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Sergio Rossi Annie Deslauriers Jozica Griçar Jeong‐Wook Seo Cyrille BK Rathgeber Tommaso Anfodillo Hubert Morin Tom Levanic Primoz Oven Risto Jalkanen 《Global Ecology and Biogeography》2008,17(6):696-707
Aim To identify temperatures at which cell division and differentiation are active in order to verify the existence of a common critical temperature determining growth in conifers of cold climates. Location Ten European and Canadian sites at different latitudes and altitudes. Methods The periods of cambial activity and cell differentiation were assessed on a weekly time‐scale on histological sections of cambium and wood tissue collected over 2 to 5 years per site from 1998 to 2005 from the stems of seven conifer species. All data were compared with daily air temperatures recorded from weather stations located close to the sites. Logistic regressions were used to calculate the probability of xylogenesis and of cambium being active at a given temperature. Results Xylogenesis lasted from May to October, with a growing period varying from 3 to 5 months depending on location and elevation. Despite the wide geographical range of the monitored sites, temperatures for onset and ending of xylogenesis converged towards narrow ranges with average values around 4–5, 8–9 and 13–14 °C for daily minimum, mean and maximum temperature, respectively. On the contrary, cell division in the cambium stopped in July?August, when temperatures were still high. Main conclusions Wood formation in conifers occurred when specific critical temperatures were reached. Although the timing and duration of xylogenesis varied among species, sites and years, the estimated temperatures were stable for all trees studied. These results provide biologically based evidence that temperature is a critical factor limiting production and differentiation of xylem cells in cold climates. Although daily temperatures below 4?5 °C are still favourable for photosynthesis, thermal conditions below these values could inhibit the allocation of assimilated carbon to structural investment, i.e. xylem growth. 相似文献
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A simple and rapid procedure for determination of intracellular acid phosphatase activity without the need for disruption of cells is described. Candida lipolytica cell suspension was treated with 0.1% Triton X-100 for 30 min at room temperature and with intermittent shaking. The enzyme assay is carried out directly with the permeabilized cell suspension. Permeabilization of the yeast cells to p -nitrophenylphosphate by Triton X-100 provides almost 100% efficiency in determining the total acid phosphatase activity compared to results obtained with disrupted yeast cells. 相似文献
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