Diurnal Rhythmicity in the Pattern of mRNAs in the Leaves of Sinapis alba

Previous studies have shown that certain specific leaf mRNAs exhibit a diurnal rhythmicity in their quantity in higher plants. To determine whether this situation is restricted to a few mRNAs, or affects a large number, we have used in vitro translation and two-dimensional polyacrylamide gel electrophoresis to analyze the mRNA complement in leaves of Sinapis alba at different times during an 8-hour/16-hour day/night cycle. A method for the visual analysis of two-dimensional polyacrylamide gel electrophoresis was also developed. This method selected, at each sampling time, spots that were significant. It then selected, between two sampling times, intensity changes that were significant at the 0.02 confidence level. During a day/night cycle, complex rhythmic changes affected about 10% of the mRNAs. Nineteen different rhythm patterns were found. These 19 patterns fell into four main classes: mRNAs that increase during the light period and decrease during the dark, mRNAs that increase and then decrease during the light period, mRNAs that decrease during the light period and increase during the dark period, and mRNAs that increase and then decrease during the dark period.     

Emission of volatile sulfur compounds from spruce trees

Spruce (Picea Abies L.) trees from the same clone were supplied with different, but low, amounts of plant available sulfate in the soil (9.7-18.1 milligrams per 100 grams of soil). Branches attached to the trees were enclosed in a dynamic gas exchange cuvette and analyzed for the emission of volatile sulfur compounds. Independent of the sulfate supply in the soil, H₂S was the predominant reduced sulfur compound continuously emitted from the branches with high rates during the day and low rates in the night. In the light, as well as in the dark, the rates of H₂S emission increased exponentially with increasing water vapor flux from the needles. Approximately 1 nanomole of H₂S was found to be emitted per mole of water. When stomata were closed completely, only minute emission of H₂S was observed. Apparently, H₂S emission from the needles is highly dependent on stromatal aperture, and permeation through the cuticle is negligible. In several experiments, small amounts of dimethylsulfide and carbonylsulfide were also detected in a portion of the samples. However, SO₂ was the only sulfur compound consistently emitted from branches of spruce trees in addition to H₂S. Emission of SO₂ mainly proceeded via an outburst starting before the beginning of the light period. The total amount of SO₂ emitted from the needles during this outburst was correlated with the plant available sulfate in the soil. The diurnal changes in sulfur metabolism that may result in an outburst of SO₂ are discussed.     

Effects of the developmental state of the tissue on the competence for flower bud regeneration in pedicel explants of tobacco

The competence of pedicel explants of tobacco (Nicotiana tabacum L. cv Samsun) to regenerate flower buds in response to auxin was manipulated by preincubating excised tissues in the absence of auxin. When exposed to 1 micromolar 1-naphthaleneacetic acid, these tissues formed fewer buds than controls that were not preincubated. The number of buds eventually formed correlated with the 1-naphthaleneacetic acid concentration in the tissue 6 hours after the start of hormone application. The internal concentrations in pretreated explants were lower than in tissues that were not pretreated due to diminished uptake per milligram fresh weight and increased hormone conjugation. The change in the developmental state induced by auxin deprivation had a dual effect on bud regeneration: (a) the pretreatment caused fewer buds to be formed at any 1-naphthaleneacetic acid concentration tested, and (b) a higher auxin concentration in the medium was required to get a maximum bud number on precultured explants. An increase of the 1-naphthaleneacetic acid concentration in the medium led to an elevated hormone level in freshly cut as well as in preincubated tissues. It was concluded that the developmental state of the tissue directly affects the maximum number of buds that can be regenerated. Apart from that there is an indirect effect exerted via modulation of the ratio between external and internal auxin concentration. The change in this ratio can be compensated for by an adjustment of the auxin concentration in the medium.     

Mechanical impedance increases aluminium tolerance of soybean (Glycine max) roots

The effect of aluminium (Al) on root elongation was studied in solution culture and sand culture. Compared to solution culture, in sand culture a ten times higher Al supply was necessary to inhibit root elongation to a comparable degree. This was due to a much lower Al uptake into the 5 mm root tips in sand culture. Fe concentrations in root tips were also lower in sand culture. Ca concentrations were higher and less depressed by Al, whereas Mg and K concentrations were not affected by the culture substrate. Regressions of Al concentrations in root tips versus inhibition of root elongation by Al revealed root damage at lower Al concentrations in sand culture. The effect of culture substrate on Al tolerance was independent of N source and could also be shown in flowing solution culture with and without sand. The results indicate that mechanical impedance in sand culture decreased Al uptake. This may be due to enhanced exudation of organic complexors thus reducing activites of monomeric Al species.     

Dynamics of African ungulate populations with fluctuating, density-independent calf survival

Leslie matrix simulations were performed, employing idealized ungulate life histories and density-independent, either random or periodic, variation in calf survival, p₀. Long-term average rate of increase was reduced whenever variation was added to p₀. The iteroparous life histories strongly buffered high-frequency vital rate variations, so that large fluctuations in p₀ resulted in relatively small fluctuations in population size. The buffering effect was greatest for species with the longest lifespans. The results suggest that wild ungulate populations will not fluctuate greatly in response to density-independent, environmental-driven vital rates. Such populations will reach high densities, thus experiencing strong density-dependent regulation, only a few times in many generations.     

The isolation and characterization of gibberellin-deficient mutants in tomato

Summary In tomato, nine independent EMS-induced mutants representing recessive mutations at three different loci (gib-1, gib-2, and gib-3) were isolated. Six of these have an almost absolute gibberellin requirement for seed germination and elongation growth. In addition, the leaves are darker green, smaller, and changed in structure as compared to wild type. The three other mutants, which germinate without GA, are allelic to specific, nongerminating mutants and have less severe mutant characteristics. The respective loci are situated on three different chromosomes. The genes identified by these mutants control steps in gibberellin biosynthesis, as endogenous gibberellins are strongly reduced.     

Salmonella-TEK, a rapid screening method for Salmonella species in food

A micro-enzyme-linked immunosorbent assay (micro-ELISA) using the Salmonella-TEK screen kit was tested for the detection of Salmonella spp. in pure cultures as well as in 30 artificially contaminated food samples and in 45 naturally contaminated food samples. Different raw, fleshy foods and processed foods were used as test products. The artificially contaminated minced meat samples were preenriched in buffered peptone water, and after incubation, different selective enrichment broths were tested. The micro-ELISA optical density values after enrichment and isolation of the different broths were very analogous. The quickest method to detect Salmonella spp. in different foods is to enrich them with Salmosyst broth, which reduces the total analysis time to 31 h. The Salmonella-TEK kit for Salmonella spp. provides a promising test for the detection of Salmonella antigens in food even when they are present at a low concentration (1 to 5 CFU/25 g). The cross-reaction of the anti-Salmonella antibodies, especially to other gram-negative bacteria, is nil.     

Inverse Diauxy in the Yeast Hansenula anomala: Mutants Derepressed for Malic Acid Utilization in the Presence of Glucose

Utilization of l-malic acid by yeast strain Hansenula anomala IGC 4380 is subject to glucose repression. Derepressed mutants were obtained with UV light by use of the nonmetabolizable glucose analog 2-deoxyglucose as a selective agent. Three mutant strains degraded l-malic acid in the presence of up to 30% (wt/vol) glucose and are of potential interest for the biological deacidification of grape must. The mutant strains, as compared with the parent strain, displayed inverse diauxy in glucose-malate medium, glucose being metabolized only after malate consumption had been completed.     

IL9 maps to mouse chromosome 13 and human chromosome 5

Mouse and human cDNA clones encoding the T-cell and mast cell growth factor P40, now designated IL-9, were used to identify DNA restriction fragment length polymorphisms (RFLPs) in sets of somatic cell hybrids and between inbred strains of mice and interspecific backcross progeny. Segregation of mouse and human chromosomes among somatic cell hybrids indicated a location on mouse chromosome 13 and human chromosome 5. RFLPs were identified among inbred strains of mice. Analysis of chromosome 13 alleles for Tcrg, Dhfr, and Il-9 in an interspecific cross between Mus musculus and NFS/N or C58/J mice indicates that IL-9 is distal to Tcrg and Proximal to Dhfr.