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971.
J. Amos R. G. Hatton T. N. Hoblyn R. C. Knight 《The Journal of Horticultural Science and Biotechnology》2013,88(3):248-258
SummaryThe effects of seed coat removal and chilling on the germination of seeds of ten cultivars of ornamental peach (Prunus persica Batsch) were investigated. Seeds were rinsed in running tap water for 48 h in order to facilitate seed coat removal. Only a few non-chilled, intact seeds germinated (e.g., 6% of ‘Hito’ seeds). Seed coat removal and no chilling resulted in some seed germination in eight of the ten cultivars, ranging from 6% to 83%. Chilling intact seeds at 5°C for up to 10 weeks resulted in greater frequencies of germination (average = 85% germination) than seed coat removal before (average = 80%) or after chilling (average = 73%). There was a linear decrease in the germination percentage with an increase in abscisic acid (ABA) content for ‘Yaguchi’,‘Kanpaku’, and ‘Kikumomo’ seeds (R = –0.66; P <0.001). The most consistent decrease in total seed ABA content (average of 64%) occurred during the 48 h rinsing period. In ‘Kanpaku’, dry seeds had an intermediate ABA content (13 ng per seed); but, in the embryonic axes, this increased from 0.03 ng to 1.2 ng per seed with an increase in the duration of the chilling period. The lowest germination percentages were found in this cultivar. These results suggest that ABA synthesis in the embryonic axes during chilling may affect the varietal characteristic of seed dormancy, and that rinsing seeds for >48 h could remove sufficient ABA to allow seed germination with minimum chilling. 相似文献
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974.
Identification and functional characterization of brainstem cannabinoid CB2 receptors 总被引:1,自引:0,他引:1
Van Sickle MD Duncan M Kingsley PJ Mouihate A Urbani P Mackie K Stella N Makriyannis A Piomelli D Davison JS Marnett LJ Di Marzo V Pittman QJ Patel KD Sharkey KA 《Science (New York, N.Y.)》2005,310(5746):329-332
The presence and function of CB2 receptors in central nervous system (CNS) neurons are controversial. We report the expression of CB2 receptor messenger RNA and protein localization on brainstem neurons. These functional CB2 receptors in the brainstem were activated by a CB2 receptor agonist, 2-arachidonoylglycerol, and by elevated endogenous levels of endocannabinoids, which also act at CB1 receptors. CB2 receptors represent an alternative site of action of endocannabinoids that opens the possibility of nonpsychotropic therapeutic interventions using enhanced endocannabinoid levels in localized brain areas. 相似文献
975.
Aimee Robinson Hong Jie Di Keith C. Cameron Andriy Podolyan Jizheng He 《Journal of Soils and Sediments》2014,14(8):1434-1444
Purpose
Nitrous oxide (N2O) is a potent greenhouse gas which is mainly produced from agricultural soils through the processes of nitrification and denitrification. Although denitrification is usually the major process responsible for N2O emissions, N2O production from nitrification can increase under some soil conditions. Soil pH can affect N2O emissions by altering N transformations and microbial communities. Bacterial (AOB) and archaeal (AOA) ammonia oxidisers are important for N2O production as they carry out the rate-limiting step of the nitrification process.Material and methods
A field study was conducted to investigate the effect of soil pH changes on N2O emissions, AOB and AOA community abundance, and the efficacy of a nitrification inhibitor, dicyandiamide (DCD), at reducing N2O emissions from animal urine applied to soil. The effect of three pH treatments, namely alkaline treatment (CaO/NaOH), acid treatment (HCl) and native (water) and four urine and DCD treatments as control (no urine or DCD), urine-only, DCD-only and urine + DCD were assessed in terms of their effect on N2O emissions and ammonia oxidiser community growth.Results and discussion
Results showed that total N2O emissions were increased when the soil was acidified by the acid treatment. This was probably due to incomplete denitrification caused by the inhibition of the assembly of the N2O reductase enzyme under acidic conditions. AOB population abundance increased when the pH was increased in the alkaline treatment, particularly when animal urine was applied. In contrast, AOA grew in the acid treatment, once the initial inhibitory effect of the urine had subsided. The addition of DCD decreased total N2O emissions significantly in the acid treatment and decreased peak N2O emissions in all pH treatments. DCD also inhibited AOB growth in both the alkaline and native pH treatments and inhibited AOA growth in the acid treatment.Conclusions
These results show that N2O emissions increase when soil pH decreases. AOB and AOA prefer different soil pH environments to grow: AOB growth is favoured in an alkaline pH and AOA growth favoured in more acidic soils. DCD was effective in inhibiting AOB and AOA when they were actively growing under the different soil pH conditions. 相似文献976.
Cell migration: integrating signals from front to back 总被引:2,自引:0,他引:2
Ridley AJ Schwartz MA Burridge K Firtel RA Ginsberg MH Borisy G Parsons JT Horwitz AR 《Science (New York, N.Y.)》2003,302(5651):1704-1709
Cell migration is a highly integrated multistep process that orchestrates embryonic morphogenesis; contributes to tissue repair and regeneration; and drives disease progression in cancer, mental retardation, atherosclerosis, and arthritis. The migrating cell is highly polarized with complex regulatory pathways that spatially and temporally integrate its component processes. This review describes the mechanisms underlying the major steps of migration and the signaling pathways that regulate them, and outlines recent advances investigating the nature of polarity in migrating cells and the pathways that establish it. 相似文献
977.
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979.
Mirica LM Vance M Rudd DJ Hedman B Hodgson KO Solomon EI Stack TD 《Science (New York, N.Y.)》2005,308(5730):1890-1892
The binuclear copper enzyme tyrosinase activates O2 to form a mu-eta2:eta2-peroxodicopper(II) complex, which oxidizes phenols to catechols. Here, a synthetic mu-eta2:eta2-peroxodicopper(II) complex, with an absorption spectrum similar to that of the enzymatic active oxidant, is reported to rapidly hydroxylate phenolates at -80 degrees C. Upon phenolate addition at extreme temperature in solution (-120 degrees C), a reactive intermediate consistent with a bis-mu-oxodicopper(III)-phenolate complex, with the O-O bond fully cleaved, is observed experimentally. The subsequent hydroxylation step has the hallmarks of an electrophilic aromatic substitution mechanism, similar to tyrosinase. Overall, the evidence for sequential O-O bond cleavage and C-O bond formation in this synthetic complex suggests an alternative intimate mechanism to the concerted or late stage O-O bond scission generally accepted for the phenol hydroxylation reaction performed by tyrosinase. 相似文献
980.