Journal of Experimental Botany

GINZBURG,, CHEN

doi: 10.1093/jxb/25.6.995pmid: N/A

Abstract The influence of GA and CCC on growth and assimilate translocation to the various plant organs in gladiolus was studied by labelling a single leaf with 14CO2 and following the distribution of the assimilates. GA promotes inflorescence growth by directing assimilate movement towards the inflorescence at the expense of the corm. CCC has a similar but smaller effect. GA and CCC both promote assimilate translocation from the labelled leaf during the period of inflorescence growth. When this period is over and the corm becomes the main sink, translocation from the labelled leaf is promoted by CCC but inhibited by GA. The effect of CCC may be only partly explained on the basis of an increase in GA turnover in gladiolus. This content is only available as a PDF. Author notes 1Contribution from the Agricultural Research Organization, The Volcani Centre, Bet Dagan, Israel. 1974 series, No. 118-E. 2Abbreviations: GA—Gibberellin A3; CCC—(2-chloroethyl)trimethylammonium chloride. © OXFORD UNIVERSITY PRESS

SAWHNEY, VIPEN, K.

doi: 10.1093/jxb/25.6.1004pmid: N/A

Abstract Tomato plants of a single-gene recessive mutant, stamenless-2 (sl2/sl2), bear abnormal stamens but produce near-normal flowers following application of gibberellic acid. Data presented here show that mutant plants have lower levels of extractable gibberellin-like substances in vegetative as well as floral parts compared with normal ones. The significance of these observations in relation to gene-controlled stamen form, and sexuality of plants is discussed. This content is only available as a PDF. Author notes 1Present address: Department of Biological Sciences, Simon Fraser University, Burnaby, B.C., Canada, V5A 1S6. © OXFORD UNIVERSITY PRESS

SEN,, SWATI;OSBORNE, DAPHNE, J.

doi: 10.1093/jxb/25.6.1010pmid: N/A

Abstract On germination of low viability embryos of rye, var. Lovasz Patonai, the rate of protein synthesis increases during the early hours of imbibition and high rates of DNA replication commence around the 9th hour. If embryos are imbibed for 3 or 6 h then dehydrated back to their original weight, their rate of protein synthesis when next imbibed closely corresponds to that of embryos germinated for a period equal to that of the hydration pre-treatment plus the duration of the second imbibition. Pre-treatment also enhances subsequent RNA synthesis and embryos hydrated for 9 h then dehydrated start major DNA synthesis at once as water is again supplied. Many changes occurring during these periods of hydration pre-treatment must therefore be stable to subsequent dehydration. Damage occurs to areas that are first active in protein and RNA synthesis if pre-treatments extend beyond 9 h and subsequent germination of the embryo is then impaired. The implications of these results are discussed in relation to the effects of hydration pre-treatments upon enhanced germination and the stability to dehydration of the products of early RNA and protein synthesis. This content is only available as a PDF. © OXFORD UNIVERSITY PRESS

WALLNER, S., J.;NEVINS, D., J.

doi: 10.1093/jxb/25.6.1020pmid: N/A

Abstract Studies of the formation and separation of cellular aggregates in Paul's Scarlet rose suspension cultures have been conducted in an attempt to resolve the basis for intercellular adherence. During the typical growth cycle, cellular aggregates begin to fragment spontaneously at about day 12 in culture. This fragmentation is accompanied by a sharp decrease in the galactose content of wall polysaccharides. At approximately this same time, there is an increase in β-glucosidase and β-galactosidase activity associated with the cell surface. The presence of a β-glucosidase inhibitor, nojirimycin, inhibits the surface β-glycosidase activity, reduces the extent to which cell wall galactose is decreased, and prevents the separation of cells. No other cell wall component examined changes in a manner consistent with cell separation. The results suggest that a galactose-containing wall polysaccharide may be involved in the maintenance of intercellular coherency and that partial removal of this component may be causally related to the spontaneous separation of cells in culture. This content is only available as a PDF. Author notes 1Present address: Food Laboratory, U.S. Army Natick Laboratories, Natick, Massachusetts, 01760. © OXFORD UNIVERSITY PRESS

COLLINS, G., B.;SUNDERLAND,, N.

doi: 10.1093/jxb/25.6.1030pmid: N/A

Abstract Haploid plantlets were obtained in large numbers in three diploid, 24-chromosome species of Nicotiana by culture of anthers at or just past the first pollen mitosis. The three species were N. Knightiana, N. raimondii, and N. attentiata. Efficiency of haploid production varied from about 10 per cent in N. attenuata cultures to 30 and 38 per cent respectively in cultures of N. raimondii and N. Knightiana. H-medium without hormones and standard cultural conditions were used. N. Knightiana appeared to be especially suitable for haploid studies on account of its high plantlet productivity, low chromosome number, and distinctive karyotype. This content is only available as a PDF. Author notes 1Permanent address: Agronomy Department, University of Kentucky, Lexington, Kentucky 40506, U.S.A. © OXFORD UNIVERSITY PRESS

EZEALA, D., O.;HART, J., W.;SABNIS, D., D.

doi: 10.1093/jxb/25.6.1037pmid: N/A

Abstract Adenosine triphosphatase activity, present in extracts of isolated phloem and xylem tissues of Heracleum mantegazzianum and the petioles of Helianthus annuus, has been fractionated on 7 per cent polyacrylamide gels into electrophoretically distinct enzymes with different properties. Extracts of whole petioles contain four enzymes capable of hydrolysing ATP, phloem extracts possess two, and xylem, one. Enzyme I, common to all the extracts, shows preferential hydrolysis of nucleoside triphosphates and is stimulated by monovalent cations. Enzyme II, of phloem and of petiole extracts, is a general phosphatase. Enzymes III and IV, of petiole extracts, are specific for nucleoside triphosphates but are unaffected by monovalent cations. All four enzymes are markedly inhibited by Mg2+. None of the enzymes is affected by ouabain or oligomycin. This content is only available as a PDF. © OXFORD UNIVERSITY PRESS

EZEALA, D., O.;HART, J., W.;SABNIS, D., D.

doi: 10.1093/jxb/25.6.1045pmid: N/A

Abstract Adenosine triphosphatase activity has been studied in fractionated extracts of isolated phloem and xylem tissues of Heracleum mantegazzianum Somm. et Lev. and of petioles of Helianthus annuus L. Enzyme activity in the microsomal fraction is maximal with ATP as substrate. Monovalent cations stimulate activity, but only below pH 7·0. Divalent cations are inhibitory. Stimulation of ATPase activity by monovalent cations is increased in preparations which have either been derived from acetone powders or pre-treated with dithiothreitol or cysteine. This content is only available as a PDF. © OXFORD UNIVERSITY PRESS

COLLIS-GEORGE,, N.;MELVILLE, M., D.

doi: 10.1093/jxb/25.6.1053pmid: N/A

Abstract Models of oxygen diffusion in respiring seeds of uniform properties and with a relatively impermeable seed coat are proposed. Specimen calculations are presented using the data of Edwards (1969) for excised charlock embryos and intact seeds. The calculated answers are very sensitive to the assumed values of the oxygen diffusion coefficient and absorption coefficient in the seed material but whatever the assumptions, the apparent dormancy of charlock seed in air may be directly related to an oxygen deficiency within the embryo tissue. The consequences of errors in measured values of the diffusion and absorption coefficients in the seed material, and of assumptions concerning the uniformity of seed material, are discussed. Since the ultimate test of a diffusion model depends upon an accurate measurement of the concentration distribution within the seed, the useful limit of development of respiration and oxygen diffusion models may have been reached because of the practical difficulties in making these measurements. This content is only available as a PDF. Author notes 1Present address: School of Geography, University of New South Wales, Sydney, Australia. © OXFORD UNIVERSITY PRESS

MILLAR, B., D.

doi: 10.1093/jxb/25.6.1070pmid: N/A

Abstract The equilibration between the water potential of air inside the psychrometer and that of calibrating solutions, soils, and plant leaves is examined. The results are compared with those in the literature and with a theory for predicting equilibration times. Techniques aimed at reducing equilibration times are devised and tested. A method which employs a psychrometer to determine the adsorption isotherm of its own wall material is used to assess the suitability of three materials for chamber construction. The main findings include: (1) Times for equilibration of solution and soil samples were as brief as 8 min and 1–3 h, respectively, and times for ‘equilibration’ of tobacco leaf samples obtained with the improved psychrometer are significantly shorter than those reported for previous designs of Spanner-type psychrometers. These improvements enhance the calibration and operational convenience of the method. (2) Current criteria for deciding the attainment of “equilibria” with leaf samples may result in a large error, termed equilibration error. With pine and wheat leaf samples this error may be more than −460 J kg−1, and about −1200 J kg−1, respectively. A criterion for reducing equilibration error is described. (3) Predicted equilibration times for leaf samples are generally far too short. Several factors that are neglected in the theory and which probably account for most of this discrepancy are described. (4) A new technique is outlined which enables up to a 15-fold reduction in the ‘equilibration’ times of pine needle samples. (5) Stainless steel (type 316) appears to be the most suitable chamber material of those tested. This content is only available as a PDF. © OXFORD UNIVERSITY PRESS

WATTS, W., R.

doi: 10.1093/jxb/25.6.1085pmid: N/A

Abstract Leaf extension rates of young maize plants were measured in the field. Large diurnal fluctuations of air temperature from about 5—35°C caused extension rates to vary from 0·4 mm h−1– 3·6 mm h−1. When the temperature of the shoot apical meristem was kept at 30–34°C, extension rates remained constant, despite diurnal fluctuations of air temperature. Leaf water potentials (ψ) above −8 or −9 bars had little apparent effect on extension rate. It was concluded that ψ gradients within leaves could account for this. This content is only available as a PDF. Author notes 1Present address: Department of Botany, University of Aberdeen, St. Machar Drive, Aberdeen AB9 2UD. © OXFORD UNIVERSITY PRESS