摘要:

Chlorella vulgarisBeijerinck, strain 211/12, uses nitrate, nitrite and ammonium at pH 8.2 but not at pH 6.4 when kept under conditions of CO2‐deprivation, as observed in cell suspensions aerated with CO2‐free air during a 20–30. h period Most of the nitrate absorbed at pH 8.2, however, was not assimilated but was released into the external medium as nitrite and ammonium. Cells ofChlorellapreviously grown in phosphate‐limited continuous cultures were unable to absorb nitrate, nitrite or ammonium under conditions of phosphate starvation at either pH 6.4 or 8.2 in cell suspensions flushed with air containing 5% CO2, However, in cell suspensions flushed with CO2‐free air, the capacity of the alga to absorb and reduce nitrate and to excrete nitrite and ammonium at pH 8.2 was restored.It is hypothesized that inChlorellathe metabolism of nitrate, nitrite and ammonium is influenced by the availability of other nutrients and controlled by the cell's carbon status at the level of ion entry into the cell. With respect to nitrate this carbon‐dependent control is distinct and works independently of that triggered by the cell's nitr

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb04259.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The effects of external K+, H+and Ca2+concentrations on the intracellular K+ concentration, [K+]i, and the K+‐ATPase activity in 2‐day‐old mung bean roots [Vigna mungo(L.) Hepper] were investigated. [K+]i, in mung bean roots was markedly decreased by external K+or H+stress and did not recover the initial value even after the stress was removed. This decrease in [K+]i, gradually disappeared with the addition of (Ca2+. Ca2+may offset the harmful effects of ion stress. Ca2+seems to have two effects on K+ transport; control of K+permeability and activation of K+uptake, although K+‐ATPase activity was inhibited by Ca2+concentrations higher than 10–4 M. We suggest that Ca2+activates K+uptake indirectly through the acidification of the

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb04260.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Five‐day‐old seedlings of oat (Avena salivaL. cv. Seger) were subjected to water‐deficit stress for two and four periods, each of 24h duration with interjacent rewatering periods of 24 h. After two and tour stress periods the fresh weight/dry weight ratio of the roots was 73 and 74% of the control value, respectively. Two stress periods did not affect the amount or composition of free, esterified and glycosylated sterols (desmethylsterols) or methylsterols (mono‐ and dimethylsterols). After four stress periods the amount of tree sterols increased by 25% on a dry‐weight basis but that of free methylsterols only slightly. The most significant increase (by over 60%) occurred in esterified sterols and methylsterols. The amount of sterols bound as glycosides and acylaled glycosides decreased slightly (by 10%) after four stress periods. The amount of glycosylated methylsterols was negligible and did not respond to water‐deficit stress. Within all component groups the proportions of individual compounds remained unaffected after two and four stress periods. The increase of the sterol levels caused by the stress is discussed in terms of a hormone‐induced synthesis leading to a changed sterol/membrane acyl lipid ratio. This has implications for the chemo‐physical properties of the root

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb04261.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Flavin mononucleotide (FMN) transfers its excitation energy to phytochrome Pr with a rate constant<8.7 × 1011 I mol‐1 s‐1. This reaction is not specific for Pr. the transfer to the phytochrome Pfr proceeds with ?5.8 × 1011 1 mol‐1 s‐1. These rate constants are lower limits because the complex‐formation constants are unknown. Assuming a horsier energy transfer a greater complex‐formation constant, as well as a greater orientation factor or a smaller distance in the complex FMN‐Pfr than in FMN‐Pr would be the possible reason for the difference between the rate constants.It is shown that the “flavin effect” can only be of physiological relevance if the local phytochrome concentration does not reach the millimolar range at the same place Under these conditions the reaction Pr Pfr proceeds more effectively, but the reaction Pr Pfr less effectively than in the absence of the donor FMN. which gives rise to a shift of the equilib

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb04262.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The pigment and quinone content of wild‐type barley (Hordeum vulgareL., cv. Svalöfs Bonus) and of two photosynthetic mutants was assayed. Wild type plants and the photosystem Hacking mutantviridis zb63contained chlorophyll a and b. whereaschlorina‐f2contained only chlorophyll a The inability of the mutant chlorina‐f2 to convert chlorophyll a into chlorophyll a appears to he the primary effect of the mutation. In both mutants, the carotenoid composition was virtually identical to that of the wild type. As compared to the wild type.chlorina‐f2contained less lutein and neoxanthin. The mutantviridis‐zb63contained less β‐carotene but more antheraxanthin and xeaxanthin than the wild type. The quinone content and composition of the wild type and the photosynthetic mutants was similar, and both mutants biosynthesized plastid quinones and chromanols starting from [14C]‐labeled tyrosine. The data indicate that carotenoid and quinone biosynthesis are not altered in the two mutants as compared t

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb04263.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Changes of cytomorphology and water permeability of inner epidermal cells ofAllium cepaL. cvs Spartan and Keep Well were investigated with the light microscope after irradiation with UV‐C (254 nm) and UV‐B (280 and 310 nm). The sequence of the investigated changes of viscosity, protoplasmic streaming, organelle shape and water permeability was the same with 254 as with 280 nm. although a higher dose of 280 nm was needed to produce the same biologically equivalent effect. However, when calculated as a percentage of the lethal dose, the initial doses that produced the effects were the same for 254 and 280 nm. No changes could he observed at the cellular level after the cells were irradiated with 310 nm. The lethal dose depended upon the time between irradiation and observation. At 254 nm it was 1.1 kJ m−2up to 1 h after irradiation and dropped to 860 J m−2when measured 24 and 48 h later. At 280 nm a dose of 2.8 kJ m−2killed the cells within I h while the dose needed after 24 and 48S h was 1.99 kJ m−2. The minimum doses which caused the different cytomorphological effects did not depend upon the observation time. Normal cell structure and functions that were altered immediately alter irradiation did not recover. Doses that were not immediately effective alter irradiation caused no later damage. Doses which increased water permeability were much higher than doses which influenced cytomorphological parameters

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb04264.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The immobilisation ofEuglena gracilisZ cells in a calcium alginate matrix maintained respiratory and photosynthetic activities and ultrastructural integrity. Moreover, immobilization did not preventEuglenacells from greening inside the gel beads. Electron microscopy demonstrated that the immobilized cells were fixed in the same cellular state as they were when the immobilization occurred. This can he explained by simultaneous reaction of both Ca2+and the alginate with the cells. Some hypotheses about the role of C2+are discussed. In addition, long term storage (2 years) in calcium alginate has been performed permitting applications in algal storage.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb04265.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

13C NMR was used to detect sugars in detached fibrous and storage roots of carrots (Daucus carotaL. cv. Chantenay Red‐Cored). The relative amounts of sucrose, glucose and fructose in storage roots of two ages and in fibrous roots were similar to those detected by a destructive, enzymatic sugar determination method. In tap roots all three sugars were present with glucose being marginally predominant in 8‐week‐old roots and sucrose being the major sugar present in 12‐week‐old roots. Glucose was the major sugar present in fibrous roots with small amounts of sucrose and no fructose detected. The results indicate that with some instrumental modification,13C NMR could be used as a non‐destructive method for measuring sugar levels in intact storage root systems during

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb04266.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Two varieties of winter wheat (Triticum aestivumL.) differing in freezing resistance (“Holme” from Sweden, freezing resistant, and “Amandus” from Germany, less freezing resistant) were hardened for five weeks by gradually reducing the day/night temperature from 20°C/15°C during the first week to 2° C/0° C during the fifth week and the photoperiod from 15 to 9 h. This treatment increased the freezing resistance of both varieties in comparison to unhardened control plants. Hardening caused an increase in osmolarity of cell sap and in the levels of proline and abscisic acid (ABA). Increase in osmolarity preceded the increase in ABA level, and proline levels increased later than ABA levels. Holme had higher values of osmolarity as well as higher levels of ABA and proline. but the differences between the two varieties were significant only for proline. Since the pressure potential remained constant or increased slightly during the hardening period, it is suggested that the accumulation of ABA is due to the hardening process and not to simple water stress caused by cold‐induced inhibition of water uptake by the root.Spraying hardened plants with 10−4M ABA 24 h before a freezing test increased freezing resistance in both varieties, but did not obliterate the differences in freezing resistance between the two varieties. Spraying hardened plants with an aqueous proline solution (10%, w/v) was without effect on freezing resistance. It is concluded that the hardening procedure causes an accumulation of ABA in winter wheat leaves and that ABA is involved in the chain of events leading to free

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb04267.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The effect of cadmium on the biosynthesis of chlorophyll has been investigated in the leaves of dark‐grown seedlings of barley (Hordeum vultureL. cv. Proctor). Cd2+ inhibited the production of chlorophyll by affecting 1) the synthesis of 5‐aminolacvulinic acid and 2) the protoehlorophyllide reductase ternary complex with its substrates. Cd2+ had no effect on the constituent enzymes that catalyse the synthesis of free protoehlorophyllide from 5‐aminolaevulinic acid. The results obtained are consistent with Cd2+ inhibiting the formation of chlorophyll by reacting with essential thiol groups in both the protochlorophyllide reductase protein and the enzyme(s) involved in the light dependent synthesis of 5‐aminolaevulin

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb04268.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY