Salinity-induced growth and some metabolic changes in three Salsola species

Three Salsola species, Salsola dendroides Pall., S. richteri (Moq.) Karel ex Litw. and S. orientalis S.C. Gmel., were compared for their salt tolerance, inorganic ionic accumulation and their biomass production in saline conditions. Seeds were grown on sterilized quartz under five salinity levels in a factorial experimental design, with four replications, in greenhouse conditions.With salinity, Na⁺ accumulation increased while K⁺ accumulation decreased. All three species showed positive shoot growth for low levels of salinity. Root growth showed almost the same trend as shoot growth, with minor exceptions. At low levels of salinity, proline accumulated more in S. dendroides plant tissues than in the tissues of the other two species. These results suggest that the proline accumulation is a good index for salinity tolerance. Soluble sugars also increased as a result of salinity.     

Identification of Kalidium species (Chenopodiaceae) by DNA barcoding

DNA barcoding is an increasingly prevalent molecular biological technology which uses a short and conserved DNA fragment to facilitate rapid and accurate species identification. Kalidium species are distributed in saline soil habitat throughout Southeast Europe and Northwest Asia, and used mainly as forage grass in China. The discrimination of Kalidium species was based only on morphology-based identification systems and limited to recognized species. Here, we tested four DNA candidate loci, one nuclear locus (ITS, internal transcribed spacer) and three plastid loci (rbcL, matK and ycf1b), to select potential DNA barcodes for identifying different Kalidium species. Results showed that the best DNA barcode was ITS locus, which displayed the highest species discrimination rate (100%), followed by matK (33.3%), ycf1b (16.7%), and rbcL (16.7%). Meanwhile, four loci clearly identified the variant species, Kalidium cuspidatum (Ung.-Sternb.) Grub.var. sinicum A. J. Li, as a single species in Kalidium.     

Distribution analysis ofAlliumL. species of the Dzhungarian Alatau

In the Dzhungarian Alatau, a large Asian mountain range, 33 species from the polymorphic genusAlliumL. have been found. They belong to the subgeneraRhizirideum,AlliumandMelanocrommyumand are distributed from the foothills to alpine belts. The geographical and genesis analysis of these species is given. Five species can be ascribed to the category of autochtonous of the region, among them one being endemic to the Dzhungarian Alatau.     

Seed germination of five Helianthemum species: Effect of temperature and presowing treatments

The germination behaviour of five Helianthemum species (H. almeriense, H. appeninum, H. cinereum, H. hirtum, H. squamatum) has been studied under controlled conditions. Constant 15, 20 or 25 °C and alternating 25/15 °C temperature regimes and 16/8 h light/dark photoperiod conditions were used. Presowing treatments applied were manual scarification, boiling water, hot water, dry heat and sulphuric acid. Germination values recorded were final germination percentage and germination rate expressed as days to reach 50% of the final germination percentage (T₅₀). Incubation temperature had no significant effect on final germination percentage for untreated seeds of the five Helianthemum species. However, variation due to temperature was significant for scarified seeds, with the lowest germination percentage attained at 25 °C. In all Helianthemum species studied, the highest germination percentages were obtained by manual scarification of seeds. Germination rate of scarified seeds decreased as germination temperature increased. The different presowing treatments investigated allowed some germination in some species, but none were any better than manual scarification. The high germination among most species studied, following mechanical rupture of the seed coat, shows that the mechanism of dormancy lies in the seed coat. The physical dormancy caused by impermeable seed-coat appears to be the main reason of poor germination of untreated seeds of Helianthemum species studied.     

Adaptive evolution of rbcL in Reaumuria soongarica (Tamaricaceae)

In the field of phylogenetic analyses, the rbcL gene encoded large subunit Ribulose-1,5-biphosphate carboxylase/oxygenase (Rubisco, EC4.1.1.39), which plays a crucial role in the process of photosynthesis for most terrestrial plants, has been considered to be conserved; however, recent controversy regarding rbcL conservation has appeared since it was proposed to be under natural selection within all principal lineages of land plants. In this study, by examining the variation of DNA and protein sequences among 17 species in the family Tamaricaceae, three nonsynonymous mutations were identified to be under positive selection. The favored sites were located in the alph-helix domains of Rubisco, with decreased hydrophobicity and increased entropy, which could facilitate CO₂ penetration into the active site of Rubisco. We also found that the expression level of rbcL in different genotypes of Reaumuria soongarica shifted in response to various stresses such as drought, temperature, salt, and light. This study not only sheds light on the functional/structural features of Rubisco in the evolution scenarios from C₃-like into C₄ in Tamaricaceae but also provides useful information on directing genetic performance to enhance photosynthesis efficiency of desert plants for sustaining fragile desert ecosystems; furthermore, it promotes the ability to cope with desert aridification and global warming.     

Growth response of the saltbush Atriplex nummularia L. to inoculation with the arbuscular mycorrhizal fungus Glomus intraradices

Plantlets of Atriplex nummularia were inoculated with the arbuscular mycorrhizal fungi Glomus intraradices in a pot experiment. Plants were grown in a low P soil. Highly significant growth response of a Chenopodiaceae was recorded for the first time. Mycorrhizal colonization of roots was well developed, internal hyphae and vesicles were observed, but not arbuscules. These observations suggest that arbuscules are not necessary to obtain significant growth stimulation from mycorrhizal inoculation. Atriplex nummularia is already used as forage crops, its high mycorrhizal dependency offers possibilities to develop this production and revegetation strategies.     

The diet of the Long-eared Owls, Asio otus, in the desert of northwest China

The contents of regurgitated Long-eared Owls (Asio otus) pellets collected in Minqin Desert Experimental Research Station of northwestern China were analysed. A total of 303 individuals representing five species of rodents and one of bird were identified in the pellets. By frequency, the most common species taken by Long-eared Owls was Meriones meridianus, followed by Cricetulus barabensis and Phodopus roborovskii. By biomass, Meriones meridianus was the most important species taken, followed by C. barabensis and Rhombomys opimus. Our results suggest that the Long-eared Owls were nocturnal hunters and fed on a wide range of animals with respect to their habitats.     

Distribution of Calanus species off Franz Josef Land (Arctic Barents Sea)

The spatial distribution of Calanus species was examined near Franz Josef Land archipelago in August 2006 and 2007. Surface and bottom water temperatures exceeded the average multiannual values. Calanus species dominated the total mesozooplankton abundance and biomass, accounting for 818 ± 178 individuals m⁻³ (mean ± SE) and 803 ± 163 mg wet weight (WW) m⁻³, respectively, in 2006. In 2007, the values were much lower (153 ± 29 individuals m⁻³ and 192 ± 17 mg WW m⁻³, respectively), reflecting the weaker influence of warm Atlantic water that year. Calanus glacialis dominated the Calanus populations, contributing 95% and 60% of the biomass in 2006 and 2007, respectively. Older copepodite stages (CIV–CV) predominated in the C. finmarchicus (69% and 76%, respectively) and C. hyperboreus populations (80% and 77%, respectively), whereas young copepodites (CI–CIII) were predominant in C. glacialis (45% and 59%, respectively). A clear negative relationship between the average water temperature and the total Calanus biomass was observed in 2006, whereas a positive correlation between these parameters was observed in 2007. The distributions of three Calanus species off Franz Josef Land were mainly associated with hydrological conditions and circulation patterns.     

Display-sites selection by houbara bustard (Chlamydotis [undulata] macqueenii) in Mori, Xinjiang, People''s Republic of China

Display-site selection by houbara bustards was studied in Mori, Xinjiang, China during the breeding seasons from April to June 2000. Most of the habitats chosen for displaying were short sub-shrubby and open areas close to high shrub patches. The displaying males clearly prefer low covered areas and avoid densely covered and high vegetation sites. The vegetation density and number of plant species at display sites were significantly lower from that at randomly selected sites. The average distance to the closest shrub patch was significantly shorter at display sites than at random sites. Plant species richness, vegetative density, vegetative cover and distance to the shrub patches are possibly the most important factors that determined the display-sites selection of houbara bustard.     

The effect of radiation on seedling growth and physiology in four species of Prosopis L. (Mimosaceae)

Domestication of wild plants needs efforts focused particularly on the development of the theoretical basis of plant responses to environmental conditions. The objective of this study was to assess the effect of radiation on seedling growth and physiology of Prosopis alba, P. chilensis, P. flexuosa and P. glandulosa. Seedlings were grown in a greenhouse and randomly assigned to three light environments: full-sun, 52% sun, and 38% sun. No significant differences were found in the rate of leaf appearance and plant height 60 days after the light treatments began. Instantaneous CO₂uptake was not affected by the light environment during leaf development and did not differ among species. Variations in radiation availability resulted in significant differences in biomass accumulation, shoot/root ratio, protein and total non-structural carbohydrates contents. The practice of shading seedlings reduces the chances of survival ofProsopis due to an increase of the shoot/root ratio and a reduction of total biomass, stored carbohydrates, and the C:N balance.     

Micropropagation of Acacia seyal Del. in vitro

In vitro mass propagation of Acacia seyal Del. was achieved using seedling shoot tip explants on Murashige and Skoog (MS) medium supplemented with 6-benzyladenine (BA) or Thidiazuron (TDZ) with ∝-Naphtalene acetic acid (NAA). The best result was obtained with BA in the presence of NAA. The greatest shoot multiplication with long shoots was observed on media containing (mg l^-1) 2·0 BA with 0·1 or 0·5 NAA and 4·0 BA with 0·1 NAA; with 6·4 and 6·7 mean number of shoots, respectively. TDZ also induced multiple shoots but most of the shoots were stunted. Microshoots were rooted better on half-MS salts supplemented with Indole-3-butyric acid (IBA). The highest rooting percentage (80%) and root number (4·9 roots/microshoot) were promoted by 4·0 mg IBA. The plantlets (90%) successfully survived acclimatization ex vitro.     

Competition as a barrier to establishment of a native perennial grass (Elymus elymoides) in alien annual grass (Bromus tectorum) communities

The alien grass Bromus tectorum dominates stable annual-plant communities that have replaced native shrub-perennial grass communities over much of the semi-arid western United States. We conducted field competition experiments between B. tectorum and a native grass, Elymus elymoides, on two sites to determine the effects of B. tectorum competition on perennial grasses, and the role of B. tectorum competition in the stability of B. tectorum-dominated communities. B. tectorum competition acting on seedling-stage E. elymoides plants greatly reduced first-year relative growth rates and biomass which, in turn, reduced second-year survival, biomass, and flowering. However, B. tectorum competition acting on older E. elymoides plants had much less effect, which may help to explain why intact perennial-plant communities are resistant to B. tectorum invasion. At the drier site, direct effects of B. tectorum competition were less, but competition and drier habitat combined to produce greater E. elymoides mortality.     

Salt stress induced apoptotic-like changes in Thellungiella halophila

With a view of studying programmed cell death （PCD） in a halophytic plant at the molecular level, we report here that apop-totic-like changes are induced by NaCl stress in Thellungiella halophila. The dose of 300 mM NaCl induced some apoptotic-like features in Thellungiella halophila cells, including the retraction of the plasma membrane from the cell wall, nuclear condensation, DNA laddering and the release of cytochrome c accompanying the increase of caspase 3-like protease activity. This process re-sulted in ultrastructural changes of mitochondria and Golgi bodies, and the appearance of autophagic vacuoles. This suggests that T. halophila suspension cell culture is an ideal system for studying severe salt stress-induced plant PCD. The results indicate that 300 mM NaCl stress-induced programmed cell death in T. halophila cells is similar to apoptosis and mitochondria play an impor-tant role in the early stage of plant PCD.     

Edible biomass production from some important browse species in the Sahelian zone of West Africa

Acacia senegal, Guiera senegalensis and Pterocarpus lucens, browse species important in the Sahelian zone of Burkina Faso were studied by the estimation of their phenological variation over time and the evaluation of edible biomass production, total and accessible directly to animals. Biomass production was also estimated using dendrometric parameters. All the three species started the foliation phase as soon as the rains started. A. senegal and P. lucens flowered before G. senegalensis and A. senegal lost leaves earlier. The fruiting phase lasted 6–7 months for all species. Accessible edible biomass varied according to the animal species, the plant species and the height of plants. G. senegalensis showed the highest proportion of accessible biomass, but P. lucens had higher total edible biomass. Goats browsing at higher height had more edible biomass at their disposal. The accessible edible biomass was weakly correlated with tree parameters, while crown diameter was the best parameter to predict total edible biomass production, with R² varying from 90% (G. senegalensis) to 98% (P. lucens) in log₁₀ transformation of dependent and independent variables. The single species models developed could be applied in similar agro-ecological zones, taking into account the height stratification of plants. Further investigations on others species are needed to be able to estimate total biomass available for browsing.     

Adaptation to living in an open arid environment: lessons from the burrow structure of the two southern African whistling rats, Parotomys brantsii and P. littledalei

This study examines interspecific differences in the architecture and field characteristics of the burrow systems of Brants' whistling rat, Parotomys brantsii, and Littledale's whistling rat, Parotomys littledalei. The two rodents are endemic to the arid west region of southern Africa. Both build complex burrow systems with numerous nest chambers and associated interconnecting tunnels, as well as a number of entrances. Burrow systems of P. littledalei are restricted to areas of good plant cover, whilst many P. brantsii burrows are situated in open locations with only limited plant cover. Further, the burrows of P. brantsii cover a much larger area than those of P. littledalei, with many more entrances. As P. brantsii feed predominantly within the boundaries of their burrows and not in the open veld, their burrow systems effectively serve as a predator refuge, into which this diurnal rodent can quickly run in the event of danger. Thus, by building large multi-holed burrow systems, P. brantsii have become independent of the protection offered by bush cover and can exist within relatively open areas within their distributional range. On the other hand, the reduced number of entrances to P. littledalei burrow systems may largely restrict this species to areas with adequate cover, including coastal and riverine bush, with which it is often associated.     

Comparison of the growth and biomass production of six acacia species in Riyadh, Saudi Arabia after 4 years of irrigated cultivation

The growth and biomass production of six acacia species were studied in the field for 4 years. The species used were Acacia asak, A. negrii, A. seyal, A. karroo, A. ampliceps, and A. stenophylla. The first three species are indigenous while the others are exotic. The results showed both A. ampliceps and A. asak with 100% survival while all A. negrii died. Acacia ampliceps attained the greatest height, diameter, relative growth rate and above-ground biomass while A. asak had the least. Height and diameter growth of acacia species decreased between warm and cold periods of the year.     

Foliar carbohydrate differs between Picea crassifolia and Sabina przewalskii with the altitudinal variation of Qilian Mountains, China

Nonstructural carbohydrates(NSC) and nitrogen metabolism strongly influence growth and development in plants. The biosynthesis of cellulose and lignin(structural carbohydrates, SC) depends largely on the supply of NSC. We desire to examine which hypothesis, carbon limitation or growth limitation, best fits the alpine plant response between NSC, SC, carbon(C), nitrogen(N) and altitude. We compared the foliar concentrations of carbohydrates, C and N between the leaves of Picea crassifolia(lower-elevation tree-line species) and Sabina przewalskii(high-elevation tree-line species) in their response to changing elevation. Our site was located in the mid-northern area of Qilian Mountains, China. We found that foliar soluble sugar(SG) concentrations were significantly higher in P. crassifolia than in S. przewalskii at the 2,700–3,400 m level. Foliar NSC levels in P. crassifolia increased at the 2,700–3,100 m level, indicating that growth was limited gradually resulting in a surplus of NSC(to conform to GLH), subsequently decreasing at the 3,100–3,400 m level, the assimilation declined leading to C deficit(to conform to CLH). SC(SC metabolism disorders at 3,100–3,400 m), C, N and starch were significantly lower in P. crassifolia than in S. przewalskii. Conversely, foliar SG concentration shows a fall-rise trend with increasing elevation for S. przewalskii. SC concentration in S. przewalskii leaves decreased with an increase of elevation and has a significantly positive correlation to N concentration marking the assimilation of plants. Therefore, the high-elevation tree-line species(S. przewalskii) utilize or store more foliar SG leading to a decrease of SG concentration for survival and growth/regrowth in an adverse environment, higher total C, N, SC, starch contents and lower NSC level. Also, their change trends along the elevational gradient in leaves of S. przewalskii indicate better assimilation strategies for SG use under environmental stress compared to P. crassifolia. This indicates that foliar C metabolism along the elevation follows the principle of the growth-limitation hypothesis(GLH) or carbon limitation hypothesis(CLH), which depends on the acclimation of different alpine life-forms to the environment.     

Spatial and temporal distribution of tenebrionid species (Coleoptera) in the Negev Highlands, Israel

Tenebrionid species composition and activity level were studied, using pitfall traps, in two sandy (dune and stabilized sand field) and four compact soil (wadi, north- and south-facing slopes, and loess plain) habitats in the Negev Desert Highlands, Israel. Each soil type had a distinctive species composition but habitats within soft types were similar both in species composition and phenologies. The number of species was not correlated with habitat primary production; it was low in sandy habitats (19 spp.) and high in compact soil (33 spp.) habitats. Within the compact soil habitats, large-size species were abundant only in the high plant-cover wadi, and the low plant-cover slopes and plain were dominated by smaller species. We suggest that low plant cover on the slopes and plain exposes large tenebrionids to predation by birds and limits them to the wadi where they are concealed and find refuge in the plant cover.