Callose formation as parameter for assessing genotypical plant tolerance of aluminium and manganese

Callose ((1,3)--glucan) formation in plant tissues is induced by excess Al and Mn. In the present study callose was spectrophotometrically quantified in order to evaluate whether it could be used as a parameter to identify genotypical differences in Al and Mn tolerance. Mn leaf-tissue tolerance of cowpea and linseed genotypes was assessed using the technique of isolated leaf tissue floating on Mn solution. Genotypical differences in the density of brown speckles on the leaf tissue (Mn toxicity symptoms) correlated closely with the concentrations of callose for both plant species. In cell suspension cultures Mn excess also induced callose formation. However, differences in tolerance of cowpea genotypes using callose formation as a parameter could only be found in cultured cowpea cells if controls cultured at optimum Mn supply showed low background callose. As soon as after 1 h, Al supply (50 M) induced callose formation predominantly in the 5-mm root tip of soybean seedlings. Callose concentration in the 0–30 mm root tips was inversely related to the root elongation rate when roots were subjected to an increasing Al supply above 10 M. Three soybean genotypes differed in inhibition of root-elongation rate and induction of callose formation when treated with 50 M Al for 8 h. Relative callose concentrations and relative root-elongation rates for these genotypes were significantly negatively correlated.     

Sampling DNA from the rhizosphere of Brassica napus to investigate rhizobacterial community structure

Variations in genotype rankings among screenings for Al tolerance in hydroponics may be related to differences in the composition of the solutions. In the present study, we investigated the involvement of Mg ions in modifying Al rhizotoxicity in soybeans. Root elongation was strongly inhibited by Al in a simple, 800 M CaSO₄ solution, but elongation increased noticeably when the solutions also contained Mg. Amelioration of Al rhizotoxicity was not associated with an increase in ionic strength of treatment solutions because Al³⁺ activities were kept constant. Concentration series experiments indicated that the Mg effect occurred in the M range, while Ca amelioration of Al toxicity occurred at mM concentrations. The positive effect of Mg on root elongation was greatest for Al-sensitive genotypes and minimized genotypic differences for Al-tolerance. The Mg protection against Al rhizotoxicity apparently does not occur with all species, because it was not observed in Atlas and Scout 66 wheat varieties. The ability of Mg to ameliorate Al toxicity in soybean at M levels suggests the involvement of distinct physiological factors.     

Polyamines and proline are affected by cadmium stress in nodules and roots of soybean plants

The effect of moderate (50 M) and high (200 M) doses of Cd were studied in relation to polyamine (Pas) metabolism, proline level and the glutamine synthetase/glutamate synthase system (GS/GOGAT) activity in nodules and roots of soybean plants during 6 days of treatment. The lower Cd concentration increased putrescine (Put) in both nodules and roots, while 200 M Cd increased Spm only in nodules and Put in roots. Spermidine (Spd) decreased in roots under both Cd concentrations. Arginine decarboxylase (ADC) and ornithine decarboxylase (ODC) were both involved in Put biosynthesis in roots. In nodules, Put formation could mainly be attributed to ODC activity. Diamine oxidase (DAO) activity was severely reduced by 50 and 200 M Cd either in nodules or roots. The GS/GOGAT system activity was depressed either with 50 or 200 M Cd, but most significantly with the highest metal concentration. Under 200 M Cd, GS activity decayed to 25% or 60% of the control in nodules and roots, respectively, while GOGAT decreased 85% in nodules and 79% in roots by day 4 of treatment. Ammonium increased greatly in nodules (200% over the controls) and roots (100%) under 200 M Cd. Proline concentration increased significantly in nodules and roots under both Cd treatments, more markedly under 200 M Cd. The relationship between Pas and proline accumulation and nitrogen assimilation is discussed.     

Empirical models to approximate calcium and magnesium ameliorative effects and genetic differences in aluminium tolerance in wheat

The activities of inorganic, monomeric aluminium (Al) species in the root environment are important in the toxicity of Al to plant roots, which may be ameliorated by increased activities of basic cations. Additionally, it has been suggested that electro-chemical processes in walls of root cells play a role in Al tolerance. Empirical models were proposed to accomodate genetic and calcium (Ca) and magnesium (Mg) ameliorative effects on Al toxicity. The models were tested using data from a solution culture study (with ionic strength 1.6 to 8.6 mM) in which wheat (Triticum aestivum L.) cvv. Warigal (Al-sensitive) and Waalt (Al-tolerant) were grown for 28 d at 0, 10 and 20 M Al, in factorial combination with 200, 400, 800 and 1600 M Ca and 100, 200, 400 and 800 M Mg. There was a poor relationship between relative total dry mass (TDM) (calculated as a percentage of the average TDM of each cultivar in the absence of added Al) and the activity of Al³⁺ or the sum of the activities of the monomeric Al species in solution. A model based on the ratios of activities of cations in solution, taking valency into consideration, was more successful, accounting for ca 85% of the observed variation in relative TDM. There were no systematic variations between observed values and those estimated by the model.     

Antagonistic interaction between auxins and the growth regulator NC 9634

The synthetic growth regulator NC 9634, [(3-phenyl-1,2,4-thiadiazol-5-yl)thio] acetic acid (NC 9634) was shown to have anti-auxin properties in bioassay tests. The inhibition of wheat coleoptile extension growth by concentrations of NC9634 up to 260 M was completely overcome by 60 M IAA, 50 M NAA or 50 M 2,4-D. In cress root tests 2.6 × 10^–7 M NC 9634 stimulated root elongation and relieved the growth inhibiting effect of 2,4-D. Extension growth of intact apple shoots was inhibited by NAA, which proved lethal at concentrations above 6.25 × 10^–4 M. NC 9634 applied in combination with the NAA, reduced this growth inhibiting effect and prevented death of shoots sprayed with high auxin concentrations.     

Seedling root response of some Kenyan bread wheat cultivars grown in acid nutrient culture solution containing aluminum

The objective of this study was to determine whether a series of Kenyan bread wheat cultivars differed in tolerance to aluminum toxicity. Fourteen Kenyan wheat cultivars representing current and former widely grown cultivars of diverse pedigree origin, and two control cultivars, Maringa (Al-tolerant) and Siete Cerros (Al-susceptible), were tested in solution cultures with 0 (control), 148, 593, and 2370 M Al at pH 4.6. Highly significant (p0.01) differences in seedling growth were observed among cultivars for root mass, root length and root tolerance index (RTI). Significant (p0.05) cultivar × treatment interactions were observed for root mass and RTI. All characters were negatively affected by increased Al concentration, with root length and root mass being affected the most. RTI is a commonly used index which measures the relative performance of individual cultivars with and without aluminum stress. High levels of tolerance to Al were identified in the Kenyan cultivars by evaluating RTI with this simple nutrient solution technique. Romany and Kenya Nyumbu had RTI values approaching those of the Al tolerant Brazilian cultivar Maringa, a spring wheat standard that has been used for high Al tolerance.     

SelectingRhizobium phaseoli strains for use with beans (Phaseolus vulgaris L.) in Kenya: Infectiveness and tolerance of acidity and aluminium

Forty strains ofRhizobium phaseoli, isolated from Kenyan soils, were tested for infectiveness on common bean (Phaseolus vulgaris L.). 28 strains were infective and a cultivar × Rhizobium interaction was observed. 48 strains were screened for tolerance of acidity and Al in liquid culture. Assessment of visible turbidity after 14 days indicated 34 strains tolerant of pH 4.5 but none tolerant of pH 3.5. No strain was tolerant of 50 M Al at pH 5.5. Three strains were tolerant of 20 M Al at pH 5.5 and 10 M Al at pH 4.5. Screening on a solid medium identified strains tolerant of 20 and 50 M Al at pH 5.5 and 4.5 which were sensitive to these treatments in liquid culture. Those strains tolerant to 20 M Al at pH 4.5 and 5.5 in liquid culture were correctly identified on the solid medium.     

Effect of aluminium on yield and plant chemical concentrations of some temperate legumes

The aluminium (Al) tolerance of 34 temperate legume species (143 genotypes, including 57 from Trifolium repens) was determined in 60 experiments over a 3 year period in a low ionic strength (2.7 × 10^-3 M) solution culture. For each genotype, the relationship between solution Al³⁺ activity (M) and relative yield was determined and the Al³⁺ activity associated with a 50% reduction in yield (Al_RY50) calculated. In addition, plant chemical concentrations were determined in at least one genotype from most species. For white clover, Al_RY50 over all genotypes had an approximately normal distribution with mean of 1.31 M for the tops and 1.51 M for the roots, and a standard deviation of about 0.4. This suggested that Al tolerance had a polygenic inheritance. For the other species tested, Al_RY50 ranged from 0.15 to 4.53 M in the tops and from 0.21 to 4.89 M in the roots. In the tops and roots, 37% and 26% respectively of the genotypes had an Al_RY50 less than 1 M, including all species tested in the genera Melilotus and Medicago. Only 8% or 23% of the genotypes, based on the tops and roots respectively, had an Al_RY50 greater than 2, including all genotypes in the species Lotus pedunculatus. Except for Lotus, there were no consistent differences between genera in plant chemical concentrations. In Lotus, concentrations of Ca, Zn, Mn and Cu in the tops and of all elements except B in the roots were lower than that of the other species. The Al_RY50 of the species was not related to plant chemical concentrations in the absence of Al. Depending on the plant element, increasing solution Al concentrations had no significant effect on plant chemical concentrations for 56–94% of the species. When a significant effect did occur, increasing Al in solution generally decreased S and K concentrations and increased Mn, Zn, Cu Fe, B and Al concentrations in the tops and roots and decreased Ca concentrations in the tops. Plant P concentrations decreased in the tops but increased in the roots. Increasing Al in solution increase plant Al at the average rate of 44 g g^-1 M ^-1 (range 20–87) in the tops and 333 g M ^-1 (range 162–616) in the roots.     

Influence of phosphate and nitrate supply on root hair formation of rape,spinach and tomato plants

Summary Experiments with tomato, rape and spinach in nutrient solutions have shown that the formation of root hairs is strongly influenced by phosphate and nitrate supply. Decreasing the phosphate concentration of the nutrient solution from 100 to 2 M P resulted in an increase of root hair length from 0.1–0.2 to 0.7 mm of the three plant species. Root hair density also increased by a factor of 2–4 when the P concentration was lowered from 1000 to 2 M. The variation of these two root properties raised the root surface area by a factor of 2 or 3 compared to plants well supplied with P. Root hair length was closely related to the phosphate content of the root and shoot material. On the other hand, spinach plants grown in a split-root experiment produced root hairs in solutions of high P concentration (1000M P) if the major part of the total root system was exposed to low P concentration (2 M P). It is therefore concluded that the formation of root hairs does not depend on directly the P concentration at the root surface but on the P content of the plant.Similar experiments with nitrate also resulted in an increase in length and density of root hairs with the decrease of concentration below 1000 M. In this case marked differences between plant species occurred. At 2 M compared to 1000 M NO₃ root hair length of tomato increased by a factor of 2, of rape by a factor of 5 and of spinach by a factor of 9. Root hair length was correlated, but not very closely, to the total nitrogen content of the plants. It is concluded, that the influence of nutrient supply on the formation of root hairs is a mechanism for regulating the nutrient uptake of plants.Dedicated to Prof. Dr. E. Welte on the occasion of his 70th anniversary.     

Silicon amelioration of aluminium toxicity in teosinte (Zea mays L. ssp. mexicana)

The influence of different Al concentrations, (0, 60 and 120 M Al) on growth and internal concentrations of Al, Si and selected organic acids was analysed in plants of teosinte (Zea mays L. ssp. mexicana), a wild form of maize from acid soils from Mexico. The plants were grown in nutrient solutions (pH 4.0) with or without 4 M silicon. Analysis with the GEOCHEM speciation program did not reveal differences between free activities of Al³⁺ in solutions with and without 4 M Si, but solutions with Si yielded lower concentrations of monomeric Al species, [Al]_mono, when analysed by a modified aluminon method. Plants grown on solutions with similar [Al]_mono, but differing in silicon, showed highly significant differences in growth and tissue concentrations of Al and organic acids. Silicon prevented growth inhibition at [Al]_mono concentrations as high as 35 M, while plants grown without Si suffered severe growth reductions with 33 M [Al]_mono. In solutions with similar [Al]_mono concentrations plants with Si had lower tissue Al concentrations and higher concentrations of malic acid than plants without Si. In view of both the significant influence of Si on the response of plants to Al toxicity and the fact that some soluble Si is always present in soil solutions, the addition of low Si concentrations to nutrient solutions used for Al-tolerance screening is recommended.     

Clonal propagation of Callistemon by tissue culture techniques

Callus development in Callistemon viminalis was readily achieved when axillary buds derived from nodal tissue were placed in a medium containing macro- and micro-nutrients, sucrose (0.06 M), inositol (300 M), nicotinic acid (20 M), pyridoxine hydrochloride (3 M), thiamine hydrochloride (2 M), riboflavin (10 M), cytokinins (5 M) and auxins (0.1 M). The presence of benzylaminopurine (5 M) and p-chlorophenoxyacetic acid (0.1 M) promoted the most vigorous callus development and sprout formation. Rooting of nodal material was rare but occurred readily following the transference of sprouts developed on callus to a basal medium containing sucrose and salts. Root initiation was stimulated, however, by the presence of auxins. Chlorophenoxyacetic acid while stimulating root initiation repressed root growth. Indole butyric acid stimulated both root initiation and shoot growth at concentrations of 0.005 to 0.1 M. The treatment of choice for rooting and shoot growth was the addition of indole butyric acid at a concentration of 0.01 M.     

Aluminum-induced secretion of both citrate and malate in rye

Aluminum (Al)-resistant mechanisms responsible for Al-induced secretion of organic acids are poorly understood. In this study, we characterized the Al-induced secretion of both citrate and malate from rye (Secale cereale L. cv. King). Secretion of organic acids increased with increasing concentration (10, 30 and 50 M) and duration of Al treatments. Neither phosphorous (P) deficiency up to 15 days nor addition of 50M lanthanum, 50 M lead, 10 M cadmium, or 200 M manganese caused secretion of organic acids, suggesting that this secretion was a specific response to Al stress. Aluminum activated citrate synthase, the main enzyme for the synthesis of citrate, but its activation occurred only in the root tip. The elongation of roots of an Al-sensitive cultivar of wheat (Tritium aestivum L. cv. Scout 66) was not inhibited by 50 M Al in the presence of externally applied 50 M citrate or 400 M malate. The secretion of citrate and malate from intact rye roots exposed to 50 M Al corresponded to 31.3 ± 1.7 M and 11.5 ± 2.5 M, respectively, in the rhizosphere based on an assumption of a 2 mm thick unstirred layer around root tips. This result indicated that Al-resistance in rye was achieved by the Al-induced synthesis of citrate in root apices followed by Al-induced specific secretion of citrate from root tips.     

Al-induced inhibition of root elongation in corn,Zea mays L. is overcome by Si addition

The effect of silicic acid on Al-induced inhibition of root elongation was investigated in corn roots (Zea mays L. cv. golden cross bantam) in 100 t M CaCl2 solution at pH 4.3. Twenty t M Al inhibited root elongation (20 h) about 70%, however, inhibition was alleviated by addition of silicic acid. The alleviative effect increased with higher silicic acid concentrations. The concentration of Al3+, the toxic species, in solution was decreased to about 15, 10, and 5 t M, respectively, from the initial concentration of 20 t M by addition of silicic acid at 500, 1000, and 2000 t M Si. Under the same concentration of Al3+, Al-induced inhibition of root elongation showed the same extent regardless of the addition of silicic acid or not by comparing 5 t M Al treatment with 20 t M Al + 2000 t M Si treatment, and 10 t M Al treatment with 20 t M Al +1000 t M Si treatment. Viability of cells on the root tip surface was decreased by Al addition. Cell viability was not improved by addition of silicic acid under the same concentration of Al3+. All these facts suggest that the alleviative effect of silicic acid on Al toxicity resulted from decreasing toxic Al3+ concentration by forming Al-Si complexes rather than from other physiological effects of silicic acid in corn roots.     

Evaluating the contribution of magnesium deficiency in the aluminium toxicity syndrome in twelve sorghum genotypes

The contribution of Mg deficiency to Al stress in twelve different sorghum (Sorghum bicolor (L.) Moench) genotypes was investigated in nutrient solution culture under conditions of low Mg supply (between 50 and 1000 M) at two pH values. At pH 4.2, 30 M Al strongly inhibited Mg uptake. When dry matter yield was plotted as a function of the plant Mg concentration, similar response curves were obtained in the absence and the presence of Al with three genotypes. With many other genotypes dry matter yields of the control (without Al treatment) and Al-stressed plants were remarkably different at similar internal Mg concentrations, suggesting that growth had been suppressed not by Mg deficiency but by another factor, i.e. Al-induced root damage. At pH 4.8, 30 M Al hardly induced root damage but reduced Mg uptake and Al-induced Mg deficiency could almost completely account for the growth reaction of all genotypes. Therefore, at this pH the efficiency of uptake or use of Mg in different genotypes was the basis of their respective susceptibility to Al toxicity. When specific root length surpassed a certain critical range below 80–100 m per g dry root, growth control by Al-induced Mg deficiency was nearly abolished. The pH and Al concentration where this range was reached depended on the Al sensitivity of the genotypes.     

Sensitivity to H- and Al ions limiting growth and distribution of the woodland grass Bromus benekenii

One pH experiment and two aluminium experiments were conducted in order to investigate the effects of H- and Al ions on growth of Bromus benekenii. Continuously flowing solution cultures were used with ion concentrations simulating natural soil solutions. In all experiments, treatment effects were more pronounced on root than on shoot growth. In the pH experiment, root growth decreased with decreasing pH within the pH range 4.5 to 3.5. The critical pH for root growth of Bromus benekenii was between 3.8 and 4.0. In the Al experiments, root growth started to decrease at 20 M of quickly reacting Al and almost ceased at 70 M Al. This characterizes Bromus benekenii as an Al sensitive species. In the pH experiment, shoot concentrations of Ca, Mg, K and P decreased with decreasing pH, but root concentrations were not affected. In the Al experiments, the Al concentrations of both shoots and roots increased with Al in the nutrient solution. At treatments of 70 M Al or higher, Ca, Mg, K and P concentrations in the shoots were reduced. The critical concentrations of H- and Al ions in the experiments were similar to the highest concentrations found at field sites of Bromus benekenii, analysed in soil solutions obtained by centrifugation technique. Both Al and H toxicity were considered to be of importance as limiting factors for the distribution of Bromus benekenii in south Sweden. Probably, Al toxicity starts to limit growth when also pH itself influences growth negatively. The importance of simulating natural soil solutions in experiments is emphazised, in order to obtain information on the importance of chemical soil factors to the distribution of plants.     

AT-1 Receptor and Phospholipase C Are Involved in Angiotensin III Modulation of Hypothalamic Noradrenergic Transmission

SUMMARY 1. We previously reported that angiotensin III modulates noradrenergic neurotransmission in the hypothalamus of the rat. In the present work we studied the effects of angiotensin III on norepinephrine release and tyrosine hydroxylase activity. We also investigated the receptors and intracellular pathways involved in angiotensin III modulation of noradrenergic transmission.2. In rat hypothalamic tissue labeled with [³H]norepinephrine 1, 10, and 100 nM and 1 M losartan (AT1 receptor antagonist) had no effect on basal neuronal norepinephrine release, whereas 10 and 100 nM and 1 M losartan partially diminished norepinephrine secretion evoked by 25 mM KCl. The AT2 receptor antagonist PD 123319 showed no effect either on basal or evoked norepinephrine release. The increase in both basal and evoked norepinephrine output induced by 1 M angiotensin III was blocked by 1 M losartan, but not by 1 M PD 123319.3. The phospholipase C inhibitor 5 M neomicin inhibited the increase in basal and evoked norepinephrine release produced by 1 M angiotensin III.4. Tyrosine hydroxylase activity was increased by 1 M angiotensin III and this effect was blocked by 1 M LST and 5 M neomicin, but not by PD 123319. On the other hand, 1 M angiotensin III enhanced phosphatidyl inositol hydrolysis that was blocked by 1 M losartan and 5 M neomicin. PD 123319 (1 M) did not affect ANG III-induced phosphatidyl inositol hydrolysis enhancement.5. Our results confirm that angiotensin III acts as a modulator of noradrenergic transmission at the hypothalamic level through the AT1-phospholipase C pathway. This enhancement of hypothalamic noradrenergic activity suggests that angiotensin III may act as a central modulator of several biological processes regulated at this level by catecholamines, such as cardiovascular, endocrine, and autonomic functions as well as water and saline homeostasis.     

Alleviation of aluminum toxicity to Rhizobium leguminosarum bv. viciae by the hydroxamate siderophore vicibactin

Acid rain solubilises aluminum which can exert toxic effects on soil bacteria. The root nodule bacterium Rhizobium leguminosarum biovar viciae synthesises the hydroxamate siderophore vicibactin in response to iron limitation. We report the effect of vicibactin on the toxicity of aluminum(III) to R. leguminosarum and kinetic studies on the reaction of vicibactin with Al(III) and Fe(III). Aluminum (added as the nitrate) completely inhibited bacterial growth at 25 M final concentration, whereas the preformed Al-vicibactin complex had no effect. When aluminum and vicibactin solutions were added separately to growing cultures, growth was partly inhibited at 25 M final concentration of each, but fully inhibited at 50 M final concentration of each. Growth was not inhibited at 50 M Al and 100 M vicibactin, probably reflecting the slow reaction between Al and vicibactin; this results in some aluminum remaining uncomplexed long enough to exert toxic effects on growth, partly at 25 M Al and vicibactin and fully at 50 M Al and vicibactin. At 100 M vicibactin and 50 M Al, Al was complexed more effectively and there was no toxic effect. It was anticipated that vicibactin might enhance the toxicity of Al by transporting it into the cell, but the Al-vicibactin complex was not toxic. Several explanations are possible: the Al-vicibactin complex is not taken up by the cell; the complex is taken up but Al is not released from vicibactin; Al is released in the cell but is precipitated immediately. However, vicibactin reduces the toxicity of Al by complexing it outside the cell.     

Endogenous ethylene requirement for adventitious root induction and growth in tomato cotyledons and lavandin microcuttings in vitro

The role of ethylene in the formation of adventitious roots in vitro was studied in tomato (Lycopersicon esculentum Mill. cv. UC 105) cotyledons and lavandin (Lavandula officinalis Chaix × Lavandula latifolia microshoots. Both systems were able to form roots on hormone-free medium evolving low amounts of ethylene. The addition of 20–50 M indole-3-acetic acid (IAA) inhibited root formation in tomato cotyledons while increasing ethylene production. Naphthaleneacetic acid (NAA, 3 M) stimulated root number in lavandin explants and induced a transient rise in ethylene evolution. Enhanced ethylene levels via the endogenous precursors 1-aminocyclopropane-1-carboxylic acid (ACC, 25–50 M) drastically impaired root regeneration and growth in tomato. In lavandin, 10 M ACC stimulated ethylene production and significantly inhibited the rooting percentage and root growth. Conversely, ACC enhanced the root number in the presence of NAA only. Severe inhibition of rooting was also caused by ethylene reduction via biosynthetic inhibitors, aminoethoxyvinylglycine (AVG, 5–10 M) in tomato, and salicylic acid (SA, 100 M) in lavandin. A strict requirement of endogenous ethylene for adventitious root induction and growth is thus suggested.Abbreviations LS Linsmaier and Skoog medium - BA N⁶-benzyladenine - NAA 1-naphthaleneacetic acid - IAA Indole-3-acetic acid - AVG Aminoethoxyvinylglycine - SA Salicylic acid - ACC 1-aminocyclopropane-1-carboxylic acid     

Grazing by a dominant rotifer Conochilus unicornis Rousselet in a mountain lake: in situ measurements with synthetic microspheres

Grazing rates of zooplankton were analysed in the summer of 1999 in Yellow Belly Lake, an oligotrophic system in the Sawtooth Mountains of Idaho (U.S.A.). The colonial rotifer Conochilus unicornis was a dominant species in the epilimnion, with densities reaching 20 colonies l^–1 (ca. 400 ind. l^–1). Clearance rates were measured with an in situ Haney Grazing chamber and synthetic microspheres 5, 9 and 23m in diameter. At epilimnetic temperatures of around 14 °C, mean clearance rates for 5m particles ranged from 30 to 65 l ind.^–1 h ^–1. Clearance rates were 2–9 times higher on the 5m spheres than on the 9 m spheres, and C. unicornis almost never fed on the 23 m spheres. Grazing rates did not change over the diel cycle. Clearance rates declined more than 10-fold as temperatures declined from 14 °C in the epilimnion to 7 °C in the metalimnion. In the epilimnion, grazing by C. unicornis was more important than grazing by crustaceans in the community, at least on particles 9m. The results show the importance of grazing by rotifers in lakes, and the significance of spatial variations that influence grazing rates.     

Axillary shoot induction and plant regeneration in Plantago ovata Forssk

Axillary shoot induction and plant regeneration were obtained in Plantago ovata. The optimum medium for inducing axillary shoots was Murashige & Skoog (MS) medium [5] supplemented with 4.6 M kinetin and 0.05 M NAA. Rooting of shoots was best on half-strength MS medium containing 5.0 M IBA and 0.05 M kinetin. The regenerated plants were similar to the control plants in karyotypic and phenotypic details.