Journal of Experimental Botany

WHITNEY, P., J.;VAUGHAN, J., G.;HEALE, J., B.

doi: 10.1093/jxb/19.3.415pmid: N/A

Abstract Most of the comparative electrophoretic studies of proteins so far utilized in plant taxonomy have concerned higher plants and the protein sources have been organs of the same physiological age. Very little work of this nature has been carried out in the field of fungal systematics. The present paper is a disc electrophoretic study of the proteins of four fungal isolates of varying taxonomic status in which special emphasis has been placed on protein patterns exhibited throughout the entire growth period. This content is only available as a PDF. © Oxford University Press

HUGHES, M., A.

doi: 10.1093/jxb/19.3.427pmid: N/A

Abstract Using DEAE-cellulose two distinct β-glucosidase enzymes have been identified in white clover; one form is primarily associated with the seed, the other with young leaves. Evidence is presented for the separate nature of β-glucosidase and β-galactosidase activity in dry seed flour and in young leaf tissue. These results are considered in relation to the function of the Li locus in white clover, which is shown to control both β-glucosidase and β-galactosidase activity in expanding leaves. This content is only available as a PDF. © Oxford University Press

CRAWFORD, R. M., M.;MCMANMON,, M.

doi: 10.1093/jxb/19.3.435pmid: N/A

Abstract The levels of alcohol dehydrogenase and malic dehydrogenase activity were investigated in the roots of various species grown for several days, in aerated and non-aerated culture solutions. The activity of these enzymes in non-aerated cultures increased but only in those species previously found to be intolerant of experimental flooding. The induction of alcohol dehydrogenase was reversible. Physiological concentrations of acetaldehyde induced alcohol dehydrogenase activity, this induction being greatest in the species intolerant of flooding. It is suggested that the ineffectiveness of the inductive stimulus in the plants tolerant of flooding contributes to their homeostatic survival properties under high water-table conditions. This content is only available as a PDF. © Oxford University Press

SMITH, F., A.

doi: 10.1093/jxb/19.3.442pmid: N/A

Abstract The uptake of C1 ions by cells of Tolypella intricata is greatly increased by light, and must be an active process. K ions in the cells (at 90–110 mM concentration) are in approximate electrochemical equilibrium with the external solution, but the K influx is affected (directly or indirectly) by cellular metabolism. The K influx is increased by light, and the increase is greater in the presence of C1 than when C1 is removed from the solution. K uptake is inhibited by chemicals which also inhibit the C1 pump.It is suggested that light increases the permeability of the plasmalemma to K, but there must also be links between K and C1 uptake. The possible nature of these links is discussed.The internal Na concentration (3–10 mM) is considerably below the expected equilibrium concentration, but the Na influx is also very low (and is not increased by light). The permeability of the plasmalemma to Na is thus very low, and there can be little active extrusion of Na under normal conditions. This content is only available as a PDF. Author notes 1Present address: Department of Botany, University of Adelaide, Adelaide, South Australin 5001. © Oxford University Press

PINFIELD, N., J.

doi: 10.1093/jxb/19.3.452pmid: N/A

Abstract Gibberellin pretreatment of hazel seeds induced significant increases in the incorporation of carbon-14 from [2-14C] acetate into both glutamate and sucrose, while the amounts of radioactivity incorporated into citrate, malate and succinate were significantly higher after pretreatment with sterile water. A ratio based on the relative amounts of carbon-14 incorporated into glutamate and into the TCA cycle acids indicates that gibberellin treatment causes a diversion of metabolites from the essentially respiratory TCA cycle into synthetic sequences such as glutamate formation. Gibberellin treatment also appears to stimulate the activity of a reversed glycolytic sequence, resulting in the production of sucrose. This content is only available as a PDF. Author notes 1Present address: Botany Department, University of Bristol. © Oxford University Press

MORESHET,, S.;STANHILL,, G.;KOLLER,, D.

doi: 10.1093/jxb/19.3.460pmid: N/A

Abstract A new method is described for measuring the stomatal resistance to diffusion in leaves. It consists of measuring the radioactivity of air samples which have diffused through a leaf from a porometer container enriched with radioactive argon(41A). Details of the calibration are given together with the methods adopted to determine the accuracy of measurement and the optimum time of sampling. Results suggest that in the material investigated the measurements obtained are essentially those of stomatal resistance.In one small experiment inter and intra plant variability in stomatal resistance was investigated; in another, the diffusion porometer was used to compare the daily march of stomatal resistance with the rate of transpiration in plants growing under four different soil-moisture regimes. This content is only available as a PDF. © Oxford University Press

SHONE, M. G., T.

doi: 10.1093/jxb/19.3.468pmid: N/A

Abstract The difference in electrical potential between the xylem exudate of isolated roots of 1-week-old maize seedlings and the culture solution surrounding the roots has been determined together with the concentrations of potassium, calcium, chloride, and sulphate in the xylem sap. The difference in electro-chemical potential (Δμ) for these ions has been calculated from the measurements. The effects on Δμ of varying the salt status of the roots, the composition of the culture solution and of 2-4-dinitrophenol have been examined. Δμ for potassium and chloride was always positive, implying that movement of these ions to the xylem sap was under metabolic constraint. However, pretreatment of the maize seedlings with potassium chloride and increasing levels of dinitrophenol in the culture solution over the exudation period caused little or no significant change in Δμ for potassium although the rate of movement of ions to the xylem was substantially reduced. For calcium, Δμ was negative with roots in dilute culture solutions in the absence of dinitrophenol, implying that calcium could enter the xylem by passive diffusion. Addition of dinitrophenol changed the sign of Δμ and thus brought about an apparently active transport of calcium.Only in the absence of competing anions was the rate of entry of chloride significantly correlated with Δμ, and no such relationship was found for potassium or calcium individually. These results encourage doubt as to whether measurements of Δμ provide a valid basis for deciding to what extent the movement of individual ions depends on specific ‘active’ or ‘passive’ transport processes.The difference in electrical potential appears to be a characteristic of the living root and to depend on the total concentration of ions in the external solution and on their rate of transfer into the xylem sap. This content is only available as a PDF. © Oxford University Press

BRIGGS, G., E.

doi: 10.1093/jxb/19.3.486pmid: N/A

Abstract The relation of the rate of passive movement of water into the absorbing region of the root to the difference between the osmotic pressures of the external solution and those of the exudate from the xylem of a detopped plant or isolated root, and also the relation of the rate of passive movement of solute to the differences of concentration of solute of electric potential are considered. This content is only available as a PDF. © Oxford University Press

BIELORAI,, HANOCH

doi: 10.1093/jxb/19.3.489pmid: N/A

Abstract The beta-ray gauging technique was used to measure the relative changes occurring in the water content of sour orange and sweet lime leaves as a result of soil wetting and drying cycles. Promethium-147 served as the radiation source and was found suitable for measuring changes in citrus leaf thickness within the range of 20 mg/cm2 (when soil moisture content was at ‘pot capacity’) to 10 mg/cm2 (when soil moisture dropped to wilting point). By using the correlation between beta-ray gauging measurements, leaf thickness, and relative turgidity, it is possible to determine the status of water in citrus leaves under different soil moisture conditions. This content is only available as a PDF. Author notes 1Contribution from the Volcani Institute of Agricultural Research (N.U.I.A.), Bet Dagan, Israel. 1968 Series, No. 1295-E. © Oxford University Press

NELMES, BRENDA, J.;PRESTON, R., D.

doi: 10.1093/jxb/19.3.496pmid: N/A

Abstract The development of the walls of the parenchyma cells of apple fruit cortex has been followed throughout two seasons under conditions which allow an assessment of wall structure as a factor involved in the keeping quality of apples. Changes in chemical compositions, in physical organization, and in cell size have been monitored throughout.Unexpectedly rapid wall synthesis occurs during cell extension but is followed, before harvest, by a period during which some pectic substances are reassimilated and in which some lability of wall components is indicated. There is a marked thinning of the wall at this stage, for which subsequent secondary thickening fails to compensate fully.Differences in cell-wall structure between apples from trees receiving different manurial treatments are most marked during cell extension, when cells from apples which keep well show symptoms consistent with a lower nitrogen level. These differences have largely disappeared by harvest, but reasons are given to indicate that the earlier stages of fruit development may have a considerable influence on potential storage life. This content is only available as a PDF. © Oxford University Press