Journal of Experimental Botany

GWÓŹDŹ, E., A.;BEWLEY, J., D.;TUCKER, E., B.

doi: 10.1093/jxb/25.4.599pmid: N/A

Abstract Desiccation of Tortula ruralis was achieved rapidly by placing the moss on the laboratory bench, or more slowly by placing it in desiccators with atmospheres of high relative humidities. Unlike the rapidly desiccated moss, the slower desiccated moss retained no polyribosomes in the dehydrated state, although polyribosome reformation and protein synthesis resumed on reintroduction of the moss to water. Protein synthesis commenced on rehydration of the slower desiccated moss at a greater rate than on rehydration of the faster desiccated moss. A lack of correlation between endogenous ribonuclease activity and polyribosome levels extracted from the moss suggests that the observed reduction in polyribosomes during desiccation was not due to their degradation but was more likely a consequence of stress-induced restriction on reinitiation of existing messenger RNA. The observed protein synthesis on rehydration of the moss was largely independent of any prior RNA synthesis. This content is only available as a PDF. © OXFORD UNIVERSITY PRESS

ROSENTHAL, GERALD, A.

doi: 10.1093/jxb/25.4.609pmid: N/A

Abstract Seeds of 29 species of canavanine-synthesizing legumes were assayed for their urease and canavanine production. All of the examined species possess detectable urease activity. In general, the leguininous seeds richest in urease also had the most canavanine. The urease content of the jack bean seed, Canavalia ensiformis (L.) DC., is formidable and disproportionally greater than the quantity of stored canavanine. The massive urease content of the seed cannot be rationalized by the magnitude of the canavanine pool. Analysis of eight species of Mucuna demonstrated that canavanine is not stored in the seeds of these plants. Mucuna species do not appear to be unique in having seeds that do not concurrently produce urease and canavanine. This content is only available as a PDF. © OXFORD UNIVERSITY PRESS

BIRAN,, I.;ROBINSON,, M.;HALEVY, A., H.

doi: 10.1093/jxb/25.4.614pmid: N/A

Abstract The partition of light radiated on to the outer epidermis of a Baccara rose petal or on to an intact petal was examined. Most of the red light was either reflected or transmitted whereas other wavelengths and especially the green range were absorbed. When the total amount of light transmitted (epidermis) or reflected (intact petal) increased, a rise in the blue range was recorded and the colour of the petal, determined objectively by CIE or Munsell's method, became more purple. Examination of the partition of light in the different layers of the petal revealed that light reflected from the outer epidermis is made up of two parts; one part is reflected directly and the other part is first transmitted through the epidermis, reaches the mesophyll, is reflected from it and is then transmitted through the epidermis. This latter part causes a shift in colour from purple to red. Colour differences between different petals on one flower and different parts of the same petal were defined objectively. The change from red to purple colour was connected with vigorous growth of either the petal or epidermal cells, respectively. The contribution of the mesophyll in changing the reflectance curve of petals is explained and it is suggested that although the mesophyll is colourless, it contributes to a great extent to the changes occurring in petal colour. This content is only available as a PDF. © OXFORD UNIVERSITY PRESS

BIRAN,, I.;ROBINSON,, M.;HALEVY, A., H.

doi: 10.1093/jxb/25.4.624pmid: N/A

Abstract ‘Blueing’ in young and senescing petals was compared in the red rose cv. Baccara. The ‘blueing’ of senescing flowers is accompanied by a bathochromic shift in the light reflectance curve, a rise in the pH value and a decrease in the malic acid concentration of the petal tissue. These factors indicate that a complex with a co-pigment is produced. Similar changes were not found in the ‘blueing’ of young flowers, where a decrease was found in pigment concentration per unit weight as well as per unit area of petal. A similar ‘blueing’ was achieved by diluting a solution of crystalline cyanin. The phenomenon of ‘blueing’ by dilution is discussed in the light of Bougeur's law. This content is only available as a PDF. © OXFORD UNIVERSITY PRESS

BIRAN,, I.;ROBINSON,, M.;HALEVY, A., H.

doi: 10.1093/jxb/25.4.632pmid: N/A

Abstract The changes in colour and in the pigment concentration of the two sides of Baccara rose petals which occur when plants are grown under various temperature regimes, were examined. The inner side of the petal is redder and the predominant pigment is pelargonin whereas the outer petal surface tends to ‘blue’, and, the predominant pigment on this side is cyanin. The cyanin: pelargonin ratio on the outer side of petals increased three-fold under the influence of low temperatures. The outer surface of petals growing for a long period under low tempertaures was ‘blue’ when compared with the red petals which had been subjected to low temperatures for a short period. The cyanin: pelargonin ratio of ‘blue’ petals was higher than that of red petals. Total pigment content was similar in both types of petal. Flowers grown under high temperatures ‘blued’ without a concomitant fall in the cyaninpel: argonin ratio. Examination of colour solutions in which the ratio between cyanin and pelargonin was varied revealed that the colour of the solution became bluer as this ratio increased. We suggest that the ‘blueing’ of Baccara rose petals is caused primarily by a dilution of the cyanin content, but when the ratio between cyaniri and pelargonin increases sharply, ‘blueing’ may also occur in dark flowers in which the total pigment content did not diminish. This content is only available as a PDF. © OXFORD UNIVERSITY PRESS

GROCHOWSKA, MARIA, J.

doi: 10.1093/jxb/25.4.638pmid: N/A

Abstract The nature and rate of degradation of carboxyl-14C-labelled indol-3y1-acetic acid (IAA-[l-14C]) were studied in apple leaves. The labelled auxin was applied to the cut surface of the growing shoot after the apical part had been removed. The respiratory CO2 absorbed by chromatographic paper as Na2CO3 then freed by phosphoric acid was quantitatively measured by an internal gas counter. It was found that the concentration of 14CO2 evolved by leaves was 77 times higher in daylight than in darkness. The ratio of 14CO2/CO2 obtained from respiration from the upper surface of leaf blades was two and seven times higher than that from the lower surface after 15 and 30 h of daylight, respectively. No such differences were noticed in darkness. Similarly, the total radioactivity of leaf tissues tripled in daylight, presumably because of photosynthetic incorporation of radioactive CO2 evolved during decomposition of LAA. These facts demonstrate the photolytic character of auxin decarboxylation in apple leaves. Prolonged darkness seemed to provoke a large metabolite withdrawal from leaves and, to some extent, to protect auxin against decarboxylation. This content is only available as a PDF. © OXFORD UNIVERSITY PRESS

SHORTESS, DAVID, K.

doi: 10.1093/jxb/25.4.647pmid: N/A

Abstract Two methods for the separation by polyacrylamide gel electrophoresis of chloroplast proteins which are completely insoluble in aqueous solution are compared. One method uses phenol, acetic acid and water, 2: 1:1, w/v/v, in 3 M urea (PAW/U) as the sample solvent with gels which contain 5 M urea and 35 per cent acetic acid. The other method involves the use of PAW/U as the sample solvent as well as the running solvent within the gel. The latter method has provided better band resolution and more consistent, repeatable results. This content is only available as a PDF. © OXFORD UNIVERSITY PRESS

PASSAM, H., C.

doi: 10.1093/jxb/25.4.653pmid: N/A

Abstract The respiration of Arum spadix mitochondria is coupled to a sub-maximal stoichiometry of ATP synthesis. The P/O ratios associated with the oxidation of succinate or malate are decreased by antimycin and increased by m-chlorobenzhydroxamic acid, an inhibitor of the alternative oxidase. The mitochondrial ATPase activity of 20–40 nmol (mg protein)−1 min−1 is independent of the maturity of the spadix and is unlikely to provide the mechanism for heat production during the odoriferous stage, which probably results from an increase in the rate of electron transport via the non-phosphorylating, cyanide-insensitive oxidase. This content is only available as a PDF. © OXFORD UNIVERSITY PRESS

TATTAR, TERRY, A.;BLANCHARD, ROBERT, O.;SAUFLEY, GEORGE, C.

doi: 10.1093/jxb/25.4.658pmid: N/A

Abstract Electrical resistance and capacitance measurements were made on woody tissues of several tree species. Each tissue was above the fibre-saturation point. Values of capacitance were inversely proportional to values of resistance in woody tissues in progressive stages of discoloration and decay. With the electrode separation used, clear woody tissues had resistances of 110 to 30 kΩ and capacitances of 0·002 to 0·110 μF. Resistance and capacitance measure ments of discoloured tissues were 29 to 8 kΩ and 0·005 to 0·040 μF, respectively, and those of decayed tissues were 5 to 1 kΩ and 0·60 to 0·110 μF. Either electrical measurement could be used to measure the stages of deterioration in woody tissues. Ground woody tissues, cellulose suspensions, starch suspensions, and wood equivalent solutions of potassium chloride had resistance and capacitance properties similar to those found in intact woody tissues. Electrical resistance and capacitance properties of woody tissues above the fibre-saturation point appear to be similar to those of dilute solutions of mobile ions. This content is only available as a PDF. Author notes 1Published with the approval of the Director of the New Hampshire Agricultural Experiment Station as Scientific Contribution No. 699. 2Present address: Shade Tree Laboratory, Dept. of Plant Pathology, University of Massachusetts, Amherst, Mass, 01002. 3Present address: U.S. Forest Service, Portsmouth, N.H. 03801. © OXFORD UNIVERSITY PRESS

KALPAN,, A.;GALE,, J.

doi: 10.1093/jxb/25.4.663pmid: N/A

Abstract The determination of osmotic potential in salt-accumulating or -secreting halophytes, by the standard pressure-bomb technique, is shown to produce artefacts. These may be avoided by the evaporative bomb technique described here. This content is only available as a PDF. © OXFORD UNIVERSITY PRESS