南斯拉夫的洞穴生物学

洞穴生物生活在地下。地下栖息场所最主要的特点是永远处于黑暗中,无自养生物,食物的种类和数量非常贫乏。当然,栖息地的大小以及其他非生物特征各有不同。来自地表食物极少的碎石间的空隙,也属于地下栖息地。但最主要的是喀斯特洞穴,尤其是在石灰岩地区形成的洞穴。溶岩流中的溶岩隧道是一类特殊     

From the population to society: The cooperative metaphors of W.C. Allee and A.E. Emerson

Conclusion John Greene has dismissed the evolutionary ethics of Simpson as a case in which science was only a tool, a weapon, in defense of positions that were essentially religious and philosophical.⁵⁷ This position adopts an amorphous view of science, in which a scientific theory can be construed to support practically any rhetorical position. The relationship between theory and rhetoric, however, is more complex; it is interactive, with the theory and the rhetoric influencing and supporting one another. It is no coincidence that Allee, Emerson, and Simpson all arrived at a biological basis of democracy and a naturalistic ethics during a period when the future of world politics and man's own morality were in question. Allee's commitment to world peace certainly antedated his theory of sociality, just as Simpson's commitment to democracy undoubtedly preceded his evolutionary views.By adopting a particular theory, however, the biologist necessarily imposes constraints on the corresponding rhetoric. Allee and Emerson could not, for example, have stressed the importance of the individual in democracy, given the orientation and framework of their biological research. There were differences among the social philosophies of Allee, Emerson, and Simpson; these differences depended, in part, on the specific evolutionary metaphors to which they subscribed. Allee's ideas with respect to cooperation were distinct from Emerson's, and both men differed strongly from Simpson on the role of the individual in evolution. The Chicago school was united by a conceptual framework that emphasized the population as the unit of selection, and the importance of cooperation in nature. But cooperation could play many roles: as a unifying principle for a theory of sociality, as an integrating mechanism in physiological functionalism, and as a biological source of hope for a society in the grips of a world war.     

Stromal free calcium concentration and light-mediated activation of chloroplast fructose-1,6-bisphosphatase

Light-mediated activation of fructose-1,6-bisphosphatase (EC 3.1.3.11) in intact spinach chloroplasts (Spinacia oleracea L.) is enhanced in the presence of 10⁻⁵ molar external free Ca²⁺. The most pronounced effect is observed during the first minutes of illumination. Ruthenium red, an inhibitor of light-induced Ca²⁺ influx, inhibits this Ca²⁺ stimulated activation. In isolated stromal preparations, the activation of fructose-1,6-bisphosphatase is already enhanced by 2 minutes of exposure to elevated Ca²⁺ concentrations in the presence of physiological concentrations of Mg²⁺ and fructose-1,6-bisphosphate. Maximal activation of the enzyme is achieved between 0.34 and 0.51 millimolar Ca²⁺. The Ca²⁺ mediated activation decreases with increasing fructose-1,6-bisphosphate concentration and with increasing pH. The data are consistent with the proposal that the illumination of chloroplasts leads to a transient increase of free stromal Ca²⁺. In dark-kept chloroplasts the steady-state concentration of free stromal Ca²⁺ is 2.4 to 6.3 micromolar as determined by null point titration. These observations support our previous proposal that light-induced Ca²⁺ influx into chloroplasts does not only influence the cytosolic concentration of free Ca²⁺ but also regulates enzymatic processes inside the chloroplast.     

Changes in Abscisic Acid and Indoleacetic Acid before and after Anthesis Relative to Changes in Abscission Rates of Cotton Fruiting Forms

Cotton (Gossypium hirsutum L.) fruiting forms exhibit pronounced changes, with age, in their probability of abscission. Large floral buds rarely abscise, but after anthesis the young fruits (bolls) have a high probability of abscising. Abscission rate reaches a peak about 5 to 6 days after anthesis and then gradually decreases. An experiment was conducted to try to determine the reason for the rapid and pronounced increase in probability of abscission just after anthesis. Cotton was grown in the field and fruiting forms of various ages from 9 days before to 9 days after anthesis were all harvested the same day and subsequently analyzed for ABA and IAA. The concentration of ABA decreased slightly at anthesis and increased gradually thereafter. In contrast, the concentration of IAA was high before anthesis and then decreased at anthesis to about one-fifth the previous concentration. IAA remained low for at least 4 days after anthesis and then increased rapidly between 7 and 9 days after anthesis. The high concentration of IAA in floral buds before anthesis is probably a major factor in their resistance to abscission. Likewise, the low concentration of IAA at anthesis and for about 4 days thereafter may promote fruit abscission during the young boll stage.     

Correlation of Stomatal Conductance with Photosynthetic Capacity of Cotton Only in a CO2-Enriched Atmosphere: Mediation by Abscisic Acid?

Some evidence indicates that photosynthetic rate (A) and stomatal conductance (g) of leaves are correlated across diverse environments. The correlation between A and g has led to the postulation of a “messenger” from the mesophyll that directs stomatal behavior. Because A is a function of intercellular CO₂ concentration (c_i), which is in turn a function of g, such a correlation may be partially mediated by c_i if g is to some degree an independent variable. Among individual sunlit leaves in a cotton (Gossypium hirsutum L.) canopy in the field, A was significantly correlated with g (r² = 0.41, n = 63). The relative photosynthetic capacity of each leaf was calculated as a measure of mesophyll properties independent of c_i. This approach revealed that, in the absence of c_i effects, mesophyll photosynthetic capacity was unrelated to g (r² = 0.06). When plants were grown in an atmosphere enriched to about 650 microliters per liter of CO₂, however, photosynthetic capacity remained strongly correlated with g even though the procedure discounted any effect of variable c_i. This “residual” correlation implies the existence of a messenger in CO₂-enriched plants. Enriched CO₂ also greatly increased stomatal response to abscisic acid (ABA) injected into intact leaves. The data provide no evidence for a messenger to coordinate g with A at ambient levels of CO₂. In a CO₂-enriched atmosphere, though, ABA may function as such a messenger because the sensitivity of the system to ABA is enhanced.     

Indole-3-acetic Acid oxidation and crocin bleaching by horseradish peroxidase

During indoleacetic acid (IAA) oxidation by horseradish peroxidase the water soluble model polyene, crocin, is bleached. IAA-oxidation and crocin bleaching are stimulated at acidic pH as well as by the monophenol p-hydroxyacetophenone. IAA oxidation and crocin bleaching are neither influenced by catalase or superoxide dismutase nor by different OH-radical scavengers, whereas both ascorbate and propylgallate are inhibitory.     

Ion Homeostasis in Chloroplasts under Salinity and Mineral Deficiency: II. Solute Distribution between Chloroplasts and Extrachloroplastic Space under Excess or Deficiency of Sulfate, Phosphate, or Magnesium

Spinach (Spinacia oleracea var “Yates”) plants grown hydroponically were exposed to an excess or deficiency of various mineral ions. Solutes were measured in leaf extracts and in isolated intact chloroplasts. Under phosphate (120 millimoles per liter NaH₂ PO₄), sulfate (200 millimolar per liter (Na₂ SO₄), or magnesium excess (150 millimolar per liter MgCl₂), concentrations of these ions in leaf extracts increased, but in chloroplasts, concentrations of all ions remained constant. Concentrations of quarternary ammonium compounds in chloroplasts increased. Under mild phosphate or magnesium deficiency, concentrations of these ions decreased in chloroplasts less than in whole leaf extracts. Under severe sulfate deficiency causing chlorosis in younger leaves, sulfate concentrations in chloroplasts remained even unchanged, despite a drastic decrease of sulfate concentrations both in green and in chlorotic leaves. Together with results from a companion study (G Schröppel-Meier, WM Kaiser 1988 Plant Physiol 87: 822-827) our data demonstrate that leaf cells are able to keep the concentrations of several mineral ions rather constant in metabolically active compartments even at extremely large variations of ion concentrations in the culture solution and in the leaves.     

Gene Expression in Developing Zea mays Embryos: Regulation by Abscisic Acid of a Highly Phosphorylated 23- to 25-kD Group of Proteins

We have earlier identified a set of proteins of 23 to 25 kilodaltons (kD), covering an isoelectric point (pI) range of 6.2 to 8.2, which accumulate gradually during normal embryogenesis of Zea mays and disappear in early germination. These polypeptides can be induced prematurely in immature embryos by abscisic acid (ABA) treatment. We report here that the more acidic protein forms are due to post-translational phosphorylation of at least two polypeptides of 23 kD, pI 8.2 and 25 kD, pI 8.0. A polyclonal antiserum was obtained which recognizes all forms of both the 23-kD and 25-kD polypeptides. Recovery of cDNA clones corresponding to these proteins was accomplished by hybridization with cDNA made from size-selected mRNA enriched for these sequences. Hybrid selection experiments demonstrate that clone MA12 specifically hybridizes with mRNAs encoding the 23-kD and 25-kD protein set which are recognized by the antiserum. By Northern hybridization analysis, the RNA encoded by clone MA12 is shown to accumulate in mature embryos and to be induced in young embryos upon ABA incubation.