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131.
Sergio Sgorbati Marisa Levi Elio Sparvoli Federica Trezzi Giovanni Lucchini 《Physiologia plantarum》1986,68(3):471-476
Cytometry and flow cytometry were used to study characteristics of fluorescence of the DNA-DAPI complex in nuclei released from different fresh and formaldehyde-fixed pea ( Pisum sativum L. cv. Lincoln) tissues. The two methods of isolation are compared and discussed as well as their possible use for quantitative analysis of DNA in plant tissues. With fixed tissues it is possible to obtain a number of nuclei sufficient for the flow cytometric analysis, even using small amounts of plant tissue. 相似文献
132.
Elly P. H. Best 《Physiologia plantarum》1986,68(3):502-510
The photosynthetic and growth characteristics of Ceratophyllum demersum L. were investigated under laboratory conditions which simulated those encountered in the plants' normal environment. The carbon fixation rate of C. demersum measured with 14 C at light and carbon saturation at pH 8.0 was 4.48 mg C (g ash-free dry weight)−1 h−1 . It was lower at pH 6.5 than at pH 8.0. The light use efficiencies in quiescent plants and actively growing plants were 6.3 and 8.7 × 10−9 kg CO2 J−1 , respectively, with corresponding maximum photosynthetic rates of 2.67 and 4.36 mg C (g ash-free dry weight)−1 h−1 . Photorespiration in actively growing plants consumed 24% of the carbon fixed. Incubation with DCMU demonstrated that about one-third was refixed. The optimum temperature for carbon fixation was 25°C. The C3 -photosynthetic pathway was the main operational route as indicated by the early photosynthetic products (largely C3 -acids) and the absence of Krantz anatomy and the chlorophyll a:b ratio (2.7). The maximum relative growth rates ranged from 0.025 to 0.041 g ash-free dry weight (g ash-free dry weight)−1 day−1 in the field (Lake Vechten, 1 to 3 m depth classes). 相似文献
133.
Growth, dry matter partitioning, and diurnal activities of RuBP carboxylase in citrus seedlings maintained at two levels of CO2 总被引:3,自引:0,他引:3
Karen E. Koch Pierce H. Jones Wayne T. Avigne L. Hartwell Allen Jr. 《Physiologia plantarum》1986,67(3):477-484
The long-term response of citrus rootstock seedlings to CO2 enrichment was examined in Carrizo estrange ( Poncirua trifoliata (L.) Raf. x Citrus sinensis (L.) Osbeck] and Swingle citrumelo ( P. trifoliate x C. parodist Macf.]. Plaotlets 14 weeks old were transferred to outdoor controlled-environment chambers and maintained for 5 months from Feb. 14 to July 21. During this period, new growth (cm) of citrange and citrumelo shoots at 660 μl1−1 was 94 and 69% greater, respectively, than at 330 μ1 1−1 . Total dry weight of both rootstock shoots had increased by over 100%. Growth of few species is affected this markedly by elevated CO2 levels.
More carbon was partitioned to above-ground organs in CO2 -enriched citrus seedlings. Stem dry matter per unit length was also 32 and 44% greater in citrange and citrumelo, respectively. Total leaf area was increased by 124% in citrange and 85% in citrumelo due to greater leaf number and size. Variations in overall relative growth rate appeared to be related to the rapid, sequential, flush-type growth in citrus, in which an entire shoot segment with its associated leaves remains an active sink until fully expanded. RuBP carboxylase (EC 4.1.1.39) activity in leaves of recently-expanded flushes was higher in citrumelo plants grown at 660 vs 330 μ1 1−1 CO2 and changed diurnally for citrange (but not citrumelo) leaves at both CO2 levels. The results are consistent with the hypothesis that positive long-term effects of CO2 enrichment may be greater in species or during growth periods where sink capacity for carbon utilization is high. 相似文献
More carbon was partitioned to above-ground organs in CO
134.
The assumption that landscapes dominated by mature vegetation are presently in carbon steady state with the atmosphere is challenged. Evidence suggests that the vegetation and soils of these landscapes are frequently disturbed and over short time periods (<300 yr) slowly sequester atmospheric carbon. The critical consideration in this argument is the time interval used to evaluate a steady state. Current models of carbon flux through the terrestrial biota limit their time considerations to 120 yr, a short and inadequate time interval for realistic assumptions about steady state in the carbon cycle of vegetation.Research performed under subcontract 19B-07762C with S. Brown and 19X-43326C with the Center for Energy and Environment Research of the University of Puerto Rico (A. E. Lugo) under Martin Marietta Energy Systems, Inc., contract DE-AC05-840R21400 with the U.S. Department of Energy. 相似文献
135.
Human cells deficient in rate of excision repair of DNA damage induced by UV-radiation, i.e., xeroderma pigmentosum (XP) cells, are much more sensitive to the mutagenic effect of UV than are cells from normal persons. The lower frequency of mutants in the latter cells has been attributed to the fact that, unlike XP cells, they excise most of the potentially mutagenic lesions before these can be converted into mutations. If semi-conservative DNA synthesis on a template still containing unexcised lesions is responsible for introducing mutations and if replication of the gene of interest, e.g., hypoxanthine (guanine)phosphoribosyltransferase (HPRT) for thioguanine resistance or the elongation factor 2 (EF-2) for diphtheria toxin resistance, occurs at a particular time during S-phase, it should be possible to shorten the time available for such repair by synchronizing cells and irradiating them just as the gene is to be replicated. The predicted result would be a much higher frequency of mutants at one part in the S-phase than at other times. To test this, cells were synchronized using the alpha-polymerase inhibitor aphidicolin, which blocks cells at the G1/S border. Autoradiography, cytofluorimetry, and incorporation of tritiated thymidine studies showed that DNA synthesis started immediately after release from aphidicolin and was completed in 8-10 h. Cells irradiated with 6 J/m2 at various times post-release were assayed for survival and mutations. The frequency of thioguanine- or diphtheria toxin-resistant cells in the population was highest in cells irradiated during the first fifth of the S-phase, i.e., 0-1.5 h post-release. It was significantly lower in cells irradiated at later times. In contrast, UV-induced cytotoxicity showed no significant time dependence during S-phase. These data suggest that the HPRT and EF-2 genes are replicated early in S-phase. 相似文献
136.
137.
H. J. Weigel 《Physiologia plantarum》1985,63(2):192-200
Photosynthetic CO2-fixation of mesophyll protoplasts of lambs lettuce [Valerianella locusta (L.) Betcke] was inhibited by short time exposure to Cd+. Inhibition was due to uptake of the metal ion into the protoplasts and increased with increasing Cd2+ concentrations and the time of preincubation. A 10 min pretreatment at 2 mM Cd2+ reduced CO2-fixation by 40–60%. Inhibition of photosynthesis was independent of the light intensity to which the protoplasts were exposed. Measurement of the lightinduced electrochromic pigment absorption change at 518nm and chlorophyll fluorescence studies revealed that primary photochemical reactions associated with the thylakoid membranes were not affected by the metal ion. Also, light activation of the ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) was not inhibited by Cd2+. Under rate-limiting CO2 concentrations, inhibition of CO2-fixation was smaller than at Vmax of CO2 reduction indicating that the carboxylation reaction of the Calvin cycle is not susceptible to Cd2+. Cd2+ treatment of protoplasts significantly extended the lagphase of CO2-supported O2-evolution and partly inhibited light activation of the glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13) and the ribulose-5-phosphate kinase (EC 2.7.1.19). Measurement of relative concentrations of [14C]-labeled Calvin cycle intermediates showed that Cd2+ caused a decrease in the 3-phosphoglycerate/triose phosphate ratio and an increase in the triose phosphate/ribulose-1,5-bisphosphate ratio. It is concluded that in protoplasts Cd2+ affects photosynthesis mainly at the level of dark reactions and that the site of inhibition may be localized in the regenerative phase of the Calvin cycle. 相似文献
138.
Root turnover and production by14C dilution: implications of carbon partitioning in plants 总被引:1,自引:1,他引:0
D. G. Milchunas W. K. Lauenroth J. S. Singh C. V. Cole H. W. Hunt 《Plant and Soil》1985,88(3):353-365
Summary Estimates of belowground net primary production (BNP) obtained by using traditional soil core harvest data are subject to a variety of potentially serious errors. In a controlled growth chamber experiment, we examined the aboveground-belowground, labile to structural tissue, and plant to soil dynamics of carbon to formulate a14C dilution technique for potential successful application in the field and to quantify sources of error in production estimates.Despite the fact that the majority of net14C movement between above- and belowground plant parts occurred between the initial labeling and day 5, significant quantities of14C were incorporated into cell-wall tissue throughout the growing period. The rate of this increase at late sampling dates was greater for roots than for shoots. Total loss of assimilated14C was 47% in wheat and 28% in blue grama. Exudation and sloughing in wheat and blue grama, respectively, was 15 and 6% of total uptake and 22 and 8% of total plant production.When root production estimates by14C dilution were corrected for the quantities of labile14C incorporated into structural carbon between two sampling dates, good agreement with actual production was found. The error associated with these estimates was ±2% compared with a range of –119 to –57% for the uncorrected estimates. Our results suggest that this technique has potential field application if sampling is performed the year after labelling.Sources of errors in harvest versus14C dilution estimates of BNP are discussed. 相似文献
139.
Conchospores from the perennial conchocelis phase of the annual, epiphytic, marine red alga Porphyra nereocystis Anderson, which in nature lives on the large annual kelp Nereocystis luetkeana (Mertens) Postels et Ruprecht, are released in culture only in response to a short-day photoperiod treatment followed by a long-day treatment. Each treatment requires a minimum of three to four weeks and is enhanced by lower temperature during the second photoperiod treatment. To our knowledge P. nereocystis is the first known dualdaylength seaweed and requires a short-day-longday treatment for completion of its life cycle. This stringent environmental control of its reproduction appears to be an adaptation to coordinate conchospore production with the seasonal availability of its host kelp Nereocystis.Abbreviations LD
long day
- SD
short day
- SLD
shortlong day 相似文献
140.
Electron transport system (ETS) activity, CO2 evolution, O2 consumption, N2-fixation (C2H2 reduction) and methanogenesis were appropriately measured in aerobic and anaerobically incubated sediment at 4, 10 and 20 ° C to better characterize these activities under different incubation conditions. ETS activity was always higher in the aerobically incubated sediment at all three incubation temperatures, whereas (C2H2 reduction was always greater in the anaerobic sediment. Carbon dioxide evolution was detected only in the aerobic sediment at 10 and 20 ° C but not at 4 ° C. Methane evolution in anaerobic sediment increased gradually with an increase in the incubation temperature. 相似文献