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2024  Vol. 42  No. 5

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Systems and Evolution
Abstract:

Hymenasplenium wusugongii Li Bing Zhang, W.B. Liao & K.W. Xu is newly recorded from Jinghong City, Yunnan Province, China. This recently described species was previously known only from Luang Prabang District in northern Laos. Hymenasplenium wusugongii is characterized by a narrowly ovate to narrowly deltoid lamina, up to 12 cm wide, with a 1-pinnate structure, an acuminate apex, and long-stalked pinnae that lack 1–2 basal basiscopic veins, making it morphologically distinct within the genus Hymenasplenium. This paper provides a detailed description of its morphological characters, along with in-situ photographs and illustrations. Voucher specimens have been deposited in the Shanghai Chenshan Herbarium (CSH) and Herbarium of Guangxi Institute of Botany (IBK).

Abstract:

The pollen morphological characters of 22 species of the genus Styrax in China were observed and analyzed by scanning electron microscopy, with the pollen morphology of seven species reported for the first time, providing evidence for taxonomic identifications and clarifying interspecific relationships among some challenging species within this genus. Results showed that: (1) The pollen types of the 22 species were primarily medium- (25–50 μm) and large-sized (50–100 μm) pollen. The pollen was tricolporate type, triangular or triangular-circular in polar view and rhombic or elliptical in equatorial view. (2) The polar axis length (P) was 36.28–55.56 μm, the equatorial axis length (E) was 16.67–36.72 μm, the P/E value was 1.41–2.18, the volume index P×E was 24.59–45.17, and the pollen germinal furrow length was 26.82–46.87 μm. (3) The pollen exine ornamentation was divided into four types, reticular, verrucate, cerebelloid, or foveolar. (4) According to cluster analysis, the 22 species of Styrax could be divided into five groups. These results show that the pollen morphological traits of Styrax differ among different species and can serve as crucial criteria for species identification and classification.

Abstract:

"Resina Draconis", also known as "Dragon's Blood Resin" or "Yunnan Hongyao", is red resin produced by the trunks of Dracaena species. Chinese "Resina Draconis" is derived from phenolic resins of D. cambodiana Pierre ex Gagnep. and D. cochinchinensis (Lour.) S. C. Chen. Due to taxonomic ambiguities between D. cambodiana and D. cochinchinensis in Chinese floras, there has been confusion in the literature regarding the source plant of Chinese "Resina Draconis". To resolve this, we examined the protologue and type materials of D. cambodiana, D. cochinchinensis, and D. angustifolia (Medik.) Roxb. and reconstructed the plastome phylogenies of 19 Dracaena species from 33 accessions. The plastome phylogenies strongly supported the division of these 19 Dracaena species into three clades. Species capable of producing phenolic resins were found in cladesⅠand Ⅲ, indicating their potential as source plants for "Resina Draconis". Notably, nine samples of D. cambodiana were not supported as monophyletic, forming two distinct groups: the Yunnan clade (D. cambodiana A) and the Hainan clade (D. cambodiana B). Morphological analysis of the protologue and neotype specimens indicated that D. cochinchinensis could not be differentiated from D. angustifolia, and thus should be considered as a synonym of D. angustifolia. Integrating phylogenetic analyses and morphological characteristics, we determined that D. cambodiana is the primary source plant of Chinese "Resina Draconis", with D. saposchnikowii Regel from South Yunnan and Dracaena sp. 2 from South Guangxi also contributing to its production. The plastome phylogenies clarified the source plants of "Resina Draconis" and elucidated the genetic relationships within the genus Dracaena, providing important information for the conservation and sustainable utilization of Dracaena germplasm resources.

Ecology and Biogeography
Abstract:

This study established 45 ecological monitoring plots in well-preserved natural forests within an altitudinal range of 400–1 800 m in the middle section of the Nanling Mountains. These plots were classified into four forest vegetation types based on elevation range and species composition. This study assessed the differences in dominant tree species and their niche characteristics along various altitudinal gradients by surveying key ecological niche parameters and evaluating the niche resource utilization hypothesis. Results indicated that: (1) Dominant species varied at different altitudes, with more pronounced differences in species composition observed at higher altitudinal differences; (2) In the evergreen broad-leaved dwarf forest at higher altitudes, dominant species exhibited a high degree of uniformity in resource requirements, accompanied by intense interspecific competition; (3) A weak positive correlation was found between the niche width of dominant species and their importance value, while a significant negative correlation was observed with the coefficient of variation of importance value. Although niche width was related to niche overlap and similarity, no clear pattern was established; (4) Species with higher importance values, larger niche widths, and smaller coefficients of variation included Castanopsis eyrei (Champ.) Tutch, Cyclobalanopsis glauca (Thunb.) Oerst, and Schima superba Gardn. et Champ., suggesting that these species are the primary constructive species in the middle section of the Nanling Mountains. These findings provide theoretical support for the sustainable management of forest ecosystems and the conservation of plant diversity in the middle section of the Nanling Mountains and beyond; (5) The division of resource utilization in forest stands at middle and low altitudes aligned more closely with the random niche boundary hypothesis in the resource utilization hypothesis of niche theory; in high-altitude areas, the resource utilization mode of forest stands conformed to the niche priority occupation hypothesis.

Abstract:

Heptacodium miconioides Rehder (seven-son flower) is listed as a vulnerable species on the IUCN Red List of Threatened Species and is also included in the List of National Key Protected Wild Plants in China. This shrub or small tree was first recorded in 1907 by Ernest Wilson in western Hubei, central China, and was later found in Zhejiang and Anhui. However, for the next 115 years, it was not observed in Hubei and was presumed to be locally extinct. In August 2022, the species was rediscovered in the Hubei Nanhe National Nature Reserve, approximately 100 km from its type locality. The discovery site is characterized by typical deciduous broad-leaved forest, dominated by Carpinus stipulata H.J.P. Winkl., Platycarya strobilacea Siebold & Zucc., H. miconioides, and Quercus variabilis Blume. Our surveys identified 151 individuals across three localities at elevations of 1 000–1 300 m. The size class structure (main stem) of the rediscovered populations is spindle-shaped, suggesting a decline due to insufficient seedling recruitment. Of the 151 newly discovered individuals, 137 (91%) produced a total of 936 suckers, averaging 6.83 suckers per plant. This prolific sprouting may compensate for the lack of seedlings, helping to maintain populations and enabling species persistence in the niche. As these populations are located in remote mountain ridges and cliffs with minimal human disturbance, the population decline may be driven primarily by internal factors. We recommend additional field surveys to identify potential undiscovered populations, alongside a comprehensive conservation plan, including in situ conservation, artificial cultivation of seedlings, ex situ conservation, and reintroduction efforts.

Abstract:

The content of non-structural carbohydrates (NSC) in different plant tissues reflects the energy allocation strategies within plant individuals. Understanding the dynamic changes in NSC under drought stress can provide insights into how plants manage resource distribution in drought conditions. In this study, two psammophyte species from southeastern Xizang (Artemisia gmelinii Weber and Hippophae rhamnoides subsp. Yunnanensis Rousi) were selected to explore the distribution dynamics of NSC in different organs (leaves, branches, coarse roots, and fine roots) under varying drought intensities. Results showed that: (1) Intensified drought stress significantly increased the root-to-shoot ratio and the accumulation of soluble sugars and NSC in branches, coarse roots, and fine roots; (2) Under drought stress, there was a preferential allocation of NSC to underground parts, with leaves and fine roots primarily accumulating NSC in the form of soluble sugars; (3) In the fine roots of A. gmelinii, the proportion of soluble sugars, starch, and NSC decreased with intensifying drought, whereas in H. yunnanensis, the proportion of soluble sugars, starch, and NSC increased with intensifying drought. This study suggests that plants mitigate drought stress by storing more soluble sugars and enhance their drought resilience by allocating more NSC to the roots.

Genetics and Breeding
Abstract:

The sugar will eventually be exported transporters (SWEET) are a recently discovered group of sugar transporters in plants, which play important roles in various physiological processes, such as plant growth, development, and abiotic and biotic stress. This study aimed to characterize the Actinidia chinensis Planch. SWEET gene family and analyze its expression during fruit development using bioinformatics methods. A total of 29 AcSWEET genes were identified, and their amino acid quantity, relative molecular weights, isoelectric points, instability coefficients, subcellular localizations, and hydrophilicity indices were analyzed. Results showed that the 29 AcSWEET genes encoded proteins with amino acid lengths ranging from 680 to 906 residues, molecular weights between 7.531 kDa and 101.266 kDa, and isoelectric points between 6.95 and 9.9. Most proteins were relatively stable hydrophobic, and localized on the cell membrane, containing 1–2 MtN3 domains. Additionally, gene structure, conserved motifs, evolutionary relationships, cis-regulatory elements, and expression patterns at different developmental stages of fruit development were systematically analyzed. Results indicated that the AcSWEET genes had 4–6 exons. Phylogenetic analysis revealed that the kiwifruit SWEET gene family was divided into four subgroups, responsible for transporting glucose, fructose, and sucrose. Genes within the same subgroup shared similar intron-exon structures and conserved motifs. Expression pattern analysis during kiwifruit development indicated that the AcSWEET genes exhibited stage-specific expression. We speculated that AcSWEET26, AcSWEET7, AcSWEET15, and AcSWEET13 may be involved in sucrose transport and accumulation in kiwifruit.

Abstract:

MADS-box genes play an important role in plant growth and development, especially in processes such as floral organ formation, flowering time regulation, and fruit development and ripening. Based on whole-genome sequencing data of Rhododendron griersonianum Balf. f. et Forrest, 81 MADS-box genes were identified and analyzed using bioinformatics methods. Phylogenetic analysis and protein structure classification divided these genes into two classes, including 24 genes in Type-Ⅰand 57 genes in Type-Ⅱ. The MADS-box genes were unevenly distributed across 12 chromosomes, with no genes located on chromosome 2. Among the 81 MADS-box genes, six pairs showed segmental duplications and one pair showed tandem duplication, all of which have undergone purifying selection. The promoter regions of the MADS-box genes contained elements involved in light response, plant growth, hormone response, and stress response. Overall, the identification of MADS-box gene family members provides a reliable reference for further studies on the biological functions of MADS-box proteins in R. griersonianum

Physiology and Development
Abstract:

Glycine max (L.) Merr. in northern China were selected as the experimental materials, with photosynthetic limitation as the primary focus of this study. A soil water-nitrogen interaction experiment was designed to explore the relationship between photosynthetic limitation and leaf instantaneous (WUEins) and intrinsic water use efficiency (WUEint). Results showed that: (1) CO2 diffusion limitations, including mesophyll limitation (lm) and stomatal limitation (lsc), gradually increased with water stress, while biochemical limitation (lb) gradually decreased. (2) The interaction between water and nitrogen reduced lm and lsc, while lb significantly increased. (3) lm and lb were negatively and positively correlated with WUEins and WUEint, respectively (P<0.05), while lsc showed no significant correlation with either. (4) Among the limiting factors, lm contributed most to soybean photosynthetic carbon assimilation and leaf water use efficiency, making it the dominant constraint on photosynthetic and water use capacity. These findings reveal the ecological effects of soil drought and atmospheric nitrogen deposition on crop photosynthetic carbon assimilation and their intrinsic relationship with water use capacity.

Review
Abstract:

Phytocyanins (PCs) are a class of plant-specific typeⅠsmall-molecule blue-copper proteins involved in regulating plant growth, development, and stress responses. Despite their importance, functional analysis of PC proteins remains limited, and their molecular mechanisms are not fully understood. This review examines the structural features, classification, and expression patterns of PC proteins. In addition, it summarizes recent advancements in the study of PC proteins, focusing on their roles in plant growth, development, and responses to biotic and abiotic stresses. Unresolved issues and challenges in PC research are also discussed. This work aims to provide a theoretical reference for understanding the molecular mechanisms of PC proteins and for breeding stress-resistant crop cultivars.

Abstract:

Spatial metabolomics is an emerging research technology that integrates mass spectrometry imaging and metabolomics to analyze the structure, concentration, and spatial distribution of endogenous metabolites within biological tissues. This approach enables the acquisition of both known and unknown metabolite information at high spatial resolution, allowing for precise localization within tissues. It is crucial for elucidating the synthesis, accumulation, and regulation of plant metabolites. This article reviews the current research status of spatial metabolomics technology, with a focus on cutting-edge applications in plant tissue research. Special attention is given to its potential and challenges in the field of single-cell plant studies, aiming to provide new avenues for studying plant growth and development and regulating spatial metabolic networks. Additionally, this technology offers crucial insights for solving problems in agricultural production, plant-based energy development, and other fields.

Abstract:

Plant sex differentiation is influenced by a combination of genetic factors, phytohormones, and environmental conditions. Sex chromosomes and sex-determining genes play a central role in regulating the development of male and female reproductive organs. Phytohormones are also key regulators in the process of plant sex differentiation, while various environmental factors impact the expression of plant sex. This paper reviews the current research on sex differentiation in higher plants, focusing on genetic determinants, phytohormonal regulation, and environmental factors. The aim of this review is to provide a reference for further in-depth study of plant sex regulation networks.

Abstract:

As important components in aquatic ecosystems, submerged macrophytes can alleviate nitrogen load and improve the healthy operation of ecosystems through direct and indirect ways. Nitrogen utilization strategies of submerged macrophytes differ significantly from those of terrestrial plants. Submerged macrophytes can uptake nitrogen not only from the overlying water, but also from pore water in sediments via above-ground and below-ground parts, respectively. To adapt to the various changes in nitrogen content in aquatic environments, submerged macrophytes exhibit two directions of nitrogen translocation, namely acropetal and basipetal translocation. To avoid the toxicity caused by high nitrogen concentrations, a trade-off exists in nitrogen utilization between the above- and below-ground parts of submerged macrophytes. The GS/GOGAT cycle and GDH pathway are the primary pathways for nitrogen assimilation in submerged macrophytes. Currently, research on submerged macrophytes lags far behind that on terrestrial plants. Further exploration of the mechanisms underlying nitrogen utilization in submerged macrophytes is still needed and a suitable genetic transformation system of submerged macrophytes is required. Molecular technologies such as gene editing can be used to identify gene function, which should promote further studies on the structure and function of key proteins.

Abstract:

The deep valleys in southwestern China experience a dry, hot climate and support savanna-like vegetation, largely shaped by the “foehn” effect. This vegetation is primarily dominated by grasses, interspersed with scattered shrubs and trees, resembling the physiognomy of savannas in other parts of the world. The savanna-like ecosystem hosts a rich diversity of species adapted to the dry, hot valley habitat, including many local endemic plants. In terms of life forms, phanerophytes dominate, accounting for 48.0% of the total species, while hemicryptophytes account for 23.3%. Regarding leaf characteristics, microphyllous and nanophyllous plants represent 42.5% and 20.6% of the total, respectively; among tree species, 39.3% have compound leaves, reflecting adaptations to arid habitats. The flora in the hot, dry valleys of southwest China are generally dominated by tropical elements, but are influenced by regional geological history and geography. Floristic similarity between the Jinshajiang and Yuanjiang river valleys is high, with 73.8% and 53.8% at the genus and species levels, respectively, representing the greatest similarity among the hot, dry valleys. The origin and evolution of this flora are closely related to major geological events in Yunnan since the Tertiary, including uplift of the Himalayas. Some species exhibit floristic affinities with the savannas of India and Africa, supporting the hypothesis that the Indian plate separated from Africa, collided with Asia, and transported African plants to the continent. The high generic similarity between the Jinshajiang and Yuanjiang river valleys supports the river capture hypothesis. In contrast, the savanna-like vegetation in the Nujiang River valley is dominated by tropical floristic elements, which is likely related to the northward push of the Indian plate into the Asian plate and the subsequent northward shift of northern Myanmar. These geological events help explain the floristic composition, characteristics, and distribution patterns of the savanna-like vegetation in the dry, hot valleys of southwestern China.