共查询到20条相似文献,搜索用时 15 毫秒
1.
Little is known about the role of mitogen-activated protein kinase 6 (MPK6) in Na+ toxicity and inhibition of root growth in Arabidopsis under NaCl stress. In this study, we found that root elongation in seedlings of the loss-of-function mutants mpk6-2 and mpk6-3 was less sensitive to NaCl or Na-glutamate, but not to KCl or mannitol, as compared with that of wild-type (WT) seedlings. The less sensitive characteristic was eliminated by adding the Ca2+ chelator EGTA or the Ca2+ channel inhibitor LaCl3, but not the Ca2+ ionophore A23187. This suggested that the tolerance of mpk6 to Na+ toxicity was Ca2+-dependent. We measured plasma membrane (PM) Na+-conducted currents (NCCs) in root cells. Increased concentrations of NaCl increased the inward NCCs while decreased the outward NCCs in WT root cells, attended by a positive shift in membrane potential. In mpk6 root cells, NaCl significantly increased outward but not inward NCCs, accompanied by a negative shift in membrane potential. That is, mpk6 decreased NaCl-induced the Na+ accumulation by modifying PM Na+ flux in root cells. Observations of aequorin luminescence revealed a NaCl-induced increase of cytosolic Ca2+ in mpk6 root cells, resulting from PM Ca2+ influx. An increase of cytosolic Ca2+ was required to alleviate the NaCl-increased Na+ content and Na+/K+ ratio in mpk6 roots. Together, these results show that mpk6 accumulated less Na+ in response to NaCl because of the increased cytosolic Ca2+ level in root cells; thus, its root elongation was less inhibited than that of WT by NaCl. 相似文献
2.
《Plant Physiology and Biochemistry》1999,37(7-8):569-576
Two tomato (Lycopersicon esculentum Mill.) lines differing in Ca2+ use efficiency (Ca2+ use efficient line 113 and Ca2+ use inefficient line 67) were subjected to salinity treatments in two separate experiments to determine whether they differed in salt tolerance. In experiment I, three NaCl and two CaCl2 treatments were imposed. The Na+ concentrations were 1.1, 100 and 150 mM and the Ca2+ concentrations were either 1.51 or 10 mM. In experiment II, one NaCl and three Ca2+ treatments (as CaCl2 or CaSO4) were imposed. The treatments consisted of 150 mM NaCl at either 1.51 mM CaCl2, 10 mM CaCl2, or 10 mM CaSO4. Response to treatments was determined by analysis of growth parameters (shoot and root dry weights, plant height, and root length). Shoot and root dry weight, and root length were depressed as salinity increased in plants lacking additional Ca2+. No significant differences in salt tolerance were detected between the two tomato lines after 24 d of salinity treatment. An important finding of this study was that root growth and length appeared to be more sensitive to the effect of CaCI2 treatment alone and to the effects of CaCl2 × NaCl treatments. This suggests that over the long term, both root growth and root length may be more sensitive indicators of salinity effects than shoots. Supplemental CaCl2 had no ameliorative effect on NaCl stress in shoot growth. The inability of Ca2+ to counter Cl− entry or toxicity may account for the lack of amelioration. Additional Ca2+ as CaSO4 improved shoot growth of plants exposed to 150 mM NaCl. In contrast, root growth and length were improved by 10 mM Ca2+ as either CaCl2 or CaSO4. 相似文献
3.
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
4.
Protective Effect of External Ca2+ on Elongation and the Intracellular Concentration of K+ in Intact Mung Bean Roots under High NaCl Stress 总被引:2,自引:0,他引:2
Nakamura Yoshiyuki; Tanaka Karo; Ohta Eiji; Sakata Makoto 《Plant & cell physiology》1990,31(6):815-821
The effects of Ca2+ in the external medium on intact mung beanroots under high NaCl stress were investigated. With increasingexternal concentrations of NaCl, mung bean roots showed suppressionof elongation and a decrease in the intracellular concentrationof K+. Addition of Ca2+ to the external medium alleviated theinhibition of root elongation under the high NaCl stress andmaintained a high intracellular concentration of K+ in the elongatingregion of the roots. This counter effect of Ca2+ against theNaCl stress on roots was correlated with the ratio of [Ca2+]/[Na+]2in the external medium. A value above 5.0 ? 104 mM1resulted in almost complete recovery of root elongation undervarious high concentrations of NaCl. Root elongation for 24h under NaCl stress was correlated with the extent to whichthe intracellular concentration of K+ was in excess of 10 mM.Maintenance of an adequate concentration of K+ in root cellsis essential for root elongation under salt stress. These findingsindicate that Ca2+ prevents the leakage of intracellular K+and thereby supports the elongation of roots under salt stress. (Received November 13, 1989; Accepted June 5, 1990) 相似文献
5.
Hideaki Matsumoto Yasushi Senoo Minobu Kasai Masayoshi Maeshima 《Journal of plant research》1996,109(1):99-105
Pea root elongation was strongly inhibited in the presence of a low concentration of Al (5 μM). In Al-treated root, the epidermis
was markedly injured and characterized by an irregular layer of cells of the root surface. Approximately 30% of total absorbed
Al accumulated in the root tip and Al therein was found to cause the inhibition of whole root elongation. Increasing concentrations
of Ca2+ effectively ameliorated the inhibition of root elongation by Al and 1 mM of CaCl2 completely repressed the inhibition of root elongation by 50 μM Al. The ameliorating effect of Ca2+ was due to the reduction of Al uptake.
H+-ATPase and H+-PPase activity as well as ATP and PPidependent H+ transport activity of vacuolar membrane vesicles prepared from barley roots increased to a similar extent by the treatment
with 50 μM AlCl3. The rate of increase of the amount of H+-ATPase and H+-PPase was proportional to that of protein content measured by immunoblot analysis with antibodies against the catalytic subunit
of the vacuolar H+-ATPase and H+-PPase of mung bean. The increase of both activities was discussed in relation to the physiological tolerance mechanism of
barley root against Al stress. 相似文献
6.
Masashi Tazawa 《Journal of plant research》1975,88(3):219-229
The cell sap of the internode ofNitella flexilis was replaced with the isotonic artificial pond water of high Ca2+-concentration (0.1 mM KCl, 0.1 mM NaCl, 10 mM CaCl2 and 275 mM mannitol) and changes in osmotic value and concentrations of K+, Na+ and Cl− of the cells were followed. When the operated cells were incubated in the artificial pond water containing 0.1 mM each of KCl, NaCl, CaCl2, they survived for only a short period of time (<10 hr). The cells did not absorb ions from the artificial pond water and showed a conspicuous decrease in the rate of cytoplasmic streaming. In such cell the concentration of K+ in the protoplasm decreased significantly. In order to reverse normal concentration gradients of K+ and Na+ across the protoplasmic layer, the cells of low vacuolar ionic concentrations were incubated in the artificial cell sap (90 mM KCl, 40 mM NaCl, 15 mM CaCl2, 10 mM MgCl2). It was found that the cells rapidly absorbed much K+, Na+ and Cl− and survived for a longer period (1–2 days). During this period the rate of cytoplasmic streaming was nearly normal. Furthermore, the cell lost much mannitol, indicating an enormous increase in permeability to it. Since both absorption of ions and leakage of mannitol at 1 C occurred at nearly the same rates as at 22 C, the processes are assumed to be passive. 相似文献
7.
Effects of salinity and turgor on calcium influx in Chara 总被引:2,自引:2,他引:0
Measurements were made of the influx of 45Ca into internodal cells of Chara corallina in solutions containing high concentrations of NaCl. Increasing salinity in the range 4–100mol m?3 NaCl resulted in a doubling of Ca2+ influx at the plasmalemma. A time-course of Ca2+ influx in 50 mol m?3 NaCl, 0.5mol m?3 CaCl2 showed that while influx at the plasmalemma increased only 1.5-fold, influx to the vacuole increased by up to 15-fold. This was interpreted as being due to inhibition of active Ca2+ efflux from the cell. The stimulation of Ca2+ influx by increasing salinity appeared to be principally a response to reduced turgor since similar stimulations were obtained when turgor was reduced by NaCl, Na2SO4 or mannitol. When cells were plasmolysed Ca2+ influx increased by 10–20-fold. The increased permeability was relatively specific for Ca2+ and was inhibitable by La3+. Survival of cells in high salt conditions was increased by 30 mmol m?3 La3+, which inhibited Ca2+ influx. Paradoxically, survival can also be extended by increasing external Ca2+ which leads to a higher influx. Therefore, it seems unlikely that the ameliorative effect of Ca2+ on the sensitivity of plants to high NaCl is mediated by Ca2+ entry across the plasmalemma. It seems more likely that the principal role of Ca2+ under these conditions is exerted externally through the control of membrane voltage and permeability. 相似文献
8.
A. M. Hamada 《Biologia Plantarum》1994,36(4):623-627
The lengths of roots and shoots, fresh and dry matter yield, and the contents of insoluble saccharides and free amino acids
were reduced with the rise in NaCl concentration. However, under combination of NaCl with Ca2+ ions, these parameters generally raised. Contents of soluble saccharides, proline and quaternary ammonium compounds increased
with increasing NaCl concentration, but under addition of CaCl2 or CaSO4, contents of these compounds were decreased. Low concentrations of NaCl stimulated soluble proteins, production, but higher
concentrations decreased the content of soluble proteins. Addition of Ca2+ in the media did not improve the soluble protein production. Insoluble proteins content was increased with the rise of salinity
level, but these effects were more pronounced with NaCl and CaCl2 or CaSO4 than with NaCl only. 相似文献
9.
We investigated the interaction of Ca2+ and auxin on root elongation in seedlings of Zea mays L. The seedlings were raised either in the presence of Ca2+ (high calcium; HC = imbibed and raised in 10 millimolar CaCl2), in the absence of additional Ca2+ (intermediate calcium; IC = imbibed and raised in distilled H2O, calcium supply from seed only), or without additional Ca2+ and subsequently depleting them of Ca2+ (low calcium; LC = imbibed and raised in distilled H2O and subsequently treated with 1 millimolar ethyleneglycol-bis-[β-aminoethylether]-N,N,N′,N′ -tetraacetic acid [EGTA]). Exposure of roots of either HC or IC seedlings to auxin concentrations from 0.1 to 10 micromolar resulted in strong inhibition of elongation. In roots of LC seedlings, on the other hand, auxin concentrations as high as 10 micromolar caused only slight inhibition of elongation. Adding 0.5 millimolar Ca2+ to LC roots in the presence of IAA allowed normal expression of the inhibitory action of the hormone. Inhibition of elongation in IC roots by indoleacetic acid was reversible upon treatment of the roots with 1 millimolar EGTA. The inhibitory action of auxin could then be re-established by supplying 0.5 millimolar Ca2+. The data indicate that Ca2+ may be necessary to the growth-regulating action of auxin. The significance of this finding is discussed with respect to the potential role of Ca2+ as a second messenger of auxin action and the relevance of this model to recent evidence for gravi-induced redistribution of Ca2+ and its role in establishing gravitropic curvature. 相似文献
10.
The optimum Ca2+ concentration for growth of cotton (Gossypium hirsutum cv. Acala SJ-2) was in the range 1 to 15 mol m–3 for plants growing in hydroponic culture with 100–150 mol m–3 NaCl. Most saline (but not sodic) soils contain higher Ca2+ concentrations. CaCl2 was inhibitory to the growth of cotton above 20–50 mol m–3. Increasing concentrations of Ca2+ in the range 0–2 mol m–2 drastically reduced Na+ accumulation in the leaves. As CaCl2 concentrations were increased above the optimum for growth there was a further reduction in leaf Na+ accumulation, but this was more than offset by increased leaf Ca2+ and Cl– concentrations. Leaf K+ concentrations were not much affected by changes in external CaCl2 concentrations. The response of Mg2+ varied from an increase to a decrease with increasing external CaCl2 and was influenced by nutritional status. There was no evidence that high Ca2+ caused a deficiency of Mg2+ in cotton. Except for Cl–, whose concentrations tended to decrease initially and then increase as the CaCl2 concentration increased, the anions were largely unaffected by changes in external CaCl2. 相似文献
11.
3′,5′-cyclic guanosine monophosphate (cGMP) is an important second messenger in plants. In the present study, roles of cGMP
in salt resistance in Arabidopsis roots were investigated. Arabidopsis roots were sensitive to 100 mM NaCl treatment, displaying a great increase in electrolyte leakage and Na+/K+ ratio and a decrease in gene expression of the plasma membrane (PM) H+-ATPase. However, application of exogenous 8Br-cGMP (an analog of cGMP), H2O2 or CaCl2 alleviated the NaCl-induced injury by maintaining a lower Na+/K+ ratio and increasing the PM H+-ATPase gene expression. In addition, the inhibition of root elongation and seed germination under salt stress was removed
by 8Br-cGMP. Further study indicated that 8Br-cGMP-induced higher NADPH levels for PM NADPH oxidase to generate H2O2 by regulating glucose-6-phosphate dehydrogenase (G6PDH) activity. The effect of 8Br-cGMP and H2O2 on ionic homeostasis was abolished when Ca2+ was eliminated by glycol-bis-(2-amino ethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA, a Ca2+ chelator) in Arabidopsis roots under salt stress. Taken together, cGMP could regulate H2O2 accumulation in salt stress, and Ca2+ was necessary in the cGMP-mediated signaling pathway. H2O2, as the downstream component of cGMP signaling pathway, stimulated PM H+-ATPase gene expression. Thus, ion homeostasis was modulated for salt tolerance. 相似文献
12.
Role of Internal Potassium in Maintaining Growth of Cultured Citrus Cells on Increasing NaCl and CaCl(2) Concentrations 总被引:1,自引:0,他引:1
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)
Shamouti orange (Citrus sinensis L. Osbeck) salt-tolerant cells were grown under low water potential conditions induced by polyethylene glycol (PEG), NaCl, and CaCl2. On the basis of equal osmotic potentials, PEG was the least inhibitory, NaCl next, and CaCl2 the most inhibitory. The relation between growth capacity and ion content can be summarized as follows. (a) Internal K+ concentration was a major factor which changed in the presence of PEG, NaCl, and CaCl2 and probably played a key role in determining growth capacity. (b) Internal concentrations of Na+, Ca2+, or Cl− could not be directly correlated with growth. (C) Internal Mg2+ concentration could be significant only in the presence of high external Ca2+ concentrations. (d) The contribution of nitrate and phosphate to the internal osmoticum was negligible. The ratio of external (Ca2+)/(Na+)2 concentration is crucial for growth. Ratios above 0.5 × 10−4 per millimolar gave maximal protection from adverse effects of NaCl. Growth capacity was found to be determined by the combination of (Ca2+)/(Na+)2 ratio and the absolute external concentration of NaCl. However, a correlation between internal K+ concentration and growth capacity seemed independent of external NaCl concentration. 相似文献
13.
Little knowledge is available about the influence of cation competition and metal speciation on trivalent chromium (Cr(III)) toxicity. In the present study, the effects of pH and selected cations on the toxicity of trivalent chromium (Cr(III)) to barley (Hordeum vulgare) root elongation were investigated to develop an appropriate biotic ligand model (BLM). Results showed that the toxicity of Cr(III) decreased with increasing activity of Ca2+ and Mg2+ but not with K+ and Na+. The effect of pH on Cr(III) toxicity to barley root elongation could be explained by H+ competition with Cr3+ bound to a biotic ligand (BL) as well as by the concomitant toxicity of CrOH2+ in solution culture. Stability constants were obtained for the binding of Cr3+, CrOH2+, Ca2+, Mg2+ and H+ with binding ligand: log KCrBL 7.34, log KCrOHBL 5.35, log KCaBL 2.64, log KMgBL 2.98, and log KHBL 4.74. On the basis of those estimated parameters, a BLM was successfully developed to predict Cr(III) toxicity to barley root elongation as a function of solution characteristics. 相似文献
14.
Incorporation of [C]Glucose into Cell Wall Polysaccharides of Cotton Roots: Effects of NaCl and CaCl(2)
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)
Cotton (Gossypium hirsutum L. cv Acala SJ-2) seedlings were grown in nutrient solutions with four combinations of NaCl (0.1 and 150 millimolar) and CaCl2 (1 and 10 millimolar) for 7 days, and then exposed to [14C]glucose for 5 hours. Uptake and incorporation of [14C]glucose into various cell wall fractions of the root tips were determined. At 1 millimolar Ca2+, treatment with 150 millimolar NaCl slightly stimulated uptake but considerably inhibited glucose incorporation into noncellulosic and cellulosic polysaccharides. Supplemental Ca2+ did not affect incorporation of glucose into the noncellulosic fraction (regardless of NaCl treatment) but completely alleviated the inhibitory effect of NaCl on glucose incorporation into cellulose. We suggest that high Na+ concentrations reduce synthesis of cellulose in cotton roots via disturbance of plasma membrane integrity and that supplemental Ca2+ counteracts this effect. The effects on cellulose biosynthesis are proposed to be related to Ca2+ displacement from the plasma membrane. 相似文献
15.
The binding of α-naphthaleneacetic acid (14C-NAA) to pelletable particulates from corn (Zea mays) coleoptiles was found to be influenced by inorganic solutes. La3+, Ca2+, and Mg2+ increased the binding whereas monovalent cations did not. The concentrations of CaCl2 which increased auxin binding were similar to those which inhibited coleoptile elongation in the presence of auxin. These results are interpreted as suggesting that the alteration of hormonal effectiveness by some inorganic solutes involves alterations in the attachment of the hormone to binding sites in the cell. 相似文献
16.
Interactions among Ca2+, Na+ and K+ in salinity toxicity: quantitative resolution of multiple toxic and ameliorative effects 总被引:5,自引:0,他引:5
Root elongation by wheat seedlings (Triticum aestivum
L. cv. Scout 66) was not inhibited by NaCl or KCl up to 130 mM in culture
solutions or by high Na+ (2 mg
g-1 FW) or K+ (4 mg
g-1 FW) in the root tissue, provided that
[Ca2+]>2 mM in the rooting medium. At [NaCl],
[KCl], or [mannitol] >250 mOs, root elongation was progressively
inhibited, irrespective of high [Ca2+]. In contrast,
shoot elongation was sensitive to any diminution of water potential, and
Ca2+ alleviated the toxicity only weakly. At solute
concentrations <250 mOs, the following interactions were observed.
Ca2+ alleviated Na+ and
K+ toxicity to roots by at least three separate
mechanisms. K+ was more toxic to roots than
Na+, but Na+ was more toxic
to shoots. Low levels of K+ relieved
Na+ toxicity, but low levels of
Na+ enhanced K+ toxicity.
Tissue concentrations of Na+ were reduced by
Ca2+ and K+ in the rooting
medium, and tissue concentrations of K+ were
enhanced by Ca2+ and Na+.
Several hypotheses relating to salinity toxicity can be evaluated, at least
for wheat seedlings. The osmoticant hypotheses (salinity intoxication
occurs because of diminished water potential) is true for shoots at all
salinity levels, but is true for roots only at high salinity. The
Ca2+-displacement hypothesis
(Na+ is toxic because it displaced
Ca2+ from the cell surface) is correct, but often of
minor importance. The K+-depletion hypothesis
(Na+ is toxic because it causes a loss of
K+ from plant tissues) is false. The
Cl--toxicity hypothesis (the apparent toxicity of
Na+ is induced by associated
Cl-) is false. The results indicate that, apart from
osmotic effects, high levels of Na+ in the rooting
medium and in the tissues are not toxic unless Ca2+
is also deficient, a condition probably leading to inadequate
compartmentation and excessive cytoplasmic accumulation. This study related
growth to ion activities at plasma-membrane surfaces. These activities were
computed by a Gouy-Chapman-Stern model then incorporated into non-linear
growth models for growth versus toxicants and ameliorants.Key
words: Calcium, potassium, salinity, sodium, toxicity
相似文献
17.
Cytoplasmic free calcium distributions during the development of root hairs of Arabidopsis thaliana 总被引:14,自引:8,他引:6
Carol L. Wymer Tatiana N. Bibikova Simon Gilroy 《The Plant journal : for cell and molecular biology》1997,12(2):427-439
In this study, confocal ratio analysis was used to image the relationship between cytoplasmic free calcium concentration ([Ca2+]c) and the development of root hairs of Arabidopsis thaliana. Although a localized change in [Ca2+]c that preceded or predicted the site of root hair initiation could not be detected, once initiated the majority of emerging root hairs showed an elevated [Ca2+]c (>1 μM) in their apical cytoplasm, compared with 100– 200 nM in the rest of the cell. These emerging root hairs then moved into a 3–5 h phase of sustained elongation during which they showed variable growth rates. Root hairs that were rapidly elongating exhibited a highly localized, elevated [Ca2+]c at the tip. Non-growing root hairs did not exhibit the [Ca2+]c gradient. The rhd-2 mutant, which is defective in sustained root hair growth, showed an altered [Ca2+]c distribution compared with wild-type. These results implicate [Ca2+]c in regulating the tip growth process. Treatment of elongating wild-type root hairs with the Ca2+ channel blocker verapamil (50 μM) caused dissipation of the elevated [Ca2+]c at the tip and cessation of growth, suggesting a requirement for Ca2+ channel activity at the root hair tip to maintain growth. Manganese treatment also preferentially quenched Indo-1 fluorescence in the apical cytoplasm of the root hair. As manganese is thought to enter cells through Ca2+-permeable channels, this result also suggests increased Ca2+ channel activity at the tip of the growing hair. Taken together, these data suggest that although Ca2+ does not trigger the initiation of root hairs, Ca2+ influx at the tip of the root hair leads to an elevated [Ca2+]c that may be required to sustain root hair elongation. 相似文献
18.
Tamotsu Imade Yasushi Sato Hajime Noguchi 《Bioscience, biotechnology, and biochemistry》2013,77(11):2131-2137
In order to clarify the interaction of calcium ion with casein, the volume change associated with the interaction was measured by dilatometric procedures. When CaCl2 was added to the casein solutions at neutral pH, a volume increase occurred and reached a constant saturated value of about 700 ml per 106 g protein with increasing CaCl2 concentrations for whole-, αs- and β-casein solutions, but there was no volume change for κ-casein solution. On the other hand, the binding of calcium ion to the casein fractions was determined by a gel filtration procedure at pH 6.0 to 9.0. The number of Ca2+ ions bound to the caseins increased with the CaCl2 concentration and pH value, and the relative order of binding capacities for the caseins was: αs-casein > whole-casein > β-casein > κ-casein.It was found that the volume changes obtained by the dilatometry were smaller than the calculated volume increases based on the assumption that these are caused by the binding of Ca2+ ion to the caseins. Therefore it is necessary to introduce another factor which reduces the volume increase due to the Ca2+ ion binding in order to reasonably explain the measured volume changes. At present it is presumed that there occurs the unfolding of peptide chain of casein molecule on Ca2+ ion binding, which has been known to decrease the volume of the protein solution. 相似文献
19.
Sodium-induced calcium deficiency in salt-stressed corn 总被引:9,自引:5,他引:4
Abstract The effect of the Na+/Ca2+ ratio in the root media on salt-stressed corn (Zea mays L. cvs DeKalb XL-75 and Pioneer 3906) was determined in greenhouse experiments. Plants grown in a complete nutrient solution salinized with 86.5 mol m?3 NaCl exhibited severe Ca2+ deficiency symptoms at the four-leaf stage. The symptoms disappeared when part of the NaCl was replaced with 10 mol m?3 CaCl2 (Na+/Ca2+ molar ratio = 5.7). Salt stress at an iso-osmotic potential of ?0.4 MPa substantially decreased shoot growth at all solution Na+/Ca2+ ratios from 34.6 to 0.26. However, the dry weights of blades at 26 d of age were much less when plants were salinized with NaCl alone, particularly that of DeKalb XL-75 which was more susceptible to Na-induced Ca2+ deficiency than was Pioneer 3906. The growth of sheaths was similarity reduced by sail stress at all Na+/Ca2+ ratios. The symptoms of Ca2+ deficiency were correlated with low Ca2+ concentrations in the leaf tissue. Ca2+ concentrations in the developing blades of NaCl-stressed plants were much lower than in control plants. As the Na+/Ca2+ ratio in the solution was decreased, Ca2+ levels increased in both the blades and sheaths while Na+ concentrations greatly decreased. DeKalb XL-75 was much less effective than Pioneer 3906 in restricting the uptake of Na+. The results clearly indicate that NaCl stress may cause lesions and unique plant responses that are not manifested on agronomic plants grown on saline soils. 相似文献
20.
Ca2+‐regulated and diurnal rhythm‐regulated Na+/Ca2+ exchanger AtNCL affects flowering time and auxin signalling in Arabidopsis
下载免费PDF全文
![点击此处可从《Plant, cell & environment》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Naomi Gonzales Yingqing Guo Honghong Hu Sunghun Park Jian Zhao 《Plant, cell & environment》2016,39(2):377-392
Calcium (Ca2+) is vital for plant growth, development, hormone response and adaptation to environmental stresses, yet the mechanisms regulating plant cytosolic Ca2+ homeostasis are not fully understood. Here, we characterize an Arabidopsis Ca2+‐regulated Na+/Ca2+ exchanger AtNCL that regulates Ca2+ and multiple physiological processes. AtNCL was localized to the tonoplast in yeast and plant cells. AtNCL appeared to mediate sodium (Na+) vacuolar sequestration and meanwhile Ca2+ release. The EF‐hand domains within AtNCL regulated Ca2+ binding and transport of Ca2+ and Na+. Plants with diminished AtNCL expression were more tolerant to high CaCl2 but more sensitive to both NaCl and auxin; heightened expression of AtNCL rendered plants more sensitive to CaCl2 but tolerant to NaCl. AtNCL expression appeared to be regulated by the diurnal rhythm and suppressed by auxin. DR5::GUS expression and root responses to auxin were altered in AtNCL mutants. The auxin‐induced suppression of AtNCL was attenuated in SLR/IAA14 and ARF6/8 mutants. The mutants with altered AtNCL expression also altered flowering time and FT and CO expression; FT may mediate AtNCL‐regulated flowering time change. Therefore, AtNCL is a vacuolar Ca2+‐regulated Na+/Ca2+ exchanger that regulates auxin responses and flowering time. 相似文献