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121.
The hydrolytic activity of lipolytic enzymes in reverse micelles can be measured continuously with Fourier Transform infrared spectroscopy (FTIR) by following in the region of the OH-stretching band the water consumption during the reaction. This possibility is unique to reverse micellar solutions, because they are optically transparent and because they contain only a limited amount of water. 相似文献
122.
Effects of Irrigation and Nitrogen on the Performance of Aerobic Rice in Northern China 总被引:1,自引:0,他引:1
Chang-Ying Xue Xiao-Guang Yang B.A.M. Bouman Wei Deng Qiu-Ping Zhang Jie Yang Wei-Xiong Yan Tian-Yi Zhang A-Ji Rouzi Hua-Qi Wang Pu Wang 《植物学报(英文版)》2008,50(12):1589-1600
Aerobic rice is a new production system in which specially-developed varieties are grown under non-flooded, non-puddled, and non-saturated soil conditions. In 2003-2004, irrigation x Nitrogen experiments were carried out near Beijing using variety HD297. Water treatments included four irrigation levels, and Nitrogen treatments included different fertilizer N application rates and different numbers of N splits. The highest yields were 4460 kg/ha with 688 mm of total (rain plus irrigation) water input in 2003 and 6 026 kg/ha with 705 mm of water input in 2004. Because of the quite even distribution of rainfall in both years, the four irrigation treatments did not result in large differences of soil water conditions. There were few significant effects of irrigation on biomass accumulation, but yield increased with the total amount of water applied. High yields coincided with high harvest index and high percentages of grain filling. The application of fertilizer N either reduced biomass and yield or kept it at the same level as 0 N and consistently reduced the percentage grain filling and 1 000-grain weight. With the highest water application, five splits of N gave higher yield than three splits, whereas three splits gave higher yield than five splits with lower water applications. 相似文献
123.
Concurrent observations of soil water potential and leaf stomata diffusion resistance were made on two, plots of wheat grown at Datun Agro-ecological Experimental Station in Beijing under two different soil water conditions. These data were further complemented by weather and physiological observation. In this paper, we mainly analysed the influence of soil water potential on the status of wheat leaf stomatal resistance. The results indicate that: (1) there is a obvious influence of soil water potential on the status of wheat leaf stomata under normal conditions and (2) there is a different upper and lower epidermis stomata of wheat leaf respond to the soil water potential. The lower epidermis stomata are more sensitive to soil water potential than upper epidermis one. (3) There is a linear relationship between the ratio of lower and upper epidermis stomata resistance and soil water potential in root layer, according to this we can diagnose the degree of wheat water deficit. 相似文献
124.
The flower is the most significant and beautiful part of plants. Flowers are very useful organs in plant developmental phenomenon.
During flower bud opening, various events takes place in a well defined sequence, representing all aspects of plant development,
such as cell division, cellular differentiation, cell elongation or expansion and a wide spectrum of gene expression. The
complexity of flower bud opening illustrates that various biological mechanisms are involved at different stages. Senescence
represents the ultimate stage of floral development and results in wilting or abscission of whole flower or flower parts.
Senescence is an active process and governed by a well defined cell death program. Once a flower bud opens, the programmed
senescence of petal allows the removal of a metabolically active tissue. In leaves, this process can be reversed, but in floral
tissue it cannot, indicating that a highly controlled genetic program for cell death is operating. The termination of a flower
involves at least two, sometimes overlapping, mechanisms. In one, the perianth abscises before the majority of its cells initiate
a cell death program. Abscission may occur before or during the mobilization of food reserves to other parts of the plant.
Alternatively, the petals may be more persistent, so that cell deterioration and food remobilization occur while the petals
are still part of the flower. The overall pattern of floral opening varies widely between plant genera, therefore, a number
of senescence parameters have been used to group plants into somewhat arbitrary categories. Opening and senescence of rose
flower is still an unsolved jigsaw in the world of floriculture industry and the mechanism behind the onset of the very early
events in the sequence still remains to be elucidated. Hence, for advancing the knowledge on the pertinent aspect of bud opening
and senescence the literature has been cited under this review. 相似文献
125.
A model for water uptake by plant roots 总被引:4,自引:0,他引:4
We present a model for water uptake by plant roots from unsaturated soil. The model includes the simultaneous flow of water inside the root network and in the soil. It is constructed by considering first the water uptake by a single root, and then using the parameterized results thereby obtained to build a model for water uptake by the developing root network. We focus our model on annual plants, in particular the model will be applicable to commercial monocultures like maize, wheat, etc. The model is solved numerically, and the results are compared with approximate analytic solutions. The model predicts that as a result of water uptake by plant roots, dry and wet zones will develop in the soil. The wet zone is located near the surface of the soil and the depth of it is determined by a balance between rainfall and the rate of water uptake. The dry zone develops directly beneath the wet zone because the influence of the rainfall at the soil surface does not reach this region, due to the nonlinear nature of the water flow in the partially saturated soil. We develop approximate analytic expressions for the depth of the wet zone and discuss briefly its ecological significance for the plant. Using this model we also address the question of where water uptake sites are concentrated in the root system. The model indicates that the regions near the base of the root system (i.e. close to the ground surface) and near the root tips will take up more water than the middle region of the root system, again due to the highly nonlinear nature of water flow in the soil. 相似文献
126.
Nuclear magnetic resonance (NMR) microimaging and proton relaxation times were used to monitor differences between the hydration
state of the nucleus and cytoplasm in the Rana pipiens oocyte. Individual isolated ovarian oocytes were imaged in a drop of Ringer's solution with an in-plane resolution of 80
μm. Proton spin echo images of oocytes arrested in prophase I indicated a marked difference in contrast between nucleoplasm
and cytoplasm with additional intensity gradations between the yolk platelet-rich region of the cytoplasm and regions with
little yolk. Neither shortening τe (spin echo time) to 9 msec (from 18 msec) nor lengthening τr (spin recovery time) to 2 sec (from 0.5 sec) reduced the observed contrast between nucleus and cytoplasm. Water proton T1 (spin-lattice) relaxation times of oocyte suspensions indicated three water compartments that corresponded to extracellular
medium (T1= 3.0 sec), cytoplasm (T1= 0.8 sec) and nucleoplasm (T1= 1.6 sec). The 1.6 sec compartment disappeared at the time of nuclear breakdown. Measurements of plasma and nuclear membrane
potentials with KCl-filled glass microelectrodes demonstrated that the prophase I oocyte nucleus was about 25 mV inside positive
relative to the extracellular medium. A model for the prophase-arrested oocyte is proposed in which a high concentration of
large impermeant ions together with small counter ions set up a Donnan-type equilibrium that results in an increased distribution
of water within the nucleus in comparison with the cytosol. This study indicates: (i) a slow exchange between two or more
intracellular water compartments on the NMR time-scale, (ii) an increased rotational correlation time for water molecules
in both the cytoplasmic and nuclear compartments compared to bulk water, and (iii) a higher water content (per unit dry mass)
of the nucleus compared to the cytoplasm, and (iv) the existence of a large (about 75 mV positive) electropotential difference
between the nuclear and cytoplasmic compartments.
Received: 18 January 1996/Revised: 29 April 1996 相似文献
127.
Osmotic stress decreases complexity underlying the electrophysiological dynamic in soybean 下载免费PDF全文
- Studies on plant electrophysiology are mostly focused on specific traits of single cells. Inspired by the complexity of the signalling network in plants, and by analogy with neurons in human brains, we sought evidence of high complexity in the electrical dynamics of plant signalling and a likely relationship with environmental cues.
- An EEG‐like standard protocol was adopted for high‐resolution measurements of the electrical signal in Glycine max seedlings. The signals were continuously recorded in the same plants before and after osmotic stimuli with a ?2 MPa mannitol solution. Non‐linear time series analyses methods were used as follows: auto‐correlation and cross‐correlation function, power spectra density function, and complexity of the time series estimated as Approximate Entropy (ApEn).
- Using Approximate Entropy analysis we found that the level of temporal complexity of the electrical signals was affected by the environmental conditions, decreasing when the plant was subjected to a low osmotic potential. Electrical spikes observed only after stimuli followed a power law distribution, which is indicative of scale invariance.
- Our results suggest that changes in complexity of the electrical signals could be associated with water stress conditions in plants. We hypothesised that the power law distribution of the spikes could be explained by a self‐organised critical state (SOC) after osmotic stress.
128.
不同人为干扰措施对天然次生灌丛土壤肥力及蓄水能力的影响 总被引:1,自引:0,他引:1
亚热带常绿阔叶林遭反复干扰后退化形成的天然次生灌丛在未管护模式下难以恢复为乔木林。在浙江省临安市选择典型天然次生灌丛,以强度人为干扰为对照、分别进行保护性干扰和适度人为干扰,探讨灌丛土壤蓄水能力和肥力质量的响应。4年试验结果表明:与强度人为干扰相比,保护性干扰和适度人为干扰后的土壤总贮水量、吸持贮水量和滞留贮水量分别提高了12.41%、5.33%、17.37%和29.13%、33.23%和26.24%;最大持水量、毛管持水量和最小持水量分别提高了23.35%、9.51%、17.55%和48.63%、56.08和71.05%;与强度人为干扰相比,保护性干扰和适度人为干扰的综合肥力分别提高了1.9%和38.5%,其中保护性干扰的水解氮、有机碳和有机质含量提高了12.11%、38.91%和38.94%,适度人为干扰的水解氮、有效磷、有机碳和有机质含量提高了61.97%、90.57%、130%和130.04%,保护性干扰和适度人为干扰的土壤综合评价指数分别提高了15.43%和58.94%。研究表明,与保护性干扰相比,适度人为干扰在土壤的蓄水保水、肥力和固碳增汇等方面更能达到预期的目标。在有条件经营的情况下,可以选择适度人为干扰措施对天然次生灌丛进行管理从而达到加快土壤恢复的目的。 相似文献
129.
130.
Removal of Cr(VI) from ground water by Saccharomyces cerevisiae 总被引:1,自引:0,他引:1
Chromium can be removed from ground water by the unicellular yeast, Saccharomyces cerevisiae. Local ground water maintains chromium as CrO4
2- because of bicarbonate buffering and pH and E
h
conditions (8.2 and +343 mV, respectively). In laboratory studies, we used commercially available, nonpathogenic S. cerevisiae to remove hexavalent chromium [Cr(VI)] from ground water. The influence of parameters such as temperature, pH, and glucose concentration on Cr(VI) removal by yeast were also examined. S. cerevisiae removed Cr(VI) under aerobic and anaerobic conditions, with a slightly greater rate occurring under anaerobic conditions. Our kinetic studies reveal a reaction rate (Vmax) of 0.227 mg h-1 (g dry wt biomass)-1 and a Michaelis constant (Km) of 145 mg/l in natural ground water using mature S. cerevisiae cultures. We found a rapid (within 2 minutes) initial removal of Cr(VI) with freshly hydrated cells [55–67 mg h-1 (g dry wt biomass)-1] followed by a much slower uptake [0.6–1.1 mg h-1 (g dry wt biomass)-1] that diminished with time. A materials-balance for a batch reactor over 24 hours resulted in an overall shift in redox potential from +321 to +90 mV, an increase in the bicarbonate concentration (150–3400 mg/l) and a decrease in the Cr(VI) concentration in the effluent (1.9-0 mg/l). 相似文献