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51.
Rangil Singh Consuelo M. Perez Cynthia G. Pascual Bienvenido O. Juliano 《Phytochemistry》1978,17(11):1869-1874
Five rices (Oryza sativa L.) differing in final grain size were studied at the midmilky stage to determine if any factor could be identified which might limit rate of starch accumulation. Only UDP glucose pyrophosphorylase activity increased with increasing grain size. Detached rice panicles incubated in liquid medium containing 1% sucrose and 0.1% glutamine, in addition to minerals and vitamins, produced grains similar to those on intact plants. Sucrose level (0–1.5%) in the medium determined the extent of dry matter and starch accumulation and influenced physiological development of the ripening grains. Chemical and enzymic composition of the grain were similar to previously reported levels in grains of intact panicles analysed at regular intervals after anthesis. Addition of 3-P glycerate or K+ to the medium did not improve dry matter accumulation in the developing grain. 相似文献
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Redox potentials in microsites of the rhizosphere of flooded rice were continuously measured for several days. Close to the root tips redox potential markedly increased. The highest increase was measured in the rhizosphere of the tips of short lateral roots. Aerobic redox conditions were reached there, except in a very strongly reduced soil. Both the extension of the oxidation zone around the root tips and the maximum redox potential reached were influenced by the reducing capacity of the soil. The radius of the redox rhizosphere varied from less than 1 mm in a strongly reduced soil up to 4 mm in a weakly reduced one. The root-induced oxidation processes in the rhizosphere depended on the atmospheric oxygen supply to the roots. 相似文献
54.
Anabaena sp., isolated from a rice paddy, was investigated for its nitrogen fixation as measured by acetylene reduction activity (ARA)
in P-limited continuous and light-limited semi-continuous cultures. Growth rate (μ) under P limitation was a function of cell
P content (q
p). Both the photosynthetic capacity (Pmax) and photosynthetic efficiency (α) increased with μ when expressed per cell, but not per unit chla. The ARA of steady-state cells under P limitation increased with μ and was linearly related to C-fixation rate. This was
apparently a consequence of the control of C-fixation by P limitation. In light-limited cells, steady state ARA, both at the
culture light intensity and in the dark, increased asymptotically with μ, but the activity in the dark was only about 51%
of that in the light. When the light level of steady-state cells grown at a high in intensity was switched to a low level,
ARA decreased exponentially with time. Dark ARA activity also showed a similar decline, but at much lower levels. Thus, ARA
depended not only on light history, but also immediate photosynthesis. Steady-state ARA at the ambient intensity or in the
dark showed a strong correlation with14C-fixation rate. ARA of light-limited cells showed the same light-saturation characteristics as their14C-fixation, with the same initial saturation intensity,I
k. The ratios of Pmax to the maximum ARA (ARAmax), and α to the slope of ARA (αara) were identical. A comparison of gross to net photosynthesis and N2 fixation suggested that there was little leakage or excretion of fixed C or N. 相似文献
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The effect of various experimental parameters upon the frequency of callus formation from cultured anthers of Oryza sativa has been investigated. Although certain medium components were found to be critical to callus formation, the concentration of these components had little effect upon the frequency of callus formation. The degree to which the callus formation frequency was influenced by cold pretreatment of the flowers was variable. Even though plants were grown under uniform conditions and flowers containing pollen in the microspore stage of development were selected for dissection, the frequency of callus formation varied nonrandomly between flowers. In experiments with populations of flowers in a physiological and developmental state favorable to callus formation 35% of plated anthers produced callus and at least 60% of these calluses gave rise to green plants. 相似文献
58.
气候变化对黑龙江省水稻障碍型冷害的影响 总被引:3,自引:0,他引:3
明确气候变化对黑龙江省水稻孕穗期和抽穗期障碍型冷害的影响,可为水稻安全生产提供科学依据。基于黑龙江省70个台站1971—2012年的气象资料和10个台站1980—2011年水稻生育期数据,结合水稻障碍型冷害指标,分析了气候变化对黑龙江省水稻障碍型冷害的影响。结果表明:(1)水稻孕穗期障碍型冷害1990s发生频率最低,2000s发生频率最高;抽穗期障碍型冷害1970s和1980s发生频率高,1990s和2000s发生频率低。(2)抽穗期障碍型冷害发生程度大于孕穗期障碍型冷害。(3)不同熟型水稻品种可种植北界逐渐北移东扩,极早熟、早熟和中熟品种可种植范围分别缩小了5、21和11个县(市),中晚熟和晚熟品种可种植范围分别扩大了14和23个县(市)。(4)随着水稻种植格局的变化,不同熟型水稻障碍型冷害均在1990s发生频率最低,2000s发生频率最高。 相似文献
59.
区域气候变化情景下气候变率对我国水稻产量影响的模拟研究 总被引:3,自引:0,他引:3
利用中国随机天气模型将中国区域气候模式RCM与作物模式CERES-Rice相连接,模拟了3种气候变率(0%,10%,20%)水平下未来气候(2050年,假定此时CO2浓度为550mg/L)对我国水稻主产区(广州,长沙,南京)灌溉水稻和雨养水稻在考虑CO2肥效与否条件下的产量,模拟结果表明;(1)气候变率对水稻产量的影响因经营方式和研究地区的不同而有差异,对灌溉水稻来说,气候变率对其产量有负面影响, 相似文献
60.