Optimal pollinator attraction strategies in Trollius ranunculoides Hemsl. (Ranunculaceae) at different altitudes: increased floral display or promotion of nectar output?

For alpine plant species, patterns of resource allocation to functional floral traits for pollinator attraction can be highly significant in adaptation to low pollinator abundance and consequent pollen limitation. Increased pollination can be achieved either through a larger floral display or production of more pollen rewards. In this study, variation in resource allocation to different components for pollinator attraction was studied along an altitudinal gradient in Trollius ranunculoides, an obligate self‐incompatible out‐crosser of the Qinghai–Tibet Plateau. We compared resource allocation to conspicuous yellow sepals (which mainly provide visual attraction) and degenerate petals (which provide the major nectar reward) between populations at four altitudes. Furthermore, we investigated the contribution of sepals and petals to pollinator attraction and female reproductive success in an experiment with sepal or petal removal at sites at different altitudes. At the level of single flowers, resource allocation increased to sepals but decreased to petals with increasing altitude. Consistent with these results, sepals contributed much more to visitation rate and seed set than petals, as confirmed in the sepal or petal removal experiment. Sepals and petals contributed to female reproductive success by ensuring visitation rate rather than visitation duration. To alleviate increasing pollen limitation with increasing altitude, resource allocation patterns of T. ranunculoides altered to favour development of sepals rather than petals. This strategy may improve pollination and reproductive success through visual attraction (sepal) rather than nectar reward (petal) over a gradient of decreasing pollinator abundance.     

Dry storage temperatures, duration, and salt concentrations affect germination of local and edaphic ecotypes of Hordeum spontaneum (Poaceae) from Israel

Hordeum spontaneum , the ancestor of cultivated barley, is mainly distributed in the Mediterranean zone of the Near East as well as in the Irano-Turanian steppes and Saharo-Arabian region; these areas receive unpredictable small amounts and distribution of rain followed by long, hot and dry summers. Caryopses of seven local ecotypes of H. spontaneum were collected in Israel from natural populations near Sede Boker, Neve Yaar, Tabigha and Mount Hermon. Three generations of these ecotypes were grown in natural conditions at Sede Boker with additional irrigation. The germination of caryopses of the third generation was tested. Due to the self pollination and atelechoric system of seed dispersal of this species, genetic ecophysiological diversity of afterripening and salt tolerance was found between the ecotypes originating from different areas, even within local populations and patches of plants that grew on different types or depths of soil at a distance of only a few meters from each other. Afterripening is important to prevent the caryopses from germinating shortly after maturation after a late rain at the beginning of the dry summer. Germination of the different ecotypes is regulated by temperature and length of post-maturation dry storage, as well as temperatures during wetting, and salinity.     

Reactivity of trypsin in reverse micelles: neglected role of aggregate size compared to water-pool components

The catalytic efficiency of trypsin was estimated in cationic reverse micelles as a function of the concentration of water-pool components and aggregate size to determine their independent influence on enzyme activity. The variation in the aggregate size/water-pool size was achieved by changing both the W0 (mole ratio of water to surfactant) and the headgroup area of surfactant through introduction of hydroxyethyl groups at the polar head. The local molar concentrations of water present inside the water-pool ([H2O]wp) of different cationic reverse micelles across varying W0 was estimated using a modified phenyl cation-trapping protocol. The [H2O]wp in cationic reverse micelles (surfactant/isooctane/n-hexanol/water) increases with W0 and attains the molarity of normal water beyond W0=40 irrespective of the nature of headgroup. Concurrently, the catalytic activity of trypsin compartmentalized within the water-pool increases with the increase in [H2O]wp upto an optimal W0=40 in organized solutions of any surfactant. The aggregate size (determined by static light scattering) also increases expectedly with W0 and noticeably with the area of the surfactant headgroup at similar W0. Since the enzyme activity rises both with the increase in water-pool size and [H2O]wp, trypsin's efficiency was compared with these two parameters across reverse micelles of varying surfactant headgroup size at similar W0 to determine their probable independent influence in regulating the enzyme activity. Noticeably, the efficiency of trypsin rises two to ninefold in spite of the [H2O]wp being distinctly lower in case of hydroxyethyl group substituted surfactants compared to cetyltrimethylammonium bromide w/o microemulsions at similar W0. Thus, the influence of the aggregate size possibly plays an important role alongwith the [H2O]wp in modulating the enzyme activity.     

Specific contributions of histone tails and their acetylation to the mechanical stability of nucleosomes

The distinct contributions of histone tails and their acetylation to nucleosomal stability were examined by mechanical disruption of individual nucleosomes in a single chromatin fiber using an optical trap. Enzymatic removal of H2A/H2B tails primarily decreased the strength of histone-DNA interactions located approximately +/-36bp from the dyad axis of symmetry (off-dyad strong interactions), whereas removal of the H3/H4 tails played a greater role in regulating the total amount of DNA bound. Similarly, nucleosomes composed of histones acetylated to different degrees by the histone acetyltransferase p300 exhibited significant decreases in the off-dyad strong interactions and the total amount of DNA bound. Acetylation of H2A/H2B appears to play a particularly critical role in weakening the off-dyad strong interactions. Collectively, our results suggest that the destabilizing effects of tail acetylation may be due to elimination of specific key interactions in the nucleosome.     

Differences in regulation of the first two M-phases in Xenopus laevis embryo cell-free extracts

The first embryonic M-phase is special, being the time when paternal and maternal chromosomes mix together for the first time. Reports from a variety of species suggest that the regulation of first M-phase has many particularities; however, no systematic comparative study of the biochemical aspects of first and the following M-phases has been previously undertaken. Here, we ask whether the regulation of the first embryonic M-phase is modified, using Xenopus cell-free extracts. We developed new types of extract specific for the first and the second M-phase obtained either from parthenogenetic or from in vitro fertilized embryos. Analyses of these extracts confirmed that the amplitude of histone H1 kinase activity reflecting CDK1/cyclin B (or MPF for M-phase Promoting Factor) activity is higher and persists longer than during the second M-phase, and that levels of cyclins B1 and B2 are correspondingly higher during the first than the second embryonic M-phase. Inhibition of protein synthesis shortly before M-phase entry reduced mitotic histone H1 kinase amplitude, shortened the period of mitotic phosphorylation of chosen marker proteins, and reduced cyclin B1 and B2 levels, suggesting a role of B-type cyclins in regulating the duration of mitotic events. Moreover, addition of exogenous cyclin B to the extract prior the second mitosis brought forward the activation of mitotic histone H1 kinase but prolonged the duration of this activity. We also confirmed that the inhibitory phosphorylation of CDK1 on tyrosine 15 oscillates between the first two embryonic M-phases, but is clearly more pronounced before the first than the second mitosis, while the MAP kinase ERK2 tended to show greater activation during the first embryonic M-phase but with a similar duration of activation. We conclude that discrete differences exist between the first two M-phases in Xenopus embryo and that higher CDK1/cyclin B activity and B-type cyclin levels could account for the different characteristics of these M-phases.     

A multi-scale perspective of water pulses in dryland ecosystems: climatology and ecohydrology of the western USA

In dryland ecosystems, the timing and magnitude of precipitation pulses drive many key ecological processes, notably soil water availability for plants and soil microbiota. Plant available water has frequently been viewed simply as incoming precipitation, yet processes at larger scales drive precipitation pulses, and the subsequent transformation of precipitation pulses to plant available water are complex. We provide an overview of the factors that influence the spatial and temporal availability of water to plants and soil biota using examples from western USA drylands. Large spatial- and temporal-scale drivers of regional precipitation patterns include the position of the jet streams and frontal boundaries, the North American Monsoon, El Niño Southern Oscillation events, and the Pacific Decadal Oscillation. Topography and orography modify the patterns set up by the larger-scale drivers, resulting in regional patterns (10²–10⁶ km²) of precipitation magnitude, timing, and variation. Together, the large-scale and regional drivers impose important pulsed patterns on long-term precipitation trends at landscape scales, in which most site precipitation is received as small events (<5 mm) and with most of the intervals between events being short (<10 days). The drivers also influence the translation of precipitation events into available water via linkages between soil water content and components of the water budget, including interception, infiltration and runoff, soil evaporation, plant water use and hydraulic redistribution, and seepage below the rooting zone. Soil water content varies not only vertically with depth but also horizontally beneath versus between plants and/or soil crusts in ways that are ecologically important to different plant and crust types. We highlight the importance of considering larger-scale drivers, and their effects on regional patterns; small, frequent precipitation events; and spatio-temporal heterogeneity in soil water content in translating from climatology to precipitation pulses to the dryland ecohydrology of water availability for plants and soil biota.     

Female moths of cotton bollworm (Lepidoptera: Noctuidae) captured by waterbasin traps baited with synthetic female sex pheromone

Cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), is one of the most important pest insects in cotton fields in China. Female moths were captured by waterbasin traps with a synthetic female sex pheromone blend in cotton fields over three years. The blend contained (Z)‐11‐hexadecenal and (Z)‐9‐hexadecenal with a ratio of 97:3. Each pheromone dispenser was impregnated with 2.0 mg of pheromone blend and 0.2 mg of antioxidant dissolved with 0.1 mL of hexane, and there was a control dispenser with a similar amount of antioxidant and solvent only. Waterbasin traps were deployed in three configurations in the fields. ‘A’ was pheromone traps only, ‘B’ was both pheromone and control traps, ‘C’ was control traps only. (i) In four plots of ‘A’, the average weekly female catch was 1.5, and more females were captured by centrally located pheromone traps, (ii) In three plots of ‘Brsquo;, control traps also captured female as well as male moths, but average weekly female catches of control traps was significantly lower than that in pheromone‐baited traps. (iii) There were significant linear relationships between the average weekly female catch and the corresponding layer in pheromone‐baited traps in both ‘A’ and ‘B’ plots, and in quadratic equations in control in ‘B’ plots. (iv) With the increase of the interval of traps, average weekly female catches per trap increased but average weekly female catches per hectare decreased. (v) Among the female moths captured by pheromone traps, 88.3% were mated female moths which each containing 1.46 spermatophores, while in control traps 86.9% of the mated female moths had 0.90 spermatophores. There was a significant difference between the average numbers of spermatophores of mated females in pheromone traps and in controls.     

大猿叶虫交配行为的观察

大猿叶虫Colaphellus bowringi Baly是十字花科上的重要害虫,一生能多次交配。本试验在25℃,光周期L∶D=12∶12条件下观察了大猿叶虫成虫连续7d的交配行为。结果表明:(1)每日平均交配(5.67±0.26)次,最高可达11次,不同日龄间的交配次数存在显著差异。(2)平均每日用于交配的时间为(238±10)min,占总时间的33.5%,最长可达493min,占总时间的68.5%,不同日龄间的交配时间有极显著差异。(3)交配持续时间最短8min,最长达289min,平均为(48±2)min;同一日内,随着交配次数增加,交配持续时间逐渐缩短;不同日龄间的交配持续时间存在显著差异。(4)相邻两次交配之间的间隔时间最短5min,最长300min,平均交配间隔(75±3)min;交配间隔时间随日龄的增加而明显延长。