摘要:

Shoots of cold‐acclimated seedlings ofPinus sylvestrisL. were subjected to low temperatures either in darkness or at a photon flux density of 1300 umol m−2s−1. CO2and water vapour exchange of the seedlings were measured at 12°C before and after treatment. Quantum yield at 12°C decreased both with decreasing temperatures below 0°C during, exposure to high light, and with increasing duration of light exposure. Quantum yield was also inhibited after treatment in darkness when needles were exposed to temperatures below their freezing point. Exposure of the pine shoots to a temperature of ‐7 to ‐8°C for 3 h in high light or darkness decreased quantum yield after thawing by ca 50 and 20%, respectively. Furthermore, light or dark exposure of the pine shoots at ‐7°C for 3 h decreased both the initial slope of the response of CO2assimilation rate to intercellular partial pressure of CO2, and the CO2assimilation rate at high partial pressures of CO2. It is concluded that excess light both at low temperatures, and freezing temperatures, cause inhibitions at the metabolic level, although the mechanisms

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb08517.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The correlation between osmotic potential and epicotyl growth in intact and decotyiized mung bean seedlings (Vigna radiata(L.) Wilczek) grown under osmotic stress was studied. The following results were obtained: 1) Epicotyl elongation in intact seedlings grown in vermiculite containing 0.2Mmannitol was not substantially affected, but was strongly inhibited in decotylized ones. 2) Osmotic potential in the epicotyl was. decreased by osmotic stress due to 0.2 M mannitol, and was increased by cotyledon excision. 3) Epicotyl elongation was well correlated with net osmotic concentration, which is. the difference in osmotic concentration between the vacuolar sap of epicotyl cells and the 0.2Mmannitol added to the vermiculite. The net osmotic concentration was also correlated with cell elongation, but not with cell division in the epicotyl. 4) The concentrations of soluble sugars, free amino acids and potassium ions in the epicotyl increased in response to osmotic stress. Cotyledon excision decreased the concentrations of soluble sugars and free amino acids, while it had no effect on potassium ion concentration.Based on these results, a role of osmoregulation in regulating epicotyl growth of mung bean is discussed in relation to osmotic stress and cotyledon excision.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb08518.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The catabolism of radiolabelled indole‐3‐acetic acid was investigated in a crude enzyme extract and a protoplast‐rich fraction from Scots pine (Pinus sylvestrisL.). Analysis by ion‐pair reverse‐phase and normal‐phase high performance liquid chromatography indicated that [14C]‐indole‐3‐methanol was a major catabolite of [2‐14C]‐indole‐3‐acetic acid in the crude enzyme system. This was confirmed by combined gas chromatograpby‐mass spectrometry which demonstrated the conversion of [2, 4, 5, 6, 7‐2H5]‐indole‐3‐acetic acid to [2H]‐indole‐3‐methanol. In addition to indole‐3‐methanol, the enzyme system converted indole‐3‐acetic acid to a number of other catabolites. Feeds with [1‐14C]‐ and [2‐14C]‐mdole‐3‐acetic acid suggest that, with the exception of two minor components, these catabolites result from decarboxylation. The effects of 2, 4‐dichlorophenol, phenol and hydrogen peroxide upon the reaction rate and product formation in the crude enzyme system were also investigated. Phenols favoured the formation of indole‐3‐methanol and enhanced the reaction rate. In contrast to the enzyme extract [14C]‐indole‐3‐methanol was only a minor product when

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb08519.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Flowers of somePhlox(Phlox x paniculataL.) varieties undergo daily colour shifts, being blue in the early morning, turning red during the day, and returning to blue in the evening. The colour shift, which occurs only in the upper (adaxial) petal surfaces, is due to the daily changes in ambient light. In the laboratory, colour shifts could be induced by 2.5 h of ultraviolet, visible or far‐red light and recorded by reflectance spectrophotometry.There are indications that irradiations with different kinds of light cause qualitatively different colour shifts, and that thus more than one photoreceptor pigment and more than one primary light reaction may be involved. The presence of phytochrome was demonstrated in petals of whitePhloxflowers by in vivo transmission spectrophotometry. It is therefore possible that colour shifts in colouredPhloxflowers are mediated by phytochrome. Possibly the movement of ions (e.g. hydrogen ions) into or out of the vacuole (where the visible pigments are located) is affected by light absorption in a pigment in the tonoplas

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb08520.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Net photosynthetic CO2exchange of 1‐year‐old plants ofCoffea arabicaL. was studied after the above‐ground parts had been exposed once or repeatedly to night temperatures in the chilling range. Chill‐reduced rates of CO2uptake (measured at 24°C and at natural CO, level) were observed after a 12 h night exposure to about 6°C. After exposure to 4°C, activity was reduced to less than half of that of the controls, and after exposure to 0.5°C the leaves suffered visible necrotic injury and were no longer able to take up Co2If the leaves were not lethally injured, net photosynthesis recovered completely within 2 to 6 days. About 25% of chill‐induced reduction of CO2uptake was due to reduced stomatal aperture and 75% to impairment of carboxylation efficiency.Chilling on successive nights at 4–6°C reduced CO, uptake progressively on each day following treatment. After 10 nights, activity was decreased to less than 10% of initial performance. Conditioning at temperatures slightly above the chilling level (e.g. 15/I2°C) for 2 weeks led to almost complete impairment of photosynthetic activity without additional chilling stress instead of improving c

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb08521.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Growth in diameter of fruits (follicles) of five cultivate ofMacadamia integrifoliaMaiden and Betche followed a single sigmoidal pattern. A rapid increase in fruit diameter began 2 to 3 weeks after anithesis and continued until weeks 14 to 16. No further increase in size was observed after 16 weeks. Growth in fresh weight of the two cnltivars observed also followed a single sigmoidal pattern. A rapid increase in fresh weight began 5 to 6 weeks after anthesis and continued until weeks 15 to 18. No further increase in fresh weight was evident after 18 weeks. Abscission of flowers and fruits occurred continuously from anthesis through fruit maturity and could be separated into three periods. The first period of abscission occurred in the first 2 weeks after anthesis and commonly involved over 90% of the flowers. The second period of abscission occurred from 3 to 8 weeks after anthesis and commonly involved over 80% of the initial set of small fruit. This period of abscission occurred prior to and concurrent with the rapid increase in growth. The third period of abscission was gradual and occurred from 9 weeks after anthesis until maturity at 28 to 30 weeks. Measurement of ethylene evolution by fruits showed a peak during weeks 3 and 4. This was prior to the peak in relative abscission rate at week 5. The fruit removal force increased from anthesis through week 12 and decreased from week 24 through maturity.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb08522.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Homogenates of 7‐day‐old oat (Avena sativaL. cv. Brighton) roots were highly fluorescent (excitation and emission maxima around 360 and 440 nm, respectively). Less than1/10as much fluorescence per g fresh weight was found in oat shoots or in wheat (Triticum aestivumL. cv. Drabant) roots or shoots. Most of the fluorescence of oat roots was found in the soluble fraction (150 000g supernatant). However, some could be detected in the plasma membrane fraction (excitation and emission maxima 365 and 417 nm, respectively), which contained a 3‐fold higher fluorescence per mg protein than the homogenate.Growth of oat or wheat in a medium containing, 10‐−5Mscopoletin (6‐methoxy‐7‐hy‐droxy coumarin), a fluorescent compound previously reported to be present in both wheat and oat roots, caused the disappearance of scopoletin from the medium (proportional to the amount of roots) and the appearance of increased fluorescence in the root homogenates but not in the shoot homogenates. In both oat and wheat roots ail of the extra fluorescence was recovered in the soluble fraction and at least in wheat it consisted of unconverted scopoletin. The concentration of scopoletin in wheat roots grown in 10‐−5Mscopoletin was around 50 nmol (g fresh weight)−1, or about five times the concentration in the growth medium. Scopoletin in the growth medium (10‐−5M) or in the assays (up to 10‐−4M) did not affect Mg2+‐, Mg2++K+‐ or Ca2+‐ATPase activities in wheat or oat roots.The fluorescence properties of the oat plasma membrane were different from those of authentic scopoletin. Either the surroundings modify the fluorescence of membrane‐associated scopoletin or the endogenous fluorescent compound is not scopoletin but a glycoside‐derivative of scopole

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb08523.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Chloroplasts developed at cold‐hardening (5°C) and non‐hardening temperatures (20°C) were compared with respect to the stability of photosynthetic electron transport activities, the capacity to produce and maintain a H+gradient and the capacity fat photophosphorylation as a function of resuspension in the presence or absence of osmoticum. The results for electron transport indicate that whole chain, photosystem I and pfaotosystem II activities in non‐hardened chloroplast thyalkoids were unaffected by resuspension in the presence of high or low osmoticum. In contrast, the same electron transport activities in cold‐hardened chloroplast thylakoids exhibited a 3‐ to 4‐fold decrease in activity when resuspended in the presence of low osmoticum. Impairment of electron transport through photosystem II of cold‐hardened thylakoids resuspended in the presence of low osmoticum was supported by room temperature fluorescence induction kinetics. Since the presence of Mn2+partially overcame this inhibition, it is concluded that this osmotically‐induced inhibition of PSII activity in cold‐hardened chloroplast thylakoids may, in part, be due to damage to the H2O‐splitting side of photosystem II. Both the initial rate and the maximum capacity for cyclic photophosphorylation were significantly inhibited in cold‐hardened as compared to non‐hardened thylakoids upon resuspension in the presence of low concentrations of osmoticum. This was correlated with an inability of the cold‐hardened chloroplast thylakoids to maintain a significant transrnembrane H+gradient. The results indicate that cold‐hardened thylakoid membranes required an osmotic concentration (0.8M) twice as high as non‐hardened thylakoids (0.4M) to produce the same initial rate of H+uptake. In addition, the capacity to produce a proton gradient in cold‐hardened thylakoids was less stable than that in non‐hardened thylakoids regardless of the osmotic concentration tested. It is concluded that development of rye thylakoid membranes at low temperature results in a differential sensitivity to low osmoticum and thus extreme caution should be exercised when comparing the structure and function of isolated thylakoids develope

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb08524.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Action potentials induced by electrical stimuli were recorded from the thalli of tfie liverwort,Conocephalum conicumL. An analysis of an equivalent circuit ofConocephalum conicumthallus in situ has shown that the multiphasic time course of extracellular recordings is caused by a branching of extracellular conduction layers and by an overlapping of action currents. As compared to the velocity of excitation propagation without short‐circuiting, more than 10 times higher rates of action potential conduction have been recorded when the plants are immersed in a low resistaace solution. Furthermore, simultaneous extra‐ and intracellular recordings from thalli in situ are presen

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb08525.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The response to light of a liverwort,Conocephalum conicumL., measured as a change in the resting potential, consists of two stages. The first stage is a slight depolarization dependent on light intensity. This plays the role of a generator potential (GP) which induces the second stage ‐ an action potential of the all‐or‐none character. Action potentials induced by light and by electrical stimuli have the same properties, i.e. identical time course, propagation velocity, and refractory periods. A summation occurs of sub threshold light stimuli and of light and electrical stimuli. The presence of 5⋅10‐−6MDCMU cancelled the light response and blocked ‐ by inhibition of the electron transport chain ‐ the mechanism leading to GP generation. However, this effect did not produce any change in the response to ele

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1985.tb08526.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY