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2019  Vol. 37  No. 3

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Systems and Evolution
Abstract:
The anatomical characteristics of the vegetative organs of Calanthe tsoongiana T.Tang et F. T. Wang were studied by paraffin sectioning to explore their ecological adaptation. Results showed that the leaf was isobilateral. Furthermore, compared with general plants, the leaves had less epidermal hair and fewer stomata, which were both distributed in the lower epidermis. The stomatal apparatus was slightly convex. The differentiation degree of the vascular bundles in the leaf was varied, and the xylem was much thicker than the phloem. The pseudobulb consisted of epidermis, ground tissue, and vascular bundles, and the ground tissue was well developed with abundant inclusions. The vascular bundles were scattered throughout the basic tissue. The root was mainly composed of the velamina, cortex, and stele. The velamina consisted of four layers of cells and the cortex was composed of 8-10 layers of parenchymal cells. The mycelium infected the cortex by destroying the velamina cells. The middle columnar channel cells were thickened on all sides, except the pericycle cells facing the xylem ridge. The vascular bundles were of radiative type and the pith, which was located in the center of the stele, consisted of parenchymal cells. Thus, the anatomical structures of the nutritive organs of C. tsoongiana showed features of a shade plant. Shade treatment and well-ventilated conditions should be provided in the processes of introduction and cultivation.
Abstract:
Dendrocalamus sinicus Chia et J. L. Sun, a rare bamboo species endemic to Yunnan Province in China, is one of the strongest woody bamboo species in the world. It occurs as two variants, i.e., straight-culmed variant (SC) and bent-culmed variant (BC). To reveal the anatomical basis of SC and BC, we collected data on culm height and morphological characteristics of shoots and young culms (emerged from ground for 0-49 d) from six clumps of D. sinicus . In addition, shoot and young culm development (0-45 d) were observed using comparative anatomy based on paraffin sectioning. Results showed that culm-height growth exhibited a "slow-fast" pattern, and the BC morphological character clearly appeared at 21-35 d, which was distinct from that of SC. The development of vascular bundles occurred earlier in BC (5-30 d) than in SC. Within BC, compared with the outer vascular bundles, the inner vascular bundles possessed smaller diameters and more fibrocytes in the fibrous sheath. Parenchyma cell differentiation occurred earlier in BC than in SC. Nuclei dyed with Safranine and Fast Green appeared in the parenchyma cells, which became regularly arranged from 20 d in BC. The parenchyma cells in the inner culm of BC were slightly smaller than those in the outer culm, whereas there was a greater number of parenchyma cells with dyed nuclei in the inner culm than in the outer culm. These results showed that the bent culm shape in BC can be identified by culm morphology during 21-35 d. The development of vascular bundles and differentiation of parenchyma cells occurred earlier in BC than in SC. Furthermore, compared with the outer culm in BC at the corresponding period, cell divisions in the inner culm were more vigorous and the degree of vascular bundle lignification was also higher.
Abstract:
Nutlet shape, pericarp micromorphology, and anatomical characters of×Bolboschoenoplectus mariqueter (Tang & F. T. Wang) and related species were observed and studied under light and scanning electron microscope. The nutlets of×Bolboschoenoplectus mariqueter were biconvex, with waveform reticulate sculpture and exocarp twice as thick as mesocarp. The species differs markedly from Bolboschoenus planiculmis (F. Schmidt) T. V. Egorova by these characters but is similar to Bolboschoenus maritimus (L.) Palla. Results showed that×Bolboschoenoplectus mariqueter should be assigned to Bolboschoenus . Furthermore, it is not synonymous with Bolboschoenus planiculmis , but could be a synonym of Bolboschoenus maritimus subsp. paludosus (A. Nelson) T. Koyama.
Ecology and Biogeography
Abstract:
The genetic diversity of Bryum argenteum Hedw. was studied based on 252 samples from 11 inland and 32 island populations using Inter-Simple Sequence Repeat (ISSR) markers. Significant genetic differentiation between island and inland populations was detected, with a higher degree of differentiation found in the island populations (Gst=0.453) compared with the continental populations (Gst=0.387). There was a significant correlation between genetic differentiation of the tested samples and their geographical origin (r=0.478, n=175, P<0.001), indicating a significant effect of geographical isolation on genetic differentiation among the populations of mosses. Genetic variation among the island populations of B. argenteum was low, varying from 29.4% to 29.7% among populations. 43 populations were divided into 10 groups based on the ISSR results using cluster analysis. Both geographic origin and environmental heterogeneity exerted marked effects on the genetic diversity of B. argenteum. The spread of propagules was likely impacted by watershed isolation to a certain degree.
Abstract:
In this study, the litter of Pinus tabuliformis Carrière and five broadleaved species was mixed and placed in litterbags for six-month early-stage mixed litter decomposition. The mixed decomposition effects and interspecific impacts of broadleaved and P. tabuliformis species on decomposition were determined. Results indicated that:(1) mixed decomposition of P. tabuliformis and Betula albo-sinensis Burk., Catalpa fargesii Bur., and Populus purdomii Rehd. showed additive effects; however, the decomposition of P. tabuliformis litter was significantly accelerated, whereas the decomposition of broadleaf litter was significantly inhibited. Mixing P. tabuliformis and Eucommia ulmoides Oliver litter inhibited the decomposition of both types of litter, whereas mixing P. tabuliformis and Acer tsinglingense Fang et Hsieh litter showed contrary results. (2) Generally, the activities of sucrase, carboxymethyl cellulase, and polyphenol oxidase in the decomposition medium of mixtures of P. tabuliformis with B. albo-sinensis,C. fargesii, or P. purdomii were significantly higher than those in the decomposition medium (soil) of P. tabuliformis, whereas they were significantly lower than those in the decomposition medium of broadleaf litter. The mixed decomposition of P. tabuliformis and E. ulmoides resulted in significantly lower activities of the above-mentioned enzymes in the decomposition medium of the mixture compared with the activities in both types of single-specific decomposition medium, whereas the mixed decomposition of P. tabuliformis and A. tsinglingense exhibited contrasting impact. Considering the effects of mixed litter decomposition on the material cycling of the ecosystem, B. albo-sinensis,C. fargesii,P. purdomii, and A. tsinglingense could be used for transformation of pure P. tabuliformis forests; however, the inhibitory effects of mixing on litter decomposition of these species should be taken into consideration. As mixed plantation hindered nutrient cycling, E. ulmoides should not be mix-planted with P. tabuliformis.
Abstract:
Climate change in tundra areas is becoming increasingly important in the context of global climate change. In this study, we established a comprehensive monitoring system to investigate the characteristics of tundra vegetation on the Changbai Mountain, with data indicating that tremendous changes have emerged in vegetation communities. In addition, obvious differences were observed in the tundra vegetation on Changbai Mountain in regard to slope direction, with the pattern in species composition and diversity of vegetation change on the northern slope found to be quite different. Results showed that:(1) Shrubs on the southern slope were dominant among vegetation communities, consistent with that observed on the northern and western slopes. However, species composition showed obvious differences in regard to slope direction, suggesting a moderate level of dissimilarity. (2) Vegetation community characteristics (e[BF].[BFY]g. biodiversity, abundance, and coverage) on the southern and northern slopes were quite similar, but differed from those on the western slope. (3) Spatial characteristics of species diversity were the same on the southern and northern slopes, and showed a single peak at mid-altitude, whereas species diversity on the western slope increased monotonously with increasing altitude. These results indicated that distinctions existed in the anti-interference ability of the vegetation communities on the different slopes. Compared with the western slope, the southern and northern slopes shared a strong vegetation community anti-interference ability. (4) Changes in vegetation on each slope were quite different. Vegetation on the southern and northern slopes was relatively stable, which differed obviously from the strong upward invasion of herbaceous plants found on the western slope. The differences in tundra vegetation based on slope direction on Changbai Mountain were due to several reasons, including background differences of each slope, environmental differences, and different responses to global climate change. It is the combination of vegetation succession and change in response to climate change under the interference of volcanoes and strong winds.
Abstract:
Desert riparian forest is a typical temperate deciduous broad-leaved secondary forest and is mainly distributed in the Tarim Basin. To better understand the mechanisms of community dynamics and species coexistence of this forest type, six 1-hm2 plots were established and divided into 150 subplots. We analyzed species composition (e.g., importance value, abundance), community structure (e.g., vertical structure, size-class structure), spatial distribution of woody plants, and floristic composition. Results indicated that community structure of the desert riparian forest was simple and species diversity was low, with 16 species, belonging to 15 genera and 12 families identified. Salicaceae had the highest importance value (28.97%) and was the dominant family in the community. When the sampling area was larger than 0.04 hm2, 87.5% of species were counted. Rare and occasional species accounted for 12.5% of all species, respectively. Floristic composition was poor, with single species, genus, and temperate components being dominant, although ancient Mediterranean components also occupied an important position, with typical temperate flora. We counted 2497 living free-standing trees in the plots. Species abundance, basal area, and importance values showed that Populus pruinosa was the obviously dominant species. The number of families, genera, and species decreased with increasing height class, and the vertical structure was composed of canopy, shrub, and herb layers, indicating apparent vertical stratification in this forest. The average DBH of all trees was 15.57 cm, and DBH size and height classes showed skewed normal distributions, with few individuals with a height lower than 2 m, indicating weak regeneration across the community. The DBH structures of P. pruinosa and P. euphratica generally were unimodal; in particular, P. euphratica lacked small DBH trees and P. pruinosa had extremely high mortality during development from seedling to young tree, thus suggesting declining populations for these two species. The spatial distribution patterns of the two dominant species were clustered and varied with diameter in different habitats. In addition, the two dominant species were spatially mutually exclusive and occupied different habitats, suggesting that interspecific competition and habitat heterogeneity may be responsible for the species coexistence and spatial distribution of dominant species.
Abstract:
The endangered relict plant Tetraena mongolica Maxim was studied, with the MaxEnt and Bioclim models used to predict potentially suitable regions. We used the knife-cutting method and environmental variable response curves to evaluate the dominant environmental factors affecting the distribution of T. mongolica. Furthermore, we used the ArcGIS natural discontinuity method to divide fitness levels. Results showed that T. mongolica was mainly distributed in the Xinjiang Uygur Autonomous Region, Tibet Region, Ningxia Hui Autonomous Region, Inner Mongolia, and the Gansu, Qinghai, Shaanxi, Shanxi, Hebei, Liaoning, Jilin, and Heilongjiang provinces in China, with a total area of 1.49×106 km2. Highly suitable zones were found in the Maowusu Sandy Land of Wuhai city, the Tengger Desert in the Alxa Left Banner, the southeastern part of Yinshan Mountain, and mountains in the Helan range. The potential distribution area of T. mongolica will be reduced to north of Inner Mongolia and western Northeast China by 2050. The Area Under Curve (AUC) average values of the two models were all above 0.8, justifying their application for predicting potential areas of T. mongolica. Among the 19 environmental variables, the main factors affecting the potential distribution of T. mongolica were average precipitation of the coldest quarter and temperature annual range, followed by the coefficient of variation of precipitation seasonality and standard deviation (SD) of temperature seasonality.
Abstract:
For trees with DBH ≥ 1 cm, we recorded species name, DBH, height, and location within Castanopsis eyrie (Champ.) Tutch. community plots in Shimentai Reserve in northern Guangdong and Xiangtoushan Reserve in central Guangdong. Plant composition, distribution pattern, dominant species, and species diversity of the communities were analyzed. Results showed that there were 112 species of vascular plants belonging to 36 families and 54 genera in the Shimentai plot, and 109 species of vascular plants belonging to 36 families and 59 genera in the Xiangtoushan plot. Both communities showed observable tropical to subtropical transition. The Shimentai plot was closely related to eastern and central China, whereas the Xiangtoushan plot had more connections to western Pacific islands, namely Taiwan and Japan. Comparative study of community characteristics in the two regions showed a high similarity at the community level and similar plant diversity indices. However, latitude was not the determining factor of plant diversity. Microenvironment, community succession processes, and human factors had greater influences on plant diversity of the local communities.
Abstract:
To study the dynamic changes in C, N, and P content and stoichiometric ratios in desert plants during different growing periods, four desert herbaceous plants, (i.e., Agriophyllum squarrosum (L.) Moq., Bassia dasyphylla (Fisch.et Mey.) O. Kuntze, Ceratocarpus arenarius L., and Suaeda glauca (Bge.) Bge.), widely distributed in Gurbantünggüt Desert, were selected. Results indicated that:Seasonal dynamics of leaf C, N, and P content and C:N, C:P, and N:P mass ratios in the four herbaceous plants showed different trends throughout the whole growth period. The variation coefficients of each index during the different growth periods also demonstrated significant differences among species. Seasonal variation analysis of leaf C, N, and P content and their stoichiometric ratios showed that seasonal variations in N and P content and C:N and N:P ratios were larger, whereas variations in C and C:P were smaller. The seasonal variation coefficients of C and C:P in the four herbaceous species ranged from 2.43% to 15.80% and from 6.77% to 18.67%, respectively. Moreover, N and P content as well as the C:N and N:P ratios ranged from 21.26%-34.38%, 11.18%-30.26%, 18.52%-27.11%, and 14.90%-25.91%, respectively. The variation coefficients of C, N, and P content and stoichiometric ratios in the four herbaceous plants during the entire growth period were sorted as:N (30.00%) > C:N (22.87%) > N:P (20.12%) > P (17.76%) > C:P (11.72%) > C (9.02%). Overall, results showed that changes in C, N, and P content and stoichiometric ratios were significantly correlated with their growth periods and plant species.
Genetics and Breeding
Abstract:
Based on our previous transcriptome analysis, a new P450 hydroxylase gene was identified and named TcCYP725A22 according to homological analysis. The TcCYP725A22 cDNA was 1500 bp in length and encoded 499 amino acids. Bioinformatics predicted that the TcCYP725A22 protein contained a transmembrane region and catalytically active domains but no signal peptide. Functional analysis of TcCYP725A22 was carried out in Saccharomyces cerevisiae strain WAT11. Western blotting results indicated that the target protein was expressed successfully in WAT11. Furthermore, LC-MS analysis showed that TcCYP725A22 expressed in yeast was able to transform taxusin to its hydroxyl derivative, indicating that it had catalytic activity.
Abstract:
The vitamin E gene TaHGGT-7AL and two other copies were cloned from Triticum aestivum L. variety ‘Kenong 199’and the sequence structure and phylogenetic relationship of the protein sequence were analyzed by bioinformatics. Results showed that the coding region of the TaHGGT-7AL gene was 1227 bp in length, encoding a total of 408 amino acids; the sequence identity of TaHGGT-7AL with the two other copies was 95.45%. The TaHGGT-7AL protein sequence had nine α-helices and showed the sequence homology with grass HGGT protein of between 58.7% and 98.5%. The three TaHGGT genes were located on the 7AL, 7BL, and 7DL chromosomes of the genome, each having a conserved domain of the UbiA prenyltransferase family associated with the membrane and a transit peptide. Phylogenetic analysis showed that TaHGGT-7AL was closely related to gramineous plants. The qRT-PCR analysis results showed that TaHGGT-7AL was only expressed in T.aestivum hulls and grains, and the highest expression was observed 13 d after flowering. Under ABA, low temperature (4℃), drought, and dark stress treatments, the expression of TaHGGT-7AL was up-regulated compared with the control; after 24h of NaCl treatment, the expression increased, indicating that TaHGGT-7AL responds to abiotic stress.
Physiology and Development
Abstract:
Changes in the postharvest physiology and fruit quality of ‘Donghong’, a novel red-fleshed kiwifruit cultivar of Actinidia chinensis Planch., under ambient and cold storage were investigated to provide theoretical and technical guidelines for fruit preservation and marketing. ‘Donghong’ fruits from an orchard in Pujiang county, Sichuan Province, were collected and stored at ambient (20℃±1℃, relative humidity 70%-75%) and cold temperatures (1.5℃ ±0.5℃, relative humidity 90%-95%). The main physiological indices of the fruit, including fruit firmness, soluble solids content (SSC), total sugar (TS) content, titratable acidity (TA) content, SSC/TA and TS/TA ratios, vitamin C (Vc) content, weight loss rate, and rot rate, were measured once a week under ambient storage and every three weeks under cold storage. Results indicated that during both ambient and cold storage, fruit firmness dropped rapidly during the first three weeks and nine weeks of ambient and cold storage, respectively, then slowed down slightly until the end of storage. Four physiological indices, including SSC, TS content, and SSC/TA and TS/TA ratios, showed similar patterns during both ambient and cold storage, first increasing sharply and then maintaining a highly stable level during cold storage or continuing to rise slightly during ambient storage. TA showed a gradual decrease from 1.12% to 0.92% during ambient storage and from 1.12% to 0.94% during cold storage. Vc content gradually increased and reached a maximum of 134.40 mg/100 g after five weeks of ambient storage, or generally increased at first, then declined slightly, and finally reached a maximum of 151.13 mg/100 g after 18 weeks of cold storage. Both the weight loss and rot rates gradually increased with storage length under both temperatures, with a rapid increase under ambient storage and extremely slow increase under cold storage. Both indices reached a maximum level of 16.09% and 20% after 33 weeks of cold storage, respectively. The main physiological indices of the ‘Donghong’ fruit exhibited obvious changes in trends after three weeks of ambient storage and nine weeks of cold storage, respectively, after which the fruits reached optimal edibility. Moreover, the ‘Donghong’ fruit largely maintained a high quality, with a very low rate of fruit rot and rarely lignified flesh during the first 24 weeks of cold storage, revealing outstanding storability.
Abstract:
Rapeseed is one of the most important oil crops in China. Most oil in rapeseed is stored in the oil bodies. In this paper, the biogenesis of oil bodies and gene expression level variations in oil body proteins and fatty acid synthesis transcription factors were investigated during embryogenesis in two Brassica napus L. cultivars (‘Westar’ and ‘Topas’) via ultrastructural observation and real-time fluorescence quantitative PCR. Results showed that oil bodies existed in early embryos of B. napus, even in the embryo proper and suspensor, 9-11 d after pollination (globular embryo stage). The gene expression level of all oil body proteins (oleosins, steroleosins, and BnCLO1), except BnCLO3, increased at the heart embryo stage and continued to increase during the embryonic development stage. The gene expression levels of fatty acid synthesis transcription factors (BnLEC1, BnL1L, BnWRI1, and BnFUS3) increased at the early stages and decreased at the late stages, but their peak times were different. The gene expression level of BnLEC1 peaked first, followed by BnL1L, BnWRI1, and BnFUS3 last. Our results showed that oil bodies exist in early embryos of B. napus, even at the globular-embryo stage, and the gene expression level of their structural proteins and transcription factors increases from the heart-embryo stage.
Review
Abstract:
Nelumbo nucifera Gaertn. belongs to the aquatic perennial herbs of Nelumbonaceae. The N. nucifera seeds exhibit strong vitality and can survive for more than a thousand years under natural and even extreme conditions. With the improvement of N. nucifera genome sequencing and gene annotation, some progress has been made in the study of the longevity mechanism of N. nucifera seeds. In this paper, the longevity mechanism is summarized from aspects of structure, morphology, anti-aging, and self-repair, and the prospects and challenges of follow-up research are discussed.
Abstract:
Natural rubber is a critical resource for the national defense industry. The tropical para rubber tree (Hevea brasiliensis (Willd. ex A. Juss.) Muell. Arg) is the only commercial source of natural rubber, and the commercialization forms are relatively single. Thus, the potential supply shortages need to be solved urgently, with particular attention on alternative rubber producing crops. The roots of Taraxacum kok-saghyz Rodin (TKS) contain a high natural rubber content, with a similar molecular structure to that produced in the rubber tree. TKS is mainly distributed in temperate and cold zones and can easily be harvested by machine. Its life cycle is short, and genetic transformation is also relatively easy. Thus, TKS is considered a promising candidate for natural rubber production. This review summarized the development history and major achievements of previous studies on rubber grass over the past 90 (1931-2018) years. An in-depth analysis was performed to highlight new achievements from the past decade. We also predicted the future roles of TKS in the natural rubber industry. This review is expected to provide a useful reference and theoretical basis for further TKS research.