Journal of Experimental Botany

SCHOCH, PAUL, G.;JACQUES,, ROGER;LECHARNY,, ALAIN;SIBI,, MONIQUE

doi: 10.1093/jxb/35.10.1405pmid: N/A

Abstract Using appropriate coloured lights, we show that phytochrome is involved in stomatal differentiation. This photoperception is located within the whole shoot. This action is also shown for in vitro leaves. The nature of the morphogenetic information is discussed. Stomatal differentiation, Phytochromy, Vigna sinensis L. This content is only available as a PDF. © Oxford University Press

SNAITH, P., J.;MANSFIELD, T., A.

doi: 10.1093/jxb/35.10.1410pmid: N/A

Abstract Evidence is presented which confirms the inhibitory action of the synthetic auxin, NAA, on stomatal opening. In contrast to the natural auxin IAA, NAA exerts effects which, in some respects, resemble those of ABA. The mode of action of NAA on the guard cells is, however, thought to be different from that of ABA. When NAA and ABA are applied together, their combined action results in a greater reduction in stomatal aperture than would be predicted from their separate effects. NAA, ABA, IAA Stomata, Commelina This content is only available as a PDF. © Oxford University Press

HENSON, I., E.

doi: 10.1093/jxb/35.10.1419pmid: N/A

Abstract Application of a heat girdle near the base of the lamina of the fifth, fully expanded leaf of young pearl millet (Pennisetum americanum [L.] Leeke) plants resulted in a decrease in solute potential, an increase in leaf dry matter content, and a decline in stomatal conductance and in the rate of CO2 assimilation. Total water potential was largely unaffected by girdling while turgor potential increased as a consequence of the decrease in solute potential. Abscisic acid (ABA) content of the leaf increased 5 to 6-fold within 1 h of girdling, then declined equally rapidly before increasing again at a slower rate. The decline in conductance was correlated with both the decrease in solute potential and the increase in ABA. To determine which of these factors could be controlling conductance, girdled leaves were exposed either to 14 h of continuous light or to a similar period of darkness followed by a brief light treatment to allow stomata to open. Girdling reduced conductance equally following darkness or light but solute accumulation occurred only in the light. ABA accumulated in girdled leaves in both darkness and light. Simultaneous measurements of conductance and CO2 assimilation showed that intercellular CO2 concentration did not increase following girdling. It was concluded that the decrease in conductance in millet leaves after girdling was most probably mediated by the increase in ABA content. Leaf girdling, Solute accumulation, Stomatal conductance, Abscisic acid; Pennisetum americanum This content is only available as a PDF. © Oxford University Press

BEHL,, RUDOLF;HARTUNG,, WOLFRAM

doi: 10.1093/jxb/35.10.1433pmid: N/A

Abstract Using modified compartmental analysis the unidirectional fluxes of abscisic acid (ABA) and their cytoplasmic and vacuolar contents in 3H-ABA preloaded barley root segments (Hordeum distichon cv. Aura) have been studied. When root segments were stressed osmotically with sorbitol (osmotic potential of the media π0 = 0.2 MPa) cytoplasmic and vacuolar contents of ABA were enhanced. Under increased stress cytoplasmic and vacuolar contents were much lower than in the unstressed controls. ABA fluxes were very sensitive to osmotic stress and ABA transport from the cytoplasm of the xylem parenchyma to the xylem vessels (φcx) was rapidly inhibited. The cultivar Aura has higher cytoplasmic and vacuolar ABA contents than the barley cultivar Kocherperle. This correlates well with the higher stress tolerance of the Aura cultivar. Abscisic acid, Compartmentation, Osmotic stress This content is only available as a PDF. Author notes 1 Present address: Pflanzenphysiologisches Institut der Universitat Gottingen, Untere Karspule 2, 3400 Gottingen, F.R.G. © Oxford University Press

PALTA, JAIRO, A.

doi: 10.1093/jxb/35.10.1441pmid: N/A

Abstract Measurements of gas-exchange, leaf water potential and the leaf diffusive conductance of the abaxial leaf surface of six cassava cultivars, M Mex 59, M Ven 218, M Col 1684, M Col 72, M Col 22, and M Col 638, were made at 48 h intervals and between 1200–1500 h, on potted plants, grown outdoors during a 58 d period of withdrawal of irrigation. Rates of net-photosynthesis of about 28 mg CO2 dm−2 h −1 were reduced to zero within the first 5 d of the drying cycle, despite the small differences in leaf water potential of 0.15 MPa. Water shortage also caused a reduction in mean conductance to < 1.0 mm s−1 at which level the control of transpiration maintained leaf water potential at > —1.6 MPa. Cultivar differences in the response of net-photosynthesis and leaf diffusive conductance to water shortage were seen within 2 d of the dry cycle and the leaf water potential was commonly 0.15 MPa lower than in the wet controls. The most vigorous cultivars (M Mex 59, M Ven 218 and M Col 1684) reduced their rates of net-photosynthesis to zero by day 5 of the dry cycle when the soil water content was depleted by 65%. Less vigorous cultivars (M Col 72, M Col 22 and M Col 638) reduced their rates of net-photosynthesis to zero by day 30, when the soil water content was depleted by 75%. Measurements are also reported of the leaf production per apex and leaf extension for leaves produced during the drying cycle. Cassava (Manihot esculenta Crantz), Gas-exchange, Leaf diffusive conductance, Water deficits This content is only available as a PDF. Author notes 1Contribution from the programme of cassava physiology, Centro Internacional de Agricultura Tropical, Cali, Colombia. 2Present address: School of Agriculture, La Trobe University, Bundoora, Victoria 3083, Australia. © Oxford University Press

DASGUPTA,, JUTHIKA;BEWLEY, J., DEREK

doi: 10.1093/jxb/35.10.1450pmid: N/A

Abstract Water stress, applied to the roots of six-day-old barley seedlings markedly reduced the capacity of their leaves to synthesize proteins during greening, a process that normally involves intense synthetic activity. Upon illumination of etiolated seedlings protein synthesis commenced most rapidly in the basal region, and then declined in activity. Thereafter, in turn, the middle and apical regions exhibited a similar pattern of synthetic activity; this is indicative of a ‘wave’ of protein synthesis progressing from the base of the leaf to the apex as greening proceeded. The synthesis of proteins varied both quantitatively and qualitatively in different regions of the leaf during greening. For example, there was a noticeable increase in ribulose-1, 5-bisphosphate carboxylase synthesis in the apical region of the leaf compared to the basal region. Water stress reduced protein synthesis in all regions of the leaf, although most effectively in the oldest, apical regions. Upon return to full water status, the basal regions recovered the most rapidly and to the greatest extent. Similar results were obtained when both intact greening leaves, and isolated segments from different regions of the leaf were used. The reduction in protein synthesis elicited by water stress was not due to a selective quantitative change in any particular protein; one protein, of an approximate molecular weight of 60 kD, appeared to be synthesized only under stress conditions. Water stress, Protein synthesis, Barley seedlings This content is only available as a PDF. © Oxford University Press

ROSINGER, C., H.;WILSON, J., M.;KERR, M., W.

doi: 10.1093/jxb/35.10.1460pmid: N/A

Abstract The effects of low temperature (5 °C and 12°C) and drought treatments on leaf soluble protein content and free amino acid content have been investigated in four species, which were ranked according to chilling-sensitivity: pea (chill-resistant), mung bean (highly chill-sensitive), and tomato and french bean (intermediate chilling-sensitivity). Drought treatment caused a 30–40% decrease in protein levels, and in all but the mung bean, a 100–200% increase in free amino acid concentration. Four days chilling at 5°C, 85% r.h. caused leaf water content to decrease by almost 50% in the mung bean, but by only approximately 6–7% in the other three species. During this treatment the leaf soluble protein content decreased in all four species although the decrease was greatest and most rapid in the mung bean, commencing with 8 h of chilling (coinciding closely with the onset of water loss), and decreasing by over 80% after 4 d. In the chill-sensitive species (but not in the pea) the decrease in protein content was accompanied by an increase in free amino acid content. However, on a mgg−1 dry wt. basis, this increase was insufficient to account for all the protein lost. When plants of each species were chilled at 5°C, 100% r.h., water loss was greatly reduced or prevented and there was no significant decrease in leaf soluble protein. It is concluded that the protein decrease which occurred at 5°C, 85% r.h., was a response to water loss and not the direct result of low temperature. However, chilling at 100% r.h. did cause an increase in free amino acid content of the chill-sensitive species, suggesting that this was a direct response to low temperature. Although drought treatment caused a 6–20 fold increase in free proline content in the leaves of the four species examined, chilling (5°C) and chill-hardening (12°C) caused little change in free proline content, indicating that the accumulation of this ‘protective’ amino acid is unlikely to contribute to the effectiveness of the chill-hardening treatment. Low Temperature, Drought, Leaf soluble protein.content, Amino acids This content is only available as a PDF. Author notes 1 Present address: 53 Chegworth Gardens, Sittingbourne, Kent ME10 1RJ, U.K. © Oxford University Press

CRAWFORD, R. M., M.;ZOCHOWSKI, Z., M.

doi: 10.1093/jxb/35.10.1472pmid: N/A

Abstract Controversy exists as to whether ethanol ever accumulates to toxic levels in anaerobic tissues of higher plants. In order to manipulate the internal concentrations of ethanol and relate these to anaerobic injury, seedlings of chickpea (Cicer arietinum L.) were incubated under strict anoxia in vessels in which the anaerobic atmosphere either remained static or else was circulated with that of a large anaerobic incubator. Incubation with a circulating, as compared with a static, anaerobic atmosphere doubled the time that the seedlings could be kept under anoxia and emerge in subsequent survival testing in the glasshouse. Circulating the anaerobic atmosphere gave a 13-fold reduction in the accumulation of ethanol in the seedlings. Parallel experiments which varied the ratio of head space relative to seedling number confirmed that the dilution of the volatile products of anoxia.increased survival. These products included carbon dioxide, ethanol and traces of acetaldehyde. While carbon dioxide may play a role in modifying glycolytic activity under anoxia, it is suggested that it is not directly toxic and that it is the reduction in ethanol concentration in the seedlings as a result of head space dilution that contributes to their increased longevity in circulating anaerobic atmospheres. Cicer arietinum L., Ethanol, Anaerobic conditions This content is only available as a PDF. © Oxford University Press

WALKER, R., R.;SEDGLEY,, M.;BLESING, M., A.;DOUGLAS, T., J.

doi: 10.1093/jxb/35.10.1481pmid: N/A

Abstract Seedlings of Rangpur lime (Citrus reticulata var. austera hybrid?) and Etrog citron (C. medica) were treated in water culture with 0, 25, 50 or 100 mol m−3 NaCl, and in sand culture with 0 or 100 mol m−3 NaCl. Leaf chloride analyses indicated that Etrog citron accumulated the most chloride at all levels of salinity. The structure, ultrastructure and concentrations of chloride and reserve assimilates of the primary root up to 50 mm back from the tip were compared between genotypes and between salt treatments. There were no differences in root anatomy in the absence of salt between the two genotypes. The hypodermal cells developed lignified and suberized walls which blocked the plasmodesmata and resulted in degeneration of the cell contents. Frequent thin-walled passage cells in the hypodermis had living contents and may represent major sites of ion uptake into the symplasm, which was connected with the stele via plasmodesmatal connections with and between the cortical cells. The primary endodermal cells had lignified casparian strips and plasmodesmata in other cell wall areas. These connections were blocked by secondary suberization of all except the endodermal passage cells opposite the protoxylem arcs. Suberization of the hypodermis and endodermis and the appearance of granular deposits in the vacuole occurred closer to the root tip of both genotypes after treatment with 100 mol m−3 NaCl. Levels of starch and triglyceride in 10 mm serial segments were similar between roots of control and salt-treated plants and increased with distance back from the root tip. Chloride concentrations increased with salt treatment but values (on a tissue water basis) were similar between genotypes and between the apical and proximal ends of the root. Reducing sugar concentrations decreased with salt treatment to a similar extent in roots of both genotypes. Citrus, Roots, Salinity This content is only available as a PDF. © Oxford University Press

TEASDALE, R., D.

doi: 10.1093/jxb/35.10.1495pmid: N/A

Abstract The specific growth rates of suspension cultured Loblolly pine (Pinus taeda) cells were used as a physiological response to copper deficiency, thereby circumventing difficulties incurred through cell wall copper adsorption and trace background contamination which complicate alternative experimental approaches. Variation in specific growth rate with copper concentration is assumed to be hyperbolic, a behaviour consistent with theoretically derived models. Growth response data are thereby interpreted to estimate background copper contamination, plus the copper dissociation constant of the uptake system, and the inhibition constant for competition by a combination of transition metal ions. Analysis of the time course of growth when cells are transferred from copper sufficiency to deficiency conditions indicates an insignificant endogenous pool of copper. Similar consideration of growth under toxicity conditions indicates that no diffusional barrier to copper influx exists. These results are interpreted to indicate that copper uptake is not mediated by a membrane carrier, but freely diffuses across the plasmalemma to bind directly to a high affinity intracellular acceptor. Copper uptake, Growth analysis, Copper nutrition, Loblolly pine, Pinus taeda, Suspension culture, Cellular nutrition, Endogenous pool This content is only available as a PDF. © Oxford University Press