Stomatal responses to changes in temperature at increasing water stress

Summary The response of stomata to a gradual increase in temperature at increasing plant water stress was studied in a hot desert habitat (Negev, Israel) in the field, but under controlled temperature and humidity conditions. Four native species (Zygophyllum dumosum, Artemisia herba-alba, Hammada scoparia, Reaumuria negevensis) and one cultivated plant (Prunus armeniaca) were used in these studies. The stomatal response to temperature was compared with the response in well-irrigated plants of the same species.At low water stress, the diffusion resistance for water vapour decreased in response to a gradual increase in temperature. Transpiration increased accordingly. This response was reversible. All species responded in the same way. The opening of stomata with increasing temperature was apparently independent of the stomatal response regulated by atmospheric humidity. At high plant water stress, the stomatal response was reversed, i.e., the stomata closed when temperature was gradually increased. This stomatal closure was also independent of the closure regulated by atmospheric humidity. The plant water potential at which the stomatal response to temperature was reversed, differed among the species investigated.     

Continuous Thermophilic Composting

Under complete mixing conditions, aerobic decomposition of mixed organic waste materials has been maintained continuously in the thermophilic phase in a 55-gal rotating drum. Temperatures ranged between 53 and 70 C. Raw material was added daily or every second day in amounts up to 18 lb per 100 lb of decomposing material. The weight of material removed ranged between 42 and 60% of the raw material added.

Factors influencing the operation of the composting unit were studied in detail.

     

Immunocytochemical studies of the Gi Protein mediated muscarinic receptor-adenylyl cyclase system

The localization of three key signal transduction components was indicated in rat heart tissue by immunocytochemical and histochemical experiment. It was shown that:

1. The M2 muscarinic receptors are localized along outer cell membranes and T-tubule membranes of cardiomyocytes but additionally at membranes of endothelial cells and fibroblasts.
2. G_iα was found along outer cell membranes of cardiomyocytes and other cells of the heart and also inside the cells of the perinuclear space in close contact to the nuclei envelope and the endoplasmic reticulum membranes. G_oα were found to be associated mainly in atrial tissue, especially at the nerval (neuronal) endings located among the cardiac muscle cells. This was shown in parallel incubation with specific neuronal antibody as a marker for these structures.
3. Adenylyl cyclase was localized along the sarcolemma and the T-tubule membranes in normal cardiomyocytes of rat and guinea pig hearts. Under ischemic conditions, the adenylyl cyclase was also seen in junctional sarcoplasmic reticulum membranes. The reasons for this changed localization need further elucidation. Binding of the adenylyl cyclase within the molecular structure of the membrane or variation of the marker penetration remain to be clarified.

     

Oxidative side reactions during dansylation of SH-compounds.

Dansyl chloride can act as an oxidizing agent on compounds which are easily oxidized. During the reaction of mercaptanes, e.g. cysteine, homocysteine, cysteamine, with dansyl chloride, the corresponding disulfides are formed and dansyl chloride is reduced to 5-dimethylaminonaphthalene 1-sulfinic acid. This reaction is so rapid that the normal dansylation can take place only after complete oxidation of all SH-compounds. Therefore only the dansyl derivatives of the corresponding disulfides are formed during normal dansylation of SH-compounds. If different SH-compounds are present in the reaction mixture mixed disulfides are formed as well. These can be separated by microchromatography on 3 X 3 cm micropolyamide sheets. Dependent on the concentration of dansyl chloride, 6 or even 15 different dansylated disulfides are formed from three different SH-compounds so that interpretation of these chromatograms is difficult. The actual dansylmercaptanes (e.g., dansylcysteine, dansylhomocysteine, dansylcysteamine) can be prepared by reduction of the dansylated disulfides with suitable reducing agents.     

Lead toxicity and phosphate deficiency in chlamydomonas

The addition of lead salts to phosphate-containing Chlamydomonas reinhardtii media caused precipitation of Pb₃(PO₄)₂, effectively removing phosphate from solution. The effect of Pb²⁺ on growth of Chlamydomonas in liquid cultures depended strictly on the ratio of the equivalents of Pb²⁺ to phosphate present. When the amount of Pb²⁺ approached equivalency with phosphate, cell growth was initially slow as cells adhered to the surface of the precipitated Pb₃(PO₄)₂. Later, cells grew at a normal rate, spread throughout the solution, and reached the same densities obtained in the absence of Pb²⁺. Cells did not survive when the amount of Pb²⁺ in the culture exceeded the equivalents of phosphate.

Elemental analysis showed that in the presence of equivalent Pb²⁺ and phosphate, considerable Pb²⁺ remained in solution. The concentration of dissolved Pb²⁺ did not vary significantly when the amount of Pb²⁺ added to the culture was increased slightly, from an amount which permitted growth to an amount which completely prevented growth. The concentration of phosphate was decreased to an undetectable level when the amount of Pb²⁺ approached equivalency with phosphate.

In the presence of the chelating agent nitrilotriacetic acid, higher concentrations of Pb²⁺ remained in phosphate-containing media. The chelated Pb²⁺ did not retard the growth of Chlamydomonas.

It appears that Pb²⁺ is not toxic to Chlamydomonas, but kills cells by depriving them of phosphate.

     

Chromosome analysis of bone marrow in mammals after treatment with isoniazid

Summary Cytogenetic investigations in bone marrow from animals treated with isoniazid (INH) were performed in seven different laboratories according to a standard protocol. The experiments were carried out in the Chinese hamster, the mouse, and the rat. In short-term studies INH was administered twice at an interval of 24 h in doses of 5, 25, and 125 mg/kg, and the animals were sacrificed 6, 12, 24, and 48 h after the second dose. In long-term studies doses of 25 and 125 mg/kg were administered thrice weekly for 12 weeks. As a rule, each group consisted of at least four animals, and 100 metaphases per animal were counted. Statistical analysis of the data showed that the incidence of chromosomal aberrations including gaps lay in the critical range for two groups in one laboratory and was significantly higher than in the control in three groups in another of the seven laboratories. From the results of both the short-term and the long-term studies in all laboratories, however, it may be concluded, that isoniazid does not induce gross chromosomal aberrations.     

Comparison between pressure-volume and dewpoint-hygrometry techniques for determining the water relations characteristics of grass and legume leaves

Summary The water relations characteristics of three grass species (Panicum maximum var. trichoglume, Cenchrus ciliaris, Heteropogon contortus), and a legume (Macroptilium atropurpureum) grown in the field were measured using both a modified pressure/volume technique with pressure bomb measurements on single leaves and a dewpoint hygrometry technique applied to fresh and to frozen and thawed leaf discs.The two techniques agreed well in the estimates of osmotic potential at full turgor and the water potential at zero turgor. However, for parameters such as the relative water content at zero turgor, bound water and bulk modulus of elasticity there was a poor correlation between the estimates from the two methods. The pressure/volume technique gave less variable results and is more convenient for field use than the hygrometry technique. The determination of the modulus of elasticity from various functions relating pressure potential to relative water content is discussed.     

Ultrastructure of Brucella abortus L-forms induced by penicillin in a liquid and in a semisolid medium

Brucella abortus L-forms were induced by 5.0 or 10.0 mug of penicillin/ml in a broth medium containing 0.3 m sucrose, and in a semisolid medium containing 10% calf serum and 20.0, 40.0, or 60.0 mug of penicillin/ml. After 96 hr of incubation, L-forms of various sizes and shapes were observed. Basic structures of the L-forms were similar whether induced in liquid or semisolid medium. L-forms had two "unit" membranes, each consisting of two outer dense layers separated by a lucent layer. A few large, irregularly shaped organisms in penicillin-treated broth cultures had additional surface material and were referred to as "transitional" forms. In contrast with L-forms, the bacterial cells were fairly uniform in size and shape, were smaller, and had a more complex cell wall structure. Small bodies limited by a "unit" membrane were present within and around numerous L-forms from liquid and semisolid medium cultures. Other internal membranous structures were also seen in some L-forms. Most Brucella L-forms described in this paper reverted to bacteria in the absence of penicillin and were structurally characteristic of unstable L-forms.     

Double-standard isotope dilution assay: I. Quantitative assay of indole-3-acetic acid

Isotope dilution analysis for the quantitation of labile compounds has been limited in applicability by the amount of sample necessary to determine specific activity. A method is described for the analysis of radiolabeled compounds which allows the direct determination of specific activity by gas chromatography. It requires the availability of the radiolabeled internal standard, as is customarily used in an isotope dilution assay, and also requires a chemically related radiolabeled compound to serve as a second internal standard. It is this second internal standard, added in known amounts, that permits quantitation of the gas chromatography. The method is illustrated by assaying indole-3-acetic acid in plant extracts using [¹⁴C]indole-3-acetic acid as the internal standard and adding [¹⁴C]indole-3-butyric acid as the second internal standard for quantitation of the gas chromatographic procedures. Used with a nitrogen-specific thermionic detector the method is selective and is sensitive at the nanogram level. The synthesis of [2-ring-¹⁴C]indole-3-butyric acid is also described.