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1.
10-5 M methyl jasmonate (JA-Me) treatment itself did not considerably change the 14CO2 fixation, parameters of room temperature chlorophyll fluorescence induction, proline content, and Na+ as well as Cl- accumulation. Salt stress (30 mM NaCl) lead to a decrease of both 14CO2 fixation and relative water content, and to an increase of proline content. Immediate nonvariable fluorescence (F0) also increased and the variable to maximal fluorescence ratio (Fv/Fm) decreased. Pretreatment with JA-Me for 3 d before salt treatment diminished the inhibitory effect of NaCl on the rate of 14CO2 fixation, protein content, and activity and content of ribulose-1,5-bisophosphate carboxylase/oxygenase. The Na+ and Cl- contents in leaves decreased in JA-Me pretreated plants. The JA-Me pretreatment prevented the increase of F0 level and restored the values of Fv/Fm. 相似文献
2.
Barley seedlings were pre-treated with 1 and 5 μM H 2O 2 for 2 d and then supplied with water or 150 mM NaCl for 4 and 7 d. Exogenous H 2O 2 alone had no effect on the proline, malondialdehyde (MDA) and H 2O 2 contents, decreased catalase (CAT) activity and had no effect on peroxidase (POX) activity. Three new superoxide dismutase
(SOD) isoenzymes appeared in the leaves as a result of 1 μM H 2O 2 treatment. NaCl enhanced CAT and POX activity. SOD activity and isoenzyme patterns were changed due to H 2O 2 pre-treatment, NaCl stress and leaf ageing. In pre-treated seedlings the rate of 14CO 2 fixation was higher and MDA, H 2O 2 and proline contents were lower in comparison to the seedlings subjected directly to NaCl stress. Cl − content in the leaves 4 and 7 d after NaCl supply increased considerably, but less in pre-treated plants. It was suggested
that H 2O 2 metabolism is involved as a signal in the processes of barley salt tolerance. 相似文献
3.
Freshly-added iron only slightly affected the growth of iron-sufficient cells of the green alga Scenedesmus incrassatulus Bohl, strain R-83, but induced accumulation of malondialdehyde (MDA) in cells and excretion of MDA in the medium. These effects were stronger in response to Fe 2+ as compared to Fe 3+, but Fe 3+ induced the release of more iron-binding chelators from these cells than Fe 2+. Fe 3+ added either in dark or in light induced release of equal concentrations of iron-complexing agents, part of which formed strong chelates with iron in the medium. Exogenously added hydrogen peroxide inhibited iron-induced release of chelators but the effect was removed by addition of the hydroxyl radical scavenger dimethylsulfoxide (DMSO). Malondialdehyde also inhibited the release of chelators. Release of chelators was induced in the absence of iron salts by photoexcited chlorophyll (Chl). The Chl-induced release was efficiently inhibited by singlet oxygen scavengers such as dimethylfuran, -carotene, sodium azide and vitamin B 6, and stimulated in D 2O or DMSO. Exogenously added catalase inhibited the release more than added superoxide dismutase. The Fe 3-induced release of chelators was also inhibited by scavengers of singlet oxygen, but was not affected by sodium azide and by ethanol. Hence both H 2O 2 and singlet oxygen were involved in induction of chelator release in the absence of iron in light. The induction of chelator release by iron in dark involved H 2O 2, but not singlet oxygen. 相似文献
4.
采用温室盆栽试验研究不同NaCl浓度(0、50 和85 mmol/L)持续胁迫接种摩西球囊霉和地表球囊霉 2种AM真菌对加工番茄耐盐性的影响。结果显示:(1)在0 mmol/L NaCl处理条件下,2种菌的番茄菌根化苗的根系活力、叶片中可溶性糖、可溶性蛋白、根系脯氨酸含量以及超氧化物歧化酶和过氧化物酶活性均高于非菌根植株,且丙二醛含量低于非菌根植株,但差异不显著。(2)在50、85 mmol/L NaCl浓度胁迫下,接种2种菌根真菌可显著提高番茄植株根系活力,促进叶片中可溶性糖、可溶性蛋白及根系脯氨酸含量的积累,显著提高叶片中与抗逆相关的超氧化物歧化酶和过氧化物酶的活性,减少丙二醛在根系中的积累;随着NaCl浓度的增加,效果更为明显。(3)RT-PCR分析显示,AM真菌和盐胁迫共同调控H +转运无机焦磷酸酶H +- PPase的表达,随NaCl浓度的增加, AVP1基因表达量下降,但菌根化番茄植株的 AVP1基因表达量显著高于非菌根植株。研究表明,接种AM真菌后,菌根化植株可通过显著促进幼苗体内渗透调节物质积累和抗氧化酶活性的提高,有效降低体内膜脂过氧化水平,同时过量表达 AVP1基因增加了番茄植株中离子向液泡膜的转运,从而缓解盐胁迫对植株的伤害,增强番茄幼苗对盐胁迫的耐性。 相似文献
5.
Suaeda fruticosa and S. monoica are important halophytes for ecological rehabilitation of saline lands. We report differential physio-chemical, photosynthetic, and chlorophyll fluorescence responses in these halophytes under 100 mM sodium chloride (NaCl), 50% strength (16.25 ppt) of seawater (SW)-imposed salinity, and 10% polyethylene glycol 6000 imposed osmotic stress at 380 (ambient) and 1200 (elevated) µmol mol–1 CO2 concentrations. SW salinity enhanced the growth in both species; however, compared with S. fruticosa, the S. monoica exhibited comparatively better growth and biomass accumulation under saline conditions at elevated CO2. Results demonstrated better photosynthetic performances of S. monoica under stress conditions at both levels of CO2, and this resulted in higher accumulation of carbon, nitrogen, sugar, and starch contents. S. monoica exhibited improved antenna size, electron transfer at PSII donor side, and efficient working of photosynthetic machinery at elevated CO2, which might be due to efficient upstream utilization of reducing power to fix the CO2. The δ13C results supported the operation of C4 CO2 fixation in S. monoica and C3 or intermediate pathway of CO2 fixation in S. fruticosa. Lower accumulation of reactive oxygen species, reduced membrane damage, lowered solute potential, and higher accumulation of proline and polyphenol contents indicated elevated CO2-induced abiotic stress tolerance in Suaeda. Higher activity of antioxidant enzymes in both species at both levels of CO2 help plants to combat the oxidative stress. Upregulation of NADP-dependent malic enzyme and NADP-dependent malate dehydrogenase genes indicated their role in abiotic stress tolerance as well as photosynthetic carbon (C) sequestration. Operation of C4 type CO2 fixation in S. monoica and an intermediate CO2 fixation in S. fruticosa could be the possible reason for the superior photosynthetic efficiency of S. monoica under stress conditions at elevated CO2. 相似文献
6.
以盆栽牛叠肚组培苗为试材,比较研究了不同浓度中性盐(NaCl、Na2SO4)和碱性盐(NaHCO3、Na2CO3)胁迫对其生长和生理指标的影响。结果显示:(1)牛叠肚幼苗生长在碱性盐(NaHCO3、Na2CO3)处理下表现出"低促高抑"现象,而在中性盐(NaCl、Na2SO4)处理下均受到不同程度的抑制。(2)随着盐碱胁迫浓度的升高,牛叠肚叶片的相对电导率呈增加趋势,丙二醛(MDA)积累波动变化;Na2SO4和NaHCO3处理下二者之间的变化趋势相似,而NaCl和Na2CO3处理下二者之间变化趋势则不同。(3)牛叠肚叶片中超氧化物歧化酶(SOD)活性随胁迫浓度增加先升高后下降,而过氧化物酶(POD)活性呈先下降后升高趋势,说明牛叠肚主要通过SOD和POD的互补作用来降低氧化伤害。(4)以相对株高生长量下降50%为标准,求得牛叠肚幼苗对NaCl、Na2SO4、NaHCO3、Na2CO34种单盐的耐受阈值分别为85.18(0.50%,W/V)、40.77(0.58%,W/V)、171.00(1.44%,W/V)、114.20(1.21%,W/V)mmol·L-1。研究表明,各盐碱胁迫使牛叠肚幼苗的生长受到不同程度的抑制,但其在一定浓度范围内通过提高抗氧化酶(SOD、POD)活性来减轻盐碱伤害,维持植株的正常生理代谢;牛叠肚幼苗对碱性盐(NaHCO3、Na2CO3)的耐受能力强于中性盐(NaCl、Na2SO4)。 相似文献
7.
The effects of salt stress were studied on the accumulation and metabolism of proline and its correlation with Na + and K + content in shoots and callus tissue of four potato cultivars, viz., Agria, Kennebec (relatively salt tolerant), Diamant and Ajax (relatively salt sensitive). Na + and proline contents increased in all cultivars under salt stress. However, K + and protein contents decreased in response to NaCl treatments. The activities of enzymes involved in proline metabolism,
Δ 1-pyrroline-5-carboxylate synthetase (P5CS) and proline dehydrogenase (ProDH) increased and decreased, respectively, in response
to elevated NaCl concentrations. The changes of P5CS and ProDH activities in more salt sensitive cultivars (Diamant, Ajax)
were more than those in the tolerant ones. Then the stimulation of synthesis in combination with a partially increase of protein
proteolysis, a decrease in proline utilization and inhibition of oxidation resulted in high proline contents in seedlings
and calli under salt stress. In callus tissue, reduced growth and cell size may be partially responsible for high proline
accumulation in response to high NaCl levels. However, although the basic proline contents in the seedlings of more salt tolerant
cultivars were higher than the sensitive ones, a clear relationship was not generally observed between accumulation of proline
and salt tolerance in potato. 相似文献
8.
To cast light upon the role of Ca 1+ and calmodulin on photosynthetic rate (P n), dark respiration (R D) and amino acid and protein contents in salinity stressed and non-stressed Chlorella cultures, the Ca 2+ chelator EGTA [ethylene glycol-bis-(2-aminoethyl ether)- N,N- tetraacetate] and the calmodulin antagonist TFP (trifluperazine) were used. TFP markedly inhibited P N while EGTA exerted a slight, if any, effect on P N. NaCl tolerance, on the other side, was markedly abolished by TFP that inhibited P N and lowered rate of proline accumulation. Calmodulin might be involved in osmoregulation and salt tolerance of Chlorella. R D, however, was markedly enhanced by EGTA and Ca 2+-free medium and hence the Ca 2+ deprivation increased stress severity exerted by NaCl. Combinations of Na + and Ca 2+ enhanced P N, decreased R D and proline content in comparison with an osmotically equivalent reference culture containing only NaCl. Addition of Ca 2+ to TFP treated cultures failed to reactivate calmodulin for proline synthesis. However, when Ca 2+ was added to EGTA-treated cultures, only relatively reduced proline contents were recorded. 相似文献
9.
Mesophyll cells from leaves of cowpea ( Vigna unquiculata [L.] Walp.) plants grown under saline conditions were isolated and used for the determination of photosynthetic CO 2 fixation. Maximal CO 2 fixation rate was obtained when the osmotic potential of both cell isolation and CO 2 fixation assay media were close to leaf osmotic potential, yielding a zero turgor pressure. Hypotonic and hypertonic media decreased the rate of photosynthesis regardless of the salinity level during plant growth. No decrease in photosynthesis was obtained for NaCl concentrations up to 87 moles per cubic meter in the plant growing media and only a 30% decrease was found at 130 moles per cubic meter when the osmotic potential of cell isolation and CO 2 fixation media were optimal. The inhibition was reversible when stress was relieved. At 173 moles per cubic meter NaCl, photosynthesis was severely and irreversibly inhibited. This inhibition was attributed to toxic effects caused by high Cl − and Na + accumulation in the leaves. Uptake of sorbitol by intact cells was insignificant, and therefore not associated with cell volume changes. The light response curve of cells from low salinity grown plants was similar to the controls. Cells from plants grown at 173 moles per cubic meter NaCl were light saturated at a lower radiant flux density than were cells from lower salinity levels. 相似文献
10.
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. CO 2 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
11.
Effects of methyl jasmonate (JA-Me) on anthocyanin accumulation, ethylene production, and CO 2 evolution in uncooled and cooled tulips ( Tulipa gesneriana L. cvs. Apeldoorn and Gudoshnik) were studied. JA-Me stimulated anthocyanin accumulation in stems and leaves from uncooled
and cooled bulbs of both cultivars. The highest level of anthocyanin accumulation was observed in leaves from cooled bulbs
treated with 200 μL/liter JA-Me. In sprouting bulbs treated with 100 μL/liter and higher concentrations of JA-Me, the ethylene
production began to increase at 3 days after treatment, being extremely greater in uncooled bulbs than in cooled ones. JA-Me
also stimulated CO 2 evolution in both cultivars, depending on its concentrations. CO 2 evolution in sprouting bulbs was not affected by cooling treatment. These results suggest that anthocyanin accumulation by
JA-Me in tulip leaves is not related to ethylene production stimulated by JA-Me.
Received October 10, 1997; accepted November 17, 1997 相似文献
12.
Salinity stress is a major factor limiting plant growth and productivity
of many crops including oilseed. The present study investigated the identification
of salt tolerant mustard genotypes and better understanding the mechanism of salinity tolerance. Salt stresses significantly reduced relative water content (RWC),
chlorophyll (Chl) content, K + and K +
/Na + ratio, photosynthetic rate ( PN), transpiration rate ( Tr), stomatal conductance ( gs), intercellular CO 2 concentration
( Ci) and increased the levels of proline (Pro) and lipid peroxidation (MDA) contents, Na +
, superoxide (O 2•−
) and hydrogen peroxide (H 2O 2) in both tolerant and
sensitive mustard genotypes. The tolerant genotypes maintained higher Pro and
lower MDA content than the salt sensitive genotypes under stress condition.
The activities of superoxide dismutase (SOD), catalase (CAT), peroxidase
(POD), glutathione peroxidase (GPX), monodehydroascorbate reductase
(MDHAR) and dehydroascorbate reductase (DHAR) were increased with increasing salinity in salt tolerant genotypes, BJ-1603, BARI Sarisha-11 and BARI
Sarisha-16, but the activities were unchanged in salt sensitive genotype, BARI
Sarisha-14. Besides, the increment of ascorbate peroxidase (APX) activity was
higher in salt sensitive genotype as compared to tolerant ones. However, the activities of glutathione reductase (GR) and glutathione S-transferase (GST) were
increased sharply at stress conditions in tolerant genotypes as compared to sensitive genotype. Higher accumulation of Pro along with improved physiological
and biochemical parameters as well as reduced oxidative damage by up-regulation
of antioxidant defense system are the mechanisms of salt tolerance in selected
mustard genotypes, BJ-1603 and BARI Sarisha-16. 相似文献
13.
Salt-induced changes in growth, photosynthetic pigments, various gas exchange characteristics, relative membrane permeability
(RMP), relative water content (RWC) and ion accumulation were examined in a greenhouse experiment on eight sunflower ( Helianthus annuus L.) cultivars. Sunflower cultivars, namely Hysun-33, Hysun-38, M-3260, S-278, Alstar-Rm, Nstt-160, Mehran-II and Brocar were
subjected to non-stress (0 mM NaCl) or salt stress (150 mM NaCl) in sand culture. On the basis of percent reduction in shoot
biomass, cvs. Hysun-38 and Nstt-160 were found to be salt tolerant, cvs. Hysun-33, M-3260, S-278 and Mehran-II moderately
tolerant and Alstar-Rm and Brocar salt sensitive. Salt stress markedly reduced growth, different gas exchange characteristics
such as photosynthetic rate ( A), water-use efficiency (WUE) calculated as A/E, transpiration rate ( E), internal CO 2 concentration ( C
i) and stomatal conductance ( g
s) in all cultivars. The effect of 150 mM NaCl stress was non-significant on chlorophyll a and b contents, chlorophyll a/b ratio, RWC, RMP and leaf and root Cl −, K + and P contents; however, salt stress markedly enhanced C
i
/C
a ratio, free proline content and leaf and root Na + concentrations in all sunflower cultivars. Of all cultivars, cv. Hysun-38 was higher in gas exchange characteristics, RWC
and proline contents as compared with the other cultivars. Overall, none of the earlier-mentioned physiological attributes
except leaf K +/Na + ratio was found to be effective in discriminating the eight sunflower cultivars as the response of each cultivar to salt
stress appraised using various physiological attributes was cultivar-specific. 相似文献
14.
为明确燕麦幼苗对松嫩盐碱草地3种主要盐分Na Cl、Na HCO_3和Na_2CO_3的适应机制,设定不同浓度梯度(48—144 mmol/L)的胁迫处理液,测定燕麦幼苗的生长与生理指标变化。结果表明,尽管试验设定的Na Cl浓度并不影响幼苗的存活率,但在各组胁迫处理下,随着浓度的增加,燕麦幼苗的分蘖数、植株高度、茎叶与根系的生物量均呈下降趋势,下降幅度为Na_2CO_3Na HCO_3Na Cl。另外,与Na Cl胁迫相比,Na_2CO_3与Na HCO_3胁迫下茎叶与根中积累了更多的有毒Na~+,同时K~+下降幅度也更大,并且根系中含有更高的Na~+与更低的K~+以及更高的Na~+/K~+。在Na Cl胁迫下,燕麦幼苗积累大量的无机Cl~-和脯氨酸来维持细胞内的渗透与离子平衡,而Na HCO_3与Na_2CO_3胁迫造成了燕麦幼苗体内阴离子的亏缺,此时幼苗主要通过积累大量的有机酸和更多的脯氨酸来维持渗透与离子平衡。上述结果表明,碱性盐Na_2CO_3与Na HCO_3对植物的胁迫伤害程度大于中性盐Na Cl,并且Na_2CO_3的毒害效应最强,而燕麦幼苗对不同的盐分胁迫伤害也有会产生不同的生理适应策略。 相似文献
15.
To investigate the salt tolerance mechanisms, Aeluropus lagopoides as a halophytic plant was used. Plants were treated with 0, 150, 450, 600, and 750 mM NaCl and harvested at 0, 4, 8, and
10 days after treatment and 1 day and 1 week after recovery. Optimal growth, measured as fresh and dry weights, occurred at
150 mM NaCl, but it was suppressed by 450, 600, and 750 mM NaCl. Recovery significantly increased fresh and dry weights only
in 750 mM NaCl-treated plants. Water content was decreased after NaCl treatment and increased after recovery. Na + and proline contents and activity of superoxide dismutase (SOD) were increased after NaCl treatment and decreased after recovery
in all treated plants. In contrast, K + content and ascorbate peroxidase activity decreased after NaCl treatment and increased after recovery in all treated plants.
Catalase (CAT) was activated only in 750 mM NaCl-treated plants. Total content of soluble protein was slightly changed after
NaCl treatment. It was concluded that proline accumulation for osmotic adjustment, SOD activation for O 2·− scavenging, and CAT activation at the higher level of salt stress to detoxify produced H 2O 2 were main A. lagopoides strategies under salt stress. A. lagopoides salt tolerance was not based on the restriction of Na + uptake. 相似文献
16.
5-氨基乙酰丙酸(ALA)是植物血红素、叶绿素等四吡咯化合物的关键生物合成前体,对植物适应非生物胁迫至关重要。为验证外源ALA对黑果枸杞幼苗生理生长的影响,该研究用300 mmol·L -1 NaCl和不同浓度(0、5、10、15、20、25 mg·L -1)的ALA共同处理黑果枸杞幼苗,并测定其相关的生理指标和生长指标,综合评价各处理幼苗的耐盐性。结果表明:(1)NaCl胁迫使黑果枸杞幼苗总生物量和叶片总叶绿素、类胡萝卜素、可溶性糖含量以及过氧化物酶(POD)活性较CK分别显著降低了33.39%、19.06%、24.38%、39.57%和47.91%(P<0.05),使黑果枸杞幼苗脯氨酸和丙二醛的含量较CK分别显著增加了165.74%和49.16%。(2)当外源ALA和NaCl同时处理时,黑果枸杞幼苗叶片类胡萝卜素和丙二醛含量、POD和过氧化氢酶(CAT)活性以及株高、总生物量均恢复至对照水平,叶片总叶绿素和脯氨酸含量以及SOD活性较CK显著增加。(3)黑果枸杞幼苗叶片叶绿素和脯氨酸含量以及抗氧化酶活性、生物量等指标随ALA浓度增加均呈先... 相似文献
17.
Plants of chick-pea ( Cicer arietinum L. cv. ILC1919)
inoculated with Mesorhizobium ciceri strain ch-191
were grown in a controlled environmental chamber, and were administered
salt (0, 50, 75, and 100 mM NaCl) during the vegetative period. Four
harvests (4, 7, 11, and 14d after treatment) were analysed. The aim was to
ascertain whether the negative effect of saline stress on nitrogen fixation
is due to a limitation on the photosynthate supply to the nodule or a
limitation on the nodular metabolism which sustains nitrogenase
activity.Plant growth was affected only by the highest NaCl concentration,
whereas nitrogenase activity was affected from 50 mM. At the first harvest,
Rubisco, PEPC and MDH activities in leaves rose with salt, but fell during
the following harvests. The increase of PEPC and MDH in nodules at the two
first samplings was clearly related to salt concentration. While 50 mM NaCl
increased GS and GOGAT in nodules at some harvests, 100 mM strongly
inhibited these activities at all the harvests. The accumulation of
proline, amino acids and carbohydrates was clearly related to salt
especially in the leaves, whereas in the nodules the protein content was
boosted by salt. Although photosynthesis declined with NaCl, the response
of nitrogen fixation to salt was more pronounced. This situation, together
with carbohydrate accumulation, suggests that the lack of photosynthate
does not cause the inhibition of nitrogenase activity under this type of
stress. The similar trend observed for the PEPC-MDH pathway and the ARA
support the hypothesis concerning the limitation in the supply of energy
substrate, mainly malate, to the bacteroids. The accumulation of compatible
solutes is more a consequence of damage produced by salt stress than of a
protective strategy. 相似文献
18.
The effects of water stress and osmotic stress (sorbitol treatment) on the production of putrescine and proline in excised rice leaves were compared. Osmotic stress and water stress were found to affect differentially the levels of putrescine and proline in excised rice leaves. Putrescine accumulation is induced by osmotic stress, whereas proline accumulation is induced by water stress. The effects of ABA on the levels of proline and putrescine are similar to those of water stress, whereas the effects of jasmonic acid methyl ester (JA-Me) are similar to those of osmotic stress. Water stress results in an increase of endogenous ABA is excised rice leaves. However, neither osmotic stress nor JA-Me has effect on endogenous ABA levels in excised rice leaves. Of particular interest is the finding that proline levels increase when putrescine levels induced by osmotic stress or JA-Me are reduced by D-arginine and -methylornithine. L-arginine and L-ornithine applied exogenously also cause an increase in proline levels. It seems that L-arginine and L-ornithine are preferentially utilized as precursors for putrescine accumulation in excised rice leaves treated with osmotic stress and JA-Me, and for proline accumulation in excised rice leaves exposed to water stress and ABA.Abbreviations
ABA
abscisic acid
- BSA
bovine serum albumin
- ELISA
enzyme-linked immunosorbent assay
- HPLC
high performance chromatography
- JA-Me
jasmonic acid methyl ester
- PVP
poly-vinylpyrrolidone 相似文献
19.
The effect of NaCl on two vital processes of cyanobacterial metabolism, viz. N 2 fixation and oxygenic photosynthesis, was studied in the cyanobacterium Nostoc muscorum grown diazotrophically. An increase in NaCl concentration suppressed the formation of heterocyst and adversely affected the
nitrogenase activity in the parent, whereas in Li +-R and Na +-R mutants NaCl stress did not cause any adverse effect. The rate of photosynthetic O 2-evolution was also adversely affected by the NaCl stress, but the magnitude was less than that of nitrogenase activity. L-Proline, the well-known osmoprotectant, provided protection to the cyanobacterium against NaCl stress. The parent strain
utilized L-proline as a nitrogen source and suppressed heterocyst formation and nitrogenase activity, while mutants showed normal heterocyst
frequency and nitrogenase activity. Therefore, it may be that the proline metabolism is altered as a result of mutation. The
intracellular levels of proline in the parent were enhanced about threefold in the medium containing 1 mol m −3 proline, while in mutants there was no significant increase in the intracellular level of proline. In the medium containing
both NaCl and proline, the intracellular level of proline was enhanced in the parent as well as in both mutant strains. This
suggests that the parent strain possessed both normal proline uptake and salt-induced proline uptake systems, whereas the
mutant strains were defective in normal proline uptake and had only salt-induced proline uptake. The over-accumulation of
proline in the presence of NaCl stress is due either to the loss of proline oxidase activity or to the accumulation of exogenous
proline.
Received: 10 July 2002 / Accepted: 13 August 2002 相似文献
20.
Callus cultures of Arachis hypogaea L. cv. JL-24 adapted to 200 mM NaCl (otherwise lethal to cells) were used for the study. Calli grew slowly when transferred to 250 mM NaCl, but the growth was enhanced when ABA was included in the medium. ABA induced increase in growth of callus was not accompanied by corresponding increase in internal free proline levels. 0.5 mM of CaCl 2 ameliorated the negative effect of NaCl indicating that cells require a specific Ca 2+/Na + ratio for their growth. Proline content also increased at this ratio thereby suggesting that increase in growth at 0.5 mM Ca 2+ may be due to an increase in proline content. However, exogenous proline did not increase the growth of callus (adapted to 200 mM), and higher concentrations even inhibited the growth. This shows that proline is not required for growth or adaptation of cells to salt stress, but is produced as a consequence of stress. 相似文献
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