摘要:

Abstract.Comparisons were made between the changes in mRNA levels induced by low night temperatures in the cold–sensitive tomato and two altitudinal ecotypes of the wild speciesL. hirsutum.Changes in mRNA levels were detected by resolvingin vitrotranslation products of poly(A)+RNA by 2‐D PAGE. The treatment was applied by first growing plants in a thermoperiod of 25/18°C and then switching to 25/6°C. All tomatoes displayed a diurnal cycling in which a set of mRNAs accumulated at the end of the 18°C nights, whereas another accumulated at the end of the 25°C days. The accumulation of night specific mRNAs was inhibited by 6°C nights in the cold sensitive tomatoes while that of the tolerant one was only marginally affected. All tomatoes showed a similar reduction in the apparent turnover rate of the day specific mRNAs during the 6°C nights. Finally, low night temperatures induced the accumulation of six to eight mRNAs in all genotypes. This number increased by 15 inL. esculentumafter the seventh night and are likely involved in stress response rather than acclimation/tolerance. The tomato is proposed as a genetic model to discriminate genes involved in acclimation/tolerance from those involved in stress

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1991.tb01376.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.The enzymatic activity of 3‐deoxy‐D‐manno‐octulosonate 8‐phosphate (KDOP) synthase was detected in eight diverse plant species, thus providing enzymological data consistent with recent reports of the presence of 3‐deoxy‐D‐manno‐octulosonate in plant cell walls. KDOP synthase from spinach was partially purified and characterized. It possessed weak activity as 3‐deoxy‐D‐arabino‐heptulosonate 7‐phosphate (DAHP) synthase. In the presence of phosphoenolpyruvate, which conferred dramatic thermostability, KDOP synthase had a catalytic temperature optimum of about 53°C. The pH optimum was 6.2, and divalent cations were neither stimulatory nor required for activity. The Km values for arabinose 5‐P and phosphoenolpyruvate were 0.27 mol m−3and about 35 mmol m−3, respectively. The kinetics of periodate oxidation of KDOP formed by spinach KDOP synthase indicate that the same stereochemical configuration exists as with bacterial KDOP. The possibility that an unregulated species of DAHP synthase found in some bacteria might in fact be a KDOP synthase exhibiting substrate ambiguity of the type seen in higher plants was examined. However, the DAHP synthase isozyme, DS‐O, fromAcinetobacter calcoaceticuswas found to be specific for erythrose 4‐P. The KDOP synthase ofAcinetobacter calcoaceticuswas also

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1991.tb01377.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Stomatal conductance, leaf water potential, soil water potential and concentration of abscisic acid (ABA) in the xylem sap were measured on maize plants growing in the field, in two treatments with contrasting soil structures. Soil compaction affected the stomatal conductance, but this effect was no longer observed if the soil water potential was increased by irrigation. Differences in leaf water potential did not account for the differences in conductance between treatments. Conversely, the relationship between stomatal conductance and concentration of ABA in the xylem sap was consistent during the experiment. The proposed interpretation is that stomatal conductance was controlled by the root water potential via an ABA message. Control of the stomatal conductance by the leaf water potential or by an effect of mechanical stress on the roots is unlikely.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1991.tb01378.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.The objective of the work reported was to answer the following questions: (1) Do stomata respond to both humidity and temperature? (2) Do these responses interact in such a way that relative humidity at the leaf surface is a more appropriate variable than water vapour saturation deficit at the leaf surface and yields a simpler description of the compound response? To answer these questions, we measured the response of leaf conductance to humidity under constant leaf temperature, and the response to increasing leaf temperature under constant relative humidity and under constant water vapour saturation deficit. We found that, inHedera helixsubsp.canariensis(Willd.) Coutinho, there was a reversible response to humidity under constant temperature, and that there was also a response to temperature under constant relative humidity. The relationship between leaf conductance and relative humidity was different when measured at the same temperature rather than at different temperatures. An inversely proportional response was consistently obtained when stomatal conductance was expressed in relation to water vapour saturation deficit. The interaction between the effects of leaf temperature and water vapour saturation deficit was not compatible with a mechanism of response to humidity and temperature based solely on relative humidity. From these data, we conclude that water vapour saturation deficit is a more appropriate variable for describing stomatal responses to humidity.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1991.tb01379.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.A simulation of the quantitative influence of altitude on photosynthetic CO2uptake capability (AP) included the effects of predicted changes (1) in air temperature (lapse rate) and (2) leaf temperature, (3) ambient pressure and CO2concentration, and (4) the diffusion coefficient for CO2in air. When a dry lapse rate (0.01°C m−1) in air temperature was simulated, significant declines (up to 14%) in APwere predicted from sea level to 4km altitude. A moist lapse rate of 0.003°C m−1resulted in less than a 4% decrease in APover the same altitude range. When natural leaf temperatures (predicted from heat balance analyses) were simulated, APwas significantly greater (∼20%) than when leaf temperatures were considered equal to air temperature for all lapse conditions. There was virtually no change in APwith altitude when predicted leaf temperatures and moist lapse conditions were simulated. There was a significant (∼10%) increase in APwith altitude when leaf temperature was held constant at 30°C (regardless of altitude) under moist lapse conditions. Future studies evaluating the effects of elevation on photosynthesis could benefit from the above considerations of the effects of natural leaf temperature regimes and prevailing lapse conditions on CO2uptake

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1991.tb01380.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Book reviewed in this articles:PLANT AND CROP MODELLING, A MATHEMATICAL APPROACH TO PLANT AND CROP PHYSIOLOGY.By JohnH. M. Thornley&IanR. Johnson

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1991.tb01381.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY