aquatica L., were studied and their chlorophyll content, stomatal traits, anatomical structure, and HCO3- utilization were analyzed, the differences between leaf structure and inorganic carbon acquisition strategies at different developmental stages were compared.Results showed that the juvenile leaves were thinner and had fewer cell layers than the mature leaves. The upper and lower surfaces of the juvenile leaves did not contain stomata, whereas the upper epidermis of the mature leaves did contain stomata. Thus, the juvenile leaf structure showed increased cell surface area and the ability to absorb inorganic carbon underwater, while the mature leaves structure better absorbed CO2 from the atmosphere. Results from pH-drift analysis indicated that the juvenile leaves exhibited better acquisition of underwater inorganic carbon as an adaptation to the submerged environment. In addition, the juvenile leaves of P. distinctus and P. octandrus used HCO3- in the water as an additional carbon source, which was beneficial for growth in the submerged environment. These results elucidate the leaf structure of heteroblastic aquatic plants at different stages of development and the adaptability of inorganic carbon acquisition strategies to the submerged and aerial environments.
Abstract:
Differences in growth characteristics, leaf morphologies, and photosynthetic characteristics of Phoebe bournei (Hemsl.) Yang saplings in unevenly aged two-layer mixed (UATLM) forest and pure forest were explored to provide a scientific basis for the construction of UATLM forest and cultivation of precious tree species. We investigated 7-year-old P. bournei saplings in Cunninghamia lanceolata (Lamb.) Hook. + P. bournei UATLM forest (CP forest), Sassafras tzumu (Hemsl.) Hemsl. + P. bournei UATLM forest (SP forest), and pure P. bournei forest. We measured the growth, leaf phenotype, leaf structure, photosynthetic pigment content, changes in photosynthetic parameters, and photosynthetic-light response curves in the three forests. Results showed that: (1) Compared with the pure forest, the DBH and height of increments saplings in the CP forest were 46.61% and 43.87% higher, respectively, while those in the SP forest were 20.75% and 26.53% lower, respectively. (2) Compared with the pure forest, the fresh weight and water content of leaves of the P. bournei saplings in the two UATLM forests were lower, leaves were thinner and slenderer, and midrib, upper epidermis, lower epidermis, palisade tissue, and spongy tissue thickness was significantly reduced. (3) Chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid contents in P. bournei saplings from the two UATLM forests were significantly higher than levels in the pure forest. (4) The net photosynthetic rate (Pn) of the saplings did not significantly differ between the pure forest and CP forest, except at 8∶00 am, while the Pn of saplings in the SP forest was significantly lower than that of the other two forests at 10∶00 am and 2∶00 pm. This study showed that the growth conditions of P. bournei saplings were better in the CP forest, while P. bournei sapling growth was inhibited in the SP forest due to shading.
Abstract:
To explore the construction process of the bamboo ramet system and its relationship with artificial management, we conducted pot experiments with mother bamboo (Phyllostachys praecox C. D. Chu et C. S. Chao 'Prevernalis’) at different ages and under different mulching soils and compared growth differences of rhizome branches of bamboo seedlings. Results showed that during ramet system construction in the potted seedlings, the development of bamboo rhizome branches was dominant. The number of rhizome branches in 2-year-old mother bamboo potted seedlings was generally higher than that of 1-year-old potted seedlings, and rhizome branches decreased with the increase in soil mulch period. The rhizome branches of potted seedlings were mainly distributed in the middle of the bamboo rhizome at the Ⅱ, Ⅲ, and Ⅳ branching grades. The rhizome branch of 1-year-old potted seedlings was more in the middle and tip of the rhizome at the Ⅱ branching grade, but more in the middle and tip of the rhizome at the Ⅲ branching grade in the 2-year-old potted seedlings. With the increase in soil mulch period, the rhizome branches tended to be distributed at the front branchings. Thus, expansion of underground branches was the main strategy used in ramet system construction in the potted seedlings. Branch growth in the 2-year-old mother bamboo and lateral buds in the middle of the bamboo rhizome greatly contributed to ramet system expansion. The longer the bamboo forest soil was mulched, the less conducive it was to rhizome branching. As the bamboo ramet system exhibited spatiotemporal expansion, the growth characteristics of rhizome branches need to be continuously observed.
Abstract:
Silver nanoparticles (AgNPs) are an emerging environmental pollutant. In this study, dormant buds of Spirodela polyrhiza were chosen to investigate the effects of AgNPs on germination, survival, and growth of propagules. Results showes that AgNPs inhibited the germination of dormant buds and high concentrations (10 mg/L) even caused death. The number and area of fronds and content of photosynthetic pigments decreased gradually with the increase in concentration after germination of dormant buds and chlorophyll a was the most sensitive parameter to AgNP toxicity. This study showed that AgNPs, as a novel pollutant, have inhibitory effects on the germination and growth of asexual propagules of aquatic plants, and thus exhibit certain ecological risks.
Review
Abstract:
Lotus (Nelumbo) is the only aquatic plant among the top 10 traditional flowers in China and has significant ornamental and economic value. Flowering period is an important characteristic affecting the ornamental value of lotus, and regulation of the flowering period is extremely significant for its production and application. Lotus usually blooms from June to August but can bloom year-round based on flowering period regulation. In this paper, we discuss research advances in lotus flowering period regulation, including definitions, characteristics, basic principles, molecular mechanisms, and regulation techniques. Future research prospects are also discussed to provide reference for further studies on lotus flowering period regulation and industrial development.