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21.
烟草耐盐愈伤组织变异体对盐渍的适应性 总被引:1,自引:0,他引:1
用组织培养及逐步增加,NaCl浓度的方法,筛选出烟草耐盐愈伤组织变异体。能耐盐(2% NaCl)的愈伤组织在2% NaCl中继代29次,再移入无盐培养基中培养11和20代后不能保持提高的耐盐性,分别退化到只耐1.5%与1.0% NaCl的水平。耐2% NaCl愈伤组织产生的再生植株自交后代,其萌发种子、幼苗及成长植株均未能表现出耐盐性,说明用选择胁迫方法所筛选出的耐盐细胞系,其耐盐性的提高属于生理适应性。 相似文献
22.
23.
Douglas P. Swain 《Evolution; international journal of organic evolution》1992,46(4):998-1013
Variation in the number of vertebrae is widespread in fishes, and is partly genetic in origin. The adaptive significance of this variation was tested by exposing larvae of the threespine stickleback (Gasterosteus aculeatus) to predation by sunfish (Lepomis gibbosus). Two vertebral characters were considered: the total number (VN) and the ratio of abdominal to caudal vertebrae (VR). Predation was selective for both characters, but selection was more directly related to VR than to VN. The direction of selection depended on larval length: as length increased, optimal VR decreased. Total selection for VR was a combination of direct selection and an indirect effect of selection acting on a correlated trait, the ratio of precaudal to caudal length. Direct and indirect selection were in opposing directions at a given larval length. Variation in vertebral number may be maintained in populations partly because the strength of selection is reduced by opposing directions between direct and indirect selection, and between total selection at different larval lengths. 相似文献
24.
Several studies have investigated the effects of logging on primate population density, and attempted to relate density differences to changes in vegetation composition. As population density in some forest primates may be considerably influenced by dietary quality, it is important to understand how the effects of vegetation changes commonly associated with logging influence primate feeding ecology. Results are presented from a study carried out in the Budongo Forest Reserve in Uganda to investigate differences in blue monkey (Cercopithecus mitis stuhlmanni) feeding ecology in forest blocks with different logging history. Dietary composition differed between logged and unlogged forest, with a higher proportion of unripe fruit consumed in logged forest. By contrast, the proportion of young leaves, invertebrates and seeds in the diet was higher in unlogged forest. Variations in the intake of fruit was also higher in unlogged forest, but feeding patterns on other dietary items were more selective. These differences in diet reflect differences in availability of different categories of food items, as determined by tree species composition, abundance and plant phenological patterns. The observed differences between feeding ecology in logged and unlogged forest are discussed in relation to primate feeding ecology and habitat composition in Budongo. 相似文献
25.
26.
27.
Morphological and life-history traits often vary among populations of a species. Traits generally do not vary independently, but show patterns of covariation that can arise from genetic and environmental influences on phenotype. Covariance of traits may arise at an among-population level when genetically influenced traits diverge among populations in a correlated manner. Genetic correlations caused by pleiotropy and/or gene linkage can cause traits to evolve together, but among-population covariance can also arise among traits that are not genetically correlated. For example, “selective covariance” can arise when natural selection directly causes correlated change in a suite of traits. Similarly, mutation, migration, and drift may also sometimes cause correlated genetic changes among populations. Because covariation of traits among populations can arise by several different processes, the evolution of suites of traits must be interpreted with great caution. We discuss the sources of among-population covariance and illustrate one approach to identifying the sources' using data on floral traits of Dalechampia scandens (Euphorbiaceae). 相似文献
28.
The lateral leaflets of Desmodium motorium exhibit rhythmic upward and downward movements with a period in the minute range. Apoplasmic K+ and H+ activities were monitored in situ in the abaxial part of the pulvini with ion-selective microelectrodes. An extracellular electric potential was recorded simultaneously. The apoplasmic H+ activity of all pulvini exhibiting a regular rhythm of the extracellular electric potential oscillated with the same period between about 10 and 20 mM. The apoplasmic K+ activity was high when the membrane potential of the motor cells was depolarized (about 36 mV) and the cells were shrunken. In contrast, the apoplasmic K+ activity was low in the swollen state of the motor cells, when the membrane potential was hyperpolarized (about -136 mV). The volatile anesthetic enflurane suppressed reversibly the movement of the leaflets. The same treatment also arrested spontaneous oscillations in the apoplasmic K+ activity in the pulvinus. The apoplasmic K+ activity oscillated roughly in phase with the K+ activity between pH 6.6 and 6.0. Application of white light disturbed the rhythm and increased the extracellular pH. Our results indicate that the physiological mechanism that drives the lateral leaflet movements of Desmodium motorium is closely related to the osmotic motors mediating the leaf movements of Mimosa, Samanea and Phaseolus.Abbreviations Em
membrane potential
- Eex
extracellular electric potential
- Hex
extracellular H+ activity
- Kex
extracellular K+ activity
- Rex
extracellular electrical resistance
B. Antkowiak was supported by the Stiftung Volkswagenwerk. 相似文献
29.
植物生活史对策的进化 总被引:19,自引:0,他引:19
植物生活史对策的进化班勇(中国林业科学院林业研究所,北京100091)EvolutionofLifeHistoryStrategyinPlants¥BanYong(ResearchInstituteofForestry,ChineseAcademyo... 相似文献
30.
Summary To assess the mechanism(s) by which intraluminal chloride concentration is raised above equilibrium values, intracellular Cl– activity (
i
Cl
) was studied in the proximal tubule ofNecturus kidney. Paired measurements of cell membrane PD (V
BL) and Cl-selective electrode PD (V
BL
Cl
) were performed in single tubules, during reversible shifts of peritubular or luminal fluid composition. Steadystate
i
Cl
was estimated at 14.6±0.6 mmol/liter, a figure substantially higher than that predicted for passive distribution. To determine the site of the uphill Cl– transport into the cell, an inhibitor of anion transport (SITS) was added to the perfusion fluid. Introduction of SITS in peritubular perfusate decreased
i
Cl
, whereas addition of the drug in luminal fluid slightly increased
i
Cl
; both results are consistent with basolateral membrane uphill Cl– transport from interstitium to the cell. TMA+ for Na+ substitutions in either luminal or peritubular perfusate had no effect on
i
Cl
. Removal of bicarbonate from peritubular fluid, at constant pH (a situation increasing HCO
3
–
outflux), resulted in an increase of
i
Cl
, presumably related to enhanced Cl– cell influx: we infer that Cl– is exchanged against HCO
3
–
at the basolateral membrane. The following mechanism is suggested to account for the rise in luminal Cl– concentration above equilibrium values: intracellular CO2 hydration gives rise to cell HCO
3
–
concentrations above equilibrium. The passive exit of HCO
3
–
at the basolateral membrane energizes an uphill entry of Cl– into the cell. The resulting increase of
i
Cl
, above equilibrium, generates downhill Cl– diffusion from cell to lumen. As a result, luminal Cl– concentration also increases.C.N.R.S. Greco 24. Part of this work was presented at the 12th annual meeting of the American Society of Nephrology, Boston, Mass. (Edelman et al., 1979). 相似文献