摘要:

31P nuclear magnetic resonance spectroscope (NMR) was used to study the response ofPhacelia tanacetifoliaseeds to dark and light conditions during the first 72 h of incubation. Changes in the chemical shifts (δ) of the pH‐dependent31P‐NMR signals from the vacuolar and the cytoplasmic orthophosphate pools were correlated with the different incubation conditions. In the dark (favorable to germination), the cytoplasmic pH remained nearly constant over the whole period considered, while the vacuolar pH shitted to more acidic values after the 24th h of incubation. In the light (inhibiting germination), the values of cytoplasmic pH tended to become more acidic than in the dark after the 24th h of incubation, while the vacuolar pH remained practically constant. When seed germination was inhibited in the dark by butyric acid (BA). a permeant weak acid, the values of cytoplasmic and vacuolar pH were similar to those of the ungerminated seeds incubated in the light. When, vice versa, seed germination was promoted in the light by fusicoccin (FC), the values of cytoplasmic and vacuolar pH were similar to those of the dark‐germinated seeds. A progressive augmentation of P, metabolism occurred both in the dark and in the light up to the 24th h of incubation. Subsequently, light blocked any further evolution of this parameter. Treatment with butyric acid in the dark again mimicked the effect of light, while FC reversed the negative effect of light. The data show that inPhacelia tanacetifoliaseeds germination is linked to a more alkaline cytoplasmic pH. The finding that the light‐dependent metabolic inhibition occurs after an early activation of metabolism, i.e. after the first 24 h. suggests that the effects of light on the cytoplasmic and vacuolar pH depend on the early metabolic processes involved in the control of the homeostasis of cell pH and/or on the inhibition of the reactivation of the transport me

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb05103.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Broad‐band UV‐B radiation inhibited hypocotyl elongation in etiolated tomato (Lycopersicon esculentumMill. cv. Alisa Craig) seedlings. This inhibition could be elicited by620 μmol m−2s−1between 320 and 800 nm), and was similar in wild‐type and phytochrome‐1‐deficientaureamutant seedlings. These observations suggest that the effect of UV‐B radiation is not mediated by phytochrome. An activity spectrum obtained by delivering 1 μmol m−2s−1of monochromatic UV radiation against a while light background (63 μmol m−2s−1showed maximum effectiveness around 300 nm, which suggests that DNA or aromatic residues in proteins are not the chromophores mediating UV‐B induced inhibition of elongation. Chemicals that affect the normal (photo)chemistry of flavins and possibly pterins (KI, NaN, and phenylacetic acid) largely abolished the inhibitor) effect of broad‐hand UV‐B radiation when applied to the root zone before irradiation. KI was effective at concentrations<10−4M, which have been shown in vitro to be effective in quenching the triplet excited stales of flavins but not fluorescence from pterine or singlet states of flavins. Elimination of blue light or reduction of UV‐A, two sources of flavin excitation, promoted hypocotyl elongation, but did not affect the inhibition of elongation evened by UV‐B. Kl applied after UV‐B irradiation had no effect on the inhibition response. Taken together these findings suggest that the chromophore of the photoreceptor system invoked in UV‐B perception by toma

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb05104.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

UV‐B radiation inhibits hypocotyl elongation in etiolated tomato (Lycopersicon esculentumMill. cv. Alisa Craig) seedlings acting through a photoreceptor system with peak apparent effectiveness around 300 nm. In order lo further characterize the response and gain insight into its potential ecological significance, the time‐course of inhibition was measured and compared with the time‐course of flavonoid accumulation in the same seedlings. When a background of strong (>620 μmol m−2s−1) white light (WL) was supplemented with low irradiance UV‐B (∼ 3 μmol m−2s−1). substantial (∼ 50%) inhibition of elongation occurred within 3 h of the light treatment. The magnitude of UV‐B‐induced elongation inhibition was similar in wild type (WT) and au‐mutant seedlings, in spite of the large differences between genotypes in rate and temporal pattern of elongation. In comparison to the effect of UV‐B on elongation, induction of flavonoid accumulation in WT and au seedlings undergoing de‐etiolation was a much slower response. Several UV‐absorbing compounds appeared to be specifically induced by light, and some of them accumulated faster under the WL + UV‐B treatment than under WL alone. However, there was little or no delectable effect of WL on flavonoid levels until up to 3 h of treatment, and the specific UV‐B effect was measurable only after 6 h of continuous treatment. Indeed. UV‐B‐screening properties of crude alcoholic extracts were not different between WL and WL + UV‐B treatments until after 9 or 24 h. When the light treatments were applied to seedlings that were just breaking through the soil surface. UV‐B was found to consistently retard seedling emergence. These results suggest that the rapid inhibition of elongation in de‐etiolating seedlings is an evolved response lo UV‐B, which may serve to minimize seedling exposure to sunlight until protective pigmentation responses (triggered by WL and

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb05105.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The presence of UV‐absorptive substances in the epidermal cells of leaves is thought to protect mesophyll tissues from the harmful effects of UV‐B radiation. We examined the influence of short‐term UV‐B exposures on UV‐absorptive (330 nm) sinapates and flavonols, and on shoot growth of theArabidopsiswild type ecotype Landsbergerectaand two mutants.114deficient in chalcone synthase, and115, deficient in chalcone/flavonone isomerase. Sequential ozone exposures were used to determine the effects of oxidative stress The levels of sinapates and flavonols on a leaf fresh weight basis increased substantially in the wild type and sinapates increased in the114mutant in vegetative vegetative/reproductive transitional and reproductive stage plants in response to short‐term (48h) UV‐B radiation. When UV‐B was discontinued the levels generally decreased lo pre‐exposure levels after 48 h in vegetative/reproductive but not in reproductive plants. Exposure to ozone before or alter UV‐B treatment did not consistently affect the levels of these UV‐absorptive compounds. Dry matter accumulation was less affected by UV‐B at the vegetative and reproductive stages than at the vegetative/reproductive stage. At the vegetative/reproductive stage, shoot growth of all 3 genotypes was retarded by UV‐B. Growth was not retarded by short‐term ozone exposure alone but when exposure to ozone followed UV‐B exposure, growth was reduced in all genotypes. Leaf cupping appeare

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb05106.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Iron inefficiency in the maize (Zea maysL.) mutantyslis caused by a defect in the uptake system for Fe‐phytosiderophores. To characterize this defect further, the uptake kinetics of Fe‐phytosiderophores inyslwas compared to the Fe‐efficient maize cultivar Alice. Short‐term uptake of59Fe‐labeled Fe‐deoxymugineic acid (Fe‐DMA) was measured over a concentration range of 0.03 to 300 μM. Iron uptake in Fe‐deficient plants followed Michaelis‐Menten kinetics up to about 30 μM and was linear at higher concentrations, indicating two kinetically distinct components in the uptake of Fe‐phytosiderophores. The saturable component had similar Km(∼ 10 μM) in both genotypes. In contrast. Vmaxwas 5.5 μmol Fe‐DMA g−1dry weight [30 min]−1in Alice, but only 0.6 μmol Fe‐DMA g−1dry weight [30 min]−1inysl. Uptake experiments with double‐labeled59Fe‐[14C]DMA suggest that in both cultivars Fe‐DMA was taken up by the roots as the intact chelate. The results indicate the existence of a high‐affinity and a low‐affinity uptake system mediating Fe‐phytosiderophore transport across the root plasma membrane in maize. Apparently, the mutation responsible for Fe inefficiency inyslaffected high‐affected uptake and led to a decrease in activi

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb05107.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The expression of the plastid photosyntheticpsbK‐I‐D‐Cgene cluster is closely regulated by light. The time courses of expression of the gene cluster in rice seedlings (Oryza sativaL. cv. Tainong 67) grown under various irradiation regimes were examined by northern and western blot analyses. The data indicated that the gene cluster is photoregulated at the transcriptional and post transcriptional levels. Blue light not only enhanced the accumulation of the overlapping transcripts present in the 7 to 8‐day dark‐grown seedlings, but also induced the accumulation of new class d transcripts encoding D2 protein and CP43. This observation confirms the conservation of blue‐light regulation ofpsbD‐psbCtranscription in plants. In etiolated seedlings, the accumulation of class e transcript encoding CP43 increased most remarkably during development: irradiation further enhanced the transcript level. Although the transcripts encoding D2 protein and CP43 are present in etiolated plants, only D2 protein is accumulated, and CP43 was not detected unless the seedlings were exposed to light. The transcript levels of RNAs d1 and f2 in green seedlings grown under a 12‐h photoperiod exhibited fluctuating patterns over the 24‐h period. The levels o1 RNAs dl and f2 also exhibited significant fluctuation during the 36‐h exposure of the etiolated seedlings to light. These data imply that the circadian regulation ofpshD‐psbCexpression takes place at the transcriptional and post

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb05108.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Stems of cut rose flowers were exposed to air at 20°C and 60% relative humidity and then placed in water. The rate of water uptake in Frisco, Sonia, Madelon, and Cara Mia roses was maximally inhibited after 72, 36, 24, and 3 h of exposure to air. respectively. Anatomical observations showed no tyloses, gums, or deposition of hydrophobic material in the xylem conduits (tracheids and vessels) of any of the investigated cultivars. Frisco, Sonia, Madelon, and Cara Mia roses showed no difference in the number, the length, the wall thickness, or the diameter of the lumina of either the tracheids or the vessels. This indicates that differences in recovery are not related to capillary diameter or length.During exposure to air the decrease in transpiration rate, fresh weight, and water potential was the same in Sonia, Madelon, and Cara Mia roses. Upon exposure to air Frisco roses lost less water than the other cultivars studied In Frisco roses stomatal conductance was similar to that of other cultivars, but the rate of cuticular transpiration was lower.It is concluded that conservation of water through low cuticular transpiration is one of the reasons for the relatively slow development of the vascular occlusion in Frisco roses, but the differences between Sonia. Madelon and Cara Mia roses were not related to their rates of transpiration

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb05109.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The consistent correlation between desiccation tolerance in orthodox seed tissue and an accumulation of certain “late embryogenesis abundant” (LEA) proteins suggests that these proteins reduce desiccation‐induced cellular damage. The aim of the present work was to test this hypothesis. Exogenous abscisic acid (ABA) was used to elevate the level of heal‐soluble LEA‐like proteins in axes from immature (30 days after flowering: mid‐development) seeds of soybean (Glycine max[L.] Merrill cv. Chippewa 64). As the LEA‐like proteins accumulated in response to ABA, the leakage of all elements after desiccation and subsequent rehydration markedly declined. Both LEA‐like protein accumulation and the decline in desiccation‐induced electrolyte leakage were apparently dependent on the presence of ABA. Both effects of ABA were inhibited by cycloheximide. Light microscopy revealed a marked effect of the ABA on cellular integrity following desiccation. Osmotic stress also caused a decrease in desiccation‐induced electrolyte leakage and stimulated the accumulation of LEA‐like proteins. Our data are consistent with the hypothesis that the LEA‐like proteins contribute to the increase in desiccation tolerance in response to ABA, and are consistent with a general protective role for these proteins i

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb05110.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

In the temperate‐zone woody speciesSalix pentandraelongation growth is regulated by the photoperiod. Long days sustain active growth, whereas short days induce cessation of apical growth, which is a prerequisite for winter hardening. It is shown that this is correlated to quantitative changes in levels of endogenous GA19GA20, and GA1. Within two short days the amount of the active GA1and its immediate precursor GA20, decreased markedly in young leaves us well as in stem tissue. Also, the amount of GA19, declined, but the decrease was delayed relative to that of GA1and GA20. The ability ofS. pentandraseedlings to respond to exogenous GA19, decreased with increasing numbers of short days. Observations that support the hypothesis that the level of GA1inS. pentandrais regulated by the photoperiod in a quantitative mode with conversion of GA19, to GA20, being one target for control.Different distribution of GAs in various plant parts was observed. The level of GA was higher in young leaves than in other plant parts, and the amount of GA19was 5–10 times higher in stem tissue than in leaves and roots. The ratios of GA8to GA1and GA20, were higher in roots as compared with other parts, as rods contained very low levels of GA1and GA20, but amounts of GA20comparable with other pa

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb05111.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Cell suspension cultures derived from shoot apex or seed callus of the wild carnationDianthus zeyheriwere treated with [8−14]benzyladenine. The metabolism of applied cytokinin was evaluated with time (30 min. 6 h. 18 h. 48 h) in the presence of both low (2 mg l−1) and high (4 mg 1−1) levels of applied 2.4‐D. Both culture types metabolised BA to produce a qualitatively similar but quantitatively different array of metabolites. The 7‐glucoside of BA was the major metabolite produced by apex‐derived cultures, and the second largest product after the riboside in those cultures originating from seed. In both systems higher auxin application promoted 7‐glucosylation with a concurrent reduction in radioactivity associated with the‘active’ cytokinins. This suggests that cytokinin‐7‐glucosyl transferase is stimulated by the auxin 2.4‐D. and may, in part, explain the observed antagonistic interaction betwee

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb05112.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY