Antitranspirant-induced increases in leaf water potential increase tuber calcium and decrease tuber necrosis in water-stressed potato plants

Experiments were undertaken with field-grown potato (Solanum tuberosum L.) plants to test the hypothesis that altering leaf:tuber water potential gradients within a plant subjected to low soil moisture will allow greater Ca accumulation in tubers and reverse Ca deficiency-related tuber necrosis. Antitranspirant formulations containing a wax emulsion and a spreader/sticker surfactant increased leaf water potential during a drought episode, significantly reducing the potential gradient that develops between leaf and tuber during a period of stress. Increased leaf water potential in treated plants was associated with decreased leaf Ca and increased tuber Ca. Tuber necrosis was found to be reduced in treated plants, thus increasing tuber quality.     

Studies on the System Regulating Proton Movement across the Chloroplast Envelope : Effects of ATPase Inhibitors, Mg, and an Amine Anesthetic on Stromal pH and Photosynthesis

Studies were undertaken to further characterize the spinach (Spinacea oleracea) chloroplast envelope system, which facilitates H⁺ movement into and out of the stroma, and, hence, modulates photosynthetic activity by regulating stromal pH. It was demonstrated that high envelope-bound Mg²⁺ causes stromal acidification and photosynthetic inhibition. High envelope-bound Mg²⁺ was also found to necessitate the activity of a digitoxinand oligomycin-sensitive ATPase for the maintenance of high stromal pH and photosynthesis in the illuminated chloroplast. In chloroplasts that had high envelope Mg²⁺ and inhibited envelope ATPase activity, 2-(diethylamino)-N-(2,6-dimethylphenyl)acetamide was found to raise stromal pH and stimulate photosynthesis. 2-(Diethylamino)-N-(2,6-dimethylphenyl)acetamide is an amine anesthetic that is known to act as a monovalent cation channel blocker in mammalian systems. We postulate that the system regulating cation and H⁺ fluxes across the plastid envelope includes a monovalent cation channel in the envelope, some degree of (envelope-bound Mg²⁺ modulated) H⁺ flux linked to monovalent cation antiport, and ATPase-dependent H⁺ efflux.     

The effect of estradiol valerate on follicular dynamics and superovulatory response in cows with Syncro-Mate-B implants

Two experiments were designed to evaluate the effect of estradiol valerate on follicular dynamics and superovulatory response in cows with Syncro-Mate-B (SMB)implants. In Experiment 1, 5 mg estradiol valerate (E(2)), injected at the same time as superstimulation treatments were initiated, resulted in fewer corpora lutea (CL), ova/embryos collected and fertilized ova (P<0.05) than if E(2) was administered with the SMB implant 7 days earlier. In Experiment 2, 31 beef cows and 26 Holstein cows were placed in one of four treatment groups. Group I (control) cows were superstimulated on Day 9 (estrus=Day 0). On Day 2, cows in Groups II, III, and IV received SMB and cows in Group III received E(2). On Day 9, cows in Group IV received E(2), and all cows were superstimulated with Folltropin. The number of CL did not differ (P>0.19) among groups. However, there were more follicles < 10 mm and fewer fertilized ova and transferable embryos (P<0.02) in Group IV cows. Ovarian ultrasonography revealed that the diameter of the largest follicle in Group III cows declined from Day 2 to Day 7 and subsequently increased until Day 13. In contrast, Groups I, II and IV were characterized by apparently linear growth between Days 2 and 13. Differences (P<0.05) were detected between Days 5 and 9. Mean diameter of the largest follicle was smaller for cows in Group III than for the remaining groups on Day 9. It was concluded that SMB did not adversely affect superovulatory response and that E(2) administration resulted in atresia of the antral follicles in the cows with SMB implants.     

The evolution of developmental strategy in marine invertebrates

Developmental mode varies widely in most animal phyla. These differences in developmental strategy exert a profound influence on the ecology and evolution of closely related species. The mechanistic alterations in ontogeny that lead to switches in developmental mode are coming under increasing scrutiny. Echinoids are one of the best-understood groups in this regard. Parallel modifications in direct-developing echinoids point to some of the key changes in oogenesis and embryogenesis that produce switches in developmental mode.     

茎用芥菜的离休培养及植株再生

植物名称:茎用芥菜(Brassica juncea var.tumida)。材料类别:幼叶、子叶。培养条件:以MS为基本培养基,诱芽培养基为:(1)MS BA 2mg/L(单位下同) NAA 0.2;(2)MS BA2 NAA0.5;(3)M8 BA4 NAA0.1.(4)MSS BA4 NAA 0.2;(5)MS BA4 NAA 1.0。生根培养基为:(6)MS NAA 0;(7)MS NAA 0.1;(8)MS NAA 0.5;(9)MS     

Phycomyces: fine structure analysis of the growing zone

Fine structure analysis of the stage IVb Phycomyces sporangiophore growing zone (GZ) was performed during steady-state growth using a computer-video digitizer and recorder. By simultaneously measuring the trajectory of two independent particles above and within the GZ, we have confirmed the previous findings of R. Cohen and M. Delbrück (1958 J Cell Comp Physiol 52: 361-388) that the GZ is not uniform. We have been unable to confirm their findings that counterclockwise rotation exists in a mature sporangiophore. The rates of rotation and elongation change independently as a function of position in the GZ. This change is not linear as would be expected if the GZ were uniform. The importance of this finding is discussed in terms of the fibril reorientation model.     

Halobacterium denitrificans sp. nov., an extremely halophilic denitrifying bacterium

Halobacterium denitrificans was one of several carbohydrate-utilizing, denitrifying, extremely halophilic bacteria isolated by anaerobic enrichment in the presence of nitrate. Anaerobic growth took place only when nitrate (or nitrite) was present and was accompanied by the production of dinitrogen. In the presence of high concentrations of nitrate (i.e., 0.5%), nitrous oxide and nitrite were also detected. When grown aerobically in a mineral-salts medium containing 0.005% yeast extract, H. denitrificans utilized a variety of carbohydrates as sources of carbon and energy. In every case, carbohydrate utilization was accompanied by acid production. A type culture has been deposited with the American Type Culture Collection, Rockville, Md. (ATCC 35960).     

Proline excretion by Escherichia coli K12

Proline excretion from proline overproducing strains of E. coli K12 has been studied as a model chemical production system. We have isolated proline overproducing mutants of E. coli and have shown that uncontrolled synthesis is not sufficient to cause excretion of this amino acid. An episomal mutation causing proline over production has been introduced into a series of otherwise isogenic strains that bear well defined, chromosomal lesions affecting the active uptake and catabolism of L-proline. A syntropism test reveals that L-proline is excreted by overproducing strains only if transport and/or catabolism are impaired. Dansyl derivatization and chromatographic analysis of culture supernatants shows that proline is the only amino acid excreted. Batch cultures of an excreting strain in an amino acid production medium yield culture supernatants containing 1 g proline/L, whereas no proline is detectable in supernatants derived from cultures of an overproducing strain with normal transport and catabolic activities. These data reveal that genetic lesions eliminating active uptake can be used to specifically enhance metabolite excretion.