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Liu J.,CAS Kunming Institute of Botany | Liu J.,University of Chinese Academy of Sciences | Zhou W.,CAS Kunming Institute of Botany | Gong X.,CAS Kunming Institute of Botany | Gong X.,Yunnan Key Laboratory for Wild Plant Resources
Frontiers in Plant Science | Year: 2015

Delimitating species boundaries could be of critical importance when evaluating the species' evolving process and providing guidelines for conservation genetics. Here, species delimitation was carried out on three endemic and endangered Cycas species with resembling morphology and overlapped distribution range along the Red River (Yuanjiang) in China: Cycas diananensis Z. T. Guan et G. D. Tao, Cycas parvula S. L. Yang and Cycas multiovula D. Y. Wang. A total of 137 individuals from 15 populations were genotyped by using three chloroplastic (psbA-trnH, atp\-atpH, and trnL-rps4) and two single copy nuclear (RPB1 and SmHP) DNA sequences. Basing on the carefully morphological comparison and cladistic haplotype aggregation (CHA) analysis, we propose all the populations as one species, with the rest two incorporated into C. diannanensis. Genetic diversity and structure analysis of the conflated C. diannanensis revealed this species possessed a relative lower genetic diversity than estimates of other Cycas species. The higher genetic diversity among populations and relative lower genetic diversity within populations, as well as obvious genetic differentiation among populations inferred from chloroplastic DNA (cpDNA) suggested a recent genetic loss within this protected species. Additionally, a clear genetic structure of C. diannanensis corresponding with geography was detected based on cpDNA, dividing its population ranges into “Yuanjiang-Nanhun” basin and “Ejia-Jiepai” basin groups. Demographical history analyses based on combined cpDNA and one nuclear DNA (nDNA) SmHP both showed the population size of C. diannanensis began to decrease in Quaternary glaciation with no subsequent expansion, while another nDNA RPB1 revealed a more recent sudden expansion after long-term population size contraction, suggesting its probable bottleneck events in history. Our findings offer grounded views for clarifying species boundaries of C. diannanensis when determining the conservation objectives. For operational guidelines, the downstream populations which occupy high and peculiar haplotypes should be given prior in-situ conservation. in addition, ex-situ conservation and reintroduction measures for decades of generations are supplemented for improving the population size and genetic diversity of the endemic and endangered species. © 2015 Liu, Zhou and Gong.

Li J.-W.,CAS Kunming Institute of Botany | Li J.-W.,Yunnan Key Laboratory for Wild Plant Resources | Li J.-W.,University of Chinese Academy of Sciences | Zhang S.-B.,CAS Kunming Institute of Botany | Zhang S.-B.,Yunnan Key Laboratory for Wild Plant Resources
Frontiers in Plant Science | Year: 2016

The susceptibility of photosystem I (PSI) and photosystem II (PSII) to chilling stress depends on plant species, and cyclic electron flow (CEF) plays an important role in photoprotection for some species under short stress periods. However, little is known about the responses of PSI and PSII to long-term chilling stress. We studied two orchid species—Cymbidium sinense and C. tracyanum— that differ in their capacity to adapt to low temperature, and exposed plants for 19 d to stress conditions that included 4°C and a light intensity of 250 to 350 µmol photons m−2 s−1. Meanwhile, we investigated their dynamic variations in Chl fluorescence and P700 parameters. After exposure to 4°C and 250 µmol photons m−2 s−1 for 6 h, PSI activity was maintained stable in both species, but stronger PSII photoinhibition was observed in C. sinense. During the long-term treatment, the maximum quantum yield of PSII was significantly reduced, with that decrease being greater in C. sinense. After 19 d of chilling treatment, the maximum photo-oxidizable P700 declined only slightly in C. tracyanum but dropped significantly in C. sinense. Linear electron flow was largely depressed during the long-term chilling treatment, especially in C. sinense. Meanwhile, C. tracyanum showed higher CEF activity than C. sinense. These results indicate that PSII is more sensitive to chilling-light stress than PSI in both species. The rate of PSII photodamage at chilling-light stress is higher in C. sinense than C. tracyanum, and CEF contributes to photoprotection for PSI and PSII under long-term chilling stress in C. tracyanum. © 2016 Li and Zhang.

Zhang S.-B.,CAS Kunming Institute of Botany | Zhang S.-B.,Yunnan Key Laboratory for Wild Plant Resources | Dai Y.,CAS Xishuangbanna Tropical Botanical Garden | Hao G.-Y.,CAS Shenyang Institute of Applied Ecology | And 4 more authors.
Frontiers in Plant Science | Year: 2015

Epiphytes that grow in the canopies of tropical and subtropical forests experience different water regimes when compared with terrestrial plants. However, the differences in adaptive strategies between epiphytic and terrestrial plants with respect to plant water relations remain poorly understood. To understand how water-related traits contrast between epiphytic and terrestrial growth forms within the Cymbidium (Orchidaceae), we assessed leaf anatomy, hydraulics, and physiology of seven terrestrial and 13 epiphytic species using a common garden experiment. Compared with terrestrial species, epiphytic species had higher values for leaf mass per unit area (LMA), leaf thickness (LT), epidermal thickness, saturated water content (SWC) and the time required to dry saturated leaves to 70% relative water content (T70). However, vein density (Dvein), stomatal density (SD), and photosynthetic capacity (Amax) did not differ significantly between the two forms. T70 was positively correlated with LT, LMA, and SWC, and negatively correlated with stomatal index (SI). Amax showed positive correlations with SD and SI, but not with Dvein. Vein density was marginally correlated with SD, and significantly correlated with SI. Overall, epiphytic orchids exhibited substantial ecophysiological differentiations from terrestrial species, with the former type showing trait values indicative of greater drought tolerance and increased water storage capacity. The ability to retain water in the leaves plays a key role in maintaining a water balance in those epiphytes. Therefore, the process of transpiration depends less upon the current substrate water supply and enables epiphytic Cymbidium species to adapt more easily to canopy habitats. © 2015 Zhang, Dai, Hao, Li, Fu and Zhang.

Bi Y.,Chinese Academy of Sciences | Bi Y.,CAS Kunming Institute of Botany | Bi Y.,University of Chinese Academy of Sciences | Bi Y.,Yunnan Key Laboratory for Wild Plant Resources | And 15 more authors.
International Journal of Climatology | Year: 2015

Southwest China has experienced significant drought during the past few years. To better understand the tendency of drought changes over time, this study applies dendroclimatological techniques to assess drought variations in Lijiang Prefecture, southwest China. So far, the longest chronology (387 years) of Picea likiangensis on the Jade Dragon Snow Mountain was constructed, and the relationships between the tree-ring width and climate variables were analysed. The spring season Palmer Drought Severity Index (PDSI) was reconstructed based on a standard chronology. Tree-ring width is positively related to precipitation and relative humidity from February to March and the PDSI from January to May. Conversely, tree-ring width is also negatively related with mean temperature from January to May, suggesting that growth of P. likiangensis is affected both by temperature and precipitation. The reconstructed PDSI showed that the Jade Dragon Snow Mountain has experienced considerable variations in spring drought conditions during the past 361 years. Four distinct periods were recognized: (1) 1650-1730, a relatively humid period with an average PDSI value above zero; (2) 1730-1860, a period with greatly fluctuating PDSI and intermittent wet periods (1746-1755, 1782-1800, and 1820-1830) and several dry periods (1735-1745, 1756-1780, 1810-1820, and 1830-1860); (3) 1870-1945, a humid period, with the highest PDSI value during 1930-1945; and (4) 1945-2011, a period with decreasing humidity. The results are consistent with hydrological studies in nearby regions and related species, as well as historical records of natural disasters. The recently observed spring drought follows a trend of decreasing humidity over the past 60 years, suggesting that a sound strategy for management and land-use planning is required to secure ecosystem and human well-being. © 2015 Royal Meteorological Society.

Zhang W.,CAS Kunming Institute of Botany | Zhang W.,Yunnan Key Laboratory for Wild Plant Resources | Zhang W.,University of Chinese Academy of Sciences | Hu H.,CAS Kunming Institute of Botany | And 3 more authors.
Frontiers in Plant Science | Year: 2016

Due to the fluctuating water availability in the arboreal habitat, epiphytic plants are considered vulnerable to climate change and anthropogenic disturbances. Although co-occurring taxa have been observed divergent adaptive performances in response to drought, the underlying physiological and morphological mechanisms by which epiphyte species cope with water stress remain poorly understood. In the present study, two co-occurring epiphytic orchids with different phenologies were selected to investigate their drought-resistance performances. We compared their functional traits, and monitored their physiological performances in a 25-days of drought treatment. In contrast to the deciduous species Pleione albiflora, the evergreen species Coelogyne corymbosa had different root anatomical structures and higher values for saturated water content of pseudobulbs. Moreover, plants of C. corymbosa had thicker leaves and epidermis, denser veins and stomata, and higher values for leaf mass per unit area and the time required to dry saturated leaves to 70% relative water content. However, samples from that species had lower values for net photosynthetic rate (An), stomatal length and chlorophyll content per unit dry mass. Nevertheless, due to greater capacity for water storage and conservation, C. corymbosa maintained higher An, stomatal conductance (gs), and instantaneous water-use efficiency during severe drought period, and their values for leaf water potential were higher after the water stress treatment. By Day 10 after irrigation was restarted, only C. corymbosa plants recovered their values for An and gs to levels close to those calculated prior to the imposition of water stress. Our results suggest that the different performance responding to drought and re-watering in two co-occurring epiphytic orchids is related to water-related traits and these two species have divergent adaptive mechanisms. Overall, C. corymbosa demonstrates drought avoidance by enhancing water uptake and storage, and by reducing water losses while P. albifloraemploys a drought escape strategy by fixing more carbon during growing season and shedding leaves and roots at dry season, leaving a dormant pseudobulb to minimize transpiration. These findings may improve our understanding of the potential effects that climate change can have on the population dynamics of different epiphytic taxa. © 2016 Zhang, Hu and Zhang.

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