Journal of Experimental Botany

RIDGE,, IRENE;OSBORNE, DAPHNE, J.

doi: 10.1093/jxb/21.4.843pmid: N/A

Abstract Purified cell-wall preparations from the epicotyl of etiolated Pisum sativum contain covalently bound peroxidases and hydroxyproline-rich proteins. Towards the end of cell elongation there is a large rise in these wall components and thereafter a continuing slow rise which is associated with increasing age of tissue. Ethylene at concentrations of 0.1 ppm or more increases both peroxidase activity and hydroxyproline levels in the walls, the greatest response occurring in immature tissue including the apical hook. Growth of these tissues is highly sensitive to ethylene which causes an inhibition of elongation in extending cells and an enhanced lateral cell expansion. We suggest that the effects of ethylene on wall-bound peroxidase and hydroxyproline are implicated in the ethylene regulation of cell growth. The covalently bound wall peroxidase was found to be extremely stable and to contain unique isoenzymes which do not occur in either the cytoplasm or in the peroxidase which is ionically bound to walls. Ethylene increases peroxidase activity in both the cytoplasmic and the ionically bound wall fractions, but there is little or no increase in their hydroxyproline content. The possible relationships between covalently bound wall peroxidase and hydroxyproline are discussed and we speculate that this peroxidase may be involved in the hydroxylation of proline in the walls. This content is only available as a PDF. Author notes 1Address after October 1970: Unit of Developmental Botany, Agricultural Research Council, Huntingdon Road, Cambridge. © Oxford University Press

SCURFIELD,, G.;NICHOLLS, P., W.

doi: 10.1093/jxb/21.4.857pmid: N/A

Abstract The ammo-acid compositions of proteins present in the sapwood and heartwood from three species of Eucalyptus, in normal, reaction, and opposite wood from Pinus radiata seedlings, and in reaction and opposite wood from Eucalyptus goniocalyx, are listed. The question of the location of protein within wood cell walls is discussed. The amounts of tyrosine found in the woods from P. radiata seedlings are incompatible both with the belief that it determines the intensity of staining of reaction wood cell walls with Millon's reagent, and that it is the source of the p-hydroxybenzaldehyde obtained when milled wood lignin is oxidized with nitrobenzene. Loss of amino acids in the presence of milled wood lignin, α-cellulose, hemicellulose, glucose, mannose, galactose, xylose, arabinose, glucuronic, and galacturonic acids is demonstrated. The presence of numerous peaks which are not indentifiable with known amino acids in the chromatograms of wood hydrolysates is believed to be due largely to the products of interaction of amino acids and sugars. Some retention of nitrogen by the residues of wood hydrolysates occurs. The significance of the results obtained with the wood samples listed above is discussed against this background. This content is only available as a PDF. © Oxford University Press

KAO,, C.;ROWAN, K., S.

doi: 10.1093/jxb/21.4.869pmid: N/A

Abstract Stratification at 0 °C accelerates subsequent germination of seed of Pinus radiata D. Don when transferred to 25 °C; the effect of low temperature is on the megagametophyte, not the embryo. Organic acids, sucrose, and organic phosphates accumulate in the seed during stratification but lipase and invertase have low activities which do not increase during treatment at 0 °C. We conclude that this accumulation of metabolites underlies the increase in rate of germination of stratified seed. Treating seeds at 0 °C rather than 5 °C separates effects due to stratification and growth. This content is only available as a PDF. Author notes 1Present address: Forestry Department, National Taiwan University, Taipei, Taiwan, China. © Oxford University Press

JEWELL, WILLIAM, J.;KULASOORIYA, S., A.

doi: 10.1093/jxb/21.4.874pmid: N/A

Abstract The variation of acetylene reduction activity and heterocyst frequency with culture age, was studied in five species of blue-green algae. The heterocyst frequency varied between 2.5 to 12.3 per cent of total cells; and the acetylene reduction activity varied 2.0-fold (average). It is suggested that an estimate of the nitrogen fixation rates in blue-green algae may be made by in situ heterocyst counts and acetylene reduction measurements. This content is only available as a PDF. Author notes 1Presently, Assistant Professor of Civil Engineering (Environmental Health Engineering Division), The University of Texas, Austin, Texas, 78712. © Oxford University Press

TRUDEL, M., J.;OZBUN, J., L.

doi: 10.1093/jxb/21.4.881pmid: N/A

Abstract Studies of fruit pigmentation at various stages of ripening showed that the chlorophylls generally decreased as the total carotenoids increase during ripening. At any stage of ripening, the carotenoid content of K-deficient fruit was lower than that of normal fruit. The relationship between the two pigment systems was altered by the K. status of the fruit. When the rate of carotenogenesis was low (green and red stages), the chlorophylls were higher in high K-fruit than in K-deficient fruit. When the rate of carotenoid synthesis was rapid (breaker to light red stages), the chlorophyll level of K-deficient fruit was higher than that of normal fruit. This content is only available as a PDF. Author notes 1Paper Number 601. Department of Vegetable Crops, Cornell University, Ithaca, New York 14850. 2Present address: Department of Crop Science, Laval University, Quebec 10e, Canada. © Oxford University Press

WALTON,, EVERILD;BUTT, V., S.

doi: 10.1093/jxb/21.4.887pmid: N/A

Abstract The preparation of an extract from leaves of spinach beet (Beta vulgaris L. ssp. vulgaris), which catalysed, the activation of cinnamate, is described. The reaction required CoA and was most rapid under nitrogen in the presence of thiol reagents. An enzyme which activated acetate was also present but was distinguishable by its indifference to thiol reagents and air during the reaction and its greater stability during storage under air. Extracts catalysing cinnamate activation could be prepared only from rapidly growing leaves at the height of the growth season. This content is only available as a PDF. Author notes 1Present address: Sir William Dunn School of Pathology, South Parks Road, Oxford. © Oxford University Press

VAUGHAN, J., G.;DENFORD, K., E.;GORDON, E., I.

doi: 10.1093/jxb/21.4.892pmid: N/A

Abstract The parental and hybrid seed of three synthesis experiments (B. oleracea × B. campeslris = B. napus) has been analysed by acrylamide gel electrophoresis for general proteins and certain enzymes. A serological study has been made of one of the synthesis experiments. The protein and enzyme patterns of the newly established hybrids are compared with those of two well-established varieties of B. napus. The results suggest that the hybrid seed has no protein which differs from those in the parental types, and that the protein spectrum of the hybrid is a summation of some of the proteins found in the parents. The analytical methods employed are discussed with particular reference to their value as an assessment of plant genotype. This content is only available as a PDF. © Oxford University Press

MEIRI,, A.;ANDERSON, W., P.

doi: 10.1093/jxb/21.4.899pmid: N/A

Abstract Observation of the water fluxes from excised maize roots at various levels of suction showed significant differences between control roots and those which have been subjected to an evacuation pre-treatment. This involved placing excised lengths of root in bathing medium in a flask which was evacuated (1 cmHg) for 10 min; during this time air bubbles emerged from the cut ends. This pre-treatment has been shown to result in an increase in the density of the root, which is ascribed to the replacement of air in the cortical intercellular spaces by bathing medium. The observed differences in the response to suction in the two groups of roots is therefore explained as a decrease in the resistance to water flow of the cortex of the treated roots. This content is only available as a PDF. Author notes 1Permanent address : The Volcani Institute for Agricultural Research, Dept. Soil and Water, Bet-Dagan, P.O.B. 6, Israel. 2Present address: Department of Botany, University of Liverpool. © Oxford University Press

MEIRI,, A.;ANDERSON, W., P.

doi: 10.1093/jxb/21.4.908pmid: N/A

Abstract Comparison of two preparations of Zea mays primary roots has shown that the salt concentration in the xylem fluid is altered as it passes through a region of the root where no absorption of salts or water from the external bathing medium can occur. Salts are secreted to the xylem by such a region, presumably from the vacuoles of the cortical cells. It has also been demonstrated that longitudinal water movement through the root cortex is negligibly small during root-pressure exudation. This content is only available as a PDF. Author notes 1Permanent address: Volcani Institute of Agricultural Research, Department. Soils and Water, P.O.B. 6, Bet-Dagan, Israel. 2Present address: Department of Botany, The University of Liverpool 3. © Oxford University Press

SHTARKSHALL, R., A.;REINHOLD,, LEONORA;HAREL,, HADASSAH

doi: 10.1093/jxb/21.4.915pmid: N/A

Abstract Amino-acid uptake by barley leaf strips was investigated with the aid of an unnatural analogue, α-aminoisobutyric acid (AIB). Negligible metabolism of this acid by the tissue was detected. Accumulatory capacity rose with ‘ageing’ of tissue in 10−4 M CaSO4. This effect was not attributable to bacterial contamination. Net uptake was linear with time for at least 5 h and proceeded against a strong concentration gradient. The rate constant for the loss of previously accumulated labelled AIB into water was one-tenth of that into unlabelled AIB. When influx and efflux were estimated separately, ‘ageing’ was found to have reduced the rate of exit by a factor of 4. The rise in influx, though proportionately smaller, was larger in absolute value. This content is only available as a PDF. © Oxford University Press