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25 February 2020, Volume 42 Issue 01
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  • Articles
    Strong intraspecific trait variation in a tropical dominant tree species along an elevational gradient
    Wumei Xu, Kyle W. Tomlinson, Jie Li
    2020, 42(01):  1-6.  doi:10.1016/j.pld.2019.10.004
    Abstract ( 238 )   HTML ( )   PDF (3860KB) ( 260 )   Save
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    Functional trait variation of plant species includes both inter- and intraspecific variation; however, traitbased plant ecology generally considers only interspecific variation while ignoring intraspecific variation. One reason for this neglect is that intraspecific variation may be negligible when compared to interspecific variation; however, direct comparisons between inter- and intraspecific variation of plant species are lacking, especially in tropical forests. Here we investigated intraspecific leaf trait variation (leaf area, specific leaf area, leaf thickness, leaf density, leaf chlorophyll content) of Pittosporopsis kerrii Craib (Icacinaceae), the most abundant tree species in the Xishuangbanna tropical seasonal rainforest in southwestern China, along an elevational gradient (703-824 m). We found a substantial range of intraspecific variation in P. kerrii that was never less than 22.1% of range of the interspecific variation among 462 tree species reported before in the same community. Moreover, with increased elevation, both leaf thickness and density increased and specific leaf area decreased significantly. It could be more important for the individuals of P. kerrii to produce thicker and denser leaves to tolerate environmental stress (e.g. soil water availability) rather than having high growth rates at the places with higher elevation in the Xishuangbanna tropical seasonal rainforest.
    Genetic characterization of the entire range of Cycas panzhihuaensis (Cycadaceae)
    Siyue Xiao, Yunheng Ji, Jian Liu, Xun Gong
    2020, 42(01):  7-18.  doi:10.1016/j.pld.2019.10.001
    Abstract ( 282 )   HTML ( )   PDF (4923KB) ( 120 )   Save
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    Cycas panzhihuaensis L. Zhou & S. Y. Yang (Cycadaceae) is an endangered gymnosperm species endemic to the dry-hot valley of the Jinsha River basin in southwest China. Although the wild C. panzhihuaensis population from Panzhihua Cycad Natural Reserve is well protected and its genetic diversity has been well assessed, the genetic characteristics of populations outside the nature reserve, which face larger risks of extinction, remain unknown. Furthermore, the population genetics and historical dynamics of this endemic and endangered species have not been examined across its entire range. In this study, to analyze the genetic diversity, phylogeographical structure and demographic history of C. panzhihuaensis from all its seven known locations, we sequenced and compared molecular data from chloroplastic DNA (psbA-trnH, psbM-trnD, and trnS-trnG), single-copy nuclear genes (PHYP, AC5, HSP70, and AAT) from 61 individuals, as well as 11 nuclear microsatellite loci (SSR) from 102 individuals. We found relatively high genetic diversity within populations and high genetic differentiation among populations of C. panzhihuaensis, which is consistent with the patterns of other Asian inland cycads. Although no significant phylogeographical structure was detected, we found that small and unprotected populations possess higher genetic diversity and more unique haplotypes, which revises our understanding of diversity within this species and deserves due attention. Analysis of demographic dynamics suggest that human activity might be the key threat to C. panzhihuaensis. Based on the genetic characterization of C. panzhihuaensis, we propose several practical guidelines for the conservation of this species, especially for the populations with small sizes.
    Crop wild relatives of Kazakhstani Tien Shan: Flora, vegetation, resources
    Gulnara T. Sitpayeva, Gulmira M. Kudabayevа, Liliya A. Dimeyeva, Nadezhda G. Gemejiyeva, Polina V. Vesselova
    2020, 42(01):  19-32.  doi:10.1016/j.pld.2019.10.003
    Abstract ( 138 )   HTML ( )   PDF (4141KB) ( 94 )   Save
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    This paper presents the results of the field study on species composition, geographical distribution, phytocoenotic diversity and resources of crop wild relatives (CWR) in Kazakhstan's ranges of the Tien Shan Mountains. Taxa of not only cultivated genera of crops are taken into account, but also a wider range of species of high socio-economic importance, including medicinal, fodder, essential oil and other species. List of CWR includes 289 species belonging to 39 families and 145 genera. Among them, 9 species listed in the Red Data book of Kazakhstan: Pistacia vera, Rheum wittrockii, Armeniaca vulgaris, Malus sieversii, Allium pskemense, Allochrusa gypsophilloides, Sorbus sibirica, Vitis vinifera and Artemisia cina. The highest plant diversity is recorded in intermountain plains and river valleys where meadow vegetation forms a high abundance of forage and resource plants. The diversity of wild fruit plants is concentrated in gallery forests. CWR of cereals are confined to dry steppe slopes in low piedmont belt. The populations of almond, pistachio, plum and cherry were recorded at dry slopes of low mountain belt. The estimation of the raw material base for 13 resource plants is given. Only Rumex tianschanicus, Berberis sphaerocarpa are recommended for industrial harvesting; for local pharmacy chain — Mentha longifolia, Origanum vulgare, O. vulgare subsp. gracile, Ziziphora clinopodioides, Hypericum scabrum, Hypericum perforatum, and five Rosa species.
    ROS and oxidative burst: Roots in plant development
    Anuj Choudhary, Antul Kumar, Nirmaljit Kaur
    2020, 42(01):  33-43.  doi:10.1016/j.pld.2019.10.002
    Abstract ( 212 )   HTML ( )   PDF (2589KB) ( 65 )   Save
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    Reactive oxygen species (ROS) are widely generated in various redox reactions in plants. In earlier studies, ROS were considered toxic byproducts of aerobic metabolism. In recent years, it has become clear that ROS act as plant signaling molecules that participate in various processes such as growth and development. Several studies have elucidated the roles of ROS from seed germination to senescence. However, there is much to discover about the diverse roles of ROS as signaling molecules and their mechanisms of sensing and response. ROS may provide possible benefits to plant physiological processes by supporting cellular proliferation in cells that maintain basal levels prior to oxidative effects. Although ROS are largely perceived as either negative by-products of aerobic metabolism or makers for plant stress, elucidating the range of functions that ROS play in growth and development still require attention.
    Impacts of CO2 elevation on the physiology and seed quality of soybean
    Guowei Zheng, Jia Chen, Weiqi Li
    2020, 42(01):  44-51.  doi:10.1016/j.pld.2019.09.004
    Abstract ( 161 )   HTML ( )   PDF (543KB) ( 35 )   Save
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    Understanding the responses of crops to elevated atmospheric carbon dioxide concentrations (E[CO2]) is very important in terms of global food supplies. The present study investigates the effects of CO2 enrichment (to 800 μmol mol-1) on the physiology of soybean plants and the nutritional value of their seeds under growth chamber conditions. The photosynthesis of soybean was significantly promoted by E [CO2] at all growth stages, but leaf area and specific leaf weight were not affected. The levels of mineral elements in the leaves decreased under E[CO2]. The soil properties after soybean cultivation under E[CO2] were not affected, except for a decrease in available potassium. Moreover, the levels of soluble sugars in the seeds were not affected by E[CO2], but the levels of natural antioxidants decreased. In addition, the level of oleic acid decreased under E[CO2]. However, levels of fatty acid peroxidation and saturation were maintained. In conclusion, E[CO2] appears to have positive effects on the growth of cultivated soybean plants, but its influence on the nutritional values of soybean seeds is complex.
    Genome-wide identification and characterization of the lateral organ boundaries domain gene family in Brassica rapa var. rapa
    Qin Yu, Simin Hu, Jiancan Du, Yongping Yang, Xudong Sun
    2020, 42(01):  52-60.  doi:10.1016/j.pld.2019.11.004
    Abstract ( 184 )   HTML ( )   PDF (8179KB) ( 58 )   Save
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    The Lateral Organ Boundaries Domain (LBD) genes encode highly conserved plant-specific LOB domain proteins which regulate growth and development in various species. However, members of the LBD gene family have yet to be identified in Brassica rapa var. rapa. In the present study, fifty-nine LBD genes were identified and distributed on 10 chromosomes. The BrrLBD proteins are predicted to encode hydrophobic polypeptides between 118 and 394 amino acids in length and with molecular weights ranging from 13.31 to 44.24 kDa; the theoretical pI for these proteins varies from 4.83 to 9.68. There were 17 paralogous gene pairs in the BrrLBD family, suggesting that the amplification of the BrrLBD gene family involved largescale gene duplication events. Members of the BrrLBD family were divided into 7 subclades (class I a to e, class II a and b). Analysis of gene structure and conserved domains revealed that most BrrLBD genes of the same subclade had similar gene structures and protein motifs. The expression profiles of 59 BrrLBD genes were determined through Quantitative Real-time fluorescent PCR (qRT-PCR). Most BrrLBD genes in the same subclade had similar gene expression profiles. However, the expression patterns of 7 genes differed from their duplicates, indicating that although the gene function of most BrrLBD genes has been conserved, some BrrLBD genes may have undergone evolutionary change.
    Defining the biosynthesis of ketocarotenoids in Chromochloris zofingiensis
    Ying Ye, Jun-Chao Huang
    2020, 42(01):  61-66.  doi:10.1016/j.pld.2019.11.001
    Abstract ( 141 )   HTML ( )   PDF (2051KB) ( 129 )   Save
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    Carotenoids are important pigments in photosynthetic organisms where they play essential roles in photoreception and photoprotection. Chromochloris zofingiensis is a unicellular green alga that is able to accumulate high amounts of ketocarotenoids including astaxanthin, canthaxanthin and ketolutein when growing heterotrophically or mixotrophically with glucose as a carbon source. Here we elucidate the ketocarotenoid biosynthesis pathway in C. zofingiensis by analyzing five algal mutants. The mutants were shown to have a single nucleotide insertion or substitution in β-carotene ketolase (BKT) gene 1, which resulted in a lack of ketocarotenoid production in Cz-bkt1-1, and decreased ketocarotenoid content in the other four mutants. These mutants accumulated much higher amounts of non-ketocarotenoids (β-carotene, zeaxanthin and lutein). Interestingly, the Cz-bkt1-5 mutant synthesized 2-fold the ketolutein and only 1/30 of the canthaxanthin and astaxanthin as its parent strain, suggesting that the mutated BKT1 exhibits much higher activity in catalyzing lutein to ketolutein but lower activity in ketolating β-carotene and zeaxanthin. Mutant and WT BKT2 gene sequences did not differ. Taken together, we conclude that BKT1 is the key gene involved in ketocarotenoid biosynthesis in C. zofingiensis. Our study provides insight into the biosynthesis of ketocarotenoids in green algae. Furthermore, Cz-bkt1 mutants may serve as a natural source for the production of zeaxanthin, lutein, and β-carotene.