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1.
Abscisic acid (ABA) content and relative water content (RWC) in second fully expanded leaves of cold hardened plants and in dehydrated leaves of freezing tolerant barley (Hordeum vulgare L. cv. Lunet) were compared. ABA content and RWC in leaves did not change during the first day of cold hardening. On the contrary, dehydration of leaves led to a decrease of RWC and to an increase of ABA content. 相似文献
2.
Michael E. Compton C. M. Benton D. J. Gray D. D. Songstad 《In vitro cellular & developmental biology. Plant》1992,28(4):197-201
Summary Maize (Zea mays L.) embryogenic type-II calli were grown on medium containing 0,0.1 μM ABA or 60 g/liter sucrose or both before dehydration of solitary somatic embryos under three relative humidity regimes for
up to 6 wk. Viability of dehydrated embryos after 2 wk rehydration was assessed by their ability to produce chlorophyll (greening),
roots, coleoptiles, and/or leaves. Only embryos sequentially pretreated with ABA and high sucrose remained viable after 2
wk of dehydration at 70% RH. Up to 34% of the somatic embryos survived 2 wk dehydration at 70% RH, whereas embryos dehydrated
at 50 or 90% RH exhibited reduced viability (8.7 and 0.8%, respectively). Approximately 15% of the embryos dehydrated at 70%
RH developed into plants, whereas 0.9 and 0% of embryos dehydrated at 50 and 90% RH produced plants. Three percent of maize
somatic embryos remained viable after 6 wk of dehydration at 70% RH, and 1.7% developed into plants. Embryo size influenced
the ability of maize somatic embryos to survive dehydration. Only embryos greater than 5 mm survived 2 wk dehydration at 70%
RH. 相似文献
3.
Abscisic acid (ABA) regulates plant adaptive responses to various environmental stresses. Oxidative cleavage of cis-epoxycarotenoids catalyzed by 9-cis-epoxycarotenoid dioxygenase (NCED) is the main regulatory step in the biosynthesis of ABA in higher plants. A NCED gene, SgNCED1, was cloned from the dehydrated leaves of Stylosanthes guianensis. The 2,241-bp full-length SgNCED1 had a 1,809-bp ORF, which encodes a peptide of 602 amino acids. The deduced amino acid sequence of SgNCED1 protein shared
high identity with other NCEDs. At the N-terminus of the SgNCED1 located a chloroplast transit peptide sequence. DNA blot
analysis revealed that SgNCED1 was a single copy gene in the genome of S. guianensis. The relationship between expression of SgNCED1 and endogenous ABA level was investigated. The expression of SgNCED1 was induced in both leaves and roots of S. guianensis under drought stress. Dehydration and salt stress induced the expression of SgNCED1 strongly and rapidly. The ABA accumulation was coincidently induced with the SgNCED1 mRNA under drought, dehydration and salt stress. The expression of SgNCED1 and ABA accumulation were also induced under chilling condition. 相似文献
4.
L. Yang C. L. Yu F. Shi Y. Q. Wei C. C. Wang H. T. Hu C. G. Cheng 《Plant Growth Regulation》2007,51(2):177-184
Cynanchum komarovii is well adapted to hot and dry adverse environments. To determine if exogenous abscisic acid (ABA) affects the growth and
dehydration tolerance of this wild plant, ABA was added into the hydroponic solution at a final concentration of 10 μM for
14 days. Root growth is less inhibited than shoot growth under well-watered condition by ABA treatment. ABA reduced the drying
rate of seedlings, indicating the acquisition of increased dehydration tolerance. Increased dehydration tolerance is associated
with osmotic adjustment and with accumulation of soluble sugars and dehydrins. Results from immunological detection showed
that a band of dehydrins with molecular mass of 28.3 kDa appeared in ABA-treated fresh seedlings, which coincided with that
in nontreated seedling dessicated for 4 h in 75% relative humidity. The increased ratio of higher to lower amide I bands in
Fourier transform infrared spectroscopy analysis indicated that the proportion of unordered structures in proteins was higher
after ABA treatment. We concluded that exogenous ABA improved dehydration tolerance of C. komarovii seedlings. 相似文献
5.
Abscisic acid (ABA) is recognised as an important hormone involved in root-to-shoot communication of drought stress in plants.
This study aimed to determine whether isolated roots can produce both free and conjugated ABA (ABA–glucose ester) and whether
Lupinus species vary in the synthesis of ABA in the roots when dehydrated. The concentration of free and conjugated ABA at 100 and
50% root water content was measured in the distal 10 mm of the roots of 3- to 5-day-old seedlings of seven Lupinus species with and without 10−5 M tetcyclacis, an inhibitor of the oxidative breakdown of ABA. When the root tips were exposed to tetcyclacis, the concentration
of free ABA increased by 20% on average, suggesting that oxidative breakdown of free ABA was limited in the isolated Lupinus roots. The concentration of free ABA of the fully hydrated plants varied significantly among genotypes and more than doubled
on average across genotypes with dehydration of the root tips to 50% water content. The concentration of conjugated ABA also
varied significantly with species, but was only one-tenth the concentration of free ABA in the roots and did not change significantly
with root dehydration or the inhibition of oxidative metabolism. The production of free ABA in response to the water deficit
varied with species from +470% in L. digitatus to +33% in L. angustifolius. The small concentration and lack of increase of conjugated ABA with water deficit suggests that it is unlikely to have an
important role as a root signal in response to soil drying in Lupinus species. 相似文献
6.
Tomohiro Kiyosue Kazuko Yamaguchi-Shinozaki Kazuo Shinozaki 《Plant molecular biology》1994,25(5):791-798
InArabidopsis thaliana L., accumulation of abscisic acid (ABA) began to increase 2 h after plants had been subjected to dehydration stress and reached maximum levels after 10h. Differential hybridization was used to isolate 26Arabidopsis cDNAs with gene expression induced by a 1 h dehydration treatment. The cDNA clones were classified into 16 groups based on Southern blot hybridization, and named ERD (early-responsive todehydration) clones. Partial sequencing of the cDNA clones revealed that three ERDs were identical to those of HSP cognates (Athsp70-1, Athsp81-2, and ubiquitin extension protein). Dehydration stress strongly induced the expression of genes for the three ERDs, while application of ABA, which is known to act as a signal transmitter in dehydration-stressed plants, did not significantly affect the ERD gene expression. This result suggests that these HSP cognates are preferentially responsive to dehydration stress inA. thaliana, and that signaling pathways for the expression of these genes under conditions of dehydration stress are not mainly mediated by ABA. We also discuss the possible functions of these three ERD gene products against dehydration stress. 相似文献
7.
Induction of alpha-amylase inhibitor synthesis in barley embryos and young seedlings by abscisic Acid and dehydration stress
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An endogenous α-amylase inhibitor was found to be synthesized in embryos of developing barley grain (Hordeum vulgare cv Bonanza). Accumulation of this protein occurred late in development (stage IV), at the same time that endogenous abscisic acid (ABA) showed a large increase. The inhibitor could be induced up to 23-fold in isolated immature embryos (stage III) by culture in ABA. Precocious germination was also blocked in stage III embryos by ABA. Dehydration stress on the isolated immature embryos also induced higher levels of the inhibitor and ABA. An even greater response to dehydration stress was observed in young seedlings, where inhibitor content increased 20-fold and ABA increased 80-fold during water stress. The high degree of correlation between ABA and inhibitor contents in in situ embryos, dehydrated embryos and young seedlings, as well as the increase in inhibitor caused by exogenously applied ABA to isolated embryos, suggests that increased α-amylase inhibitor synthesis in response to dehydration stress is mediated by ABA. 相似文献
8.
Straight-chain saturated fatty acids (C6-C11) and abscisic acid (ABA) accumulate in the leaves of Phaseolus vulgaris L. and Hordeum vulgare L. under water stress. ABA and certain of the fatty acids, particularly decanoic and undecanoic acid, can inhibit stomatal opening and cause stomatal closure in epidermal strips of Commelina communis L. depending on the incubating medium used. 10-4 M (±)-ABA inhibits opening in media containing either high or relatively low concentrations of KCl but causes closure only in the latter medium. The fatty acids (at 10-4 M) prevent opening in both media while significant closure of open stomata was caused only by undecanoic acid in both media and, additionally, by decanoic acid in the low-KCl medium. 10-4 M formic acid also caused stomatal closure and prevented opening to significant extents in the low-KCl medium (it was not tested in the high-KCl medium). The efficacy of undecanoic acid in causing 50% inhibition of opening is about three orders of magnitude lower than that of ABA. At a concentration of 10-3 M, nonanoic, decanoic and particularly undecanoic acid and all-trans-farnesol cause increased cell leakage in Beta vulgaris L. root tissue. Undecanoic acid (10-4 M) also causes some loss of guard cell integrity in C. communis within 1.5 h of treatment. ABA (10-4 M) reduces transpiration rates in barley and C. communis leaves when applied via the transpiration stream but decanoic and undecanoic acids did not have this effect. Transpiration was not affected when ABA or the fatty acids were applied to the leaf surfaces.Abbreviations ABA
abscisic acid
- RWC
relative water content
- SCFA
short-chain fatty acids
Deceased May 1977 相似文献
9.
How OJ Nordøy ES 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2007,177(5):535-542
The purpose of this study was to answer the question of whether dehydrated harp seals (Phoca groenlandica) are able to obtain a net gain of water from the intake of seawater. Following 24 h of fasting, three subadult female harp
seals were dehydrated by intravenous administration of the osmotic diuretic, mannitol. After another 24 h of fasting, the
seals were given 1,000 ml seawater via a stomach tube. Urine and blood were collected for measurement of osmolality and osmolytes,
while total body water (TBW) was determined by injections of tritiated water. In all seals, the maximum urinary concentrations
of Na+ and Cl− were higher than in seawater, reaching 540 and 620 mM, respectively, compared to 444 and 535 mM in seawater. In another experiment,
the seals were given ad lib access to seawater for 48 h after mannitol-induced hyper-osmotic dehydration. In animals without
access to seawater, the mean blood osmolality increased from 331 to 363 mOsm kg−1 during dehydration. In contrast, the blood osmolality, hematocrit and TBW returned to normal when the seals were permitted
ad lib access to seawater after dehydration. In conclusion, this study shows that harp seals have the capacity to gain net
water from mariposa (voluntarily drinking seawater) and are able to restore water balance after profound dehydration by drinking
seawater. 相似文献
10.
Drying rate and dehydrin synthesis associated with abscisic acid-induced dehydration tolerance in Spathoglottis plicata orchidaceae protocorms 总被引:6,自引:0,他引:6
Dehydration tolerance of in vitro orchid protocorms was investigated under controlled drying conditions and after abscisic acid (ABA) pretreatment. Protocorms were obtained by germinating seeds on Murashige and Skoog (MS) medium containing 10% (v/v) coconut water, 2% (w/v) sucrose and 0.8% (w/v) agar, and were dehydrated in relative humidities (RH) ranging from 7% to 93% at 25 degrees C. The critical water content of dehydration tolerance was determined, using the electrolyte leakage method. Drying rate affected the critical water content. Slow drying under high RH conditions achieved the greatest tolerance to dehydration. ABA pretreatment decreased the drying rate of protocorms, and increased dehydration tolerance. Improved tolerance to dehydration after ABA treatment was correlated with the effect of ABA on drying rate of protocorms. When critical water content of protocorms dried under different RH was plotted as a function of actual drying rate, no significant difference in tolerance to dehydration was observed between ABA-treated and control protocorms. ABA pretreatment and dehydration of orchid protocorms induced the synthesis of dehydrin, especially under the slow drying conditions. ABA pretreatment also promoted dry matter accumulation such as carbohydrates and soluble proteins and increased the concentration of K(+) and Na(+) ions in protocorms. The ABA-induced decrease in drying rate was correlated with lower osmotic potential, the enhanced maturity of protocorms and the accumulation of dehydrin in protocorms during pretreatment. 相似文献
11.
Thompson AJ Jackson AC Parker RA Morpeth DR Burbidge A Taylor IB 《Plant molecular biology》2000,42(6):833-845
Two genes encoding enzymes in the abscisic acid (ABA) biosynthesis pathway, zeaxanthin epoxidase (ZEP) and 9-cis-epoxycarotenoid dioxygenase (NCED), have previously been cloned by transposon tagging in Nicotiana plumbaginifolia and maize respectively. We demonstrate that antisense down-regulation of the tomato gene LeZEP1 causes accumulation of zeaxanthin in leaves, suggesting that this gene also encodes ZEP. LeNCED1 is known to encode NCED from characterization of a null mutation (notabilis) in tomato. We have used LeZEP1 and LeNCED1 as probes to study gene expression in leaves and roots of whole plants given drought treatments, during light/dark cycles, and during dehydration of detached leaves. During drought stress, NCED mRNA increased in both leaves and roots, whereas ZEP mRNA increased in roots but not leaves. When detached leaves were dehydrated, NCED mRNA responded rapidly to small reductions in water content. Using a detached leaf system with ABA-deficient mutants and ABA feeding, we investigated the possibility that NCED mRNA is regulated by the end product of the pathway, ABA, but found no evidence that this is the case. We also describe strong diurnal expression patterns for both ZEP and NCED, with the two genes displaying distinctly different patterns. ZEP mRNA oscillated with a phase very similar to light-harvesting complex II (LHCII) mRNA, and oscillations continued in a 48 h dark period. NCED mRNA oscillated with a different phase and remained low during a 48 h dark period. Implications for regulation of water stress-induced ABA biosynthesis are discussed. 相似文献
12.
Control of hyperhydricity of mango somatic embryos 总被引:3,自引:0,他引:3
Mary-Joy Monsalud Helena Mathews Richard E. Litz Dennis J. Gray 《Plant Cell, Tissue and Organ Culture》1995,42(2):195-206
Hyperhydricity of immature somatic embryos has been a limiting factor for the development of highly embryogenic suspension cultures of many important mango cultivars. Reversion of hyperhydricity was achieved in two ways: 1) heart-stage somatic embryos (2–3 mm length) were partially dehydrated under controlled conditions at high relative humidity (RH) for 24–48 h and 2) the gelling agent (Gel-Gro) concentration of the plant growth medium was increased from 2.0 to 6.0 g l-1. Partially dehydrated immature somatic embryos were normal in appearance. Somatic embryos that were partially dehydrated germinated precociously when cultured on maturation medium. Although abscisic acid (ABA) did not reverse hyperhydricity of primary somatic embryos, ABA did stimulate the reversal of this abnormal pattern of development among secondary embryos. ABA (500 M) inhibited precocious germination and permitted somatic embryo maturation. Partially dehydrated, immature somatic embryos (4–7 mm long) remained viable for up to 32 days in the absence of maturation medium under high RH.Abbreviations 2,4-d
2,4-dichlorophenoxyacetic acid
- ABA
abscisic acid
- BA
6-benzyladenine
- RH
relative humidity 相似文献
13.
da Silveira LT Junta CM Monesi N de Oliveira-Pelegrin GR Passos GA Rocha MJ 《Cellular and molecular neurobiology》2007,27(5):575-584
Summary 1. This study presents a time course analysis of the messenger RNA (mRNA) levels of c-fos, vasopressin (VP), and oxytocin (OT) in the paraventricular (PVN) and supraoptic nucleus (SON), following acute and chronic dehydration by water deprivation.
2. Male Wistar rats were separated into five groups: nondehydrated (control group) and dehydrated for 6, 24, 48 and 72 h. Following water
deprivation, animals were decapitated, their blood was collected for hematocrit, osmolality, and plasma sodium measurements,
and brains were removed for dissection of both PVN and SON.
3. As expected, the hematocrit, osmolality, plasma sodium, and weight loss were increased after water deprivation. In SON,
a significant increase in both VP and OT mRNA expression was observed 6 h after dehydration reaching a peak at 24 h and returning to basal levels of expression at
72 h. In the PVN, an increase in both VP and OT mRNA expression occurred 24 h after dehydration. At 72 h the VP and OT mRNA expression levels had decreased but they were still at higher levels than those detected in control animals.
4. These results suggest that SON is the first nucleus to respond to the dehydration stimulus. Additionally, we also observed
an increase in c-fos mRNA expression in both PVN and SON 6 h after water deprivation, which progressively decreased 24, 48, and 72 h after the
onset of water deprivation. Therefore, it is possible that c-fos may be involved in the modulation of VP and OT genes, regulating the mRNA expression levels on a temporally distinct basis within the PVN and SON. 相似文献
14.
Polypodium vulgare L. is a desiccation-tolerant fern that can withstand successive dry periods in its life cycle. To better understand this mechanism, the current study was undertaken to assess the role of phenolic compounds in rhizome dehydration and determine their localisation in the rhizome cells after enforced dehydration in mannitol solution or controlled desiccation with or without abscisic acid (ABA) pretreatment. Phenolic distribution at the subcellular level was studied using gold particle-complexed laccase. Cells from different tissues: cortical parenchyma, endodermis and stelar elements--pericycle, sieve cells and vascular parenchyma were observed under a transmission electron microscope (TEM). The content of phenolic compounds was greater in ABA-untreated rhizomes after enforced dehydration in mannitol solution and subsequent rehydration. After controlled desiccation the phenolic content significantly increased in ABA-untreated rhizomes. A large number of phenolic compound deposits were present in all types of rhizomatous cells. Phenolics were widely distributed in the vacuoles of all cells, and in the secondary cell walls of sieve cells, although scattered labelling was hardly ever observed in the primary cell walls. In dehydrated and plasmolysed cells from the cortex and endodermis, phenolic compounds were present in the apoplastic compartments between the plasma membranes and the cell walls. There is evidence that abscisic acid plays a role as a crucial antioxidant resulting in no damage and a lower level of phenolic increase as compared to ABA-untreated rhizomes. Moreover, the location of phenolics suggests a protective chemical barrier against environmental stresses. 相似文献
15.
P. C. Morris E. W. Weiler S. E. Maddock M. G. L. Jones J. R. Lenton D. J. Bowles 《Planta》1988,173(1):110-116
Levels of endogenous abscisic acid (ABA) in immature wheat (Triticum aestivum cv. Timmo) and barley (Hordeum vulgare cv. Golden Promise) embryos have been determined by enzyme-linked immunosorbent assay. Embryos of both cereal species showed an increase in ABA content during development on the parent plant. Immature embryos were excised and cultured in vitro on nutrient media that led to precocious germination or on media containing 9% (w/v) mannitol that maintained their developmental arrest. Barley and wheat embryos responded to these culture conditions in an identical manner with respect to changes in morphology, fresh weight, protein and lectin content. However, in complete contrast, the ABA content of barley embryos increased by an order of magnitude during culture on mannitol, whereas that of wheat embryos showed no significant change. The results are discussed within the context of the role of ABA in the regulation of embryo development.Abbreviations ABA
abscisic acid
- BGA
barley-germ agglutinin
- dpa
days post anthesis
- ELISA
enzyme-linked immunosorbent assay
- GC-MS
gas chromatography-mass spectrometry
- WGA
wheat-germ agglutinin 相似文献
16.
Uptake of 3H-labelled (±)-abscisic acid (ABA) into isolated barley (Hordeum vulgare L.) epidermal cell protoplasts (ECP) was followed over a range of pH values and ABA concentrations. The present results show that ABA uptake is not always linearly correlated with the external concentration of undissociated ABA (ABAH). At pH 7.25, ABA uptake exhibited saturation kinetics with an apparent K
m value of 75 mmol·m–3 to tal ABA. This saturable transport component was inhibited by pretreating the protoplasts with 1 mol·m–3
p-chloromercuribenzenesulfonic acid at pH 8.0, conditions that minimized the uptake of this acid sulfhydryl reagent. Moreover, the rate of (±)-[3]HABA uptake was reduced by addition of 0.1 mol·m–3 (±)-ABA to 41%, whereas the same concentration of (±)-ABA was approximately half as effective (46% of the inhibitory effect). Thus, it was concluded that only (±)-ABA competes for an ABA carrier that is located in the epidermal cell plasma membrane. The permeability of the epidermal cell plasma membrane was studied by performing a Collander analysis. At pH 6 the overall plasma-membrane permeability of epidermal cells was similar to that of guard cells but was about two times higher than that of mesophyll cells.Abbreviations ABA
abscisic acid
- ABA–
anion of ABA
- ABAH
undissociated ABA
- 2,4-D
2,4-dichlorophenoxyacetic acid
- DMO
5,5-dimethyloxazolidine-2,4-dione
- ECP
deepidermal cell protoplast
- Kr
partition coefficient
- Mr
relative molecular mass
- NEM
N-ethylmaleimide
- PCMBS
p-chloromercuriben zenesulfonic acid
- Ps
permeability coefficient
We are grateful to Barbara Dierich for expert technical assistance, to Prof. H. Gimmler (Lehrstuhl für Botanik I, Universität Würzburg, FRG) for helpful discussions and to the Deutsche Forschungsgemeinschaft (SFB 251, TP 3) for financial support. 相似文献
17.
Radioactive (±)-abscisic acid (ABA), supplied via the transpiration stream to light-grown leaves of Hordeum vulgare was catabolized to 2′-hydroxymethyl ABA. Identification was made by capillary gas chromatography-mass spectrometry (GC-MS). 相似文献
18.
Expression of "Dehydrin-Like" Proteins in Embryos and Seedlings of Zizania palustris and Oryza sativa during Dehydration
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Proteins inducible by dehydration and abscisic acid (ABA), termed dehydrins or RAB (Responsive to ABA) proteins, have been identified in a number of species and have been suggested to play a role in desiccation tolerance, particularly during seed development. Seeds (caryopses) of North American wild rice (Zizania palustris var interior [Fassett] Dore) are tolerant of dehydration to <10% moisture content (fresh weight basis) only under restricted dehydration and rehydration conditions. In comparison, seeds of paddy rice (Oryza sativa L.) readily tolerate desiccation to <5% water content. Expression of “dehydrin-like” proteins in Zizania and Oryza seedlings and embryos was examined to investigate the relationship between the presence of such proteins and desiccation tolerance. [35S]Methionine labeling of newly synthesized proteins showed that seedlings (first leaf stage) of both Zizania and Oryza synthesized a novel “heat-stable” protein of apparent molecular weight = 20,000 when dehydrated to <75% of their initial fresh weight. ABA (100 micromolar) induced synthesis of a protein with similar electrophoretic mobility in both species. Western blots using antiserum raised against maize (Zea mays L.) dehydrin detected a protein band from dehydrated Zizania shoots and mature embryonic axes that comigrated with the labeled 20-kilodalton polypeptide. Northern blots using a cDNA for an ABA-responsive protein from Oryza (rab 16a) showed that both seedlings and excised embryonic axes of Zizania accumulated RNA similar in sequence to rab 16a in response to water loss. Zizania seedlings and embryonic axes were also capable of ABA accumulation during dehydration. The intolerance of Zizania seeds to dehydration at low temperature is apparently not due to an absence of dehydrin-like proteins or an inability to accumulate ABA. 相似文献
19.
A. Cousson 《Biologia Plantarum》2009,53(1):53-62
The present study investigated whether Ca2+ mobilization independent of phosphoinositide-specific phospholipase C (PI-PLC) would delay wilting in Arabidopsis thaliana (L.) Heynh. cv. Columbia through mediating stomatal closure at abscisic acid (ABA) concentrations rising beyond a drought-specific
threshold value. In wild type (WT) epidermis, the PI-PLC inhibitor (U73122) affected the stomatal response to 20 μM ABA but
not to 30 μM ABA. Disruption in GTP-binding protein ά subunit 1 (GPA1) affected the stomatal response to 30 μM ABA, but not
to 20 μM ABA. In the gpa1-4 mutant, the inhibitory effects of the Ca2+ buffer, 1,2-bis(0-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA), the inactive mastoparan analogue, mas17 and the antagonist of cyclic ADP-ribose synthesis, nicotinamide,
were differentially attenuated on 30 μM ABA-induced stomatal closure. By contrast, the NADPH oxidase atrbohD/F double mutation fully suppressed inhibition of 20 μM ABA-induced stomatal closure by BAPTA or U73122 as well as inhibition
of 30 μM ABA-induced stomatal closure by BAPTA, mas17 or nicotinamide. On the contrary, The Al resistant alr-104 mutation modulated ABA-induced stomatal closure by a stimulatory effect of U73122 and an increased sensitivity to mas17,
nicotinamide and BAPTA. Compared to WT, the atrbohD/F double mutant was more hypersensitive than the gpa1-4 mutant to wilting under the tested water stress conditions, whereas wilting was delayed in the alr-104 mutant. Since the atrbohD/F mutation breaks down ABA-induced Ca2+ signalling through fully preventing apoplastic Ca2+ to enter into the guard cells, these results showed that a putative guard cell GPA1-dependent ADP-ribosyl cyclase activity
should contribute to drought tolerance within PI-PLC-independent-Ca2+-mediated ABA signalling. 相似文献
20.
Effect of leaf water status and xylem pH on metabolism of xylem-transported abscisic acid 总被引:4,自引:0,他引:4
Metabolism and distribution of xylem-fed ABA were investigated in leaves of maize (Zea mays) and Commelina communis when water stress and xylem pH manipulation were applied. 3H-ABA was fed to excised leaves via the transpiration stream. Water stress was applied through either a previous soil-drying before leaves were excised, or a quick dehydration after leaves were fed with ABA. Xylem-delivered ABA was metabolised rapidly in the leaves (half-life 0.7 h and 1.02 h for maize and Commelina respectively), but a previous soil-drying or a post-feeding dehydration significantly extended the half-life of fed ABA in both species. In the first few hours after ABA was fed into the detached leaves, percentages of applied ABA remaining unmodified were always higher in leaves which received water stress treatments than in control leaves. However the percentage decreased to below the control levels several hours later in leaves which received a previous soil-drying treatment prior to excision, but had then been rehydrated by the xylem-feeding process itself. One possible explanation for this could be a changed pattern of compartmentalisation for xylem-carried ABA. A post-feeding dehydration treatment also changed the distribution of xylem-fed ABA within the leaves: more ABA was found in the epidermis of Commelina leaves which had been dehydrated rapidly after ABA had been fed, compared to the controls. The levels of xylem-delivered ABA remaining unmodified increased as the pH of the feeding solution increased from 5 to 8. The results support the hypothesis that water stress and a putative stress-induced xylem pH change may modify stomatal sensitivity to ABA by changing the actual ABA content of the leaf epidermis. 相似文献