Physiological responses of Plantago algarbiensis and P. almogravensis shoots and plantlets to low pH and aluminum stress

We investigated the impact of low pH and aluminum (Al) stress on the growth, nutrients concentration, chlorophyll a fluorescence, photosynthetic pigment contents, proline and carbohydrate accumulation in shoots and plantlets (leaves and roots) of Plantago almogravensis and P. algarbiensis. Both species accumulated considerable and similar amounts of Al in their tissues, mainly in the roots. The presence of Al caused a significant reduction on root elongation in P. algarbiensis. Low pH and Al induced significant changes on nutrient accumulation, but no significant alterations on the maximum efficiency of PSII (F _v/F _m), quantum yield of PSII photochemistry (?_PSII), quantum yield of regulated energy dissipation (?_NPQ) and quantum yield of non-regulated energy dissipation (?_NO) were detected in both species in response to these stresses. However, Al increased significantly the non-photochemical quenching and the chlorophyll b content and decreased the PSII excitation pressure (1 ? q _p) in P. almogravensis leaves. Both stress treatments induced carbohydrate accumulation in the shoots and roots of this species, but not in leaves. In P. algarbiensis, low pH and Al decreased the photosynthetic pigment contents in the shoots, whereas Al stimulated the carbohydrate accumulation in the leaves. Although our data showed that both species are tolerant to Al³⁺ and H⁺, P. almogravensis appeared to be more adapted to maintain cellular physiology and growth under those conditions.     

Differences in Al tolerance between Plantago algarbiensis and P. almogravensis reflect their ability to respond to oxidative stress

We evaluated the impact of low pH and aluminum (Al) on the leaves and roots of Plantago almogravensis Franco and Plantago algarbiensis Samp., focusing on energy partitioning in photosystem II, H₂O₂ levels, lipid peroxidation, electrolyte leakage (EL), protein oxidation, total soluble protein content and antioxidant enzyme activities. In both species, Al triggered more changes in oxidative metabolism than low pH alone, particularly in the roots. We found that Al increased the levels of H₂O₂ in P. algarbiensis roots, but reduced the levels of H₂O₂ in P. almogravensis leaves and roots. Neither low pH nor Al affected the spatial heterogeneity of chlorophyll fluorescence, the maximum photochemical efficiency of PSII (F_v/F_m), the actual quantum efficiency of PSII (?_PSII) or the quantum yields of regulated (?_NPQ) and nonregulated (?_NO) energy dissipation, and there was no significant change in total soluble protein content and EL. In P. algarbiensis, Al increased the carbonyl content and the activities of superoxide dismutase (SOD) and catalase (CAT) in the roots, and also CAT, ascorbate peroxidase and guaiacol peroxidase activities in the leaves. In P. almogravensis, Al reduced the level of malondialdehyde in the roots as well as SOD activity in the leaves and roots. We found that P. almogravensis plantlets could manage the oxidative stress caused by low pH and Al, whereas the P. algarbiensis antioxidant system was unable to suppress Al toxicity completely, leading to the accumulation of H₂O₂ and consequential protein oxidation in the roots.     

Aluminum inhibits root growth and induces hydrogen peroxide accumulation in Plantago algarbiensis and P. almogravensis seedlings

We have evaluated the impact of aluminum (Al) on germination, relative root growth, Al accumulation in roots tips, H₂O₂ levels, plasma membrane integrity, pigment levels, protein content, and the activities of superoxide dismutase (SOD) and catalase (CAT) in seedlings of the endangered Portuguese species Plantago algarbiensis and Plantago almogravensis. We found that up to 400 μM Al had no impact on the germination percentage in either species but inhibited root growth in a concentration-dependent manner (more severely in P. algarbiensis). Al accumulation in the root tips of both species was concentration dependent up to 200 μM but declined thereafter despite the absence of membrane damage. We observed a concentration-dependent induction of SOD activity but no change in CAT activity resulting in the accumulation of H₂O₂ (a known growth inhibitor), although its impact in P. almogravensis may be partially ameliorated by the accumulation of carotenoid pigments. Our data suggest an association between Al uptake, H₂O₂ production, and the inhibition of root growth during early seedling development in P. algarbiensis and P. almogravensis, although the latter is more tolerant towards higher concentrations of the metal.     

Peanut nodulation kinetics in response to low pH.

In this work, the peanut nodulation kinetics by acid-sensitive and tolerant isolates under acid stress condition was analyzed. The results demonstrated that the acid pH produced a decrease in the number of nodules formed only when peanut plants were inoculated with acid-sensitive isolates but increased steadily by the addition of 10 mM Ca2+, reaching higher values than those obtained at pH 7.0. On the contrary, the peanut nodulation by acid-tolerant isolates was not affected by this stressing condition. These data suggest that acid-tolerant isolates could be used as a potential source of strains for preparing highly effective inoculants for peanut plants growing in acid soils.     

The response of high and low polyamine-producing cell lines to aluminum and calcium stress

The diamine putrescine (Put) has been shown to accumulate in tree leaves in response to high Al and low Ca in the soil, leading to the suggestion that this response may provide a physiological advantage to leaf cells under conditions of Al stress. The increase in Put is reversed by Ca supplementation in the soil. Using two cell lines of poplar (Populus nigra × maximowiczii), one with constitutively high Put (resulting from transgenic expression of a mouse ornithine decarboxylase – called HP cells) and the other with low Put (control cells), we investigated the effects of reduced Ca (0.2–0.8 mM vs. 4 mM) and treatment with 0.1 mM Al on several biochemical parameters of cells. We found that in the presence of reduced Ca concentration, the HP cells were at a disadvantage as compared to control cells in that they showed greater reduction in mitochondrial activity and a reduction in the yield of cell mass. Upon addition of Al to the medium, the HP cells, however, showed a reversal of low-Ca effects. We conclude that due to increased ROS production in the HP cells, their tolerance to low Ca is compromised. Contrary to the expectation of deleterious effects, the HP cells showed an apparent advantage in the presence of Al in the medium, which could have come from reduced uptake of Al, enhanced extrusion of Al following its accumulation, and perhaps a reduction in Put catabolism as a result of a reduction in its biosynthesis.     

Comparison of the Respiratory Metabolism of Plantago lanceolata L. and Plantago major L.

Bryce, J. H. and ap Rees, T. 1985. Comparison of the respiratorymetabolism of Plantago lanceolata L. and Plantago major L.—J.exp. Bot. 36 1559–1565. The aim of this work was to discover if the respiratory metabolismof the roots of Plantago lanceolata L. differed from that ofthe roots of Plantago major L. Measurements of oxygen uptakeand dry weight of excised root systems during growth of seedlingsprovided evidence that the two species differed in the amountof respiration needed to support a given increase in dry weight.Excised root systems were given a 6-h pulse in [U-¹⁴C]sucrosefollowed by a 16.5-h chase in sucrose. The detailed distributionof ¹⁴C amongst the major components of the roots at the endof the pulse and the chase revealed no significant differencebetween the two species. Patterns of ¹⁴CO₂ production from [1-¹⁴C],[2-¹⁴C], [3,4-¹⁴C], and [6-¹⁴C]glucose of excised root systemsfrom plants of three ages were similar for the two species.It is suggested that there is no conclusive evidence for anysignificant inherent difference in the respiratory metabolismof the roots of the two species. Key words: ¹⁴C sugar metabolism, respiration, roots, Plantago     

Growth and functional responses of different cultivars of Lotus corniculatus to aluminum and low pH stress

Aluminum toxicity is an important stress factor in acid soils. Growth, respiration and permeability properties of root cells were studied in five cultivars of Lotus corniculatus subjected to aluminum (Al) or low pH stress. The cultivars showed significant differences in root elongation under stress conditions, which correlated with changes in membrane potential (E_M) of root cortical cells. A pH drop from 5.5 to 4.0 resulted in significant membrane depolarization and root growth inhibition. The strongest inhibition was observed in cv. São Gabriel (33.6%) and least in cv. UFRGS (25.8%). Application of an extremely high Al concentration (2 mM) stopped the root growth in cv. INIA Draco, while inhibition in cv. UFRGS reached only 75%.The E_M values of cortical cells of Lotus roots varied between −115 and −144 mV. Treatment with 250 μM of AlCl₃ (pH 4) resulted in rapid membrane depolarization. The extent of the membrane depolarization ranged between 51 mV (cv. UFGRS) and 16 mV (cv. INIA Draco). The membrane depolarization was followed by a loss of K⁺ from Al-treated roots (2 mM Al) and resulted in a decrease of the diffusion potential (E_D). The total amount of K⁺ in Al-treated roots dropped from 31.4 to 16.8 μmol g⁻¹ FW in sensitive cv. INIA Draco, or from 26.1 to 22.7 μmol g⁻¹ FW in tolerant cv. UFGRS. The rate of root respiration under control conditions as well as under Al treatment was higher in cv. INIA Draco than in cv. UFRGS. Al-induced inhibition of root respiration was 21–34% of the control.     

珍稀濒危植物张氏红山茶花的花发育形态及生理特性研究

以珍稀濒危植物张氏红山茶为材料,对其花发育形态及分化过程中生理指标动态变化进行了研究.采用定株调查的方法,通过观察、统计、解剖等确定张氏红山茶盛花期花芽着生位置并划分5个发育阶段,以分光光度法测定了5个发育阶段可溶性糖、可溶性蛋白和核酸含量等的动态变化.结果表明:盛花期花芽着生位置主要在枝条顶端,占70.0％;花芽和叶...     

Resistance of Streptococcus bovis to acetic acid at low pH: relationship between intracellular pH and anion accumulation.

Streptococcus bovis JB1, an acid-tolerant ruminal bacterium, was able to grow at pHs from 6.7 to 4.5, and 100 mM acetate had little effect on growth rate or proton motive force across the cell membrane. When S. bovis was grown in glucose-limited chemostats at pH 5.2, the addition of sodium acetate (as much as 100 mM) had little effect on the production of bacterial protein. At higher concentrations of sodium acetate (100 to 360 mM), production of bacterial protein declined, but this decrease could largely be explained by a shift in fermentation products (acetate, formate, and ethanol production to lactate production) and a decline in ATP production (3 ATP per glucose versus 2 ATP per glucose). YATP (grams of cells per mole of ATP) was not decreased significantly even by high concentrations of acetate. Cultures supplemented with 100 mM sodium acetate took up [14C]acetate and [14C]benzoate in accordance with the Henderson-Hasselbalch equation and gave similar estimates of intracellular pH. As the extracellular pH declined, S. bovis allowed its intracellular pH to decrease and maintained a relatively constant pH gradient across the cell membrane (0.9 unit). The decrease in intracellular pH prevented S. bovis from accumulating large amounts of acetate anion. On the basis of these results it did not appear that acetate was acting as an uncoupler. The sensitivity of other bacteria to volatile fatty acids at low pH is explained most easily by a high transmembrane pH gradient and anion accumulation.     

Iridoid glucosides in Plantago alpina and P. Altissima

Two species of Plantago, namely P. Alpina and P. altissima were investigated. From the former, nine iridoid glucosides and verbascoside were isolated. Together with the known iridoids gardoside, geniposidic acid, 8-epi-loganic acid, mussaenosidic acid, aucubin, monomelittoside and melittoside, two new glucosides were found: 10-O-acetylgeniposidic acid and alpinoside, another compound with a 10-O-acetyl group. From P. altissima verbascoside and isoverbascoside were isolated together with the known iridoids gardoside, 8-epi-loganic acid, catalpol, aucubin, and hookerioside as well as the new compound desacetylhookerioside.     

Intranuclear accumulation of plant tubulin in response to low temperature

Summary. Concurrently with cold-induced disintegration of microtubular structures in the cytoplasm, gradual tubulin accumulation was observed in a progressively growing proportion of interphase nuclei in tobacco BY-2 cells. This intranuclear tubulin disappeared upon rewarming. Simultaneously, new microtubules rapidly emerged from the nuclear periphery and reconstituted new cortical arrays, as was shown by immunofluorescence. A rapid exclusion of tubulin from the nucleus during rewarming was also observed in vivo in cells expressing GFP-tubulin. Nuclei were purified from cells that expressed GFP fused to an endoplasmic-reticulum retention signal (BY-2-mGFP5-ER), and green-fluorescent protein was used as a diagnostic marker to confirm that the nuclear fraction was not contaminated by nuclear-envelope proteins. These purified, GFP-free nuclei contained tubulin when isolated from cold-treated cells, whereas control nuclei were void of tubulin. Furthermore, highly conserved putative nuclear-export sequences were identified in tubulin sequences. These results led us to interpret the accumulation of tubulin in interphasic nuclei, as well as its rapid nuclear export, in the context of ancient intranuclear tubulin function during the cell cycle progression. Correspondence and reprints: Department of Plant Physiology, Faculty of Science, Charles University, Viničná 5, 128 44 Prague 2, Czech Republic.     

Oxygen consumption and ammonia excretion in the detritivore caddisfly Limnephillus sp. exposed to low pH & aluminum

Respiration and excretion were measured relative to pH and aluminum in three nymphal weight groups of a detritivore caddisfly. Although a reduction in respiration rates was consistently observed within all stages exposed to a pH of 4 and 0.3 mg 1⁻¹ of aluminum, the differencewas not statistically significant among treatments. Excretion rates, on the other hand, were significantly increased throughout the low pH treatment, but not when exposed to low pH and aluminum combined. The derived O:N ratios indicate low pH causes a shift to a protein-oriented metabolism which was most pronounced in the smallest size group. Aluminum mitigates this effect.     

Cross-species amplification of primers developed from Plantago major and P. intermedia in two Hawaiian Plantago species from the section Plantago

Thirty-nine primers, developed from the sister species Plantago major and P. intermedia, were tested in two Hawaiian Plantago species from the section Plantago. Eight primers were polymorphic, of which three were published earlier, and five are new ones presented here. Amplification and polymorphism levels appeared to be high in these Hawaiian species. These markers will be valuable for further mating system and evolutionary studies in species from the section Plantago that are closely related to P. major and P. intermedia.     

Differential accumulation of S-adenosylmethionine synthetase transcripts in response to salt stress

NaCl stress causes the accumulation of several mRNAs in tomato seedlings. An upregulated cDNA clone, SAM1, was found to encode a S-adenosyl-L-methionine synthetase enzyme (AdoMet synthetase). Expression of the cDNA SAM1 in a yeast mutant lacking functional SAM genes resulted in high AdoMet synthetase activity and AdoMet accumulation. We show that tomato plants contain at least four SAM isogenes. Clones corresponding to isogenes SAM2 and SAM3 have also been isolated and sequenced. they encode predicted polypeptides 95% and 92% identical, respectively, to the SAM1-encoded AdoMet Synthetase. RNA hybridization analysis showed a differential response of SAM genes to salt and other stress treatments. SAM1 and SAM3 mRNAs accumulated in the root in response to NaCl, mannitol or ABA treatments. SAM1 mRNA accumulated also in leaf tissue. These increases of mRNA level were apparent as soon as 8 h after the initiation of the salt treatment and were maintained for at least 3 days. A possible role for AdoMet synthetases in the adaptation to salt stress is discussed.     

Biosynthesis and accumulation of D-ononitol in Vigna umbellata in response to drought stress

Metabolic responses to water deficit that lead to an accumulation of cyclitols, have been examined in rice bean ( Vigna umbellata [Thunb.] Ohwi et Ohashi). Imposition of drought stress by withholding water from the soil for 9 days led to an accumulation of D-ononitol (lD-4- O -methyl- myo -inositol) which was most pronounced in leaves (from 33 to 88 umol g⁻¹ dry mass). However, the activity of the enzyme myo-inositol 6-O -methyltransferase (m6OMT, EC 2.1.1.X), which catalyzes the synthesis of ononitol from myo -inositol and S -adenosyl-L-methionine (AdoMet), increased in stems but not in leaves during the drought stress experiment. Detailed analysis of different plant parts revealed that the accumulation of ononitol in leaves was linearly related to stem m6OMT activity during drought stress, indicating that m6OMT may control the in vivo biosynthetic rate of this cyclitol. The availability of myo -inositol, required for enhanced rates of ononitol synthesis by m6OMT, increased during the stress experiment, while the capacity to synthezise AdoMet by S -adenosyl-L-methionine synthetase (SMS, EC 2.5.1.6) decreased. However, the high capacity for degradation of S -adenosyl-L-homocysteine (AdoHcy; a potent competitive inhibitor of m6OMT) by the enzyme S -adenosyl-L-homocysteine hydrolase (SHH, EC 3.3.1.1) provided favourable conditions for ononitol biosynthesis during the whole stress treatment.     

Resistance of Streptococcus bovis to acetic acid at low pH: relationship between intracellular pH and anion accumulation

Streptococcus bovis JB1, an acid-tolerant ruminal bacterium, was able to grow at pHs from 6.7 to 4.5, and 100 mM acetate had little effect on growth rate or proton motive force across the cell membrane. When S. bovis was grown in glucose-limited chemostats at pH 5.2, the addition of sodium acetate (as much as 100 mM) had little effect on the production of bacterial protein. At higher concentrations of sodium acetate (100 to 360 mM), production of bacterial protein declined, but this decrease could largely be explained by a shift in fermentation products (acetate, formate, and ethanol production to lactate production) and a decline in ATP production (3 ATP per glucose versus 2 ATP per glucose). YATP (grams of cells per mole of ATP) was not decreased significantly even by high concentrations of acetate. Cultures supplemented with 100 mM sodium acetate took up [14C]acetate and [14C]benzoate in accordance with the Henderson-Hasselbalch equation and gave similar estimates of intracellular pH. As the extracellular pH declined, S. bovis allowed its intracellular pH to decrease and maintained a relatively constant pH gradient across the cell membrane (0.9 unit). The decrease in intracellular pH prevented S. bovis from accumulating large amounts of acetate anion. On the basis of these results it did not appear that acetate was acting as an uncoupler. The sensitivity of other bacteria to volatile fatty acids at low pH is explained most easily by a high transmembrane pH gradient and anion accumulation.     

铁胁迫下大豆光合和磷/铁性状对磷素的响应

为了明确低铁胁迫下磷素用量对大豆光合和磷/铁性状的影响及基因型差异,为磷、铁肥的合理施用提供理论依据,以前期筛选的6个磷高效基因型和6个磷低效基因型大豆为供试材料,设4个P∶Fe配比处理,分别为0∶30、30∶30、150 ∶30和300∶30(μmol·L-1),对大豆叶绿素荧光特性和磷、铁利用率进行了测定,利用单株...     

Differential regulation of sorbitol and sucrose loading into the phloem of Plantago major in response to salt stress

Several plant families generate polyols, the reduced form of monosaccharides, as one of their primary photosynthetic products. Together with sucrose (Suc) or raffinose, these polyols are used for long-distance allocation of photosynthetically fixed carbon in the phloem. Many species from these families accumulate these polyols under salt or drought stress, and the underlying regulation of polyol biosynthetic or oxidizing enzymes has been studied in detail. Here, we present results on the differential regulation of genes that encode transport proteins involved in phloem loading with sorbitol and Suc under salt stress. In the Suc- and sorbitol-translocating species Plantago major, the mRNA levels of the vascular sorbitol transporters PmPLT1 and PmPLT2 are rapidly up-regulated in response to salt treatment. In contrast, mRNA levels for the phloem Suc transporter PmSUC2 stay constant during the initial phase of salt treatment and are down-regulated after 24 h of salt stress. This adaptation in phloem loading is paralleled by a down-regulation of mRNA levels for a predicted sorbitol dehydrogenase (PmSDH1) in the entire leaf and of mRNA levels for a predicted Suc phosphate synthase (PmSPS1) in the vasculature. Analyses of Suc and sorbitol concentrations in leaves, in enriched vascular tissue, and in phloem exudates of detached leaves revealed an accumulation of sorbitol and, to a lesser extent, of Suc within the leaves of salt-stressed plants, a reduced rate of phloem sap exudation after NaCl treatment, and an increased sorbitol-to-Suc ratio within the phloem sap. Thus, the up-regulation of PmPLT1 and PmPLT2 expression upon salt stress results in a preferred loading of sorbitol into the phloem of P. major.     

The immune response of white shrimp Litopenaeus vannamei and its susceptibility to Vibrio alginolyticus under low and high pH stress

White shrimp Litopenaeus vannamei (also known as Penaeus vannamei) held in 34 per thousand seawater at pH 8.2 were injected with tryptic soy broth (TSB)-grown Vibrio alginolyticus at 8 x 10(5) colony-forming units (cfu) shrimp(-1), and then transferred to tanks at pH 6.5, 8.2 (control) and 10.1, respectively. After 24-168 h, the mortality of V. alginolyticus-injected shrimp that were transferred to pH 6.5 and pH 10.1 tanks was significantly higher than that of V. alginolyticus-injected shrimp held at pH 8.2. In another experiment, L. vannamei held at pH 8.2 following transfer to pH 6.5, 8.2 (control) and 10.1 for 6, 12, 24, 72 and 120 h were examined for immune parameters, phagocytic activity, and the clearance efficiency of shrimp against V. alginolyticus. The results indicated that the shrimp that were transferred to pH 6.5 and 10.1 showed significantly decreased phenoloxidase (PO) activity, respiratory burst, phagocytic activity, and clearance efficiency against V. alginolyticus over 6-72 h; significantly decreased superoxide dismutase (SOD) activity over 6-24h; and decreased total haemocyte count (THC) over 12-72 h. Shrimp transferred to pH 10.1 showed significantly decreased granular cell counts, and THC after 6h, and decreased SOD activity after 72 h. The immune parameters of shrimp transferred to pH 6.5 and 10.1 returned to the original values after 120 h. However, shrimp transferred to pH 6.5 still maintained lower phagocytic activity, and clearance efficiency against V. alginolyticus, and shrimp transferred to pH 10.1 still maintained lower clearance efficiency against V. alginolyticus. It was therefore concluded that low pH and high pH stress decrease the resistance of white shrimp L. vannamei against V. alginolyticus and decrease several parameters of the immune response.     

吲哚乙酸对铝胁迫下栝楼生理响应及DNA损伤的缓解作用

为探究IAA(吲哚乙酸)对铝胁迫下栝楼生理响应及DNA损伤的缓解,本研究以河北安国栝楼(耐铝品种)和浙江浦阳栝楼(铝敏感品种)为材料进行水培试验,研究300、800 μmol·L^-1(分别用Al₃₀₀和Al₈₀₀表示)铝环境下不同浓度IAA(0、10、25、50、75 μmol·L^-1,分别以I₀、I₁₀、I₂₅、I₅₀和I₇₅表示)对2个栝楼品种的抗氧化酶活性、丙二醛(MDA)、光合特性、根系活力、叶绿素含量和DNA损伤的影响。结果表明: 与对照相比,铝胁迫条件下,安国和浦阳品种栝楼的超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性、光合作用能力、根系活力等生理指标受到不同程度的抑制,MDA含量明显升高,DNA损伤加重。铝胁迫条件下,与无IAA喷施相比,10～50 μmol·L^-1IAA作用下安国和浦阳栝楼的SOD、CAT和POD酶活性最大增幅分别为15.0%、31.2%、72.3%和13.8%、26.9%、26.4%,叶绿素含量显著增加49.9%和17.9%,MDA积累量减少39.2%和22.4%,荧光参数得到明显改善。25 μmol·L^-1IAA使安国和浦阳栝楼根系活力显著增加159.1%和90.9%,50 μmol·L^-1IAA可有效减缓2个品种栝楼根系DNA拖尾现象,尾部 DNA 百分含量与尾部距离的乘积(OTM)值最大降幅可达27.6%。10～50 μmol·L^-1 IAA能有效提升铝胁迫下栝楼的生理活性,减缓DNA损伤程度,且安国品种的耐铝胁迫能力大于浦阳品种。