摘要:

Relationships between growth parameters and root respiration under various conditions of salinity were investigated in seedlings of the grey mangroveAvicennia marina(Forsk.) Vierh. Growth, root/shoot ratios, leaf succulence and osmotic potential of leaves were measured for seedlings grown for 6–8 weeks in 100, 50, 25 and 0% seawater. Oxygen uptake of root segments, from distal to proximal ends of roots, was measured for all treatments. Total growth was maximal in 25% seawater, highest leaf succulence was obtained in 50% seawater, and highest leaf osmotic potential in 100% seawater. Oxygen uptake in distal root segments, as measured both by Clark oxygen electrode and Warburg manometry, showed a stimulation in the presence of salt that closely paralleled growth stimulation. The rates of respiration were highest in 25% seawater. The oxygen uptake was not stimulated by salt per se, since concentrations higher than 25% were associated with a decline in rate of oxygen uptake from the maximum. Values for the respiratory quotient approximated to one in all treatments.Avicennia marinahas been reported to exclude from its roots about 90% of the salt in the surrounding medium. It might have been expected that increased concentrations of salt in the growth medium would be associated with a standard salt respiration response in the roots; however, this was not obtaine

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04549.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Absorption of ammonium from solutions of ammonium chloride by maize (Zea maysL. cv. GS‐2) tissue was studied. In contrast to an initial rapid phase of absorption in root tissue, a one hour lag period was recorded in leaf tissue. The maximum rate of uptake was observed at 5–10 mMNH4Cl in both tissues. Roots had a Kmvalue of 1.0 mMand Vmaxof 24.3 μmol ammonium (g fresh weight)−1h−1, whereas the leaf tissue had a higher Km(4.1 mM) and a lower Vmax(8.7 μmol). There was a concentration dependent increase in ethanol soluble and insoluble fractions of organic nitrogen during ammonium supply. The optimum pH for ammonium absorption for both tissues was 7.4. The optimal concentration of CaCl2for ammonium absorption was 5 mMwhereas that of KCl was only 1 mM. In both tissues, the absorption was inhibited substantially by DCMU, DNP, cycloheximide, lincomycin, sodium tungstate, sodium arsenate and to some extent also by the anions nitrate and sulfate. It is suggested that a carrier is involved in an active uptake of ammonium in the lea

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04550.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Potato (Solanum tuberosumL. cv. Katahdin) disks produce ethyline in increasing amounts from 6 to 24 h incubation in buffer at pH 4.0. Ethylene production is increased 2–3 times in the presence of 50 mMCaCl2. Levels of endogenous 1‐amino‐cyclopropane‐1‐carboxylic acid (ACC) increase in parallel with ethylene production, and ACC levels are 3–5 times higher in calcium‐treated disks than in controls. Most of the calcium‐induced stimulation of ethylene production can be accounted for by its effect on ACC production, indicating that the primary effect of calcium is on a step of ethylene biosynthesis preceeding ACC production. However, calcium may also have an effect on conversion of ACC to ethylene, since a consistent increase in ACC‐de‐pendent ethylene production was observed in the presence of calcium. Production of ethane, a marker of lipid peroxidation, was reduced by calcium, so it is possible that membrane stabilization by calcium could be involved in its effects on

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04551.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Marked increases were found in the content of total soluble sugars, reducing sugars and ATP in winter wheat (Triticum aestivumL. cv. Frederick) during cold hardening. The changes in soluble sugars and ATP of spring wheat (T. aestivumL. cv. Glenlea) grown under similar conditions were less pronounced. The increase in ATP content during hardening of winter wheat was not associated with significant changes in the content of ADP or AMP. The adenylate energy charge did not change during hardening in either cultivar, but it was higher in the winter cultivar under both growth conditions. This difference could be related to the cold hardiness capacity of winter wheat.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04552.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The role of protein synthesis in senescence and in the inhibition of senescence by light and kinetin was studied in barley (Hordeum vulgareL. cv. Hassan) leaves with different inhibitors of protein synthesis. A comparison of the actions of D‐ and L‐chloramphenicol was made to compensate for the effects of D‐chloramphenicol not mediated by inhibition of protein synthesis. The involvement of phytochrome was also studied. The results suggest that: 1) cytoplasmic protein synthesis is required for senescence in the light and in the dark; 2) chloroplasts, in the dark, synthesize protein which accelerates senescence; 3) kinetin inhibits the synthesis by chloroplasts of senescence‐accelerating protein; 4) light changes the type of protein synthesized by chloroplasts from those accelerating to those retarding senescence; and 5) lightretar‐dation of senescence is mediated by phytochrome and, probably, by photophos‐

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04553.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Rythmical changes in the transcriptional activity of embryo chromatin during development and maturation of grain of triticale (cv. MT‐3) have been observed. The template availability and RNA polymerase (EC 2.7.7.6) 1 and II activities were high at the beginning of embryo development (20 to 30 days) and lowest at days 35 to 40 after anthesis, after which they increased to the end of maturation (60 days). Grains from three important periods of development (20, 40 and 60 days after anthesis; that is milk, wax and full ripeness, respectively) were used for germination, and chromatin was isolated from embryos and seedlings. A dramatic increase in the activity of both RNA polymerases and template availability was observed after 48 h of germination. The increase in template availability depended also on the ripeness stage of the grain used for germinatio

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04554.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Water and ion fluxes of intact root systems ofPyrus communisL. cv. Old Home × Farmingdale 97 immersed in a nutrient solution were determined at various pressures and temperatures. Water flux (Jvwas normalized on the basis of initial flow rates of a root system after 30 min at 0.50 MPa and 25°C, expressed as the ratio Qv. Qvresponded linearly to pressures between 0.20 and 0.62 MPa, implying a constant root hydraulic conductivity (Lp) within this range. Similarly Qvwas linearly related to temperatures between 7 and 35°C; however, large, rapid temperature changes resulted in a break of the Arrhenius plot of Qvversus the reciprocal of temperature, Abscisic acid (ABA) from 2 × 10−6to 10−4M, applied to intact root systems, increased Qvwithin 10–20 min, with the effect leveling off after 1.5 h. At a pressure of 0.50 MPa, ABA at 10‐4Menhanced Qvby 28%. The stimulation of Qvwas not due to the ethanol solvent since 0.13 or 1.33% ethanol decreased Qv‐, The osmotic potential of the xylem fluid was determined and was used to calculate total normalized solute flux. The results suggest that ABA‐induced or ethano1‐induced changes in Qvwere mainly due to changes in Lpand not to changes in ion trans

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04555.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Stable free radicals, together with horseradish peroxidase, promoted degradation of indole‐3‐acetic acid (IAA). These reactions were retarded by the free radical scavengers Bromoxynil, Na‐benzoate and kinetin. Certain free radicals promoted, but the free radical scavenger Bromoxynil retarded ethylene production in apple slices and mung bean stem tissues. The interdependency of free radicals and free radical scavengers in systems controlling IAA levels and ethylene production is disc

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04556.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Acidity fluctuation, CO2gas exchange, δ13C value, PEP carboxylase and RuBP carboxylase activities in aerial roots of selected thick‐leaved orchid hybrids (ArachnisandAranthera) were studied. Both aerial roots and leaves showed acidity fluctuation over a 24 h period. Dark acidification in aerial roots was enhanced at low temperature (15°C). Aerial roots had δ13C values close to those of leaves which have been previously demonstrated to possess crassulacean acid metabolism. Variation in δ13C values along the length of the roots was observed; the root tip having a less negative δ13C value (—13.34%‰) than the older portions of the roots (—14.55%‰). There was no net CO2fixation by aerial root, although1432CO2fixation was observed in light and in darkness. The pattern of fluctuation in activities of PEP carboxylase and RuBP carboxylase in aerial roots was similar to that obtained for the leaves. In both aerial roots and leaves, PEP carboxylase activity was several times higher than that of Ru

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04557.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Light, excision and sucrose increased extractable phenylalanine ammonia‐lyase (PAL) activity from hypocotyl tissue of sunflower (Helianthus annuusL. cv. Peredovik) to 2–6 times the basal level. Intact sunflower seedlings or whole hypocotyls incubated in water or 0.1 M sucrose exhibited, in continuous light, a pattern in which PAL peaked 4 and 28 h after the beginning of the illumination. When 0.5 cm long hypocotyl segments were incubated in water or 0.1 M sucrose, they exhibited, both in continuous light and in the dark, a pattern in which PAL rose during an initial period of 10 h (assay in sucrose and light) to 48 h (assay in water and dark) and then remained nearly constant at a high value for at least the next 10 h. When whole hypocotyls were incubated in 0.1 M sucrose, a third pattern in PAL activity was found in which PAL peaked after 28 h and subsequently declined. In all the above systems the increase in PAL activity was significantly reduced by cycloheximide. Furthermore, the subsequent decay of PAL activity following illumination was prevented by delayed transfer to cycloheximide. It is suggested that the results can be explained on the basis of a turnover mechanism involving continued de novo enzyme synthesis and subsequent synthesis of a PAL‐inactivating s

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04558.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY