摘要:

Split‐root cultured grey alder,Alnus incana(L.) Moench., was grown in sand in cuvettes with a continuous supply of nutrient solution. During the drought treatment for up to 9 days the supply of solution was withheld from one of the split‐root halves. After 2–3 days of treatment, soil water became depleted and the unwatered root halves were at a constant drought stress, water potential (Ψnodules) = ‐1.1 to ‐1.6 MPa. Nitrogenase activity in the dry half decreased to about 70% of the initial value during the first 2–3 days and then stayed at this level. The water supply to the shoot from the wet root half was high and only a temporary slight decrease in photosynthesis and stomatal conductance was found in drought‐stressed split‐root plants. Labelling studies showed a reduced translocation of photoassimilates to the dry nodules. The fixation of CO2in the nodules seemed to be more tolerant to drought than nitrogenase activity. During the drought treatment there was an osmotic adjustment from ‐0.9 to ‐1.7 MPa, but no change in the storage of starch in the nodules. In alders where parts of the root system is kept dry these roots acclimate and continue a persistent

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb05299.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Carbon allocation and partitioning were investigated in the first internode of light‐grownSinapís albaL. seedlings exposed to white light (WL) with or without supplementary far‐red light (FR). In the internode, supplementary FR increased the rates of extension‐growth and the accumulation of radiolabeled carbon (fed through the leaves), reducing sugars (even per unit volume), starch, hemicellulose and cellulose, but had no effect on the levels of sucrose and ammonium oxalate‐solubilised cell wall carbohydrates, on invertase activity or on the use of additional sucrose fed through the leaves. In source leaves, supplementary FR had no effect on photosynthesis rates and reduced the accumulation of radiolabeled carbon. Mechanical reduction of stem extension‐growth responses to supplementary FR did not affect internode carbohydrate or carbon accumulation responses. Supplementary FR provided only to one leaf had no effect on internode extension growth but increased carbon accumulation in the internode. provided that supplementary FR and radiolabeled carbon were both given to the same leaf. Phytochrome‐mediated effects on carbon partitioning are not the mere consequence of internode extension‐growth responses. Some additional control point(s) (e.g. leaf‐source strength) must be under the direct influenc

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb05300.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

We have demonstrated the correlation between cell division and the expression of a histone H2A‐encoding gene,His2A, in Norway spruce. Picea abies (L.) Karst and used a cDNA clone in in situ hybridization experiments to monitor the cytokinin‐induced cell division during early stages of adventitious bud development. A general stimulation of division of epidermal and cortical cells followed upon the cytokinin treatment. After two weeks in culture a high mitotic activity was detected only in single cells or small groups of cells in the epidermis and subepidermal cell layers. These cells presumably constitute the early stages of meristem primordia. The small clusters of dividing cells enlarge and subsequently form adventitious buds. Cells of the meristem and needle primordia of adventitious buds divide frequently as do the corresponding cells in vegetative buds. A quiescent center is distinguished within the apical meristem of vegetative buds. These cells, in the summit of the domed meristem, divide with a considerably lower frequency than cells in the flanking region. Differences in the temporal expression pattern of the histone H2A gene in cells of the vascular tissue, detected between embryos germinating in vitro and bud‐induced embryos, suggest that the cytokinin treatment affects the timing of cell divisions in the differentiating proca

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb05301.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Application of linoleic and linolenic acids toPhalaenopsisandDendrobiumflowers enhanced their senescence and promoted ethylene production. This effect was specific to unsaturated fatty acids which serve as substrates for lipoxygenase action, and did not occur following similar treatments with saturated fatty acids. Several major lipoxygenase pathway metabolites including jasmonic acid methyl ester, traumatic acid,trans‐2‐hexenal andcis‐3‐hexenol also enhanced flower senescence. Jasmonic acid methyl ester promoted ethylene production byPhalaenopsisflowers. In contrast, treating flowers with the lipoxygenase inhibitors salicylhydroxamic acid andn‐propyl gallate. which inhibite(d) lipoxygenase activity in vitro, had no effect on pollination‐induced senescence of the flowers. Furthermore, during the 50‐h period following pollination, there was no increase in lipoxygenase activity inPhalaenopsisflowers. During the 10‐h period from pollination ofDendrobiumflowers until the initiation of ethylene production, there was no effect of pollination on jasmonate levels in either the perianth or the columns. These results suggest that lipoxygenase activity and jasmonates are not directly involved in pollination‐inducedPhalaenopsisandDendrobium

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb05302.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The effect of 2‐chloroethylphosphonic acid (ethrel) on cell growth patterns and per‐oxidase activity (EC 1.11.1.7) and location in young Norway spruce cuttings (Picea abies[L.] Karst.) was investigated. The peroxidase activity in a fraction containing soluble and membrane bound enzymes show a diurnal variation, with decreased activity during the light period and a corresponding increase during the following dark period. The decrease during the day could to some extent be counteracted by treatment with ethrel. It appears that ethrel affects only peroxidases in the isolated membrane fraction, since peroxidases bound to the cell wall were not affected by ethrel. In vitro experiments indicated that the hydrophobicity of soluble peroxidases was increased by treatment with ethylene. Cytochemical localization of peroxidase activity in differentiating tracheids revealed a clear ethrel‐induced increase in the tonoplast. It appears that ethylene affects soluble peroxidases in vivo in such a way that they are directed to a more hydrophobic environment, like the tonoplast. Treatment with ethrel also changed the appearance of the rough endoplasmic reticulum (ER) and Golgi apparatus. Dilated ER cisternae were observed on electron micrographs, as a result of treatment with ethrel. The number of vesicles produced by the Golgi apparatus and also the amount of vesicles fusing with the plasma membrane in secondary‐wall‐forming tracheids increased considerably. The results clearly indicate that the stimulatory effect of ethylene in spruce seedlings on lignification and cell wall formation, is due to a general stimulation on both synthesis, transport and secretion of cell wall material and not on a stimulation of peroxidase activity as reported for othe

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb05303.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

In the present study we investigated the proposal that the γ‐aminobutyrate (Gaba) shunt in developing soybean (Glycine max[L.] Merr.) seeds is associated with hypoxia. The ontogeny and pH profile of enzymes associated with glutamate metabolism (glutamate decarboxylase [EC 4.1.1.15]. Gaba transaminase [EC 2.6.1.19], succinic semialdehyde dehydrogenase [EC 1.2.1.16], glutamate dehydrogenase [EC 1.4.1.2], glutamate:oxaloacetate transaminase [EC 2.6.1.1], glutamate:pyruvate transaminase [EC 2.6.1.2] and 2‐oxoglutarate dehydrogenase complex [EC 1.2.4.2]) and hypoxia (alcohol dehydrogenase [ADH, EC 1.1.1.1] and pyruvate decarboxylase [PDC, EC 4.1.1.1]) were determined in cotyledons, nucellus and seed‐coat tissues. Gaba‐shunt enzymes were ubiquitous in the developing seed. Activities of enzymes catalyzing glutamate‐C entry into the Krebs cycle via 2‐oxoglutarate were generally greater than those of Gaba‐shunt enzymes. In cotyledons, the activity of ADH increased throughout seed development (up to 72 days after anthesis [DAA]), whereas PDC was static during early development, then increased. In contrast, the activities of ADH and PDC in maternal tissues (nucellus and seed coat) were initially high, then declined dramatically after 37 DAA. The adenylate energy charge (AEC) = ([ATP]+0.5 [ADP])/ ([ATP]+ [ADP] + [AMP]) of soybean seeds from fruits (37 DAA) frozen in situ was low (0.67±0.01) compared to the AEC of adjacent pod tissue (0.82 ± 0.04) and cotyledons exposed to air (0.84 ± 0.01). A 60‐min time‐course study showed that the rate of [U‐14C]‐glutamate catabolism by an intact excised cotyledon at 37 DAA was markedly lower at 8 and 0% O2than at 21%; the pool size of [14C]‐Gaba was unaffected. The data indicated that: (1) Gaba‐shunt activity is not a response to limited glutamate deamination/transamination: (2) the soybean seed is hypoxic; and (3) the relative partitioning of glutamate‐C through glutamate decarb

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb05304.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Ethylene is known to accelerate flower senescence, but the sequence of events that links its interaction with the tissue and the final senescence symptoms is still obscure. Recently, 1‐methylcyclopropene (1‐MCP) was found to inhibit ethylene‐induced wilting in flowers. This work was carried out in order to investigate the effects of 1‐MCP on cellular senescence symptoms in petunia flowers following expossure to ethylene. Cut petunia (Petunia hybrida) flowers that were exposed to ethylene for 12 h at concentrations of 1–12 ppm wilted sooner than their untreated counterparts. This effect was abolished by a 6‐h pre‐treatment with 1‐MCP. Immediately following the ethylene treatment, decreases in petal fresh weight and total protein content were measured, along with higher electrolyte leakage, and lower membrane lipid fluidity and protein content. When applied alone, 1‐MCP had relatively little impact on these parameters. However, when the flowers were treated with 1‐MCP prior to the ethylene treatment, ethylene had no effect. These results indicate that while ethylenes effects on wilting were obvious 3 days after the treatment, cellular parameters were affected already at the end of the treatment. Since 1‐MCP repressed these early ethylene effects, it was concluded that it interferes with ethylene action in petunia flowers at a rather early stage, long be

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb05305.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

From the premise that desiccation‐induced damage is associated with a free‐radical mechanism of injury, we address the hypothesis that expression of desiccation damage is dependent on metabolism. The effects of temperature and O2concentration on the expression of damage were studied in germinating bean (Phaseolus vulgarisL. cv. Pole Kentucky Wonder) axes and maize (Zea maysL. cv. Kelvedon Glory) radicles submitted to flash drying. Damage in desiccation‐tolerant and ‐intolerant material was assessed by measurements of electrolyte leakage and accumulation of a stable free radical. In desiccation‐tolerant material leakage rates remained low during water removal. In contrast, in desiccation‐intolerant tissues, leakage profiles revealed the presence of a critical moisture content below which leakage rates increased sharply. In the desiccation‐intolerant stage, a highly significant correlation was found between critical moisture contents and temperatures of drying. The concentration of the stable radical was lower if tissues were dried below 15°C and higher when tissues were dried at 30°C and above. Both leakage and build up of free radicals were highly sensitive to O2concentrations: damage was lower when tissues were dried in the presence of N2, but increased several‐fold when tissues were exposed to O2concentrations between 2 and 100%. In contrast, neither temperature nor O2concentrations affected electrolyte leakage in desiccation‐tolerant samples. Treatment with a respiration inhibitor (KCN) prior to drying reduced the desiccation sensitivity of tissues, as noted by a reduction of the critical moisture content. We conclude that the expression of desiccation damage depends on the drying history and that factors that limit metabolism also reduce the incidence of

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb05306.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The filamentous non‐N2‐fixing cyanobacteriumPhormidium laminosum(strain OH‐1‐p.Cl1) was able to utilize glutamine as the sole nitrogen source. The addition to ammonium‐grown cultures of the irreversible inhibitor of glutamine synthetase activity L‐methionine‐D, L‐sulfoximine (MSX) inhibited cell growth. Supplying glutamine to the culture restored cell growth. This re‐established growth was not due to interference by glutamine of MSX uptake by the cells, since glutamine synthetase (GS, EC 6.3.1.2) activity remained completely inhibited by MSX even when glutamine was simultaneously present. Both glutamine and ammonium exerted a negative effect on nitrate reductase (NR. EC 1.7.7.2) and nitrite reductase (NiR, EC 1.7.7.1) in vivo. This negative effect was reversed by MSX. When glutamine was added to MSX‐treated cells, intracellular glutamine level was high, but the activity of both reductases remained at a high level. These results suggest that the presence of the active form of glutamine synthetase is required for the in vivo prevention of nitrate assimilation caused by amm

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb05307.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Mycorrhizal colonization of roots, fresh weight, content of cysteine, γ‐glutamylcysteine (γEC). glutathione (GSH), thiol groups in Cu‐binding peptides (CuBP), and the uptake of Cu were measured in roots and shoots of maize (Zea maysL., cv. Honeycomb F‐1) grown in quartz sand, with Cu at 0, 4.5, 9, 15 and 30 μg g−1added with or without inoculum of the arbuscular‐mycorrhizal fungus (AMF)Glomus intraradices. In control plants (no Cu added) AMF significantly reduced shoot growth, but did not affect root growth. At an external Cu supply of 9 μg (g quartz sand)−1or higher, both mycorrhizal colonization and growth of roots and shoots of mycorrhizal and non‐mycorrhizal plants were significantly reduced.With up to 9 μg Cu g−1, mycorrhizal colonization increased the content of cysteine, γEC and GSH in the roots. However, the amount of thiols in CuBPs was not increased by mycorrhizal colonization in Cu‐treated plants and no differences in Cu uptake were detected between non‐mycorrhizal and mycorrhizal plants. A CuBP‐complex with a relative molecular mass of 7300 and a SH:Cu ratio of 1.77:1 was separated on a Sephadex G‐50 column from both non‐inoculated and inoculated roots of Cu‐treated plants. HPLC chromatography of the CuBPs of both non‐inoculated and inoculated roots resulted in a similar peak pattern, indicating that no additional CuBPs were formed by the fungus. In conclusion, our results do not support the idea that

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb05308.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY