Mobilization of calcium in glasshouse tomato plants by localized scorching.

It is postulated here that significant amounts of calcium will be mobilized into the plant by the scorching of one old leaf. This postulate was tested using large (6 m) tomato plants in the glasshouse. Brief scorching with a blowlamp was shown to release some 35% of the leaf's water into the plant. A range of measurements was used to estimate the kinetics and magnitude of this flow. The flow was found to carry a pulse of up to 50% of the leaf's total calcium into the plant, probably via the xylem, and was estimated to increase xylem calcium levels transiently by a factor of about 80. The potential value of scorching treatments in combating calcium-deficiency disorders is discussed.     

Comprehensive mapping of mutations in the SARS-CoV-2 receptor-binding domain that affect recognition by polyclonal human plasma antibodies

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Ethylene-induced growth and proton excretion in the aquatic plant Nymphoides peltata

In the presence of auxin, ethylene can promote growth in petioles of N. peltata (S.G. Gmel.) O. Kuntze. Acid buffer will also stimulate growth in the tissue and, in abraded petiole segments, ethylene-stimulated growth is accompanied by a marked acidification of the medium. Auxin stimulates growth in this tissue and, for various auxin and ethylene treatments, the amount of growth is closely correlated with the degree of medium acidification. The results are consistent with predictions of the ‘acid-growth’ theory, and provide the first evidence that ethylene acts by an ‘acid-growth’ mechanism.     

Conservation of Glycerolated Cultures of Ochromonas danica and O. malhamensis at −10 C

SYNOPSIS. Ochromonas danica in a complex natural growth medium dies at 6–10 C in 4 days; O. malhamensis in ∼2 days. O. danica grown in the medium supplemented with 4.0% glycerol survived at −10±2 C for 35 days, and with 8% glycerol 29 days. O. malhamensis lasted only to 5 days in these media supplemented with 4% glycerol. Ethylene glycol and dimethylsulfoxide were too toxic to be effective. Difficulties in freeze-preservation of certain other phagocytic cells, notably blood granulocytes having comparatively simple flexuous outer membranes, add interest to use of O. danica and O. malhamensis as test organisms for preservation methods, especially in the convenient, inexpensive -10 to -20 C range. Biphasic media with an overlay of distilled water serve for conservation at room temperature. Problems of mutational erosion of these photosynthetic phagotrophs are discussed.     

Trehalose and α-glucan mediate distinct abiotic stress responses in Pseudomonas aeruginosa

An important prelude to bacterial infection is the ability of a pathogen to survive independently of the host and to withstand environmental stress. The compatible solute trehalose has previously been connected with diverse abiotic stress tolerances, particularly osmotic shock. In this study, we combine molecular biology and biochemistry to dissect the trehalose metabolic network in the opportunistic human pathogen Pseudomonas aeruginosa PAO1 and define its role in abiotic stress protection. We show that trehalose metabolism in PAO1 is integrated with the biosynthesis of branched α-glucan (glycogen), with mutants in either biosynthetic pathway significantly compromised for survival on abiotic surfaces. While both trehalose and α-glucan are important for abiotic stress tolerance, we show they counter distinct stresses. Trehalose is important for the PAO1 osmotic stress response, with trehalose synthesis mutants displaying severely compromised growth in elevated salt conditions. However, trehalose does not contribute directly to the PAO1 desiccation response. Rather, desiccation tolerance is mediated directly by GlgE-derived α-glucan, with deletion of the glgE synthase gene compromising PAO1 survival in low humidity but having little effect on osmotic sensitivity. Desiccation tolerance is independent of trehalose concentration, marking a clear distinction between the roles of these two molecules in mediating responses to abiotic stress.