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101.
102.
白额鹱卵壳的扫描电镜观察 总被引:11,自引:2,他引:9
本文报道白额鹱卵壳的壳膜、孔锥层、海绵层、表层等的超微结构,并对卵壳元素进行TN-5500能谱分析。 相似文献
103.
A crown rot disease in wheat caused by the fungusFusarium graminearum Schw. Group 1 is a widespread problem in chronically Zn-deficient Australian soils. A link between crown rot and Zn deficiency
was established by Sparrow and Graham (1988). This paper reports a test of a further hypothesis, that wheat genotypes more
efficient at extracting zinc from low-zinc soils are more resistant to infection by this pathogen. Three wheat cultivars (Excalibur,
Songlen and Durati) of differential Zn efficiency were tested at three zinc levels (0.05, 0.5 and 2.0 mg Zn kg−1 of soil) and three levels ofF. graminearum S. Group 1 inoculum (0.1 g and 0.3 g kg−1 live chaff-inoculum and control having 0.1 g kg−1 dead chaff inoculum). Six weeks after sowing dry matter production of shoots and roots was decreased byFusarium inoculation at 0.05 mg and 0.5 mg kg−1 applied Zn.Fusarium inoculum at 0.1 g was as effective as 0.3 g kg−1 for infection and decreasing dry matter. The infection at the basal part of culm decreased significantly by increasing the
rate of Zn application. Excalibur, a Zn-efficient cultivar (tolerant to Zn deficiency) produced significantly more shoot and
root dry matter, and showed less disease infection compared with Zn-inefficient cultivars (Durati and Songlen) at low (0.05
mg Zn kg−1 soil) and medium (0.5 mg Zn kg−1 soil) Zn fertilization rates. Higher rate of Zn fertilization (2.0 mg Zn kg−1 soil) reduced the disease level in Durati to the level of Excalibur but the disease level of Songlen was still high, indicating
its high Zn requirement and or sensitivity to crown rot. The data on Zn uptake show that Excalibur, being Zn-efficient, was
able to scavenge enough Zn from Zn-deficient soil, we suggest that besides sustaining growth Excalibur was able to build and
maintain resistance to the pathogen; inefficient cultivars needed extra Zn fertilization to achieve performance comparable
to that of Excalibur. The present study indicates that growing Zn-efficient cultivars of wheat along with judicious use of
Zn fertilizer in Zn-deficient areas where crown rot is a problem may sustain wheat production by reducing the severity of
the disease as well as by increasing the plant vigour through improved Zn nutrition. ei]Section editor: R Rodriques-Kalana 相似文献
104.
Riki van den Boogaard Miriam de Boer Erik J. Veneklaas Hans Lambers 《Physiologia plantarum》1996,98(3):493-504
We have investigated the water use efficiency of whole plants and selected leaves and allocation patterns of three wheat cultivars (Mexipak, Nesser and Katya) to explore how variation in these traits can contribute to the ability to grow in dry environments. The cultivars exhibited considerable differences in biomass allocation and water use efficiency. Cultivars with higher growth rates of roots and higher proportions of biomass in roots (Nesser and Katya) also had higher leaf growth rates, higher proportions of their biomass as leaves and higher leaf area ratios. These same cultivars had lower rates of transpiration per unit leaf area or unit root weight and higher biomass production per unit water use. They also had higher ratios of photosynthesis to transpiration, and lower ratios of intercellular to external CO2 partial pressure. The latter resulted from large differences in stomatal conductance associated with relatively small differences in rates of photosynthesis. There was little variation between cultivars in response to drought, and differences in allocation pattern and plant water use efficiency between cultivars as found under well-watered conditions persisted under dry conditions. At the end of the non-watered treatment, relative growth rates and transpiration rates decreased to similar values for all cultivars. High ratios of photosynthesis to transpiration, and accordingly high biomass production per unit of transpiration, is regarded as a favourable trait for dry environments, since more efficient use of water postpones the decrease in plant water status. 相似文献
105.
The differentiation of phloem anastomoses linking the longitudinal vascular bundles has been studied in stem internodes of Cucurbita maxima Duchesne, C. pepo L. and Dahlia pinnata Cav. These anastomoses comprise naturally occurring regenerative sieve tubes which redifferentiate from interfascicular parenchyma cells in the young internodes. In all three species, severing a vascular bundle in a young internode resulted in regeneration of xylem to form a curved by-pass immediately around the wound. The numerous phloem anastomoses in these young internodes were not involved in this process, the regenerated vessels originating from interfascicular parenchyma alone. Conversely, in mature internodes of Dahlia, the regenerated vessels originated from initials of the interfascicular cambia, and their phloem anastomoses did not influence the pattern of xylogenesis. On the other hand, in old internodes of Cucurbita, in which an interfascicular cambium was not yet developed, the parenchyma cells between the bundles had lost the ability to redifferentiate into vessel elements, and instead, regenerated vessels were produced in the phloem anastomoses. Thus, the wounded region of the vascular bundle was not bypassed via the shortest, curved pathway, but by more circuitous routes further away from the wound. Some of the regenerated vessels produced in the phloem anastomoses were extremely wide, and presumably efficient conductors of water. It is proposed that the dense network of phloem anastomoses developed during evolution as a mechanism of adaptation to possible damage in mature internodes by providing flexible alternative pathways for efficient xylem regeneration in plants with limited or no interfascicular cambium.This paper is dedicated to the memory of the late Isaac Blachmann (deceased 19 November 1995), father-in-law of the senior author, for encouragement and advice throughout the yearsThis research was supported by an International Scientific Exchange Award to R.A. from the Israel Academy of Sciences and The Royal Society. 相似文献
106.
Peter T. Katzmarzyk William R. Leonard Merrill A. Stephen Peter R. Berti Allen G. P. Ross 《American journal of physical anthropology》1996,99(4):537-545
Estimates of daily energy expenditure are important for many areas of research in human ecology and adaptability. The most common technique for estimating human energy expenditure under field conditions, the factorial method, generally relies on activity-specific energy costs derived from published sources, based largely on North American and European subjects. There is concern that such data may not be appropriate for non-Western populations because of differences in metabolic costs. The present study addresses this concern by comparing measured vs. predicted energy costs at rest and during sub-maximal exercise in 83 subjects (52 males, 31 females) from three subsistence-level populations (Siberian herders and high-land and coastal Ecuadorian farmers). Energy costs at rest (i.e., lying, sitting and standing) and while performing a standard stepping exercise did not significantly differ among the three groups. However, resting energy costs were significantly elevated over predicted levels (+16% in men, +11% in women), whereas exercising costs were comparable to predicted values (?6% in men, +3% in women). Elevations in resting energy needs appear to reflect responses to thermal stress. These results indicate that temperature adjustments of resting energy costs are critical for accurately predicting daily energy needs among traditionally living populations. o 1996 Wiley-Liss, Inc. 相似文献
107.
Rebamipide, a novel antipeptic ulcer drug, 2-(4-chlorobenzoylamino)-3-[2(1H)-quinolinone-4-yl]-propionic acid, was studied for its inhibitory effect on gastric xanthine oxidase activity and type conversion of the enzyme that has a profound role in free radical generation. Intraperitoneal administration of rebamipide at 60 mg/kg body weight reduced gastric mucosal hemorrhagic lesions and lipid peroxidation, which was proportional to the inhibitory effect of rebamipide on alcohol-induced xanthine oxidase-type conversion and enzyme activity. It was also observed that the activity of xanthine oxidase was significantly inhibited by administration of rebamipide at 60 mg/kg body weight, leading to a significant reduction of lipid peroxide content in alcohol-treated rats. The results suggest that alcohol-induced gastric mucosal lesions might be, in part, due to the increased activity of xanthine oxidase and type conversion rate of the enzyme and the protective effect of rebamipide on gastric mucosal lesions would result from its ability to protect against oxidative stress on gastric mucosal lesions of alcohol-treated rats. 相似文献
108.
生长光强对亚热带自然林两种木本植物稳定碳同位素比、细胞间CO2浓度和水分利用效率的影响 总被引:24,自引:1,他引:23
生长于100%、40%和16%自然光下的荷木和黧蒴幼苗叶片稳定碳同位素比(δ13C,-‰),细胞间CO2浓度(Ci)和水分利用效率(WUE)有一定的差别。16%和40%弱光下,δ13C的负值增加-0.54J‰到-0.89‰。Ci增大8.1-13.2μiL-1,WUE则下降6-24%。结果表明,叶片的水分和气体交换特性受生长光强的调节,叶片的δ13C值可反映其生长过程中受光的强弱状况。 相似文献
109.
Energetic constraints and foraging efficiency 总被引:2,自引:1,他引:1
Previous research considers foraging options that differ interms of their gross rate of gain b and rate of energy expenditurec. This research argues that maximizing efficiency b/c willmaximize net energetic gain when there is an upper limit onthe amount of energy that can be assimilated. This analysisdoes not include the expenditure during the time for which theanimal is unable to forage because of this constraint. Whenthis expenditure is included, maximizing efficiency is no longeroptimal. Instead the best feeding option is the one with thehighest value of b/(c c1), where c, is the metabolicrate when the animal is not foraging. 相似文献
110.
Summary Chickpea was micropropagated by axillary shoot proliferation (ASP) and modified single node culture (MSNC) methods. Maximum
propagule proliferation occurred on Murashige and Skoog (MS) medium enriched with 1–10 μM N6-benzyladenine and 0.01 μM α-naphthaleneacetic acid. The propagules were rooted on MS medium containing 1 μM 3-indolebutyric acid and B5 vitamins. Regenerated plants were fertile and phenotypically similar to control plants grown from seed. The MSNC method was
four times more efficient than the ASP method in terms of the number of plants produced per explant. 相似文献