摘要:

Photosystem II (PSII) from Cu‐deficient pea plants (Pisum sativumL., cv. Lincoln) has been investigated for electron transport activity, Cu content, and changes in some lipid components. Total fatty acid content was lower that in control plants, with an additional shift in the C18fatty acid patterns. Less α‐linolenic and more linoleic and oleic acids were found. PSII preparations from Cu‐depleted plants showed a decreased carotenoid content in light harvesting chlorophylla/bcomplex of photosystem II (LHCII) and additional variations in pigment composition of pigment‐protein complexes. In the green algaDunaliellathe effect of Cu deficiency on fatty acid composition was similar to that in pea plants, but the influence on the carotenoid pattern was much less pr

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb08756.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Both chlorophyllaandband polypeptides of the photosynthetic apparatus are found in gymnosperm seedlings. germinated and grown in absolute darkness. The photosystem II (PSII) activity is, however, limited, probably due to an inactive oxygen evolving system. In the present study dark‐grown seedlings of Scots pine (Pinus sylvestrisL.) were transferred to light and changes in antenna size and the activation process of PSII were investigated using fluorescence measurements and quantitative western blotting. It was found that the activation process is rapid, requires very little light and that strong light inhibits the process. It takes place without any changes in the primary reactions of PSII. Furthermore, all polypeptides except the major light‐harvesting chlorophylla/b‐binding protein complex of PSII (LHCII) were present in dark‐grown seedlings in amounts comparable to the light treated control. The dark‐grown seedlings had the same LHCII polypeptide composition as light treated seedlings, and the LHCII present seemed to be fully connected to the reaction centre. The results indicate that activation of PSII in dark‐grown conifer seedlings resembles the photoactivation process of angiosperms. This implies that the fundamental processes in the assembly of the photosystem II complex is the same in all plants, but that the regulation differs between dif

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb08757.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Subcellular compartmentation of pyrophosphate (PP1) was determined by rapid membrane filtration of evaeuolated oat mesophyll protoplasts. By improving both the extraction procedure and its assay via bioluminescence, PP1recovery from samples was quantitative and linear down to below 200 fmol. Based on the content of the different fractions obtained after membrane filtration and compared to the respective pools of marker metabolites [cytosol, fructose 2,6‐bisphosphate (F26BP); chloroplast stroma, ribulose bisphosphate] rather than enzymes, we found ca 2/3 of the total cellular content to be chloroplast‐assotiated. Referred to compartmental volumes, cytosolic and stromal concentrations of PP1were nearly equal (70–100 μM). PP1was higher in evacuolated compared to racuotated protoplasts which indicates a possible role of the tonoplast‐located H+pumping PP1ase in regulating the cellular pool size of PP1. During dark‐light‐transition the pool sizes of PP1changed only marginally in both vacuolated and evacuolated protoplasts, while there were pronounced changes in those of F26BP, starch and sucrose. Thus our findings support the notion that the cellular pool size of PP1is kept rather constant. They are, however, in contrast to the assumption that appreciable PP1levels only exist in

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb08758.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The effects of cropping, nutrition and water supply on accumulation and distribution of biomass and nutrients for apple trees on‘M9’root systems were examined using trees growing in lysimeters. For 3‐year‐old ‘Golden Delicious’ trees, cropping significantly increased total biomass, although leaf and root biomass were reduced. For 3‐year‐old‘Golden Delicious', ‘Coxs Orange’ and ‘Gloster’ trees, cropping only in the third year reduced root biomass by 39 to 45%. Cropping did not affect water use by trees of any cultivar early in the season, but increased water use later in the season for ‘Gloster’ trees. For trees with fruit, total non‐structural carbohydrate (TNC) contents at the end of the season were highest in fruit (up to 1 400 g plant−1). For trees without fruit, TNC contents were generally highest in the roots (up to 110 g planr−1). Supplying trees with nutrient solution diluted to 10% of the standard composition increased the root biomass for ‘Golden Delicious’ trees only, but decreased biomass of above‐ground tissues for all cultivars. Reducing the nutrient supply decreased water and nutrient uptake, and reduced nutrient contents within vegetative parts of the tree more than within roots. For ‘Golden Delicious’ trees, restricting the water supply to 50% or 25% of that consumed by control trees significantly reduced above‐ground biomass, but root biomass was not significantly affected. The N, P and K. contents for the trees were also reduced by water stress, due to reduced contents within above‐ground organs. Water stress reduced the TNC and starch contents of all tissues, except the roots. These results are discussed in relation to the efficie

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb08759.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

In previous studies on the causes of imbibitional leakage in dry polien we have presented data which suggest that the leakage is due to a gel to liquid crystalline phase transition in membrane phospholipids during the rehydration event. In the present study we greatly extend and confirm those results. A supplemented phase diagram for the hydration dependent transition temperature of membrane phospholipids in pollen is presented. In pollen containing>0.05 g H2O g−1dry weight at the time of imbibition, this phase diagram for the phospholipids precisely predicts the conditions for rehydration under which germination is maximal and leakage is minimal. However, in extremely dry pollen, containing<0.05 g H2O g−1dry weight the predictive value of the phase diagram for phospholipids in the pollen is not in agreement with data for germination and leakage. Thus, an alternative explanation must be sought for leakage in these circumstances. We examined the available evidence and suggest here that a modified form of the non‐bilayer phase hypothesis proposed by Simon (1974) may apply in the specialized case of extremely dry

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb08760.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Grand Rapids lettuce (Lactuca salivaL.) seeds entered into a state of secondary dormancy (thermodormancy) when they were imbibed at 40°C for 72 h. The effect of 40°C in inducing thermodormancy was largely reduced by imbibing seeds at 40°C in solutions of polyethylene glycol (PEG), mannitol and NaCl. Despite similar water potentials of solutions, NaCl pretreatment was more effective. Subsequent germination in the dark at 25°C of saline, high‐temperature‐pretreated seeds required only gibberellic acid (GA3), as was the case with nonthermodormant seeds. Thermodormancy reduced total respiratory capacity (VT) and increased the ratio of alternate pathway (Valt) to cytochrome pathway (Vcyt) respiration. This was prevented by saline pretreatment. Ethylene production and protein synthesis were depressed in thermodormant seeds, and this was partly alleviated by saline pretreatment. The patterns of protein synthesis in saline‐ and nonsaline‐freated seeds at 40°C were similar, differing only in that the saline treated seeds produced in addition a 78 kDa polypeptide. The pattern of protein synthesis at 40°C differed significantly from

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb08761.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The induction of freezing tolerance by abscisic acid (ABA) or cold treatment in suspension cultured cells ofSolanum commersoniiwas studied. Both ABA (50–100 μM) at 23°C and low temperature (4°C) increased freezing tolerance in culturedSolanum commersoniicells from a LT50(freezing temperature at which 50% cells were killed) of —5°C (control) to —11.5°C in 2 days. Cold‐induced freezing tolerance reached its maximum at 2 days and remained constant throughout the cold acclimation period of 11 days. The freezing tolerance induced by ABA, however, showed a rapid decline 2 to 5 days after initiation of ABA treatments. Addition of ABA (100 μM) to the culture medium at the inception of low temperature treatment did not enhance freezing tolerance of the cells beyond the level attainable by either treatment singly. Poly(A+)‐RNA was isolated from the respective treatments, translated in a rabbit reticulocyte lysate cell free system, and the translation products were resolved by two dimensional polyacrylamide gel electrophoresis (ID‐PAGE). Analysis of the in vitro translated products revealed changes in the abundance of approximately 26 products (encoding for polypeptides with M, of 14 to 69 kDa and pl of 4.90 to 6.60) in ABA‐treated cells 12 h after treatment, and 20 (encoding for polypeptides with Mrof 12 to 69 kDa, with pl of 4.80 to 6.42) in cells exposed to 4°C for 12 h. There were only 5 novel translation products observed when the ABA‐treated cells reached the highest level of freezing tolerance (2 days after the initiation of ABA treatment). Changes in translatable RNA populations during the induction of freezing tolerance in cells treated with either ABA or low tem

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb08762.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The effect of boron excess and deficiency on H+efflux from excised roots from sunflower (Heliarahus annuusL. cv. Enano) seedlings and on plasma membrane H+‐ATPase (EC 3.6.1.35) in isolated KI‐washed microsomes has been investigated. When seedlings were grown in media with toxic levels of H3BO3(5 mM) or without added boron and exposed to light conditions, an inhibition of the capacity for external acidification by excised roots was observed as compared to roots from seedlings grown with optimal H3BO3concentration (0.25 mM). Toxic and deficient boron conditions also inhibited the vanadate‐sensitive H+‐ATPase of microsomes isolated from the roots. The mechanism of boron toxicity was investigated in vitro with microsorne vesicles. A strong effect of boron on the vanadate‐sensitive, ATP‐dependent H+transport was found, but the vanadate‐sensitive phospho‐bydrolase activity was not affected. These results suggest that boron could exert an effect on the plasma membrane properties, directly or indirectly regulating, p

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb08763.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Susceptibility of alfalfa (Medicago salivaL. cv. Aragón) nodules and leaves to water stress has been investigated. Nodule acetylene reduction activity (ARA), leaf CO2exchange rate (CER) as well as soluble protein, proline and total soluble sugar (TSS) contents were determined during drought. Water status was estimated as water potential (Ψw) and Relative water content (RWC) of the respective tissues. Maximum rates of ARA required higher Ψwthan CER. Nodules had lower RWC for a given Ψwthan leaves. Water stress reduced soluble protein content in both tissues; however, the decline in soluble protein content was detected at greater Ψwin nodules than in leaves. Proline and TSS increased in leaves and nodules, and again the threshold Ψwtriggering such accumulation was higher in nodule tissues. Oior results suggest that alfalfa nodules are more susceptible to water shortage than leaves. Effects of accumulated TSS and proline upon leaf and nodule physiology are discussed in relation to protein stability (proline), pH control (proline) and osmotic adjustment (proiine and TSS). The TSS accumulation induced by water stress suggests that substrate shortage would not be the primary effect of drought on nodule act

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb08764.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The effect of drought upon phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31), malate ddiydrogenase (MDH; EC 1.1.1.37), alcohol dehydrogenase (ADH; EC 1.1.1.1) andβ‐hydroxybulyrate dehydrogenase (β‐OH‐BDH; EC 1.1.1.30) enzyme activities as well as the leghemoglobin (Lb), malate and ethanol contents of alfalfa nodules (Medicago sativaL. cv. Aragon) were examined. Both the ieghemoglobin (Lb) content and the Lb/soluble protein ratio were significantly reduced at a nodule water potential (Ψnod) of—1.3 MPa. At lower Ψnod, Lb content decreased further, but the ratio remained unchanged. Slight stress (—1.3 MPa) drastically affected acetylene reduction activity (ARA; 60% reduction) whereas in vitro PEPC activity was main‐tained at relatively constant values. As stress progressed (—2.0 MPa), a simultaneous reduction in both activities was observed. Severe stress (Ψnodlower than —2.0 MPa) stimulated in vitro PEPC. Bacteroidβ‐J‐OH‐BDH activity was stimulated by slight (—1.3 MPa) and moderate (—2.0 MPa) drought. MDH activity rose in slightly stressed nodules (Ψnod—1.3 MPa). Greater water deficits sharply decreased MDH activity to values significantly lower than those found in control nodules. Nodule malate content followed the same pattern as MDH. The plant fraction of the nodule showed constitutive ADH activity and contained ethanol. ADH was stimulated at slight (— 1.3 MPa) and moderate drought levels (—2.0 MPa). Ethanol content showed similar behavior to ADH activity. Inhibition of ARA, reduction of Lb content and stimulation of the fermentative metabolism induced by water stress suggest some reductio

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb08765.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY