共查询到20条相似文献,搜索用时 46 毫秒
1.
Water stress-induced ABA accumulation is a cellular signaling process from water stress perception to activation of genes
encoding key enzymes of ABA biosynthesis, of which the water stress-signal perception by cells or triggering mechanism of
the ABA accumulation is the center in the whole process of ABA related-stress signaling in plants. The cell biological mechanism
for triggering of ABA accumulation under water stress was studied in leaves ofVicia faba. Mannitol at 890 mmol ·kg-1 osmotic concentration induced an increase of more than 5 times in ABA concentration in detached leaf tissues, but the same
concentration of mannitol only induced an increase of less than 40 % in ABA concentration in protoplasts. Like in detached
leaf tissues, ABA concentration in isolated cells increased more than 10 times under the treatment of mannitol at 890 mmol
· kg-1 concentration, suggesting that the interaction between plasmalemma and cell wall was essential to triggering of the water
stress-induced ABA accumulation. Neither Ca2+-chelating agent EGTA nor Ca2+channel activator A23187 nor the two cytoskeleton inhibitors, colchicine and cytochalasin B, had any effect on water stress-induced
ABA accumulation. Interestingly water stress-induced ABA accumulation was effectively inhibited by a non-plasmalemma-permeable
sulfhydryl-modifier PCMBS (p-chloromercuriphenyl-sulfonic acid), suggesting that plasmalemma protein(s) may be involved in
the triggering of water stress-induced ABA accumulation, and the protein may contain sulfhydryl group at its function domain. 相似文献
2.
Abscisic Acid accumulation in spinach leaf slices in the presence of penetrating and nonpenetrating solutes 总被引:1,自引:1,他引:0
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Abscisic acid (ABA) accumulated in detached, wilted leaves of spinach (Spinacia oleracea L. cv Savoy Hybrid 612) and reached a maximum level within 3 to 4 hours. The increase in ABA over that found in detached turgid leaves was approximately 10-fold. The effects of water stress could be mimicked by the use of thin slices of spinach leaves incubated in the presence of 0.6 molar mannitol, a compound which causes plasmolysis (loss of turgor). About equal amounts of ABA were found both in the leaf slices and in detached leaves, whereas 2 to 4 times more ABA accumulated in the medium than in the slices. When spinach leaf slices were incubated with ethylene glycol, a compound which rapidly penetrates the cell membrane causing a decrease in the osmotic potential of the tissue and only transient loss of turgor, no ABA accumulated. Ethylene glycol was not inhibitory with respect to ABA accumulation. Spinach leaf slices incubated in both ethylene glycol and mannitol had ABA levels similar to those found when slices were incubated with mannitol alone. Increases similar to those found with mannitol also occurred when Aquacide III, a highly purified form of polyethylene glycol, was used. Aquacide III causes cytorrhysis, a situation similar to that found in wilted leaves. Thus, it appears that loss of turgor is essential for ABA accumulation.
When spinach leaf slices were incubated with solutes which are supposed to disturb membrane integrity (KHSO3, 2-propanol, or KCl) no increase in ABA was observed. These data indicate that, with respect to the accumulation of ABA, mannitol caused a physical stress (loss of turgor) rather than a chemical stress (membrane damage).
相似文献3.
4.
Abstract Using the method of compartmental analysis, the ion fluxes and compartment concentrations of Ca2+, K+ and Cl- have been compared in the untreated vegetative frond and the abscisic acid (ABA) induced turion of Spirodela polyrrhiza. The ABA-induced turion is characterized by reduced Ca2+ exchange across the tonoplast and low vacuolar Ca2+ concentration relative to the vegetative frond. In addition the turion exhibits a higher plasmalemma flux with a correspondingly high Ca2+ concentration in the cytoplasm. The concentration of K+ and Cl- is much lower in the cytoplasm of the ABA-induced turion than in the vegetative frond with the influx/efflux ratio at both the plasmalemma and the tonoplast being less than 1, a finding exhibited also in dormant storage tissue. Treatment of vegetative fronds with ABA for 18 h resulted in a reduced K+ plasmalemma efflux relative to untreated vegetative fronds and a concomitant increase in the cytoplasmic concentration. There was no rapid effect of ABA on Ca2+, K+ or Cl- fluxes through either membrane. These results are consistent with the notion that drastic changes in ion fluxes and concentrations in the turion are a secondary consequence of ABA-induced development, possibly due to prior regulation by ABA of enzymes inherent to processes involved in membrane transport. 相似文献
5.
Catalina Cabot John V. Sibole Joan Barceló Charlotte Poschenrieder 《Journal of Plant Growth Regulation》2009,28(2):187-192
Previous results showed that in short-term NaCl-treated beans increased leaf abscisic acid (ABA) concentration was triggered
by Na+ but not by Cl-. In this work, the specificity of ABA signaling for Na+ homeostasis was studied by comparing the plant’s responses to solutions that modified accumulation of ABA and/or Na+ uptake and distribution, such as supplemental Ca2+, increased nutrient strength, different isosmotic composition, application of exogenous ABA, fluridone (an ABA inhibitor)
and aminooxiacetic acid (AOA, an ethylene inhibitor). After fluridone pretreatment, salt-treated beans had lower Na+ uptake and higher leaf Na+ exclusion capacity than non-pretreated plants. Moreover, Na+ uptake was increased and leaf Na+ exclusion was decreased by AOA and ABA. NaCl and KCl similarly increased leaf ABA and decreased transpiration rates, whereas
supplemental Ca2+ and increased strength nutrient solution decreased leaf ABA and leaf Na+. These results show (1) a non-ion-specific increase in ABA that probably signaled the osmotic component of salt, and (2)
increased ABA levels that resulted in higher leaf Na+ concentrations due to lower Na+ exclusion or increased root-shoot Na+ translocation. 相似文献
6.
Abscisic acid introduced into the transpiration stream accumulates in the guard-cell apoplast and causes stomatal closure 总被引:8,自引:1,他引:7
Petioles of water‐sufficient intact Vicia faba L. plants were infused with 1 µm abscisic acid (ABA) to simulate the import of root‐source ABA. This protocol permitted quantitative ABA delivery, up to 300 pmol ABA over 60 min, to the leaf without ambiguities associated with perturbations in plant–water status. The ABA concentrations in whole‐leaf samples and in apoplastic sap increased with the amount infused; ABA degradation was not detected. The ABA concentration in apoplastic sap was consistent with uptake of imported ABA into the leaf symplast, but this interpretation is qualified. Our focus was quantitative cellular compartmentation of imported ABA in guard cells. Unlike when leaves are stressed, the guard‐cell symplast ABA content did not increase because of ABA infusion (P = 0·48; 3·0 ± 0·5 versus 4·0 ± 1·2 fg guard‐cell‐pair?1). However, the guard‐cell apoplast ABA content increased linearly (R2 = 0·98) from ?0·2 ± 0·5 to 3·1 ± 1·3 fg guard‐cell‐pair?1 (≈ 3·1 µm ) and was inversely related to leaf conductance (R2 = 0·82). Apparently, xylem ABA accumulates in the guard‐cell wall as a result of evaporation of the apoplast solution. This mechanism provides for integrating transpiration rate and ABA concentration in the xylem solution. 相似文献
7.
When 14C-labelled abscisic acid ([14C]ABA) was supplied to isolated protoplasts of the barley leaf at pH 6, initial rates of metabolism were about five times higher in epidermal cell protoplasts than in mesophyll cell protoplasts if equal cytosolic volumes were considered. In spite of the fact that epidermal cells make up only about 35% of the total water space in barley leaves, and despite the small cytosolic volume of these cells, in intact leaves all epidermal cells would thus metabolize half as much ABA per unit time as the mesophyll cells (0–27 and 0–51 mmol h?1 m?3 leaf water). Therefore, under these conditions epidermal cells seem to be a stronger sink than mesophyll cells for ABA that arrives via the transpiration stream. However, at an apoplastic pH of 7–25, which occurs in stressed leaves, the proportion of total metabolized ABA would be much smaller in epidermal than in mesophyll cells (0–029 and 0–204 mmolh?l m?3 leaf water). Our results indicate that under conditions of slightly alkaline apoplastic pH the epidermis may serve as the main source for fast stress-dependent ABA redistribution into the guard cell apoplast. This is partly the result of ABA transport across the epidermal tonoplast, which is dependent on the apoplastic pH and possibly on the cytosolic calcium concentration. The cuticle seems to be of no particular importance in stress-induced apoplastic ABA shifts and cannot be regarded as a significant sink for high ABA concentrations under stress. 相似文献
8.
Signalling process of water stress‐induced abscisic acid (ABA) accumulation was investigated in maize (Zea mays L.) leaf and root tissues. Potent free‐radical scavengers and reducing agents, N‐acetyl cysteine (NAC) and cystein (Cys), significantly inhibited or nearly completely blocked dehydration‐induced ABA accumulation. Dithiothreitol (DTT), a reducing agent but not a free‐radical scavenger, also significantly inhibited such accumulation whereas solely free‐radical scavengers, dimethyl sulphoxide (DMSO) and melatonin (Mela), had no effects. Moreover, water stress‐induced ABA accumulation was not affected either by free radicals, such as superoxide anion and hydrogen peroxide, or by oxidants such as KIO4. These observations suggest that the blocking of water stress‐induced ABA accumulation resulted from the reducing effect, rather than from anything associated with free radicals. The disulphide bond might be crucial to the reactivity of some signal element(s) in the signalling process of water stress‐induced ABA accumulation. To test the hypothesis, we used a sulfhydryl modifier, iodoacetamide (IOA), and found that it nearly totally blocked the water stress‐induced ABA accumulation. Furthermore, an impermeable sulfhydryl modifier, p‐chloromercuriphenylsulphonic acid (PCMBS), could also inhibit the water stress‐induced ABA accumulation in the leaf tissues. These results indicate that water stress‐perception protein(s) or receptor(s) may be located on the plasmalemma and a sulfhydryl group in the extracellular domain is critical to the reactivity of the speculated water stress receptors. Cys, DTT and IOA did not lead to a decrease of the baseline ABA level, i.e. in non‐stressed roots. Result indicates that their blocking of water stress‐induced ABA accumulation occurred upstream of the ABA biosynthesis pathway, i.e. in the signalling process that initiates such accumulation. 相似文献
9.
Tsuzuki T Takahashi K Inoue S Okigaki Y Tomiyama M Hossain MA Shimazaki K Murata Y Kinoshita T 《Journal of plant research》2011,124(4):527-538
Mg-chelatase H subunit (CHLH) is a multifunctional protein involved in chlorophyll synthesis, plastid-to-nucleus retrograde
signaling, and ABA perception. However, whether CHLH acts as an actual ABA receptor remains controversial. Here we present
evidence that CHLH affects ABA signaling in stomatal guard cells but is not itself an ABA receptor. We screened ethyl methanesulfonate-treated
Arabidopsis thaliana plants with a focus on stomatal aperture-dependent water loss in detached leaves and isolated a rapid transpiration in detached leaves 1 (rtl1) mutant that we identified as a novel missense mutant of CHLH. The rtl1 and CHLH RNAi plants showed phenotypes in which stomatal movements were insensitive to ABA, while the rtl1 phenotype showed normal sensitivity to ABA with respect to seed germination and root growth. ABA-binding analyses using 3H-labeled ABA revealed that recombinant CHLH did not bind ABA, but recombinant pyrabactin resistance 1, a reliable ABA receptor
used as a control, showed specific binding. Moreover, we found that the rtl1 mutant showed ABA-induced stomatal closure when a high concentration of extracellular Ca2+ was present and that a knockout mutant of Mg-chelatase I subunit (chli1) showed the same ABA-insensitive phenotype as rtl1. These results suggest that the Mg-chelatase complex as a whole affects the ABA-signaling pathway for stomatal movements. 相似文献
10.
Liuxin Xiang Yuxian Xia Yingfan Cai Jijun Liu Xiaohong He Quan Sun Xiaoyan Wang Yuyin Fu Yonghong Fan Daiwen Dong Guanfan Zhou Jinjuan Shen Yihua Liu 《Journal of Plant Biology》2013,56(3):168-175
The first tuber mustard calmodulin-like (CML) gene BjAAR1 (Brassica juncea var. tumida Tsen et Lee Abiotic stress and Abscisic acid (ABA) Responsive gene 1) was cloned and characterized. The protein encoded by BjAAR1 contains four predicted Ca2+ binding sites (EF-hand motif) and its recombinant protein can bind Ca2+ in vitro. qRT-PCR showed that the expression level of BjAAR1 was rather high in non-swollen stem of tuber mustard and largely reduced in swollen stem. Expression of BjAAR1 enhanced ABA- and stress-induced gene expression in Arabidopsis (Arabidopsis thaliana). Transgenic plants also exhibited hypersensitivity to NaCl, mannitol, and ABA during the seed germination and post-germination stages. ABA biosynthesis inhibitor, norflurazon (NF), rescued hypersensitivity phenotype of transgenic plants to NaCl and mannitol, indicating that BjAAR1 functions in multiple abiotic stresses response through ABA-dependent process. 相似文献
11.
Yanliang Guo Jingyi Zhu Jiahe Liu Yuxing Xue Jingjing Chang Yong Zhang Golam Jalal Ahammed Chunhua Wei Jianxiang Ma Pingfang Li Xian Zhang Hao Li 《Plant, cell & environment》2023,46(1):171-184
Precocious leaf senescence can reduce crop yield and quality by limiting the growth stage. Melatonin has been shown to delay leaf senescence; however, the underlying mechanism remains obscure. Here, we show that melatonin offsets abscisic acid (ABA) to protect photosystem II and delay the senescence of attached old leaves under the light. Melatonin induced H2O2 accumulation accompanied by an upregulation of melon respiratory burst oxidase homolog D (CmRBOHD) under ABA-induced stress. Both melatonin and H2O2 induced the accumulation of cytoplasmic-free Ca2+ ([Ca2+]cyt) in response to ABA, while blocking of Ca2+ influx channels attenuated melatonin- and H2O2-induced ABA tolerance. CmRBOHD overexpression induced [Ca2+]cyt accumulation and delayed leaf senescence, whereas deletion of Arabidopsis AtRBOHD, a homologous gene of CmRBOHD, compromised the melatonin-induced [Ca2+]cyt accumulation and delay of leaf senescence in Arabidopsis under ABA stress. Furthermore, melatonin, H2O2 and Ca2+ attenuated ABA-induced K+ efflux and subsequent cell death. CmRBOHD overexpression and AtRBOHD deletion alleviated and aggravated the ABA-induced K+ efflux, respectively. Taken together, our study unveils a new mechanism by which melatonin offsets ABA action to delay leaf senescence via RBOHD-dependent H2O2 production that triggers [Ca2+]cyt accumulation and subsequently inhibits K+ efflux and delays cell death/leaf senescence in response to ABA. 相似文献
12.
Abscisic Acid is not the only stomatal inhibitor in the transpiration stream of wheat plants 总被引:27,自引:3,他引:27
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xylem sap was collected from the transpiration stream of wheat (Triticum aestivum L.) plants and assayed for the presence of an inhibitor of transpiration using leaves detached from well-watered plants. Transpiration of detached leaves was reduced by nearly 60% by sap collected from plants in drying soil, and to a lesser extent (about 25%) by sap from plants in well-watered soil. As the soil dried the abscisic acid (ABA) concentration in the sap increased by about 50 times to 5 × 10−8 molar. However, the ABA in the sap did not cause its inhibitory activity. Synthetic ABA of one hundred times this concentration was needed to reduce transpiration rates of detached leaves to the same extent. Furthermore, inhibitory activity of the sap was retained after its passage through an immunoaffinity column to remove ABA. Xylem sap was also collected by applying pressure to the roots of plants whose leaf water status was kept high as the soil dried. Sap collected from these plants reduced transpiration to a lesser extent than sap from nonpressurised plants. This suggests that the inhibitory activity was triggered partly by leaf water deficit and partly by root water deficit. 相似文献
13.
Slama I Ghnaya T Messedi D Hessini K Labidi N Savoure A Abdelly C 《Journal of plant research》2007,120(2):291-299
Sesuvium portulacastrum is a halophytic species well adapted to salinity and drought. In order to evaluate the physiological impact of salt on water
deficit-induced stress response, we cultivated seedlings for 12 days, in the presence or absence of 100 mmol l−1 NaCl, on a nutrient solution containing either 0 mmol l−1 or 25 mmol l−1 mannitol. Mannitol-induced water stress reduced growth, increased the root/shoot ratio, and led to a significant decrease
in water potential and leaf relative water content, whereas leaf Na+ and K+ concentrations remained unchanged. The addition of 100 mmol l−1 NaCl to 25 mmol l−1 mannitol-containing medium mitigated the deleterious impact of water stress on growth of S. portulacastrum, improved the relative water content, induced a significant decrease in leaf water potential and, concomitantly, resulted
in enhancement of overall plant photosynthetic activity (i.e. CO2 net assimilation rate, stomatal conductance). Presence of NaCl in the culture medium, together with mannitol, significantly
increased the level of Na+ and proline in the leaves, but it had no effect on leaf soluble sugar content. These findings suggest that the ability of
NaCl to improve plant performance under mannitol-induced water stress may be due to its effect on osmotic adjustment through
Na+ and proline accumulation, which is coupled with an improvement in photosynthetic activity. A striking recovery in relative
water content and growth of the seedlings was also recorded in the presence of NaCl on release of the water stress induced
by mannitol. 相似文献
14.
The relationship between leaf growth and ABA accumulation in the grass leaf elongation zone 总被引:8,自引:1,他引:7
Detached barley (Hordeum vulgare L.) shoots, maintained at different air temperatures and VPDs, were fed ABA via the sub-crown internode in a leaf elongation assay. Analysis of variance of leaf elongation rate (LER) showed significant effects of temperature (T), fed [ABA] and the interaction T × [ABA]. However, the interaction became non-significant when LER was modelled against the [ABA] of the elongation zone, [EZ-ABA] When detached barley shoots were fed sap from droughted maize (Zea mays L.) plants, sap [ABA] could not explain the growth inhibitory activity. Measurement of [EZ-ABA] accounted for this ‘unexplained’ growth inhibition. The detached shoot experiments indicated that [EZ-ABA], and not xylem sap [ABA], was an appropriate explanatory variable to measure in droughted plants. However, ABA accumulation in the elongation zone could not explain a 35% growth reduction in intact droughted plants; thus we considered an interaction of water status and ABA. Using a coleoptile growth assay, we applied mild osmotic stresses (ψ=0 to ?0.06 MPa) and 10?4 mol m?3 ABA. Individually, these treatments did not inhibit growth. However, osmotic stress and ABA applied together significantly reduced growth. This interaction may be an important mechanism in explaining leaf growth inhibition of droughted plants. 相似文献
15.
The rate of Ca2+ accumulation in plasmalemma vesicles isolated from quiescent and sprouting potato (Solanum tuberosum L.) tubers and the effect of 10?5–10?10 M jasmonic acid on the accumulation of Ca+2 in plasmalemma vesicles and its efflux were studied. It was found that potato tuber plasmalemma contains a Ca+2,Mg+2-ATPase whose activity decreases upon the transition from forced quiescence to growth. The direction of the effect of jasmonic acid on Ca+2,Mg+2-ATPase (stimulation or suppression) depends on the physiological state of tubers and the phytohormone concentration. 相似文献
16.
Cytosolic Ca2+· ([Ca2+]i, and elongation growth were measured in the roots of Arabidopsis thaliana. Exposure of plant tissues to high NaCl and abscisic acid (ABA) concentrations results in a reduction in the rate of growth, but the mechanism by which growth is inhibited is not understood. Both NaCl and ABA treatments are known to influence [Ca2+]i, and in this study we measured the effects of salinity and ABA on [Ca2+]i in cells from the meristematic region of Arabidopsis roots. The Ca2+-sensitive dye Fura-2 and ratiometric techniques were used to measure [Ca2+]i in cells of the root meristem region. Resting [Ca2+]i was found to be between 100 and 200 μmol m?3 in roots of untreated plants. Resting [Ca2+]i changed in response to changes in the [Ca2+] surrounding growing roots. An increase of external [Ca2+] increased [Ca2+]i; conversely, a decrease of external [Ca2+] decreased [Ca2+]i. Exposure of roots to NaCl caused a rapid reduction of [Ca2+]i, a response that was proportional to the external NaCl concentration. Thus, as the NaCl concentration was increased, [Ca2+]i in root meristematic cells decreased. Root elongation was also inhibited in proportion to the external NaCl concentration, with maximal inhibition occurring at 120 mol m?3 NaCl. The [Ca2+]i of root meristem cells also changed in response to ABA, and the magnitude of the effect of ABA was dependent upon ABA concentration. Treatment with 0.2 mmol m?3 ABA caused a momentary increase in [Ca2+]i followed by a decrease after 15 min, but 10 mmol m?3 ABA caused an immediate decline in [Ca2+]i. There was a strong positive correlation between [Ca2+]i and root elongation rates. Experiments with the ABA-deficient Arabidopsis mutant aba-3 indicated that the reduction in [Ca2+]i brought about by NaCl was unlikely to be mediated via changes in endogenous ABA. Experiments with solutes such as sorbitol, KCl and NaNO3 indicated that the effects of NaCl could be mimicked by other solutes and was not specific for NaCl. 相似文献
17.
半夏缓慢生长法保存及体细胞变异的ISSR检测 总被引:1,自引:0,他引:1
以添加了不同浓度的甘露醇、PP333和ABA的培养基对半夏试管苗进行缓慢生长法保存,并对保存材料再生后代的体细胞变异进行检测。结果显示,甘露醇、PP333和ABA均能有效抑制试管苗生长,且存活率高;最佳浓度分别为甘露醇2%~4%,PP3332.0mg·L-1,ABA 2.0~4.0mg·L-1。保存在添加了2%~4%甘露醇或2.0mg·L-1 PP333培养基上的植株未检测到变异,而保存在添加了2.0~4.0mg·L-1 ABA培养基上的植株检测到1条新增标记和1条缺失标记,位点变异率为1.7%,个体变异率为30%。研究表明,ABA不宜用于半夏试管苗的缓慢生长法保存,但有助于新突变体的产生,在种质创新上具有特殊意义。 相似文献
18.
Regulation of proline accumulation in Arabidopsis thaliana (L.) Heynh during development and in response to desiccation 总被引:1,自引:0,他引:1
Significant differences were observed in the amount and proportion of free amino acids in different organs of Arabidopsis thaliana (L.) Heynh, ecotype Columbia. The most notable were found for proline, which formed 17–26% of the total free amino acid concentration in reproductive tissues (floret and seed), but only 1–3% of the total free amino acid concentration in vegetative tissues (rosette leaf and root). Proline accumulation was associated with tissues that had relatively low water contents. Tissues which displayed high water contents, such as rosette leaves, contained low levels of proline. A significant increase in the levels of proline accumulation occurred in plants subjected to experimentally induced low water potentials as compared to unstressed plants. For instance, an 8–10-fold increase in proline was observed in the presence of 120 mmol kg?1 NaCl or KCl, and a 20-fold increase was stimulated by 60 mmol kg?1 PEG. However, in addition to the accumulation of proline, massive accumulation of Na+, K+ and Cl? ions occurred in tissues of plants stressed with salt. No significant differences were observed in mineral ions in plants stressed with PEG. Isotope tracer experiments with 14C compounds established that glutamate, ornithine and arginine are precursors of the proline biosynthesis induced by PEG in response to low water potentials in Arabidopsis thaliana. We conclude that the accumulation of proline in response to PEG occurs through increased biosynthesis. 相似文献
19.
Violaxanthin is an abscisic Acid precursor in water-stressed dark-grown bean leaves 总被引:9,自引:4,他引:5
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The leaves of dark-grown bean (Phaseolus vulgaris L.) seedlings accumulate considerably lower quantities of xanthophylls and carotenes than do leaves of light-grown seedlings, but they synthesize at least comparable amounts of abscisic acid (ABA) and its metabolites when water stressed. We observed a 1:1 relationship on a molar basis between the reduction in levels of violaxanthin, 9′-cis-neoxanthin, and 9-cis-violaxanthin and the accumulation of ABA, phaseic acid, and dihydrophaseic acid, when leaves from dark-grown plants were stressed for 7 hours. Early in the stress period, reductions in xanthophylls were greater than the accumulation of ABA and its metabolites, suggesting the accumulation of an intermediate which was subsequently converted to ABA. Leaves which were detached, but not stressed, did not accumulate ABA nor were their xanthophyll levels reduced. Leaves from plants that had been sprayed with cycloheximide did not accumulate ABA when stressed, nor were their xanthophyll levels reduced significantly. Incubation of dark-grown stressed leaves in an 18O2-containing atmosphere resulted in the synthesis of ABA with levels of 18O in the carboxyl group that were virtually identical to those observed in light-grown leaves. The results of these experiments indicate that violaxanthin is an ABA precursor in stressed dark-grown leaves, and they are used to suggest several possible pathways from violaxanthin to ABA. 相似文献
20.
Hua Xing Lingling Tan Lizhe An Zhiguang Zhao Suomin Wang Chenglie Zhang 《Plant Growth Regulation》2004,42(1):61-68
Nitric oxide (NO) and reactive oxygen species (ROS) play important roles in both abscisic acid (ABA) signaling and stress-induced ABA accumulation. However, little is known about their physiological roles in the whole plant. In this study, the effects of NO and ROS on leaf water control and the roles of ABA were determined using wheat (Triticum aestivum L.) seedlings. As compared with the control, osmotic stress reduced leaf water loss (LWL) while it increased leaf ABA content. The effects of osmotic stress on LWL and ABA contents were partially reversed by NO scavengers or NO synthase (NOS) inhibitors. Furthermore, sodium nitroprusside (SNP) at concentrations between 0.01 and 10 mM all reduced LWL efficiently and induced ABA accumulation in a dose-dependent manner. When ABA synthesis was inhibited by fluridone or actidione, the effects of SNP on LWL were partially reversed. These results suggest that NO is involved in leaf water maintenance of wheat seedlings under osmotic stress, and one of the possible mechanisms is by stimulating ABA synthesis. The ROS scavengers used in our experiments had no effects on either LWL or ABA accumulation induced by osmotic stress. However, all ROS induced LWL reduction and ABA accumulation significantly. Hydrogen peroxide had the same effects as SNP on LWL and induced ABA accumulation in a dose-dependent manner but had a maximal effect at 1 mM. Fluridone reversed the effects of H2O2 on both LWL reduction and ABA accumulation, while actidione had no effect. These results suggest that ROS are also involved in leaf water maintenance of wheat seedlings by stimulating ABA biosynthesis, but with a different mechanism to that of NO. The ABA-independent mechanism in NO/ROS regulation of leaf water balance is discussed, in relation to our results. 相似文献