摘要:

Ultraweak light emission (UWLE) was measured from leaves of various chilling‐sensitive (Lycopersicon esculentum, Cucumis sativusandPhaseolus vulgaris) and ‐tolerant (Pisum sativumandVicia faba) plants after exposure to low (4‐7°C) temperature in the light. UWLE increased upon chilling treatment combined with illumination with 200 µmol m−2s−1PAR in all plants, by about 30% in tolerant and by more than 100% in sensitive plants. It increased more when applied together with 400 µmol m−2s−1PAR: by 90‐100% and by 250‐280% in chilling‐tolerant and ‐sensitive plants, respectively. Free radical production was detected by spin‐trapping EPR spectroscopy in thylakoid membranes isolated from the chilling‐treatedLycopersicon esculentumandVicia fabaleaves. After 12 h chilling at 200 µmol m−2s−1PAR, free radical production was approximately 3 times greater in the former than in the latter species. The same ratio was approximately 6 if chilling was carried out at 400 µmol m−2s−1PAR, indicating the role of photooxidative stress in chilling injury.Our results also confirm that the stress‐induced increase in UWLE is an indicator of free radical production and offers the possibility of using UWLE for monitoring the effect of chilling on temper

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1996.980201.x

出版商:Munksgaard International Publishers    

年代:1996

数据来源: WILEY

摘要:

Zinc and manganese loading into developing wheat grain is little understood at present. The objective of this work was to investigate factors that may affect the rate of transport of Zn and Mn into developing wheat grain of cultured ears. Ears 18‐22 days post‐anthesis were cultured in solutions containing labelled Zn and Mn. The effect of additions of Cu, Fe, citrate, malate and EDTA to the culture solution was observed. The effect of humidity and awn removal as well as the sucrose status of the ears on Zn and Mn transport was also investigated. The effect of high concentration of Zn and Mn on [14C]‐sucrose transport was determined. High humidity almost completely blocked transport of Zn and Mn into the grain. Awn removal reduced the transport of Zn and Mn to the lemma but not the grain. When the ears were depleted of sucrose (by maintaining them in the dark prior to labelling) transport of Zn and Mn to the grain was reduced compared to ears cultured with sucrose. The presence of Cu reduced the loading of Zn into the grain. There was little effect of Cu on Mn transport or Fe on either Zn or Mn transport. High concentrations of Zn and Mn in the culture solution did not affect [14C]‐sucrose loading into the grain but loading of Zn and Mn was limited at high concentrations suggesting membrane saturation. This study demonstrates that sucrose status and humidity clearly influence the transport of Zn and Mn into the grain, and that other ions may influence Zn and Mn tr

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1996.980202.x

出版商:Munksgaard International Publishers    

年代:1996

数据来源: WILEY

摘要:

The modulation of the expression of thiol proteases during both senescence and development was investigated Proteolytic activity and some thiol proteases were analyzed in unpollinated tomato (Lycopersicon esculentumMill. cv. Rutgers) ovaries during presenescence and during early fruit development induced by treatment with gibberellic acid (GA) or by natural pollination. Proteolytic activity in extracts was tested on azocasein and by observing degradation of the ribulose‐1,5‐bisphosphate carboxylase large subunit in western blots. There was no correlation between total activity and protein content. Thiol proteases were analyzed by western blot with antibodies raised against papain and a recombinant tomato C14 thiol protease. A 58‐kDa polypeptide was recognized by both antibodies and two more polypeptides of 47 and 36 kDa were detected with the second one. All these polypeptide levels increased in untreated unpollinated ovaries at the presenescent stage. Natural pollination or GA treatment of unpollinated ovaries resulted in decreases of these polypeptides at an early developmental stage. The same pattern was observed for the levels of C14 mRNA. Our results suggest that the expression of C14 thiol protease occurs in unpollinated ovaries at the presenescent stage and that it can be suppressed by factors that induce fruit set and develo

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1996.980203.x

出版商:Munksgaard International Publishers    

年代:1996

数据来源: WILEY

摘要:

Dark‐grown, 10‐day‐old bean seedlings (Phaseolus vulgarisL. cv. Morocco) were transferred to continuous light, and the resulting changes in growth rate and concentration of 3‐hydroxy‐β‐ionone, an endogenous growth inhibitor, were monitored. The growth rate of the first internodes of the seedlings decreased rapidly and leveled off 20 h after onset of light. This plateau value was about 25% of the growth rate of the non‐irradiated control. The concentration of 3‐hydroxy‐β‐ionone in the internodes of the irradiated seedlings increased rapidly and reached a plateau value after 16 h. This increased level of the inhibitor was about 5 times the level in the non‐irradiated control. The changes in the levels of the inhibitor in the internodes reflected the light‐induced growth inhibition of the internodes. The longitudinal distribution of the growth inhibitor along the first internodes of the seedlings was closely correlated with the light‐induced growth inhibition of the corresponding region of the internodes. The present results suggest that the endogenous growth inhibitor 3‐hydroxy‐β‐ionone may play an important role in the inhibition by light of

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1996.980204.x

出版商:Munksgaard International Publishers    

年代:1996

数据来源: WILEY

摘要:

The involvement of ethylene and 1‐aminocyclopropane‐1‐carboxylic acid (ACC) in shade‐induced kernel abortion at an early kernel growth stage was investigated. Changes in levels of glucose, sucrose, starch, ACC and ethylene were measured during the first 6 days after pollination (DAP) at sampling intervals of 12 or 24 h. In response to shading treatment, dry weight accumulation of apical kernels ceased within 96 h after pollination (HAP). Glucose levels in shaded kernels 12 HAP were significantly higher than in control kernels, while sucrose and starch levels were similar until 48 HAP. In the shade treatment ACC and ethylene levels increased rapidly around 24 HAP in both apical and basal kernels. When ACC was applied to ears at 32 HAP and 5 DAP, dry weight accumulation was significantly reduced only in apical kernels of 32 HAP. Significant reduction in endosperm nuclei number was also found in both shaded and ACC‐treated kernels. The results of the present study suggest that ethylene may be involved in the processes leading to kernel abortion in maize. Kernels at the very early developmental stages seem to be most sensitive to

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1996.980205.x

出版商:Munksgaard International Publishers    

年代:1996

数据来源: WILEY

摘要:

In the present study we explored the possibility of assessing the allocation of photons absorbed by photosystem II (PSII) antennae to thermal energy dissipation and photosynthetic electron transport in leaves of several plant species under field conditions. Changes in chlorophyll fluorescence parameters were determined in situ over the course of an entire day in the field in sun‐exposed leaves of two species with different maximal rates of photosynthesis,Helianthus annuus(sunflower) andVinca major. Leaves ofVinca minor(periwinkle) growing in a deeply shaded location were also monitored. We propose using diurnal changes in the efficiency of open PSII centers (F′v/F′m) in these sun and shade leaves to (a) assess diurnal changes in the allocation of absorbed light to photochemistry and thermal energy dissipation and, furthermore, (b) make an estimate of changes in the rate of thermal energy dissipation, an analogous expression to the rate of photochemistry. The fraction of light absorbed in PSII antennae that is dissipated thermally (D) is proposed to be estimated from D = 1‐F′v/F′m, in analogy to the widely used estimation of the fraction of light absorbed in PSII antennae (P) that is utilized in PSII photochemistry from P = F′v/F′m× qP(where qPis the coefficient for photochemical quenching; Genty, B., Briantais, J.‐M.&Baker, N. R. 1989. Biochim. Biophys. Acta 990: 87‐92). The rate of thermal dissipation is consequently given by D × PFD (photon flux density), again in analogy to the rate of photochemistry P × PFD, both assuming a matching behavior of photosystems I and II. Characterization of energy dissipation from the efficiency of open PSII centers allows an assessment from a single set of measurements at any time of day; this is particularly useful under field conditions where the fully relaxed reference values of variable or maximal fluorescence needed for the computation of nonphotochemical quenching may not be available. The usefulness of the assessment described above is compared with other currently used parameters to quantify nonphotochemical and photochemical chlorophyll

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1996.980206.x

出版商:Munksgaard International Publishers    

年代:1996

数据来源: WILEY

摘要:

Gamma irradiation (1.0 kGy) of intact, newly harvested, mature muskmelon fruit (Cucumis meloL. var.reticulatusNaud.) appears to have an immediate deleterious effect, but also a long‐term beneficial effect, on the integrity and function of the plasma membrane (PM) of hypodermal mesocarp tissue. The initial consequences of gamma irradiation included an increase in the free sterol:phospholipid ratio, resulting at least in part from deglycosylation of steryl glycosides, a decrease in the spinasterol:7‐stigmastenol ratio in each of the PM steryl lipids (free sterols, steryl glycosides, and acylated steryl glycosides), and a decrease in H+‐ATPase activity. Irradiation did not increase protein loss, suggesting that the decrease in H+‐ATPase activity resulted from either direct inactivation of the enzyme or altered PM ordering caused by the steryl lipid modifications. The long‐term beneficial effects of irradiation, observed following 10 days of commercial storage, included greater retention of total PM protein, a diminished decline in total PM phospholipids (PL) and in the PL:protein ratio, and maintenance of greater overall H+‐ATPase activity (activity was the same as in controls on a per mg protein basis, but there was>30% more protein in the PM of stored irradiated fruit). These results indicate that 1 kGy gamma irradiation administered prior to storage slowes the progression of two key parameters of senescence, PM protein loss and PL

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1996.980207.x

出版商:Munksgaard International Publishers    

年代:1996

数据来源: WILEY

摘要:

Acyl lipids and pigments were analyzed in young plants of garden pea, spring wheat and spinach exposed to<5 or 65 nl l−1ozone 12 h per day for 6 days. In one set of experiments, the plants were exposed to14CO2for 2 h 3 days prior to ozone exposure. The plants responded differently to the moderately enhanced level of ozone used Spinach was not at all sensitive while in both pea and wheat, leaves of different ages differed in ozone sensitivity. In pea, ozone sensitivity increased with leaf age. In the second and third oldest leaves, the amounts of galactolipids per leaf area and the proportions of 18:3 of the total lipid extract and of phosphatidylglycerol decreased. In the second oldest leaf, ozone also caused a decreased proportion of 18:3 of monogalactosyldiacylglycerol. In the fourth oldest leaf, lipid composition and galactolipid unsaturation was unaffected, but ozone caused decreased leaf expansion resulting in increased acyl lipid content per leaf area. In both the first and second leaves of wheat, ozone fumigation caused a marked decrease in the content of monogalactosyldiacylglycerol and in the first leaf, the contents of phosphatidylcholine and phosphatidylethanolamine increased. The proportion of 18:3 in phosphatidylcholine was larger in ozone‐fumigated than in control plants, while the reverse applied for phosphatidylglycerol. In the oldest sampled leaves of pea and wheat, ozone caused an increase in the radioactivity associated with β‐carotene, indicating increased turnover. Thus, while spinach was unaffected, in both pea and wheat ozone caused a decrease in the proportion of chloroplast membrane lipids to non‐chloroplast membrane lipids in older leaves while younger leaves were less s

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1996.980208.x

出版商:Munksgaard International Publishers    

年代:1996

数据来源: WILEY

摘要:

The stimulation of the plasma membrane (PM) H+‐ATPase by boric acid was studied on a microsomal fraction (MF) obtained from ungerminated, boron‐dependent pollen grains ofLilium longiflorumThunb. which usually need boron for germination and tube growth. ATP hydrolysis and H+ transport activity increased by 14 and 18%, respectively, after addition of 2‐4 mMboric acid. The optimum of boron stimulation was at pH 6.5‐8.5 for ATP hydrolysis and at pH 6.5‐7.5 for H+transport. No boron stimulation was detected when vanadate was added to the MF, whereas an increase of 10‐20% in ATP hydrolysis and H+transport was still measured in the presence of inhibitors specific for V ‐type ATPase (nitrate and bafilomycin) and F‐type ATPase (azide), respectively. A vanadate‐sensitive increase in ATP hydrolysis activity was also observed in partially permeabilized vesicles (0.001%[w/v] Triton X‐100) suggesting a direct interaction between borate and the PM H+‐ATPase rather than a weak acid‐induced stimulation. Additionally, we measured the effect of boron on membrane voltage (Vm) of ungerminated pollen grains and observed small hyperpolarizations in 48% of all experiments. Exposing pollen grains to a more acidic pH of 4 caused a depolarization, followed in some experiments by a repolarization (21%). In the presence of 2 mMboron such hyperpolarizations, perhaps caused by an enhanced activity of the H+‐ATPase, were measured in 58% of all tested pollen grains. The effects of boron on Vmmay be reduced by additional stimulation of a K+inward current of opposite direction to the H+‐ATPase. All experiments indicate that boron stimulates an electrogenic transport system in the plasma membrane which is sensitive to vanadate and has a pH optimum around 7, i.e. the plasma membrane H+‐ATPase. A boron‐increased PM H+‐ATPase activity in turn may stimulate germi

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1996.980209.x

出版商:Munksgaard International Publishers    

年代:1996

数据来源: WILEY

摘要:

The metabolism and the in vitro effects of the cytokinin N6‐(3‐hydroxybenzyl)adenine (meta‐topolin, mT) were compared with those of N6‐benzyladenine (BA), N6‐benzyl‐9‐(2‐tetrahydropyranyl)adenine (BPA) and N6‐benzyladenine‐9‐riboside ([9R]BA) in micropropagatedSpathiphyllum floribundumSchott cv. Petite. In vitro, BA, BPA and [9R]BA were mainly converted into the stable derivative N6‐benzyladenine‐9‐glucoside ([9G]BA), located at the basal part of the plant. N6‐(3‐O‐β‐D‐glucopyranosyl)benzyladenine‐9‐riboside {(OG)[9R]mT} was the main derivative of mT. This new cytokinin‐O‐glucoside, which was present in all plant parts, was metabolized much faster than [9G]BA during acclimatization. The effect of BA and mT on in vitro shoot and root production and post vitro rooting was compared. Only mT combined a good shoot production with in vitro root formation. The plants that developed on medium with 10 µMor more mT rooted better during acclimatization than those develope

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1996.980210.x

出版商:Munksgaard International Publishers    

年代:1996

数据来源: WILEY