摘要:

The relationship between freezable water and cold hardiness during acclimation was studied using vegetative buds from several apple (Malus domesticaBorkh) cultivars and from one saskatoonberry (Amelanchier alnifoliaNutt. cv. Smoky) cultivar. According to leakage data and visual assessments of cortical browning, vegetative buds of all cultivars were most tolerant to subfreezing temperatures in January. The hardy condition was also associated with maximum tolerance to desiccation. Qualitative features of freezing exotherms (number of peaks and temperature of the transition) were not correlated with the hardy condition in the tissues. However, the amount of unfrozen water, determined by quantifying the energy of the exotherms, increased with increasing hardiness. In buds that survived exposure to −45°C, freezing reduced the intracellular water content, but only to levels above the critical moisture content for desiccation damage. In buds that did not survive exposure to −45°C, freezing reduced the water content to levels equal to or less than the critical moisture content for desiccation damage. These observations suggest that the freezing of water in nonhardy tissue dried the tissue to moisture levels at which severe dehydration damage occurred. It appears that acclimation of vegetative apple buds involves at least two processes: (1) an increase in tolerance to dehydration and (2) an increase in the level of unfreezable

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb02162.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Cuttings ofPopulus nigraL. cv. Loenen andPopulus maximowicziiHenri ×Populus nigraL. cv. Rochester were exposed for 6 weeks in open‐top chambers to investigate effects of realistic mixtures of ozone, sulphur dioxide, and nitrogen oxides on carbohydrate levels. Whereas the total main nonstructural carbohydrates in the leaves were reduced, those in the roots were nearly not affected. The reduction in leaf carbohydrates was associated with a significant decrease in starch. In contrast, sucrose and especially glucose were increased, causing a shift in the starch to sucrose and the starch to glucose ratios. The effects were strongest in the older leaves of both cultivars, with cv. Loenen, especially, responding to ozonic mixtures. In the petioles, sucrose and glucose were unchanged or, in some cases, decreased. The alterations in carbohydrate levels were coupled to a reduction in both total fresh weight of leaves and total dry matter of roots, and were attributed to an air pollution‐dependent demand for energy and carbon in le

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb02163.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Syringostatin is a newly discovered phytotoxin produced by a phytopathogenic bacteriumPseudomonas syringaepv. syringae lilac isolate. The effects of syringostatin and the similar phytotoxins, syringomycin and syringotoxin, on H−‐ATPase activity were investigated using cultured mung bean (Vigna radiataL. cv. Ryokuto) cells or plasma membrane vesicles isolated from mung bean hypocotyls.31P‐NMR analysis of cultured cells treated with syringostatin revealed that the cytoplasmic pH was decreased. When plasma membrane was prepared by a two‐step method (Dextran gradient followed by a sucrose gradient). syringostatin, syringomycin and syringotoxin inhibited the H+‐ATPase activity in a dose‐dependent manner. In contrast, these toxins stimulated H+‐ATPase activity when plasma membrane was prepared by a one‐step method (sucrose gradient). While these toxins inhibited the H+‐ATPase activity of inside‐out plasma membrane vesicles, the H+‐ATPase activity of right‐side‐out vesicles was stimulated. The detergent. Triton X‐100, abolished this stimulatory effect of the toxins on the H+‐ATPase of right‐side‐out vesicles and of one‐step purified plasma membrane. The toxins also inhibited the activity of the plasma membrane H+‐ATPase solubilized with deoxycholate and Zwittergent 3–14. Taken together, these results indicate that these toxins exert their effects partly by a detergent‐like action on the plasma membra

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb02164.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Physiological responses ofAgropyron desertorumandPseudoroegneria spicata, two common cold desert perennial tussock grass species of the North American Great Basin, were evaluated during and after a period of imposed drought in a pot study. The timing and the pattern of response of leaf water potential (Ψ1), stomatal conductance (gs), and root growth were strikingly similar in both species during and after drought. The severity of stress influenced the magnitude of Ψ1and gs, but had little effect on the timing of these responses. Although drought inhibited total root length in prestressed plants, within 4 days after relief of drought both species showed similar increases in root growth which exceeded those of the control. Despite similarities in their root growth responses to increased soil water availability, the two grasses differed in their capacity to restore N uptake following drought. By 14 days after rewatering, N uptake in the prestressedAgropyronhad recovered to levels of control plants, although both root biomass and root lenght were much less than those of the controls. This is attributed to elevated root uptake kinetics. Restoration of N uptake by prestressedPseudoregneriawas much less effective during the same perio

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb02165.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The activities of 5’‐methylthioadenosine (MTA) nucleosidase (EC 2.2.2.28) and 5‐methylthioribose (MTR) kinase (EC 2.7.1.100) were related to changes in ethylene biosynthesis in tomato (Lycopersicon esculentumMill. cv. Rutgers) and cucumber (Cucumis sativusMill. cv. Poinsett 76) fruit following wounding and chemically induced stresses. Stress ethylene formation in wounded tomato and cucumber tissue continued to increase after wounding, reached its peak by 3h, and then declined. The activities of MTA nucleosidase and MTR kinase increased parallel to stress ethylene in both tissues. At peak ethylene formation, MTA and MTR kinase activities were 2‐ to 4‐fold higher in wounded than in intact tissue. Wounded, mature‐green tomato tissue treated with specific inhibitors of MTA nucleosidase and MTR kinase showed a significant reduction in the activities of these enzymes, which was concomitant with a decline in stress ethylene biosynthesis. When mature‐green tomato discs were infiltrated with [14CH3] MTA and wounded, radioactive MTR and methionine were formed. Incubation of mature‐green tomato discs with Cu2+and Li+in the presence of kinetin increased ethylene biosynthesis. MTA nucleosidase activity was higher than that of the control in the presence of Cu2+but not in the presence of Li+, while MTR kinase activity was lower than that of the control in both Cu2+and Li+treatments. Data indicate that MTA nucleosidase and MTR kinase are required for wound‐induced ethylene biosynthesis but not for chemical stress‐induced ethylene by C

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb02166.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Orchard‐grown dwarf apple (Malus domesticaBorkh.) trees selected from a hybrid population were propagated by tissue culture but had a growth pattern similar to standard cv. Golden Delicious plants when grown at constant 27°C instead of the expected dwarf pattern of growth. Shoot elongation was markedly reduced, with or without gibberellin A1(GA1) or GA4treatment, when trees were grown in an environment where day temperature was maintained at 35°C for 2 h in a ramped regime (night 20°C day ramped to 35°C, held for 2 h and ramped down to 20°C night over a 14‐h photoperiod). Application of GA1or GA4partially overcame growth retardation resulting from prior paclobutrazol treatment of both standard and dwarf trees grown at constant 27°C and of standard trees grown in the ramped environment. However, these GAs had no effect on paclobutrazol‐treated or untreated dwarfs grown in the ramped regime. Gas chromatography‐mass spectrometry with labelled internal standards was used to quantify GA1, GA3, GA8, GA19, GA20and GA29in extracts from standard and dwarf plants grown either at a constant 27°C or in a 20‐30‐20°C ramped temperature regime. Standard plants, which elongate quite rapidly in either environment, had similar levels of these GAs in both temperature regimes. The slowly growing dwarfs in the ramped temperature environment contained three times more GA19than the rapidly elongating dwarfs grown at 27°C. The concentrations of the other GAs were reduced to ca 40% or less in plants grown in the ramped temperature regime compared with those grown at 27°C. These data suggest that shoot elongation of dwarf plants is sensitive to elevated temperatures both as a result of reduced responsiveness to GAs and because of a reduction in the concentration of GA1, apparently as a result of a lower rate of conversion of GA19to GA20. It is possible that the altered GA metabolism may be a consequence of the cha

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb02167.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Apple (Malus domesticaBorkh.) trees were propagated by budding from selected fully grown hybrids that ranged in height from 1.5 to 8 m. The growth and development of the selected budded trees after 7 years in the orchard was similar to that of the parent trees. Additional grafting studies showed that the dwarfism was not associated with the roots. Differences in photosynthetic activity and associated processes were not related to the size difference between tissue culture‐propagated orchard‐grown standard cv. Golden Delicious and dwarf hybrid trees. Applications of GA3did not stimulate elongation of shoots of dwarf trees. Shoots of both standard and dwarf trees started to develop in mid‐April when they contained nearly the same amounts of GA1, GA3and GA8, but standard shoots contained higher concentrations of GA19, GA20and GA29. On 2 June standard shoots were almost three times the length of dwarf shoots, but the number of leaves and area per leaf were nearly the same. The relative amounts of GAs on 12 May and 2 June for both plant types were similar to those on 20 April, except that GA19, GA20, GA1and GA29levels had declined. Gibberellin levels in standard shoots declined further between 2 and 22 June, after which there was no further shoot elongation or production of new leaves. Between 2 June and the end of the growing season, when summer temperatures were high, dwarf shoots continued to elongate slowly and to develop new leaves, which expanded little. During this time, the GA19content of dwarf shoots nearly doubled, whereas the amounts of GA20, GA1, GA29and GA8declined. By the end of the season, standard shoots were 40 cm in length with 20 leaves and dwarf shoots were 28 cm in length, but with 36 leaves. High summer temperatures appear to induce loss of GA‐responsiveness in orchard‐grown dwarf trees and to cause a reduced rate of conversion of GA19to GA20in these

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb02168.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The lateral leaflets ofDesmodium motorium(Houtt.) Merr. exhibit ultradian up‐ and down movements, which are paralleled by oscillations of the membrane potential of motor cells in the pulvinus. By different treatments we have tested the hypothesis that both that both oscillation‐types are causally related. The reactions of the leaflet movement and the membrane potential were evaluated by the following approaches. (1) Application of vanadate. an inhibitor of the proton pump in the plasmalemma. and N2suppressed leaflet movements and finally arrested the leaflet in the lower position. Before the oscillations damped out, a strong lengthening in period was found. This indicates that the pump is part of the ultradian clock. A period lenthening and a final suppression of the rhythm by vanadate was also seen in the extracellular electric potential of the pulvinus. Intracellular recordings in situ showed that vanadate application depolarized the motor cells. (2) Light of high fluence rates diminished the amplitude of the oscillations of the membrane potential of single motor cells and shortened the period. The same effects were observed when monitoring the lateral leaflet movement. The leaflet always moved towards the direction of the light. whether it was applied from the abaxial or from the adaxial part of the pulvinus. (3) When light was applied to the pulvinus of lateral leaflets. which had spontancously stopped moving in an upper position. oscillations were induced transiently. This effect was also found for the membrane potential of motor cells in the pulvinus. ‐ Our results thus provide further evidence that the membrane potential controls the volume state of the motor cells in the pulvinus of lateral leaflets ofDesmodium mot

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb02169.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The above‐ground parts of two years old seedlings of Douglas fir (Pseudotsuga menziesii) were exposed to filtered air, NH3, NO2+, SO2(66, 96 and 95 μg m−3, respectively), to a mixture of NO2+NH3(55 + 82 μg m−3) or SO2+NO2(128 + 129 μg m−3), for 8 months in fumigation chambers. Both chlorophyll fluorescence and gas exchange measurements were carried out on shoots which had sprouted at the beginning of the exposure period. The chlorophyll fluorescence measurements were performed after 3 and 5 months of exposure (average shoot age 70 and 140 days, respectively). Light response curves of electron transport rate (J) were determined, in which J was deduced from chlorophyll fluorescence. In addition, light response curves of net CO2assimilation were determined after 5 months of exposure. After 3 months of exposure (average shoot age 70 days) all exposure treatments showed a lower maximum electron transport rate (Jmax) as compared to the control shoots (filtered air). A large reduction (45%) was observed for shoots exposed to SO2+NO2. During the exposure period between 3 and 5 months (average shoot age 70 and 140 days, respectively) a decrease of Jmaxwas observed for all treatments. Jmaxhad further declined some time after termination of the exposure, when average shoot age was 310 days.Shoots exposed to SO2and SO2+NO2also showed a reduction in maximum net CO2assimilation (Pmax) as compared to the control shoots. However, shoots exposed to NO2showed no reduction and even a higher Pmaxwas observed for shoots exposed to NH3or NO2+NH3. Needles of these treatments also showed a higher chlorophyll content which might explain the contradictory results obtained for these treatments: the increased amount of photosynthetic units counteracts the reduction in Jmaxand consequently no reduction in Pmaxis measured. Shoots exposed to SO2and SO2+NO2also showed a reduction in maximum stomatal conductance (gs). However, the stomatal opening was larger than could be expected on basis of their (maximum) CO2assimilation rate. Consequently, water use efficiency of these shoots was lower than that of the control shoots. Also shoots exposed to NO2had a lower water use efficiency due to a significantly higher maximum gs. Shoots exposed to NH3showed a high transpiration rate in the dark, indicating imperfect stomat

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb02170.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Long term fumigation of 4‐year‐old spruce trees with ozone concentrations up to 200 nl l−1has only minor effects on the photosynthetic activities measured as chlorophyllafluorescence. Nevertheless, it drastically changes the turnover of the D‐1 reaction center polypeptide of photosystem II. During summer, fumigation with ozone for 2 weeks resulted in an almost 4‐fold stimulation of the light dependent incorporation of [14C] leucine into the D‐1 protein in the exposed trees. The amount of immunodetectable D‐1 protein remained constant when based on chlorophyll. This indicates that exposure to ozone stimulates both the synthesis and the degradation of the D‐1 protein. When spruce trees were exposed during winter for 4 weeks to 100 and 200 nl l−1ozone, respectively, an almost 3‐fold increase of the amount of immunodetectable D‐1 protein per chlorophyll in the exposed trees was observed. This can be explained by a varying stimulation of D‐1 protein synthesis and degradation depending on the different physiological conditions. Since so far the D‐1 protein has been found only as a component of photosystem II reaction centers, one has to assume that the relative content of photosystem II reaction centers also increases under certain stress conditions. The increased turnover of the D‐1 protein in trees exposed to ozone explains the synergistic effects of stress conditions and high light intensities

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb02171.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY