Embryo induction and regeneration from root explants of Medicago truncatula after osmotic pre-treatment

Embryo induction and regeneration from suspension culture of two Medicago truncatula cvs. (cv. R 108 1 and cv. Jemalong) have been studied. The influence of osmotic pre-treatment (1 M solution of sucrose for 48 h and 72 h) of roots as an initial explant, on embryogenic efficiency of the suspension culture was assessed. In comparison to the control, the level of abscisic acid (ABA) increased significantly after osmotic stress. The increased ABA level did not correlate with the induction of embryogenesis neither with the improved embryogenic potential of cv. R 108 1. The shortest regeneration period and the highest percent of conversion to plants were found in cv. R 108 1 after 72-h pre-treatment of roots. The efficiency of somatic embryo conversion was less after 48-h pre-treatment and much less for the untreated control. Osmotic stress did not positively affect the process of embryogenesis from root explants of cv. Jemalong, confirming its cultivar dependence. A single cell suspension fraction was produced in both Medicago trunacatula cvs. during the somatic embryo maturation stage. A higher embryogenic potential than the initial suspension culture was established only for the cell suspension originating from 72-h pre-treated roots of cv. R 108 1. The data confirms that the process of somatic embryo induction and embryo conversion from root explants of cv. R 108 1 could be promoted by osmotic stress pre-treatment.     

Comparison of Salt-Induced Osmotic Adjustment and Trigonelline Accumulation in Two Soybean Cultivars

21-d-old seedlings of the soybean (Glycine max) cvs. Essex and Forrest were treated with NaCl in a step-wise manner over 9 d (3 d 30 mM, 3 d 70 mM, and 3 d 100 mM) and maintained under 100 mM NaCl for an additional 14 d. During salt treatment, osmotic potential decreased more in cv. Forrest relative to cv. Essex. In non-stressed leaf tissue, cv. Forrest contained more trigonelline (TRG) relative to cv. Essex. During salt treatment, TRG amounts increased in cv. Forrest but were unchanged in cv. Essex. Both cvs. osmotically adjusted in response to salt stress; the maximal osmotic adjustment was 0.80 and 0.18 MPa in cv. Forrest and cv. Essex, respectively. This revised version was published online in June 2006 with corrections to the Cover Date.     

Impacts of NaCl stress on plant growth and mineral nutrient assimilation in two cultivars of strawberry

Two strawberry (Fragaria × ananassa Duch.) cvs Korona and Elsanta differing in their tolerance to NaCl salinity were exposed to 40 and 80 mmol NaCl L^?1 for over 4 months in the growing seasons of 2002 and 2003, respectively. However, the osmotic potential, i.e. the NaCl concentration of the root medium, varied during the experiments, because Hoagland solution and demineralized water were added usually once a week in order to push NaCl uptake on the one hand, but to allow leaching the soil after application of demineralized water on the other. Leaching the soil should quickly improve the water relations of the plant, but not affect salt levels within the plant. This strategy was chosen to reduce the effects of water stress and to focus onto the salt-specific impacts of NaCl stress. The salt stress reduced fresh and dry matter of the whole plants and photosynthetically active leaf area, especially in cv. Elsanta. Typical leaf symptoms of Na and Cl stress were detected in both cvs and the combined effects of both toxic ions resulted in the leaf scorching symptoms. Na uptake of both cvs was similar, but distribution of Na within plants was different. Korona was able to protect leaves more efficiently from Na accumulation.Under NaCl stress Korona plants achieved a significant increase of K content in leaves and crowns, while Elsanta showed an increase of K in fruits and petioles. The accumulation of K under evaluated NaCl levels suggests an efficient K uptake system in strawberry plants. Concentrations of Ca were not significantly affected, with the exception of rising levels in roots of Elsanta plants. Concentrations of Mg, Mn and Fe significantly decreased in leaves, while those of Mg and Mn remarkably rose in crowns of both cvs. N content in leaves, petioles, and roots of both cvs increased. In addition it rose in fruits and crowns in cv. Elsanta. A significant limitation of N uptake by competition with Cl did not occur in these plants. Concentrations of P increased in roots and petioles of both cvs, and in fruits of cv. Elsanta. With respect to Zn and Cu, significant concentration changes related to NaCl stress could not be detected.     

Response of French bean cultivars to water deficits: Changes in endogenous hormones, proline and chlorophyll

Effects of water stress at different stages of plant growth on leaf relative water content (RWC), osmotic potential (Ψos) and changes in contents of chlorophyll, abscisic acid (ABA), zeatin riboside (t-ZR), ethylene and proline in six cultivars of French bean (Phaseolus vulgaris L.) were studied. Under water stress, Ψos and RWC were highest in cv. Contender and lowest in cvs. IIHR-909 and Sel-2. The increase in contents of ABA and proline was marked in cv. Contender followed by cv. UPF-626. Decrease in t-ZR and chlorophyll contents was prominent in cv. IIHR-909. Ethylene production surged in all the cultivars under 4- and 8-d stress and declined under 12-d stress. This revised version was published online in August 2006 with corrections to the Cover Date.     

Ion diffusion potentials across mycoplasma membranes determined by a novel method using a carbocyanine dye

The influence of transmembrane ion fluxes on mycoplasma membrane potentials was studied. Electric membrane potential was calibrated vs fluorescence intensity of a potential-sensitive carbocyanine dye according to delta psi = (RT/F) X log([aIN(1 - IN) - b]/Kint), where IN = I/I0, I0 = maximal fluorescence intensity (obtained for delta psi----infinity), and a and b are constants. Fluorescence intensity was calibrated vs membrane potential by inducing a K+ diffusion potential. The calibration procedure was based on the assumption that in the presence of valinomycin the membrane potential was determined entirely by K+ diffusion. Then the dependence of fluorescence intensity on the external K+ concentration, Kext, could be described by Ival = I0[1 + a/(Kext + b)]-1. For Mycoplasma mycoides subsp. capri and enterococci, the constants were determined from experimental data using nonlinear least-squares computer-assisted methods. The validity of our assumption was proved using the "null-point" method. Here the Ca2+ ionophore A23187 and varying external Ca2+ concentrations were used to change the membrane potential experimentally. K+ and Na+ diffusion potentials significantly contributed to mycoplasma membrane potential whereas Cl- had no influence. Under growth conditions the mycoplasma membrane potential was estimated to be delta psi = -68 mV.     

Analysis of early responses to drought associated with field drought adaptation in four Sahelian groundnut (Arachis hypogaea L.) cultivars

Groundnut (Arachis hypogaea L.) is the most important oil and cash crop in the sub-Sahelian tropics. Plant adaptation to drought, i.e. cultivars (cvs) that can maintain yield when water is limited, is a complex phenomenon which is not yet fully understood. This study aimed to identify traits expressed at the early stages of the cycle that could reveal cv differences in drought adaptation in the field. The field productivity of four Sahelian groundnut cvs was assessed during three crop seasons in Bambey (Senegal). The same cvs grown in rhizotrons were subjected to early drought stress and to a desiccation test to assess cell membrane tolerance. Between-cv differences were found with respect to pod yield, biomass production, water use efficiency (WUE), stomatal regulation and cell membrane tolerance. Two strategies to cope with water deficit were identified. The first behaviour was characterised by high rapid water loss, late stomatal closure and low cell membrane damage during drought. These traits are all found in the semi-late Virginia cv 57-422 and, into a lesser extent, in the early Spanish cv Fleur 11. For both cvs, biomass production was boosted under favourable conditions in rhizotrons but the semi-late cv had poor pod yield under end-of-season water deficit conditions. The second strategy involved opposite characters, leading to the maintenance of a higher water status, resulting in lower photosynthesis and yield. This characterised the early Spanish cv 73-30, and also, to some extent, the early Spanish cv 55-437. Earliness associated with high WUE, stomatal conductance and cell membrane tolerance, were the main traits of Fleur 11, a cv derived from a Virginia × Spanish cross, which was able to maintain acceptable yield under varying drought patterns in the field. These traits, as they were detectable at an early stage, could therefore be efficiently integrated in groundnut breeding programmes for drought adaptation.     

Soil salinity effect on soluble saccharides,phenol, fatty acid and mineral contents,and respiration rate of garlic cultivars

The effect of salinity on contents of water, soluble saccharides, phenols, minerals and on respiration rate in bulbs of five garlic (Allium sativum L.) cultivars differing in salinity tolerance was determined. Cultivar HG-6 was found to be the most tolerant followed by cvs. G-l and G-42, and cv. Aru the least tolerant to salinity. The cultivars which were tolerant showed lesser reduction in water content of the bulbs by salinity. Initial contents of phenolic compounds and sulphur were comparatively low in salinity tolerant cultivars but they increased under high salinity levels whereas reverse was found in salt sensitive cultivars. The fatty acids profile did not show significant changes under saline conditions. Contents of K and Ca were reduced, content of Na was increased and there were no changes in the contents of N, Mn, Cu, Zn and Fe. The changes in soluble saccharides content and respiration rate were not found to be associated with the salinity tolerance.     

In vitro Growth and Leaf Composition of Grapevine Cultivars as Affected by Sodium Chloride

In vitro proliferated shoot culture of six grape genotypes (Vitis vinifera L.) were screened for tolerance to NaCl (0 to 200 mM). The cv. Perlette was found to tolerate 175 mM NaCl followed by cvs. Pusa Seedless and Beauty Seedless 150 mM NaCl. Na, K, Cl, Ca and Mg content increased upto 100 mM NaCl in most of the genotypes. Total sugar and proline content of stem tissue gradually increased under NaCl stress while leaf chlorophyll a+b content declined. Studies suggest that the in vitro screening procedure can be used for ranking the grape genotypes for salinity tolerance.     

Water relations of Capsicum genotypes under water stress

Pepper species and cultivars, Capsicum annuum cv. Bell Boy, C. annuum cv. Kulai and C. frutescens cv. Padi, differing in drought tolerance were investigated for their water relations, stomatal responses and abscisic acid (ABA) content during water stress. C. frutescens cv. Padi exhibited a greater osmotic adjustment than C. annuum cultivars. Stomatal conductance of cv. Bell Boy was more sensitive to water stress than that of cvs. Kulai and Padi. In all pepper genotypes, stomatal closure was triggered in the absence of a large decrease in leaf water status. ABA content in xylem sap and leaf was higher in C. annum cultivars compared to C. frutescens cv. Padi. This revised version was published online in July 2006 with corrections to the Cover Date.     

Changes in free amino acids and osmotic adjustment in leaves of water-stressed bean

Bean ( Phaseolus vulgaris L. cv. Topcrop) plants were raised in a growth chamber in small pots or flower boxes and kept at full water regime until the full development of primary leaves (14–16 days). Both potted and flower box-grown plants were subjected to a gradually increased water stress of about 60–70 kPa day⁻¹ leaf water potential (stressed plants) or full water regime (control). The water potential, osmotic potential and turgor pressure in freshly detached primary leaves and osmotic potential at zero turgor were calculated using pressure/volume curves. Changes in free amino acids and amides were also measured in parallel trials. Water relation parameters documented that in the stressed leaves there was moderate osmotic adjustment, which was more evident in the potted plants. If considered 0% ionised, the accumulation of free amino acids and amides (μmol g⁻¹ H₂O) accounts for a van't Hoff's value of about 10.2 kPa in the small pot-grown and 5.5 kPa in the box-grown plants. The values are twice as high if considered 100% ionised. Proline accumulation accounted for about 6.4% of the pool enlargement in the potted plants and 22.3% in the flower box plants.     

Drought Effects on Membrane Lipids and Photosynthetic Activity in Different Peanut Cultivars

The effects of drought on thylakoid acyl lipid composition, photosynthetic capacity (P _max), and electrolyte lekage were evaluated in two-months-old peanut cultivars (57-422, 73-30, GC 8-35) growing in a glasshouse. For lipid studies, plants were submitted to three treatments by withholding irrigation: control (C), mild water stress (S1), and severe water stress (S2). Concerning membrane and photosynthetic capacity stability, drought was imposed by polyethylene glycol (PEG 600). In the cv. 73-30 a sharp decrease in the content of thylakoid acyl lipids was observed, already under S1 conditions, whereas cv. 57-422 was strongly affected only under S2. Cv. GC 8-35 had the lowest content of acyl lipids under control conditions, a significant increase under S1 conditions, and only under S2 a decrease occurred. Thus concerning lipid stability, cv. 73-30 was the most sensitive. Among lipid classes, phospholipids and galactolipids were similarly affected, as was MGDG relatively to DGDG. Water deficit imposed by PEG induced a higher increase in electrolyte leakage in cv. 73-30 than in the other cvs. A positive relationship between acyl lipid concentration and membrane integrity was found in all studied cvs. A positive association between acyl lipid concentration, membrane integrity, and P _max was found in the cvs. 57-422 and 73-30.     

Betaine accumulation in salt-stressed sorghum

Two analytical methods for measuring betaine were compared in a study of betaine accumulation in salt-stressed sorghum. Spectrophotometric determination of betaine as the p -bromophenacyl ester is highly sensitive and specific. However, a periodide assay was found to be more convenient for screening numerous plant samples without undue sacrifice in accuracy.
The accumulation of betaine in grain sorghum [ Sorghum bicolor (L.) Moench] cvs NK 265 and Double TX was measured in salt-stressed plants grown hydroponically and in the field and in drought-stressed potted plants. Neither drought nor mild salinity (-0.2 MPa) stress was effective in stimulating betaine accumulation. However, when the osmotic potential of the culture solution was lowered to -0.8 MPa, betaine levels in the shoots rose rapidly for 12 days after initiation of salination, and then declined, apparently because of dilution by plant growth. In young leaf blades, betaine was strongly accumulated up to 70–75 μmol (g dry weight)⁻¹; the concentration in leaf sheaths was less than 6 μmol (g dry weight)⁻¹.
In the field, betaine levels in salt-stressed sorghum increased 6- to 7-fold over the basal level of the control plants. In a comparable study of two wheat species ( Triticum aestivum L. cv. Probred and T. durum Desf. cv. 1000-D), betaine increased only 3- to 4-fold over unstressed plants.     

Effect of lead on nitrate reductase activity and alleviation of lead toxicity by inorganic salts and 6-benzylaminopurine

A concentration dependent decrease in root nitrate reductase (E.C.1.6.6.1) activity (NRA) by 0.1 to 2.0 mM lead acetate was noticed in three cultivars of Vigna radiata (L.) Wilczek (K851, MH8320 and ML337). Leaf NRA, on the other hand, increased significantly with increasing lead concentration which was more pronounced in cvs. MH8320 and ML337 than in cv. K851. Total nitrogen content of root and shoot was generally increased due to supply of the lead acetate, whereas the total nitrogen content of the colyledons was hardly affected in cvs. MH8320 and ML337 and decreased in cv. K851 during the early growth phase. The inhibition of root NRA could be alleviated by addition of inorganic salts (K2HPO4 and KNO3, but not CaCl2) or 6-benzylaminopurine (BAP) in the incubation medium. Lead mediated inhibition of root NRA was similar in light and dark grown seedlings, but lead induced increase in leaf NRA was more pronounced in the light than in the dark. This revised version was published online in August 2006 with corrections to the Cover Date.     

盐胁迫下盐地碱蓬体内无机离子含量分布特点的研究

用不同浓度NaCl溶液处理盐地碱蓬（Suaeda salsa)植株后,测定并比较老叶、幼叶及根部的无机离子含量和对K的选择性,叶片及根部的Na^ 、Cl^-含量随盐度的增加而升高,且累积趋势相似,盐胁迫下根部Na^ 、Cl^-及总离子含量（K^ 、Na^ 、Ca^2 ,NO3^-,Cl^-)明显低于叶片,说明盐地碱蓬地盐胁迫下,以叶片优先积累大量离子（如Na^ ,Cl^-) 为其适应特征。NaCl处理下,叶片的K^ ,Ca^2 含量低于对照,但随盐度的增加保持相对稳定,而根部K^ 含量,K/Na比、对K的选择性则高于叶片,这对盐胁迫下地上部的K^ 亏缺有一定补偿作用。低盐度处理（100mmol/LNaCl)促进NO3^-的吸收,另外随盐度的增加,叶片渗透势下降,渗透调节能力增强,幼叶渗透势低于老叶,但渗透调节能力相同。     

Differences in growth and water relations among Phaseolus vulgaris cultivars in response to induced drought stress

Relatively little ecophysiological research has been conducted to determine the responses to drought of Phaseolus vulgaris. Four bean cultivars (cvs.) from Brazil, A320, Carioca, Ouro Negro and Xodó were submitted to an imposed water deficit in order to evaluate the importance of some adaptive mechanisms of drought resistance through the analysis of growth parameters, water status, gas exchange and indicators of tolerance mechanisms at the cellular level. During the drought treatment, relative growth rates were more reduced for A320 and Xodó than Carioca and Ouro Negro. A320 closed its stomata very rapidly and complete stomatal closure was obtained at Psi(w)=-0.6 MPa, in contrast to the other cvs. where stomata were fully closed only at Psi(w)=-0.9 MPa. Net assimilation rates were closely related to stomatal conductances. Mechanisms at the cellular level appeared to be mostly important for higher tolerance. Carioca and Ouro Negro, when compared to A320 and Xodó, were characterized by having better drought tolerance mechanisms and higher tissue water retention capacity leading to a better growth under water deficits. The leaf dehydration rates of those cvs. were slow whereas those of the drought sensitive cvs. were rapid. The results were confirmed by the electrolyte leakage test and leaf osmotic potential measurements, which indicated higher membrane resistance and osmotic adjustment in the two tolerant cvs. Carioca and Ouro Negro. It appears from this study that despite being cultivated in the same geographical region, the four cvs. of P. vulgaris displayed somewhat different drought adaptive capacities for prolonged drought during the vegetative phase.     

钠、钾、钙和葡萄糖对白斑狗鱼精子活力的影响

观察了白斑狗鱼精子在0～679．6kPa NaCl、KCl、葡萄糖溶液和0～339．8kPa CaCl2溶液中的活动情况。在NaCl、KCl、葡萄糖溶液中,白斑狗鱼精子快速运动时间和寿命的变化规律基本一致,精子活动最适渗透压介于339．8～453．0kPa。K^ 有延长精子寿命的作用。外源性葡萄糖可被精子利用,增强精子活力．延长精子寿命。56．7kPa CaCl2对精子活动有抑制作用,并引起精子聚集,该效应随着Ca^2 浓度升高而增强。     

Separating multiple, short-term, deleterious effects of saline solutions on the growth of cowpea seedlings

? Reductions in plant growth as a result of salinity are of global importance in natural and agricultural landscapes. ? Short-term (48-h) solution culture experiments studied 404 treatments with seedlings of cowpea (Vigna unguiculata cv Caloona) to examine the multiple deleterious effects of calcium (Ca), magnesium (Mg), sodium (Na) or potassium (K). ? Growth was poorly related to the ion activities in the bulk solution, but was closely related to the calculated activities at the outer surface of the plasma membrane, {I(z)}?°. The addition of Mg, Na or K may induce Ca deficiency in roots by driving {Ca2+}?° to < 1.6 mM. Shoots were more sensitive than roots to osmolarity. Specific ion toxicities reduced root elongation in the order Ca2+ > Mg2+ > Na+ > K+. The addition of K and, to a lesser extent, Ca alleviated the toxic effects of Na. Thus, Ca is essential but may also be intoxicating or ameliorative. ? The data demonstrate that the short-term growth of cowpea seedlings in saline solutions may be limited by Ca deficiency, osmotic effects and specific ion toxicities, and K and Ca alleviate Na toxicity. A multiple regression model related root growth to osmolarity and {I(z)}?° (R2=0.924), allowing the quantification of their effects.     

Ca^2＋参链霉素对大鼠颈动脉窦压力感受器反射影响中的作用

在２３只隔离灌流颈动脉窦区的麻醉大鼠上,观察了链霉素（ｓｔｒｅｐｔｏｍｙｃｉｎ,ＳＭ）对动脉压力感受器反射影响的离子机制。结果：（１）用ＳＭ（２００μｍｏｌ／Ｌ）隔离灌流大鼠颈动脉窦区时,压力感受器机能曲线向右上方移位,曲线最大斜率及反射性血压下降幅度均减小（Ｐ〈０．０１）,提示ＳＭ对压力感受器反射的抑制作用;（２）预先灌流高Ｃａ＾２＋溶液（４ｍｍｏｌ／Ｌ）后,可部分消除ＳＭ（２００μｍｏｌ／Ｌ）     

Partial decline of Arachis hypogaea L. photosynthesis triggered by drought stress

Photosynthetic capacity (PC) of three peanut cultivars (Arachis hypogaea L. cvs. 57-422, 73-30, and GC 8-35) decreased during drought stress (decline in relative water content from ca. 95 to 70 %) and recovered two days after rewatering. Mild water stress was not limiting for the total ribulose-1,5-bisphosphate carboxylase/oxygenase activity, since this enzyme activity increased under drought. Photosystem (PS) 2 and PS1 (the latter only in cv. GC 8-35) electron transport activities decreased under drought. The ratio of the variable to maximal chlorophyll fluorescence (Fv/Fm) decreased mainly in the cv. GC 8-35. All cultivars showed decreases in photochemical quenching (qP) and quantum yield of PS2 electron transport (Φe). Increase of basal fluorescence (F0) was observed in the cvs. 73-30 and GC 8-35, while the cv 57-422 showed a decrease. After rewatering a sharp increase was observed in the majority of the parameters. Thus under the present stress conditions, the cv GC 8-35 was the most affected for all the parameters under study. The cv. 57-422 showed a higher degree of tolerance being gradually affected in photosynthetic capacity (PC) in contrast to the two other cvs. which showed a sharp decrease in PC at the beginning of the drought cycle. This revised version was published online in September 2006 with corrections to the Cover Date.