Phenotypic plasticity and growth temperature: understanding interspecific variability.

The subject of this review is the impact of long-term changes in temperature on plant growth and its underlying components. The discussion highlights the extent to which thermal acclimation of metabolism is intrinsically linked to the plasticity of a range of biochemical and morphological traits. The fact that there is often a trade-off between temperature-mediated changes in net assimilation rates (NAR) and biomass allocation [in particular the specific leaf area (SLA)] when plants are grown at different temperatures is also highlighted. Also discussed is the role of temperature-mediated changes in photosynthesis and respiration in determining NAR values. It is shown that in comparisons that do not take phylogeny into account, fast-growing species exhibit greater temperature-dependent changes in RGR, SLA, and NAR than slow-growing plants. For RGR and NAR, such trends are maintained within phylogenetically independent contrasts (i.e. species adapted to more-favourable habitats consistently exhibit greater temperature-mediated changes than their congeneric counterparts adapted to less-favourable habitats). By contrast, SLA was not consistently more thermally plastic in species from favourable habitats. Interestingly, biomass allocation between leaves and roots was consistently more plastic in slow-growing species within individual phylogenetically independent contrasts, when plants were grown under contrasting temperatures. Finally, how interspecific variations in NAR account for an increasing proportion of variability in RGR as growth temperatures decrease is highlighted. Conversely, SLA played a more dominant role in determining interspecific variability in RGR at higher growth temperatures; thus, the importance of SLA in determining interspecific variation in RGR could potentially increase if annual mean temperatures increase in the future.

Hormonal changes induced by partial rootzone drying of irrigated grapevine.

Partial rootzone drying (PRD) is a new irrigation technique which improves the water use efficiency (by up to 50%) of wine grape production without significant crop reduction. The technique was developed on the basis of knowledge of the mechanisms controlling transpiration and requires that approximately half of the root system is always maintained in a dry or drying state while the remainder of the root system is irrigated. The wetted and dried sides of the root system are alternated on a 10-14 d cycle. Abscisic acid (ABA) concentration in the drying roots increases 10-fold, but ABA concentration in leaves of grapevines under PRD only increased by 60% compared with a fully irrigated control. Stomatal conductance of vines under PRD irrigation was significantly reduced when compared with vines receiving water to the entire root system. Grapevines from which water was withheld from the entire root system, on the other hand, show a similar reduction in stomatal conductance, but leaf ABA increased 5-fold compared with the fully irrigated control. PRD results in increased xylem sap ABA concentration and increased xylem sap pH, both of which are likely to result in a reduction in stomatal conductance. In addition, there was a reduction in zeatin and zeatin-riboside concentrations in roots, shoot tips and buds of 60, 50 and 70%, respectively, and this may contribute to the reduction in shoot growth and intensified apical dominance of vines under PRD irrigation. There is a nocturnal net flux of water from wetter roots to the roots in dry soil and this may assist in the distribution of chemical signals necessary to sustain the PRD effect. It was concluded that a major effect of PRD is the production of chemical signals in drying roots that are transported to the leaves where they bring about a reduction in stomatal conductance.

Tolerance of salinized floodplain conditions in a naturally occurring Eucalyptus hybrid related to lowered plant water potential.

Rising saline groundwater and reduced flooding frequency are causing dieback of Eucalyptus largiflorens F. Muell. along the Murray River in Australia. A green-leaved variant of E. largiflorens, which is probably a hybrid with a local mallee species (E. gracilis F. Muell.), tolerates saline conditions better than the more common grey-leaved variant. The green variant exhibited more negative water potentials than the grey variant, and comparison with soil water potential profiles indicated that the green variant extracted water from slightly higher up the soil profile where the salt content was lower but the soil was drier. However, the stable isotopes of water (2H and 18O) in the xylem did not differ significantly between paired green and grey trees, suggesting that both variants used the same water source. The green variant may be able to extract water for a longer period from a given point in the soil profile and tolerate a higher salt concentration around its roots than the grey variant. Predawn leaf water potentials of both variants decreased with increasing salinity of groundwater and decreasing depth to the groundwater, probably because the roots were being progressively confined to soil with lower matric potential as groundwater discharge through transpiration progressively salinized soil up the profile. The green variant had a lower assimilation rate and stomatal conductance than the grey variant, although the differences were not statistically significant during most of the year. Discrimination of 13C indicated that the green variant had a higher leaf internal CO2 concentration than the grey variant, indicative of a greater biochemical limitation on photosynthesis, perhaps resulting from the effects of operating at lower water potentials. The green variant had significantly lower stem hydraulic conductivity than the grey variant, probably because of its smaller xylem vessel diameter and higher degree of embolism. The more conservative water use of the green variant and its ability to operate at lower water potential than the grey variant appear to underlie its ability to tolerate conditions of reduced useable water above the saline groundwater. This advantage appears to outweigh the costs of increased xylem embolism and reduced assimilation.

Genetic manipulation of alcohol dehydrogenase levels in ripening tomato fruit affects the balance of some flavor aldehydes and alcohols

Tomato (Lycopersicon esculentum) plants were transformed with gene constructs containing a tomato alcohol dehydrogenase (ADH) cDNA (ADH 2) coupled in a sense orientation with either the constitutive cauliflower mosaic virus 35S promoter or the fruit-specific tomato polygalacturonase promoter. Ripening fruit from plants transformed with the constitutively expressed transgene(s) had a range of ADH activities; some plants had no detectable activity, whereas others had significantly higher ADH activity, up to twice that of controls. Transformed plants with fruit-specific expression of the transgene(s) also displayed a range of enhanced ADH activities in the ripening fruit, but no suppression was observed. Modified ADH levels in the ripening fruit influenced the balance between some of the aldehydes and the corresponding alcohols associated with flavor production. Hexanol and Z-3-hexenol levels were increased in fruit with increased ADH activity and reduced in fruit with low ADH activity. Concentrations of the respective aldehydes were generally unaltered. The phenotypes of modified fruit ADH activity and volatile abundance were transmitted to second-generation plants in accordance with the patterns of inheritance of the transgenes. In a preliminary taste trial, fruit with elevated ADH activity and higher levels of alcohols were identified as having a more intense "ripe fruit" flavor.

Breast cancer: demands of illness.

This study explores the qualitative experience of illness demands from the woman's own perspective by asking, "What is the impact of breast cancer on the daily lives of women of childbearing age?" Semistructured interviews with 79 women newly diagnosed with breast cancer were transcribed and analyzed to discern illness demands. Content analysis yielded 14 domains of illness demands: treatment issues, change in life context or perspective, acceptance of the illness, social interaction or support, physical changes, reconstructing the self, uncertainty, loss, making comparisons, acquiring new knowledge, making choices, mortality issues, financial or occupational concerns, and making a contribution. Illness demands are experienced in every aspect of a woman's life, including her identity, daily routines, family and social experience, and her perception of the past, present, and future. This study details in the women's own language the considerable adjustments brought on by a diagnosis of breast cancer.

Salinity effects on the stomatal behaviour of grapevine.

An investigation of the time-course of inhibition of photosynthesis in salt-stressed grapevine (Vitis vinifera L.) leaves revealed two types of stomatal behaviour. Up to tissue concentrations of 165 mM chloride the inhibition was due to a uniform decrease in stomatal conductance, as indicated from autoradiograms of 14 CO2 fixation and no change in the relationship of assimilation to calculated intercellular partial pressure of CO2 (A-C1 ) compared with control plants. The occurrence of non-stomatal inhibition of photosynthesis at higher levels of leaf chloride, suggested by a decline in the slope of the calculated (A-C1 ) relationship, was associated with non-uniform 14 CO2 uptake over the leaf surface similar to that previously observed for ABA-treated and water-stressed grapevine leaves where non-stomatal inhibition of photosynthesis was shown to be an artifact arising from non-uniform stomatal behaviour. These observations also provide an explanation for the stimulation of photorespiration during salt stress.

A monoclonal antibody to (S)-abscisic acid: its characterisation and use in a radioimmunoassay for measuring abscisic acid in crude extracts of cereal and lupin leaves.

A monoclonal antibody produced to abscisic acid (ABA) has been characterised and the development of a radioimmunoassay (RIA) for ABA using the antibody is described. The antibody had a high selectivity for the free acid of (S)-cis, trans-ABA. Using the antibody, ABA could be assayed reliably in the RIA over a range from 100 to 4000 pg (0.4 to 15 pmol) ABA per assay vial. As methanol and acetone affected ABA-antibody binding, water was used to extract ABA from leaves. Water was as effective as aqueous methanol and acetone in extracting the ABA present. Crude aqueous extracts of wheat, maize and lupin leaves could be analysed without serious interference from other immunoreactive material. This was shown by measuring the distribution of immunoreactivity in crude extracts separated by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC), or by comparing the assay with physicochemical methods of analysis. Analysis of crude extracts by RIA and either, after TLC purification, by gas chromatography using an electron-capture detector or, after HPLC purification, by combined gas chromatography-mass spectrometry (GC-MS) gave very similar ABA concentrations in the initial leaf samples. However, RIA analysis of crude aqueous extracts of pea seeds resulted in considerable overestimation of the amount of ABA present. Determinations of ABA content by GC-MS and RIA were similar after pea seed extracts had been purified by HPLC. Although the RIA could not be used to analyse ABA in crude extracts of pea seeds, it is likely that crude extracts of leaves of several other species may be assayed successfully.

Stomatal closure fully accounts for the inhibition of photosynthesis by abscisic acid.

The partial pressure of intercellular CO2 calculated from gas exchange data for abscisic acid-treated leaves of grapevine (Vitis vinifera L.) and sunflower (Helianthus annuus L.) does not indicate the average intercellular CO2 of the leaf. The latter can be determined from chlorophyll fluorescence quenching information and accurately modelled from gas exchange data. Stomatal closure can fully account for previously assumed non-stomatal inhibition of photosynthesis. Autoradiograms show that abscisic acid induces non-uniform gas exchange over small areas of the leaf.

DIURNAL CHANGES IN THE PHOTOSYNTHESIS OF FIELD-GROWN GRAPE VINES.

Field studies of the gas exchange of Riesling grape vines (Vitis vinifera L.) showed large diurnal changes in net photosynthesis during the period of rapid sugar accumulation by fruit. The onset of the decline in photosynthesis occurred earlier in the day for vines without fruit. Decreases in photosynthesis were approximately proportional to changes in stomatal conductance. Despite the accompanying large changes in stomatal conductance, changes in intercellular CO2 concentration were small and mathematical analysis showed that stomatal changes accounted for only 20 to 40% of the change in assimilation rate. The CO2 compensation point, oxygen enhancement of photosynthesis, light and temperature responses of the leaf did not vary throughout the day. Stimulation of photorespiration was therefore not responsible for the non-stomatal inhibition of photosynthesis. No obvious correlation existed between the decline in leaf photosynthesis and daily changes in leaf water potential. A field study of Colombard grape vines revealed that frequently watered vines which had received irrigation 2 d prior to measurement showed little change in photosynthetic rate over the day compared with vines subjected to a more usual watering cycle, which had last been irrigated 18 d prior to measurement. Possible non-stomatal factors responsible for the reduction in photosynthesis during the day are discussed.

The effect of fruit-removal on cytokinins and gibberellin-like substances in grape leaves.

Removal of fruit from potted cuttings of Vitis vinifera L. increased the concentration of a cytokininglucoside in leaf tissue extracts and decreased the level of extractable gibberellin-like substances. The glucoside (of zeatin riboside) is not present in xylem exudate of V. vinifera L., and appears to be synthesized in the leaves. Berry extracts contain zeatin-riboside and smaller amounts of cytokinin-glucoside. The changes in the level of these hormones are discussed in relation to previous results on abscisic acid and phaseic acid levels in grape leaves.

The Incorporation of Photosynthates by Meloidogyne javanica.

The root-knot nematode, Meloidogyne javanica, incorporated (1)C from its host after exposure of the plant to (1)CO. This uptake was relatively slow and was not detected in nematodes exposed to a labelled plant for periods of 2 and 4 h, but was after 24 h. Nematodes were grown in plants previously infected at weekly intervals to provide animals at various stages of growth. Plants were harvested 24 h after exposure to the label and the rate of incorporation per unit area of nematode was measured. This rate was found to be related to the nematode's physiological age and reached its peak at the time egg-laying commenced, after which it started to decline. The results support the hypothesis that the nematode functions as a metabolic sink.

Abscisic Acid and stomatal regulation.

The closure of stomata by abscisic acid was examined in several species of plants through measurements of CO(2) and H(2)O exchange by the leaf. The onset of closure was very rapid, beginning at 3 minutes from the time of abscisic acid application to the cut base of the leaf of corn, or at 8 or 9 minutes for bean, Rumex and sugarbeet; rose leaves were relatively slow at 32 minutes. The timing and the concentration of abscisic acid needed to cause closure were related to the amounts of endogenous abscisic acid in the leaf. Closure was obtained in bean leaves with 8.9 picomoles/cm(2). (+)-Abscisic acid had approximately twice the activity of the racemic material. The methyl ester of abscisic acid was inactive, and trans-abscisic acid was likewise inactive. The effects of stress on levels of endogenous abscisic acid, and the ability of very small amounts of abscisic acid to cause rapid closure suggests that stomatal control is a regulatory function of this hormone.

The red light controlled production of gibberellin in etiolated wheat leaves.

Most of the gibberellin activity detectable in extracts of etiolated wheat leaf tissue occurs in a bound form. There is a rapid increase in extractable gibberellin-like substances following exposure of the tissue to red light with a concomitant fall in the amount of bound gibberellin. Actinomycin-D and AMo 1618 do not inhibit this initial phase of red light stimulated gibberellin production.It is concluded that red light stimulated gibberellin production in etiolated wheat leaf tissue is due to release from a bound form and to synthesis.

The hormonal control of wheat leaf unrolling.

The unrolling of etiolated wheat leaf sections in the dark is stimulated by the application of gibberellic acid (GA3). GA3 is most effective if applied for a short time at the beginning of incubation. Kinetin also stimulated leaf unrolling in the dark. AMO1618 and CCC inhibit red light and kinetin-stimulated unrolling. Gibberellin-like substances extracted from red light-treated leaf tissue are effective in stimulating leaf unrolling.Ethylene production in leaf sections is stimulated by IAA, GA3 and kinetin and inhibited by ABA. A brief exposure to red light decreases the ability of the tissue to produce ethylene. It is concluded that ethylene plays no important role in the control of leaf unrolling by red light or by the application of hormones.

Phytochrome and hormonal control of expansion and greening of etiolated wheat leaves.

Unrolling of etiolated wheat leaf segments is stimulated by short periods of exposure to red light. Both gibberellic acid and kinetin will stimulate unrolling in the dark, whereas abscisic acid (ABA) inhibits the unrolling response to these two hormones and to red light. Exposure to 5 minutes of red light leads to a rapid increase in endogenous gibberellin levels in etiolated wheat leaves, and this increase is followed by a rapid decline. Pre-treatment with ABA inhibits the increase in gibberellin levels in response to red light, but the ihibitory effect of ABA on unrolling cannot be ascribed only to its effect on gibberellin levels. Pre-treatment with red light reduces the lag-phase in chlorophyll development when wheat leaf segments are subsequently exposed to white light; the effect of red light may be replaced by pre-treatment with kinetin, but gibberellic acid is relatively ineffective in this respect.