摘要:

Water stress inhibits germination of chick‐pea seeds and produces specific changes in gene expression. some of which are coincident with those induced by the exogenous application of abscisic acid (ABA). Three cDNA clones, GAB‐8, GAB‐9 and GAB‐11, were previously identified as under the regulation of ABA and osmotic stress in embryonic axes of germinating chick‐pea. Here we try to establish a relationship between the changes in gene expression induced by ABA and stress conditions during germination and those naturally occurring during the desiccation process that leads to seed maturation. Our results show that the germinative capacity of chick‐pea is related to the water content of the organ. In vitro translation of the mRNAs from developing seed reveals that in the later stages of seed maturation some polypeptides appear that previously were found to be regulated by ABA and by water deficit in germinating seeds. Hybridization by northern blot of embryogenic mRNAs with GAB‐8. GAB‐9 and GAB‐11 clones shows that the mRNAs corresponding to such clones only appear in the later phases of seed formation, coinciding with seed dehydration, and persisting until seeds became fully mature. The results suggest that these mRNAs are probably related to the response to dehydration that occurs during seed maturation, and that the pattern of expression of these ABA‐regulated clones coincides with that of the established late embryogenesis

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb00776.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Segments cut from the next‐to‐last (peduncular‐1) internode ofAvena sativaL. cv. Victory (oat) shoots elongate as much as 10‐fold in response to gibberellic acid (GA3). The objective of the present investigation was to differentiate the effects of GA3on growth from its effects on wall synthesis (measured gravimetrically and through the incorporation of [14C]‐glucose) by using several cell wall synthesis inhibitors with widely varying mechanisms of action. Four compounds, viz. monensin, cycloheximide, lanthanum, and galactose. caused (1) relatively little inhibition of either cell wall synthesis or elongation in segments without GA3, (2) roughly proportionate, dose‐dependent inhibition of elongation and wall synthesis in GA3‐treated segments and (3) generally greater inhibition of GA3‐promoted uptake of radioactivity than of wall incorporation or elongation. Two other compounds, colchicine and 2,6‐dichlorobenzonitrile (DCB). (1) inhibited GA3‐induced elongation considerably more than cell wall synthesis and (2) caused swelling (radial expansion). especially of GA3‐treated segments. DCB‐treated internodal cells apparently compensated for inhibited cellulose synthesis by greater synthesis of matrix polysaccharide (beginning between 3 and 6 h). While normal cellulose synthesis was not required for short‐term (up to 6 h) GA3‐induced elongation or for long‐term hormone‐promoted radial expansion, it was required for sustained GA3‐induced elongation. These results indicate that GA3‐promoted cell wall loosening (manifested as radial expansion) and cell wall synthesis inAvenainternodes occur at least partially independently of any hormonal effect on the orientati

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb00777.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The expression of two β‐amylase loci was analysed in the developing seeds of two inbred lines of rye (Secale cereale L.), one of which was a β‐amylase deficient mutant. Enzymatic activity and the contents of enzymatic protein and mRNA specific for each of an endosperm‐characteristic and ubiquitous β‐amylase were determined throughout the course of caryopsis development. Both loci were expressed in the developing normal line caryopses according to different temporal and quantitative patterns. The ubiquitous enzyme‐specific locus β‐Amy 2 was expressed earlier; both mRNA and enzymatic protein accumulated to a maximum extent at 10 to 15 days after pollination. In contrast, the highest content of mRNA for endosperm β‐amylase (encoded by the β‐Amy I locus) was found 20 days after pollination, and the corresponding enzymatic protein accumulated throughout seed development. The expression of the β‐Amy I locus was 30‐ to 40‐fold higher than that of the β‐Amy 2 locus in terms of maximum specific mRNA accumulation. The expression product of only the β‐Amy 2 locus was found in the developing mutant line caryopses. The expression pattern of this locus was similar in the developing normal and mutant line seeds in terms of the temporal accumulation of mRNA and enzymatic protein. However, an approximately 4‐fold higher level of ubiquitous β‐amylase‐specific mRNA was found in the mutant than in the normal line caryopses, and the content of ubiquitous β‐amylase protein decreased to near zero at seed maturity in the mutant line, but not in the normal line, caryopses. The enzymatic activities of both β‐amylases appeared to be regulate

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb00778.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Samples ofPrasiola crispawere collected in Antarctica throughout a 13‐month period and analysed for free amino acids by HPLC. There was a marked increase in the levels of proline with the onset of winter, concurrent with a decrease in the other predominant amino acids. In January, proline constituted 1.2 ± 0.1 μ mol (g dry weight)−1. whereas by mid‐April it was the major component at 28.4 ± 2.9 μ mol (g dry weight)−1. When winter samples were thawed in a growth cabinet, their proline content declined to 4.3 ± 0.5 μ mol (g dry weight)−1after 7 days. Measurements of photosynthetic quantum yield indicated that winter samples ofP. crispaalso recovered photosynthetic activity upon thawing. Amino acids and other solutes are involved in the preservation of photosynthetic activities during freezing and it seems probable that proline is involved in cryoprotection in this species. In summer samples, there was no evidence that proline levels inP. crispaincreased with the conductivity of the water in which they wer

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb00779.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Although some studies have reported an interaction between boron (B) and calcium (Ca2+) in higher plants, there is little evidence for a similar relationship in cyanobacteria. The present study was designed to determine the effect of a supplement of boron to Ca2+‐deficient cultures ofAnabaenaPCC 7119 andSynechococcusPCC 7942. Grown under Ca2+deprivation,Anabaenahad a slow growth rate and a low photosynthetic pigment content that was related to an inhibition of photosynthesis. Ca2+‐deficient cells showed a lack of cohesiveness of the heterocyst envelope layers, which was consistent with a rapid decline in nitrogenase activity. A supplement of B led to partial recovery from the effects caused by lack of Ca2+. Similarly, low Ca2+had inhibitory effects on growth and metabolism ofSynechococcuscultures. In this case, the effect of a B supplement depended on the concentration of Ca2+in the growth medium. When Ca2+was present at normal concentration. B was not required, at least no more than trace amounts. However, when the Ca2+concentration decreased, B was required at increasing levels. An effect of boron on uptake and/or on the binding of Ca2+in cyanobacteria is propo

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb00780.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The effects of enhanced UV‐B (290‐320 nm) radiation on two native Mediterranean pines (Pinus pineaL.,Pinus halepensisMill.) were recorded during a one‐year field study. Plants received ambient or ambient plus supplemental UV‐B radiation (simulating a 15% stratospheric ozone depletion over Patras. Greece, 38.3°N. 29.1°E) and only natural precipitation, i.e. they were simultaneously exposed to other natural stresses. particularly water stress during summer. Supplemental UV‐B irradiation started in early February, 1993 and up to late June, no effects were observed on growth and photochemical efficiency of photosystem II, as measured by chlorophy II fluorescence induction. Water stress during the summer was manifested in the control plants as a decline in the ratio of variable to maximum fluorescence (Fv/Fm), the apparent photon yield for oxygen evolution (φl) and the photosynthetic capacity at 5% CO2(Pm). In addition, a partial needle loss was evident. Under supplemental UV‐B radiation, however, the decreases in Fv/Fm, φi, and Pm. as well as needle losses were significantly less. Soon after the first heavy autumn rains. photosynthetic parameters in both control and UV‐B treated plants recovered to similar values. but the transient summer superiority of UV‐B irradiated plants resulted in a significant increase in their dry weight measured at plant harvest. during late January. 1994. Plant height. UV‐B absorbing compounds, photosynthetic pigments and relative water content measured at late spring. late summer and at plant harvest, were not significantly affected by supplemental UV‐B radiation. The results indicate that enhanced UV‐B radiation may be beneficial for Mediterranean pines through a partial alleviation of the adverse

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb00781.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

We have previously shown that gibberellic acid (GA) plays an important role in the regulation of anthocyanin synthesis and flavonoid gene transcription in developing petunia corollas. The aim of the present work was to examine the possible role of methyl jasmonate (JA‐Me) in the regulation of these processes. JA‐Me induces anthocyanin biosynthesis and chalcone synthase (chs) and dihydroflavonol 4‐reductase (dfr) gene expression in detached corollas. JA‐Me promoted β‐glucuronidase (GUS) activity in corollas of transgenic plants carrying thegusgene driven by achspromoter, indicating that it acts at the level of transcription initiation. Whereaschsinduction by GA3started after 5 h and was durable. that of JA‐Me was more rapid but transient. Anthocyanin synthesis was induced by wounding and this effect was enhanced by JA‐Me. Wounding also induced an increase in jasmonate content in detached corollas. The kinetics ofchsanddfrmRNA accumulation following wounding was similar to that caused by JA‐Me but not to that caused by GA3. Our results suggest that JA‐Me does not play a role in the natural developmental regulation of corolla pigmentation but that it may mediate wound‐induced changes in flavonoi

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb00782.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

We investigated the effect of temperature during growth and development on the relationship between light‐harvesting capacity, indicated by chlorophyll concentration, and light‐utilization potential, indicated by light‐ and bicarbonate‐saturated photosynthetic oxygen evolution, inSolanum tuberosumL. cv. Norland. Conal plantles were transplanted and grown at 20°C for 2 weeks before transfer to 12, 16, 20, 24 and 28°C for 6 weeks. After 4 weeks of the temperature treatments, leaf tissue fresh weights per area were one‐third higher in plants grown at 12°C vs those grown at 28°C. Conversely, chlorophyll content per area in tissue grown at 12°C was less than one‐half of that of tissue grown at 28°C at 4 weeks. Photosynthetic capacity measured at a common temperature of 20°C and expressed on a chlorophyll basis was inversely proportional to growth temperature. Leaf tissue from plants grown at 12°C for 4 weeks had photosynthetic rates that were 3‐fold higher on a chlorophyll basis than comparable tissue from plants grown at 28°C. These results suggest that the relationship between light‐harvesting capacity and light‐utilization potential varies 3‐fold in response to the growth temperatures examined. The role of this response in avoidance of

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb00783.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Chlorophyllin (Chlin), the Mg‐chlorin obtained from chlorophyll (Chl) was employed as substrate of Mg‐dechelatase. The release of Mg2+was associated with a shift of absorption from 644 to 687 nm. Changes of absorption at 687 nm were taken as a measure of Mg‐dechelatase activity present in preparations of oilseed rape thylakoids. Absorption changes were correlated linearly with enzyme dose. The pH optimum of Mg release from Chlin was ca 9 with a broad flank down to pH 7. The reaction showed saturation kinetics with an apparent Kmvalue of ca 17 nM. The activity was inhibited in the presence of cysteamine or reduced glutathion. There was no effect of the thiol reagent N‐ethyl maleimide. The bulk of dechelatase activity was associated with the chloroplast membranes. The enzyme is partially latent and the appearance of full activity requires the solubilization of thylakoids with detergent. The highest activities were detected in mature green rape cotyledons. During dark‐induced senescence the activity declined at roughly the same rate as Chl was lost in the le

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb00784.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Light‐triggered membrane potential changes in cells of a liverwortAnthocerosare greatly enhanced by the ionophorous uncouplers nigericin and monesin. Stimulation of the light‐triggered electrical response (LTER) by nigericin occurred concomitantly with inhibition of a slow decline in the chlorophyll fluorescence, which suggests that the transmembrane pH gradient in thylakoids is not essential for generation of LTER at the plasma membrane. The extent of monensin‐stimulated LTER remained high under a diminished driving force for the ionophore‐induced proton‐cation exchange across the plasma membrane (elevation of the external Na+concentration from 1 to 50 mM), which indicates that energy uncoupling in chloroplasts is more related to the electric response enhancement than the induction of the H+/K+(Na+) exchange at the plasma membrane. Enhancement of LTER by ionophores occurs in parallel with stimulation of light‐triggered pH changes (alkalinization) in the vicinity of the cell surface, which suggests an association of trans‐membrane H+fluxes with LTER. The results are consistent with the hypothesis that illumination produces a temporary inhibition of the plasma membrane H+pump with a subsequent activation of gated channels and transient rapid depolarizatio

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb00785.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY