摘要:

A comparative analysis of glycolate excretion in 11 cyanobacteria showed that 8 strains, although grown and assayed in air, excreted glycolate. The largest quantities were excreted by the filamentous strainsPlectonema boryanum73110 andAnabaena cylindrica(Lemm). The carbon lost by excretion was at most 9% of the net fixed carbon in air for heterocystous cyanobacteria but increased (up to 60%) in some strains under a high pO2(0.03 kPa CO2in pure O2). A.cylindricaexcreted glycolate at a maximum level of 2 and 10 μmol (mg chla)−1h−1in air and at high pO2, respectively. The excretion continued for several hours. Increases in light intensity and pO2and a shift in pH from 7 to 9 increased the amount of glycolate excreted.A. cylindricaalso showed the most O2‐sensitive fixation of CO2. In vitro activity of phosphoglycolate phosphatase (EC 3.1.3.18) was found in all strains tested, with the highest activities noted forGloeobacter violaceus7.82 andGloeothece 6909and for young cultures ofA. cylindrica. The lowest activities were found inAnabaena7120 andAnacystis nidulans625, strains excreting no or only minor quantities of gly

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb06160.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The mechanism for uptake of glycolate in the cyanobacteriumAnabaena7120 and its capacity to metabolize glycolate were examined. The uptake of [14C]‐glycolate in light, at pH 7, consisted of an initial rapid phase (≤60s) and a second slower phase. The latter obviously represents metabolism as the glycolate dehydrogenase inhibitor 2‐pyridylhydroxymethanesulfonic acid (HPMS) did not affect the initial uptake phase while the second phase was strongly reduced. The sulfhydryl reagent N‐ethylmaleimide (NEM) inhibited uptake of glycolate and the uptake was reduced by lactate, glycerate and glyoxylate, Treatment with triphenylmethylphosphonium (TPMP+), a lipophilic cation collapsing ΔΨ only slightly reduced the uptake of glycolate. At pH 7.0, the F0F1‐ATPase inhibitor N, N′‐dicyclohexylcarbodiimide (DCCD) and the uncoupler carbonylcyanidem‐chlorophenylhydrazone (CCCP) abolished the uptake. Inhibition of photophosphorylation by dark‐treatment and presence of 3‐(3′,4′‐dichlorophenyl)‐1, 1‐dimethylurea (DCMU) also reduced the uptake. Decreasing the pH in the range of 10 to 5.5 increased the uptake. In contrast to the situation at pH 7. CCCP did not affect the initial glycolate uptake at pH 5.5. We conclude that the uptake of glycolate is a carrier‐mediated process which, at pH 7, is dependent on a H+‐ATPase to create the ΔpH across the membranes needed for uptake, while at pH 5.5 the uptake of glycolate is not ATP‐dependent. The capacity to metabolize glycolate was at least 50 μmol (mg chla)−1h−1in young cultures. In o

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb06161.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Exogenously applied abscisic acid (ABA) substantially suppressed the elongation of hypocotyl segments of etiolated squash (Cucurbita maximaDuch. cv. Houkou‐Aokawaamaguri) after a 3 h lag period, without changes in the osmolalities of the apoplastic and symplastic solutions in the segment.Segments with the outer tissues removed elongated more rapidly than unpeeled segments (whole segments). ABA did not suppress the elongation of peeled segments. When the segments were incubated in [14C]‐glucose, radioactivity was more effectively incorporated into the cell wall fractions of the outer than into those of the inner tissue. ABA significantly inhibited the incorporation of radioactivity into hermicellulose and cellulose of the outer tissue prior to the suppression of segment elongation, but it did not inhibit the incorporation into the pectic traction of the outer tissue or into any of the cell wall fractions of the inner tissue. These results indicate that ABA primarily affected the outer tissue, in which it specifically reduced the synthesis of hemicellulose and cellulose prior to the ABA‐mediated suppression of g

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb06162.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Changes in photosynthesis and water relations of remaining leaves and regrowth over the first 50 days following shoot decapitation were studied inPopulus deltoidesBartr. ×nigraL. I‐262 (DN22) andPopulus maximowiczii×nigraL. MN9 to determine if these changes were correlated with the reinvigoration of growth that occurs after shoot decapitation. There was a 7‐fold increase in net photosynthesis of the remaining leaves 5 days after shoot removal, indicating a rapid, substantial reinvigoration. Diurnal photosynthetic patterns of retained stump leaves and new coppice leaves showed that decapitation increased the photosynthetic potential of tissue by increasing net photosynthetic rates in the early afternoon, thereby eliminating the post‐midday reduction typical of intact plants. The retained stump leaves exhibited lower midday xylem pressure potentials than comparable leaves on intact plants due to higher stomatal conductance, suggesting that an alleviation of plant moisture stress was not the cause of enhanced net photosynthesis of retained leaves. The results suggest that leaves of intact plants typically photosynthesize well below their capacity and that growth of new stump sprouts coincides with higher photosynthetic rates of coppice

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb06163.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Photosynthesis, growth, and carbon partitioning of vigorous coppice shoots were compared with the slower growing intact shoots ofPopulus maximowiczii×nigraL. MN9 to determine the relationship between carbon partitioning and photosynthetic rate. Relative height growth rate of coppice shoots was 2.2 times that of intact shoots with net photosynthetic rate 1.9 times that of intact shoots. Coppice leaves exported a larger proportion of newly‐fixed assimilate (11% compared with 6%) after a 4‐h chase. The greater export from coppice leaves was correlated with a greater proportion of [14C]‐labelled photosynthate deposited as starch in stems 4 cm below the point of label application. Coppice leaf assimilate levels were reduced to 15% that of leaves on intact plants, but coppice leaves had twice the concentration of labelled sucrose. Carbohydrates constituted 55% of the water‐soluble [14C]‐labelled photosynthate in leaves of coppice shoots compared with 40% in intact shoots. The results suggest that carbon allocation and partitioning in coppice shoots were altered towards production and export of new assimilate, and support the hypothesis that photosynthetic rate is responsive to sink demand for a

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb06164.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Responses of abaxial and adaxial stomata ofPopulus trichocarpaTorr.&Gray. × P.deltoidesBartr. (ex Marsh.) cv. Unal to incident light, sudden darkening and leaf excision in the light and in the dark were studied on 5‐year‐old trees in the field using diffusion porometry. Stomatal closure in the dark was found to be incomplete in most cases studies. Stomata closed after leaf excision in the dark within 90 min. Stomatal closure after darkening of an entire tree or an entire branch (white the rest of the tree was in the light) was slower, and complete stomatal closure was noticed only for adaxial stomata after 3 h. Adaxial stomata were more reactive and sensitive than abaxial stomata to sudden darkening and leaf excision in the light and the dark. In all treatments, stomatal response was more responsive in mature leaves than in young, still expanding le

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb06165.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Changes in the contents of ethanol, lactate and malate were determined at different activities of the plasma membrane H+pump [in the presence and absence of fusicoccin (FC)] and at different O2availability in cultured cells ofAcer pseudoplatanusL. FC induced acidification of the medium under all tested conditions of O2availability. At low O2concentrations both ethanolic and lactic fermentations occurred, and FC markedly stimulated lactate production but had no effect on ethanol production. There was also a small, stimulating effect of FC on malate production. At high O2concentrations no ethanol production was observed and lactate production was reduced. Under these conditions the stimulating effect of FC on lactate production decreased, while that on malate production increased. FC‐induced synthesis of lactate and malate is interpreted as depending on the activation of lactate dehydrogenase (EC 1.1.1.27) and phosphoenolpyruvate carboxylase (EC 4.1.1.31) (alkaline pH optima), respectively, due to the alkalinization of the cytoplasmic pH resulting from the stimulation of the H+pump by FC. These results suggest that the balance between the two pH stat systems depends on the availability of O

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb06166.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Patterns of spring development of lateral buds of mulberry (Morus albaL. cv. Shin‐ichinose) coppice shoots on 11‐year‐old low‐pruned stumps varied in response to girdling, pruning and arching. The erect controls showed a weak acrotonic (apex‐favoring) growth habit, in which the majority of the buds, including the basal ones, sprouted and elongated in mid‐ and late April, and hence there was a prolonged imposition of dominance on the upper laterals in mid‐ and late May. In contrast, early spring girdling or pruning enhanced the activity of the upper buds of the proximal (lower) halves of the girdled stems or of the pruned stems, resulting in considerable dominance of the laterals from such buds in late April. Arching markedly inhibited buds on the under side of the arched stems, leading to poor shoots. By late April, the buds on the adaxial (upper) side readily grew into new vertical shoots, which dominated over the lateral ones.When studied by a multiple‐node‐cutting test, increased length of segments of post‐dormant mulberry stems was accompanied by decreased bud activity of the segments and by decreased breaking ability of the lower buds within the segments, suggesting the importance of roots in the weak acrotonic habit of the erect stem in spring. By contrast, the acropetal influences of the attached stems can in part affect dominance relationships, perhaps mediated through competition for factors translocated from the roots. Continuous basal applications of abscisic acid inhibited bud break and shoot growth of the postdormant stem segments, but these inhibitory effects could be reversed by applied gibberellic acid A3(GA3).Two phases of lateral bud dormancy in erect mulberry coppice shoots were identified. The first was characterized by a smaller breaking capacity in the upper buds than in the lower ones and hence by a basitonic (base‐favoring) gradient in bud growth potential. The second phase corresponded to a restoration of these capabilities in the upper buds and to a change towards a linear gradient in bud growth potential, with disappearance of the dormant condition, in February and March. This gradient change during dormancy release may represent the physiological basis for the weak acrotonic habit of erect mul

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb06167.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The effects of copper (CuCl2) on active and passive Rb+(86Rb+) influx in roots of winter wheat grown in water culture for 1 week were studied. External copper concentrations in the range of 10–500 μMin the uptake nutrient solution reduced active Rb+influx by 20–70%, while passive influx was unaffected (ca 10% of the Rb+influx in the Cu‐free solution). At external Rb+concentrations of up to 1 mM, Cu exposure (50 μMdecreased Vmaxto less than half and increased Kmto twice the value of the control. Short Cu exposure reduced the K+concentration in roots of low K+status. Pretreatment for 5 min in 50 μMCuCl2prior to uptake experiments reduced Rb+influx by 26%. After 60 min pretreatment with Cu, the corresponding reduction was 63%. Cu in the cultivation solution impeded growth, especially of the roots. The Cu concentration in the roots increased linearly with external Cu concentration (0–100 μM) while Cu concentration in the shoots was relatively unchanged. The K+concentration in both roots and shoots decreased significantly with increased Cu in the cultivation solutions. Possible effects of Cu on membranes and ion transport mechanisms ar

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb06168.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Young spruce trees [Picea abies(L.) Karst.) exposed to acidic fog (pH 3) showed a disintegration of the epicuticular waxes of the current year's needles as compared with trees treated with a fog of pH 5. The fog treatment was followed by a period in which the trees received different water supply. Under water stress conditions, trees that had been exposed to the acidic fog showed significantly higher transpiration rates than control trees that were treated with a fog of pH 5. The water loss of the controls was 0 at the middle of the photoperiod, while the trees pretreated with acidic fog still showed a substantial transpiration rate at this time. Water loss of excised twigs measured in the dry atmosphere of a desiccator also provided evidence that the water holding capacity of needles pretreated with acidic fog was affected. There is evidence that particularly the cuticular transpiration was increased by pretreatment with acidic fog. The xylem water potential of twigs pretreated with acidic fog was significantly lower than that of twigs pretreated with a fog of pH 5, while the osmotic potential was not affected by the different fog treatments. It is suggested that in draught years trees with a damaged cuticle caused by acidic fog will be affected in their resistance against water stress. In this way acidic fog could be involved in forest decline now widely spread in Central Europe.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb06169.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY