Maternal salinity environment affects salt tolerance during germination in Anabasis setifera： A facultative desert halophyte

The effects of maternal salinity and light incubation on the salinity tolerance of the facultative halophyte Anabasis setifera during their germination stages were assessed. Seeds were collected from non-saline habitats in Egypt and saline habitats in the United Arab Emirates （UAE）. The seeds of the two populations were germinated in 0, 100, 200, 400, 600 and 800 mM NaCI, and incubated at 25℃/15℃ in both 12-h light and 12-h darkness regimes and continuous darkness. Significantly more seeds germinated in the Egyptian population than in the UAE population. Salinity tolerance was significantly greater with the Egyptian population than with the UAE population, especially under the conditions of higher salinities. The difference in salinity tolerance between the seeds of two populations was attributed to their seed mass. In addition, germination was significantly faster for the Egyptian population than for the UAE population. Most of the saline treated seeds were able to recover their germination when transferred to distilled water, but this depended on their maternal salinity and light incubation. Recovery from higher salinities was significantly better for the seeds under darkness than for those under light in the UAE population, but the reverse was true for the seeds in the Egyptian population. The higher salinity tolerance for the A. setifera seeds from the non-saline Egyptian population and the lower salinity tolerance for the seeds from the saline UAE population cannot explain their natural distribution. Further studies about other possible roles, such as levels of different promoting and inhibiting phytohormones, are needed to understand the importance of salinity as an environmentally induced maternal effect.

Assessing Conservation Values of Forest Communities in Nanda Devi Biosphere Reserve: Plant Diversity, Species Distribution and Endemicity

Present study has been conducted in a biodiversity rich Nanda Devi Biosphere Reserve between 2000-3800 m in two different forest physiognomy holding sites to analyze the structure and composition of the forest communities including richness of native, non native and endemic species,and suggest conservation values at community and reserve level.A total of 60 sites were sampled and grouped in 11 and 8 communities for two representative sites Pindari-Sunderdhunga-Kafni(PSK) and Lata-Tolma-Phagti(LTP) respectively.From the sampled sites, 451 species(11.8%, 53 trees;17.71%, 80 shrubs; and 70.51%, 318 herbs) have been recorded.In general, PSK site represented 73.6% and LTP site represented only 54.9% of the total plant species recorded in the study area.Out of total species in PSK site, native species contributed 59.6%(198spp.) and 24.7% species were endemic and near endemic.In LTP site, 66.5% species were Himalayan natives and 33.5% were endemic and near endemic.The species richness ranged from 4-23 ind ha-1(tree),3-18 ind ha-1(sapling), 5-19 ind ha-1(seedling) in PSK site and 4-18 ind ha-1(tree), 4-11 ind ha-1(sapling), 4-16 ind ha-1(seedling) in LTP site.The density ranged from 260-535 ind ha-1(tree), 145-633 ind ha-1(sapling), 1450-8170 ind ha-1(seedling) in PSK site and 599-1211 ind ha-1(tree), 70-951 ind ha-1(sapling),470-1665 ind ha-1(seedling) in LTP site.Species diversity for trees ranged from 0.73-3.37, saplings,0.64-2.67, seedlings, 0.70-2.51, shrubs, 1-2.34 and herbs, 2.02-3.21 in PSK site and 0.63-1.61, saplings,0.76-1.36, seedlings, 0.35-1.79, shrubs, 0.98-2.73 and herbs, 2.48-3.61 in LTP site.These recorded values were almost comparable with the studies conducted in sub-tropical, temperate and sub-alpine regions of the west Himalaya.In some cases the values were slightly higher than the reported values.The important communities with high conservation values have been identified based on different ecological parameters and species distribution.Among all the prioritized communities, Mixed Silver firRhododendron-Maple community in PSK site and Taxus wallichana- A.pindrow mixed community in LTP site supports maximum richness and density of native and endemic species.This study calls for development of adequate strategy and action plan for the conservation and management of habitats, species,and communities under changing climate and socioeconomic scenarios, so that sustainable utilization of the species could be ensured.

Evaluating germinability of eight desert halophytes under long-term seed storage: Implications for conservation

Ex situ conservation in seed banks is a potential complementary conservation strategy for native plant species.It is well established that ex situ seed banking of native wild plants prolongs seed viability and thereby preserves genetic and species diversity for future use.We evaluated ex situ storage potential of eight halophytic species from deserts in the United Arab Emirates(UAE)by studying seed germination.Specifically,we examined the germinability of freshly collected seeds and seeds stored for three years in a seed bank.We also examined the effect of light conditions on fresh and stored seed germination.Fresh seeds of seven of the eight species tested had a higher germination rates under 12/12 h light/dark fluctuations than did those exposed to total darkness.Storage reduced light sensitivity in Halocnemum strobilaceum,Suaeda aegyptiaca,Salsola drummondii and Salsola imbricata,but increased the requirement for light in Arthrocnemum macrostachyum.In Anabasis setifera,storage decreased germination percentage when there was a 12-hour light/dark fluctuation,but increased germination rate when exposed to the dark treatment.Storage significantly reduced germination in both the light/dark and dark treatments in Suaeda vermiculata and S.aegyptiaca.Germination speed also responded differently to storage;whereas Timson's index significantly increased in A.macrostachyum and H.strobilaceum,it significantly decreased for S.drummondii,S.aegyptiaca and S.vermiculata.Germination of these species at a range of temperatures requires further testing;additionally,we strongly suggest that these laboratory findings be complemented by field studies.

Delayed seed dispersal species and related traits in the desert of the United Arab Emirates

The ability of plants to safely retain seeds in the mother plant is an adaptive mechanism described in many desert plants.However,research about delayed seed dispersal species in the desert of the United Arab Emirates(UAE)is lacking.This study aims to identify these delayed seed dispersal species and assess the relationships of the presence of delayed seed dispersal with plant growth form,habit,spatial dispersal,antitelechoric mechanism,and seed release time.The relationships between the presence of delayed seed dispersal and the above studied traits were assessed by using the Pearson Chi-square test and Nonlinear Principal Components Analysis(NLPCA).Results showed that a total of 46 delayed seed dispersal species were recorded(15.0%of 307 studied species)and the highest incidence occurred in the Fabaceae family(17.4%).Delayed seed dispersal species were predominantly perennial plants(73.9%)with spatial restricted dispersal(67.4%),which released seed in the dry season(45.7%).The dominant groups of delayed seed dispersal species were persistent fruits species and synaptospermy(28.3%).All graminoids showed persistent lignified fruits,while prostrate annuals were basicarpic species with myxospermy.Sandy habitats had the highest number of delayed seed dispersal species(54.3%),whereas salt flats had the lowest(23.9%).In the desert of the UAE,delayed seed dispersal species spread seeds until the end of the dry and windy season,thus breaking seed dormancy at this time and ensuring seed germination in the next arrival of the rainy season.This morphological and ecological adaptation of delayed dispersal species is essential to the survival and sustainable development of vegetation in desert environments.

Enhanced photocatalytic activities of silicon nanowires/graphene oxide nanocomposite:Effect of etching parameters

Homogeneous and vertically aligned silicon nanowires(SiNWs)were successfully fabricated using silver assisted chemical etching technique.The prepared samples were characterized using scanning electron microscopy,transmission electron microscopy and atomic force microscopy.Photocatalytic degradation properties of graphene oxide(GO)modified SiNWs have been investigated.We found that the SiNWs morphology depends on etching time and etchant composition.The SiNWs length could be tuned from 1 to 42μm,respectively when varying the etching time from 5 to 30 min.The etchant concentration was found to accelerate the etching process;doubling the concentrations increases the length of the SiNWs by a factor of two for fixed etching time.Changes in bundle morphology were also studied as function of etching parameters.The SiNWs diameter was found to be independent of etching time or etchant composition while the size of the SiNWs bundle increases with increasing etching time and etchant concentration.The addition of GO was found to improve significantly the photocatalytic activity of SiNWs.A strong correlation between etching parameters and photocatalysis efficiency has been observed,mainly for SiNWs prepared at optimum etching time and etchant concentrations of 10 min and 4:1:8.A degradation of92%was obtained which further improved to 96%by addition of hydrogen peroxide.Only degradation efficiency of 16%and 31%has been observed for bare Si and GO/bare Si samples respectively.The obtained results demonstrate that the developed SiNWs/GO composite exhibits excellent photocatalytic performance and could be used as potential platform for the degradation of organic pollutants.