Effects of silicon supply on apoplastic manganese concentrations in leaves and their relation to manganese tolerance in cowpea (Vigna unguiculata (L.) Walp.)

The effects of silicon (Si) supply on manganese (Mn) toxicity symptoms and Mn and Si concentrations in the leaf apoplast in a Mn-sensitive cowpea cultivar (Vigna unguiculata (L.) Walp. cv. TVu 91) were investigated in solution culture experiments. When 1.44 mM Si was supplied concurrently with 50 M Mn, the Mn toxicity symptoms were clearly avoided without decreasing the total Mn concentration. On the other hand, the symptoms were not completely alleviated when the plants were pretreated with 1.44 mM Si and then exposed to 50 M Mn without concurrent Si supply. Plants of both of these treatments exhibited lower Mn concentrations in the apoplastic washing fluids but higher amounts of adsorbed Mn on the cell walls than the plants treated with 50 M Mn without Si supply. However, the difference in Mn concentration between plants with continuous and interrupted Si supply was not significant. Moreover, the Mn concentration in the apoplastic washing fluids of the plants with continuous supply of 1.44 mM Si and 50 M Mn and not showing Mn toxicity symptoms was higher than that of the plants grown at 10 M Mn without Si supply which showed distinct Mn toxicity symptoms. These results show that Si supply alleviates Mn toxicity not only by decreasing the concentration of soluble apoplastic Mn through the enhanced adsorption of Mn on the cell walls. A role of the soluble Si in the apoplast in the detoxicification of apoplastic Mn is indicated.     

Distribution of magnesium in wheat (Triticum aestivum L.) in relation to supply

The aims of this study were to describe the distribution of magnesium (Mg) and its retranslocation within wheat, in order to develop diagnostic procedures for Mg deficiency. Plants were grown in solution culture with both constant supply (0, 5, 10, 20, 40, 80, 160 MMg) and discontinued supply (40 M and 160 M decreased to nil).Magnesium was depleted from old leaves when Mg supply to the roots was halted. However, initial deficiency symptoms occurred on young leaves under constant but inadequate supply, contrasting with previous reports. Magnesium concentrations were also lower in young leaves compared to old leaves. Symptoms of yellowing and necrosis occurred if the leaf tissue contained <1194 gg^–1, irrespective of leaf age. The minimum Mg concentration in whole shoots associated with maximum shoot weight was 932 gg^–1; for the youngest emerged blade (YEB) it was 861 gg^–1. Symptoms were apparent on the young leaf before a reduction in shoot weight was measurable. The concentration of Mg in the YEB and whole shoot were better related to solution Mg concentration than was the Mg concentration in the old leaf.     

Response of honelocust (Gleditsia triacanthos L.) to soil solution aluminium

Honeylocust (Gleditsia triacanthos L.) seedlings were grown for 72 days in soil from a BC horizon of a Spodosol altered by adding four levels of AlCl₃. Saturated paste extracts from controls to the highest AlCl₃ treatment contained, respectively, 85 to 831 M Al, 834 to 163 M Ca and 316 to 35 M Mg and had a pH of 4.4 to 4.0 Leaf, stem, and root concentrations of Al and P increased while those of Mg, Ca, and Zn decreased with increasing levels of Al. Growth decreased as Al, Al/Ca, and Al/Mg ratios in the extract increased. Growth was negatively related to tissue concentrations of Al, P, and Zn and positively related to tissue Mg and Ca. Growth was more closely correlated to elemental concentrations in the saturated paste extracts than in the SrCl₂ extracts (1 part 0.01M SrCl₂: 1 part moist soil).The research was supported by EPRI grant RD 2365-01 and by the University of Minesota College of Forestry and Minnesota Agricultural Experiment Station Project 074; listed as Minnesota Agricultural Experiment Station Scientific Series Paper.     

Callus growth and plant regeneration in diverse cultivars of cucumber (Cucumis sativus L.)

The growth and differentiation of callus tissues derived from cotyledons of ten cultivars ofCucumis sativus L. were investigated. Cotyledonary explants from all ten cultivars formed callus tissue on Murashige and Skoog (MS) medium supplemented with 0.5 M 2,4-dichlorophenoxyacetic acid and 5 M 6-benzylaminopurine. Fresh weight of the callus tissues averaged 1 to 8 g per flask after five weeks of culture. Shoot development was achieved in three cultivars, Hukchinju, Manchoonchoungjang and Seoul, on MS medium supplemented with 0.5 M -naphthaleneacetic acid and 5 M 6-benzylaminopurine. Reducing the 6-benzylaminopurine concentration to 0.01 M resulted in root formation on callus tissues and on shoots transferred to this medium. All cultivars gave the same response in tests of root formation, but shoot regeneration from callus culture of cucumber cotyledons was dependent on genotype with cultivar Manchoonchoungjang exhibiting the best shoot differentiation capability among the genotypes examined. Examination of mitotic metaphase from the regenerants revealed that all were tetraploid.     

An efficient adventitious shoot regeneration system for Zhanhua winter jujube (Zizyphus jujuba Mill.) using leaf explants

The direct induction of adventitious shoots from leaf explants obtained from adult plants of Zhanhua winter jujube, an elite variety of Zizyphus jujuba Mill., is reported. The percentage of leaf explants producing shoots and the average number of shoots per explant were significantly improved when 10-day-old leaves were explanted onto Woody Plant Medium and maintained initially in the dark. The plant growth regulator thidiazuron (TDZ) was effective in stimulating shoot regeneration from leaf explants of Zhanhua winter jujube. The highest efficiency of shoot formation was observed with a 20-day culture in the dark on WPM containing 4.54 M TDZ and 2.85 M indoleacetic acid (IAA). The regenerated shoots were transferred to MS medium containing 0.89 M benzyladenine and 5.77 M gibberellic acid for growth. When the shoots were about 2 cm in height, they were transferred to Nitsch medium supplemented with 1.14 M IAA and 2.46 M indolebutyric acid to induce rooting. This system of adventitious shoot production from leaf explants of adult plants could be useful for the genetic engineering and polyploidization of winter jujube.     

Differential response of six cowpea (Vigna unguiculata (L.) Walp) cultivars to liming in an ultisol

Summary The differential response of six cowpea (Vigna unguiculata (L.) Walp) cultivars to liming was assessed in a greenhouse trial using an Ultisol (Typic Paleudult) from southeastern Nigeria. Lime rates from 0 to 5.0 t/ha were applied to give a range of soil pH, determined in 11 soil/water from 4.25 to about 7.0. Without liming, relative dry matter yields of tops ranged between 46.6 and 76.8 percent. Significant yield responses to the first lime increment (0.5 t/ha) were observed particularly in the less tolerant cultivars and maximum yields were generally obtained with application of 1.6 to 2.5 t/ha lime.Among the six cultivars, TVu 4557 and Ife Brown were most tolerant, Vita-1 and Vita-3 were moderately tolerant, and TVu 1977-OD and TVu 4552 were least tolerant to soil acidity. The latter two cultivars were the most poorly nodulated when grown in the unlimed soil. The first lime increment enabled excellent nodulation to be achieved in all cultivars. Nitrogen analyses on tops confirmed the visual symptoms of nitrogen deficiency in two cultivars (Vita-1, TVu 1977-OD) grown in the unlimed soil. Analysis of data on chemical composition of plant tops and chemical soil characteristics gave indications that aluminium toxicity is the major growth limiting factor for cowpeas in this soil.This study, albeit with a limited range of cowpea germplasm clearly indicates that cowpea possesses considerable potential as a grain legume on strongly acid soils (pH<5.0), even in circumstances where lime is not available. Low rates of lime (0.5 t/ha or less) will greatly expand the available choice of cultivars.     

Proteomic analysis of salt stress and recovery in leaves of Vigna unguiculata cultivars differing in salt tolerance

Key message

Cowpea cultivars differing in salt tolerance reveal differences in protein profiles and adopt different strategies to overcome salt stress. Salt-tolerant cultivar shows induction of proteins related to photosynthesis and energy metabolism.

Abstract

Salinity is a major abiotic stress affecting plant cultivation and productivity. The objective of this study was to examine differential proteomic responses to salt stress in leaves of the cowpea cultivars Pitiúba (salt tolerant) and TVu 2331 (salt sensitive). Plants of both cultivars were subjected to salt stress (75 mM NaCl) followed by a recovery period of 5 days. Proteins extracted from leaves of both cultivars were analyzed by two-dimensional electrophoresis (2-DE) under salt stress and after recovery. In total, 22 proteins differentially regulated by both salt and recovery were identified by LC–ESI–MS/MS. Our current proteome data revealed that cowpea cultivars adopted different strategies to overcome salt stress. For the salt-tolerant cultivar (Pitiúba), increase in abundance of proteins involved in photosynthesis and energy metabolism, such as rubisco activase, ribulose-5-phosphate kinase (Ru5PK) (EC 2.7.1.19), glycine decarboxylase (EC 1.4.4.2) and oxygen-evolving enhancer (OEE) protein 2, was observed. However, these vital metabolic processes were more profoundly affected in salt-sensitive cultivar (TVu), as indicated by the down-regulation of OEE protein 1, Mn-stabilizing protein-II, carbonic anhydrase (EC 4.2.1.1) and Rubisco (EC 4.1.1.39), leading to energy reduction and a decline in plant growth. Other proteins differentially regulated in both cultivars corresponded to different physiological responses. Overall, our results provide information that could lead to a better understanding of the molecular basis of salt tolerance and sensitivity in cowpea plants.     

Micropropagation of four cultivars of Saskatoon berry (Amelanchier alnifolia NUTT.)

In vitro culture establishment, shoot proliferation, ex vitro rooting and dormancy breaking of the newly rooted plantlets were examined on Saskatoon berry (Amelanchier alnifolia NUTT.) cultivars Northline, Pembina, Smoky and Thiessen. Shoot-tip explants taken from actively growing plants were better for culture initiation than dormant buds. MS gave the most satisfactory results of the media formulations. Optimal shoot proliferation occurred at 8.8 and 13.3 M BA. Higher BA concentrations caused culture deterioration during long-term maintenance. Auxin treatments significantly stimulated ex vitro rooting of shoots in all cultivars. The best rooting was achieved with IAA/NAA (2.8/1.1 M) mixture. Satisfactory results were also obtained with commercial powder formulation, Rootone F, containing IBA/NAA mixture. Foliar application of BA and GA₄₊₇ was successful in breaking dormancy of newly rooted plantlets. Combinations of these two growth regulators caused formation of axillary shoots and vigorous plant growth. There were significant differences in the cultivar responses to culture conditions and treatments with growth regulators. The best culture establishment and the highest rate of shoot proliferation was observed in cv. Thiessen; the best rooting and the most vigorous post-dormancy growth was recorded in cv. Smoky. Cultivar Northland gave the most erratic responses.Abbreviations BA benzyladenine - cv(s) cultivar(s) - GA gibberellin - IAA indoleacetic acid - IBA indolebutyric acid - NAA naphthaleneacetic acid - MS Murashige & Skoog's medium     

Effects of external phosphorus supply on internal phosphorus concentration and the initiation,growth and exudation of cluster roots in Hakea prostrata R.Br.

The response of internal phosphorus concentration, cluster-root initiation, and growth and carboxylate exudation to different external P supplies was investigated in Hakea prostrata R.Br. using a split-root design. After removal of most of the taproot, equal amounts of laterals were allowed to grow in two separate pots fastened together at the top, so that the separate root halves could be exposed to different conditions. Plants were grown for 10 weeks in this system; one root half was supplied with 1 M P while the other halves were supplied with 0, 1, 25 or 75 M P. Higher concentrations of P supplied to one root half significantly increased the P concentration of those roots and in the shoots. The P concentrations in root halves supplied with 1 M P were invariably low, regardless of the P concentration supplied to the other root half. Cluster root initiation was completely suppressed on root halves supplied with 25 or 75 M P, whereas it continued on the other halves supplied with 1 M P indicating that cluster-root initiation was regulated by local root P concentration. Cluster-root growth (dry mass increment) on root halves supplied with 1 M P was significantly reduced when the other half was either deprived of P or supplied with 25 or 75 M P. Cluster-root growth was favoured by a low shoot P status at a root P supply that was adequate for increased growth of roots and shoots without increased tissue P concentrations. The differences in cluster-root growth on root halves with the same P supply suggest that decreased cluster-root growth was systemically regulated. Carboxylate-exudation rates from cluster roots on root halves supplied with 1 M P were the same, whether the other root half was supplied with 1, 25 or 75 M P, but were approximately 30 times faster when the other half was deprived of P. Estimates of root P-uptake rates suggest a rather limited capacity for down-regulating P uptake when phosphate was readily available.     

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.     

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.     

Plant regeneration from hairy-root cultures transformed by infection with<Emphasis Type="Italic"> Agrobacterium rhizogenes</Emphasis> in<Emphasis Type="Italic"> Catharanthus roseus</Emphasis>

Hypocotyl explants of Catharanthus roseus produced hairy roots when cultured on Murashige and Skoog (MS) basal medium after infection by Agrobacterium rhizogenes. Explants gave rise to adventitious shoots at a frequency of up to 80% when cultured on MS medium supplemented with 31.1 M 6-benzyladenine and 5.4 M -naphthaleneacetic acid. There was a significant difference in the frequency of adventitious shoot formation for each hairy-root line derived from a different cultivar. Plants derived from hairy roots exhibited prolific rooting and had shortened internodes. Approximately half of the plants had wrinkled leaves and an abundant root mass with extensive lateral branching, but otherwise appeared morphologically normal. Plants with hairy roots that were derived from the cultivar Cooler Apricot developed flowers with petals that were white in the proximal region, whereas the wild-type flower petals are red. PCR and Southern blot analyses revealed that plants derived from hairy roots retained the Ri TL-DNA.Abbreviations BA 6-Benzyladenine - MS Murashige and Skoog medium - NAA -Naphthaleneacetic acid - SH Schenk and Hildebrandt mediumCommunicated by I.S. Chung     

Feeding behaviour of Aphis craccivora (Koch) on cowpea cultivars with different levels of aphid resistance

The feeding activity of Aphis craccivora (Koch) was monitored on cowpea plants of aphid-susceptible (Vita 7) and aphid-resistant (TVu 801) cultivars, using an AC electronic feeding monitoring system. Waveforms corresponding to salivation, phloem ingestion and non-phloem ingestion were observed. Aphids probing on the resistant cultivar showed a significantly reduced ingestion of phloem sap compared with those aphids which fed on the susceptible cultivar. The insect also made more brief and repeated probes on TVu 801. In addition, the duration of non-probing activities and non-phloem ingestion was shorter on the susceptible than on the resistant cultivar.     

The extrafloral nectaries of cowpea (Vigna unguiculata (L.) Walp): I. Morphology,anatomy and fine structure

The cowpea bears two distinctive types of extrafloral nectaries. One, on the stipels of trifoliolate leaves, consists of a loosely demarcated abaxial area (1–2 mm diameter) of widely-spaced trichomes (papillae) borne on a stomata-free epidermis, and lacking a specific vascular supply. Each trichome has up to eight apical (head) cells, two to four intermediate cells, and a single large stalk cell. The secretory faces of the apical cells bear wall ingrowths and an easily detached cuticle. The wall separating the stalk cell and the underlying epidermal cell(s) has a mean plamodesmatal frequency of 25/m². The second type of nectary consists of a large elliptical mound of tissue (short and long axes about 2 mm and 4 mm) formed between a pair of flowers on an inflorescence stalk. It comprises four to eight cone-shaped subnits of secretory tissue, each with a circular secretory orifice and an individual supply of phloem, but not of xylem. Cells of the secretory tissue of the nectary subunits separate as they mature, and nectar flows to the orifice through the resulting intercellular spaces. Intact secretory cells and cellular debris are extruded into the nectar. Some of the sieve elements terminating in the inner secretory tissue exhibit open sieve pores. Each mature secretory cell contains many small (2 m diameter) spherical protein bodies and one to three large (up to 2–3 m diameter 15 m long), paracrystalline bodies. These inclusions are absent or not fully developed in inner, less mature regions of the secretory tissue. Mechanisms of secretion are proposed for the two classes of nectary, including estimates of flux of sugar into the trichomes of the stipel nectary.     

Thidiazuron Promotes <Emphasis Type="Italic">In Vitro</Emphasis> Plant Regeneration of <Emphasis Type="Italic">Arachis correntina</Emphasis> (<Emphasis Type="Italic">Leguminosae</Emphasis>) via Organogenesis

Arachis correntina (Burkart) Krapov. & W.C. Gregory is a herbaceous perennial leguminous plant growing in the Northeast of the Province Corrientes, Argentina. It is important as forage. The development of new A. correntina cultivars with improved traits could be facilitated through the application of biotechnological strategies. The purpose of this study was to investigate the plant regeneration potential of mature leaves of A. correntina in tissue culture. Buds were induced from both petiole and laminae on 0.7% agar-solidified medium containing 3% sucrose, salts and vitamins from Murashige and Skoog (MS) supplemented with 0.5–25 M thidiazuron (TDZ). Shoot induction was achieved by transference of calli with buds to MS supplemented with 5 M TDZ. Fifty-four percent of the regenerated shoot rooted on MS + 5 M naphthaleneacetic acid. Histological studies revealed that shoots regenerated via organogenesis.     

An alternative propagation method ofAnanas through nodule culture

A micropropagation scheme forAnanas comosus Merr. was developed using nodule culture. Nodules were induced from leaf-base or chopped shoot-base explants on modified half-strength MS medium supplemented with 2.69-5.37 M NAA and 4.44 M BA and could be maintained long-term as nodules. The nodules proliferated into more nodules when chopped into pieces of 1–3 mm and placed onto the same medium. They regenerated shoots when transferred to medium supplemented with 0.54–10.74 M NAA and 0.44–8.88 M BA. The regeneration capacity of nodules is higher than that of direct regeneration or callus. Maximum regeneration was obtained from culture medium containing 0.54 M NAA and 0.44 M BA, where shoots could be observed as early as within 2 weeks. Many shoots formed roots in the same medium in which they were regenerated after 10 subcultures, but the best rooting occurred in medium containing 0.54 M NAA and 0.44 M BA. Rooted plantlets ofA. comosus Merr. could be routinely produced at 6-week intervals.Abbreviations NAA naphthaleneacetic acid - BA 6-benzylaminopurine     

In vitro regeneration of Hagenia abyssinica (Bruce) J.F. Gmel. (Rosaceae) from leaf explants

A protocol for shoot regeneration of Hagenia abyssinica (Bruce) J.F. Gmel. has been developed using leaf explants originating from in vitro seedlings and mature material. The explants were cultured on Murashige and Skoog medium containing various concentrations of -naphthaleneacetic acid and thidiazuron (TDZ). Concentrations of TDZ lower than 1.0 M promoted direct shoot regeneration, but higher concentrations promoted callus induction. Around 96–100% regeneration was obtained between 1.0 and 10 M TDZ. The average number of shoots per explant at 1.0 M TDZ was 8.4±4.8. Among the different explants used, the highest percentage of regeneration and shoots per explant was obtained from complete leaf explants. A significant (P0.05) difference in regeneration capacity was observed among the five genotypes examined. The resulting shoots were multiplied on multiplication medium, rooted and acclimatised in a greenhouse.     

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.     

Effects of thidiazuron and N6-benzylaminopurine on shoot regeneration of Phalaenopsis

Adventitious bud formation from the vegetative buds of the flower stalks of Phalaenopsis occurred on Vacin and Went medium with 15% coconut water and 5 to 40 M thidiazuron (TDZ) or 40 M N⁶-benzylaminopurine. The highest efficiency of induction was achieved with 5 or 10 M TDZ. Adventitious buds developed into shoots on VWC medium. TDZ was more effective than BAP in stimulating the axillary buds of intact shoots to develop. Regenerated shoots rooted after about two months of culture on VWC medium with 1% sucrose. Shoot tips excised from the regenerated shoots initiated protocorm-like bodies after two months of culture on VWC medium.Abbreviations VWC medium Vacin and Went medium with 15% (by volume) coconut water - TDZ thidiazuron - BAP N⁶-benzylaminopurine - Plbs protocorm-like bodies     

Nodulation,nitrogen fixation,leaf area,and sugars content inLablab purpureus as affected by sulfur nutrition

Summary In order to explore interrelations between S nutrition, soluble sugars, leaf area, nodulation and N₂ fixation, greenhouse experiments were done with several levels of S added to perlite-sand cultures or to a moderately S-deficient soil. Sulfur had indirect effects on nodulation and N₂ fixation, possibly by improving sugars supply and N metabolism.In perlite-sand culture, leaf area increased with concentrations of supplied S up to 50 and 200 M for symbiotic and N-treated plants respectively, then decreased at higher concentrations. Plant yield and total sugars content (mg per plant) for the N-treated plants behaved similar to leaf area in response to added S but in the symbiotic plants maximum values were obtained at 100 M S. In soil, Mo had no effect on growth but interacted significantly with S in affecting total sugars content. High levels of S depressed sugars content at low Mo but raised it at high Mo.Sulfur increased the N content of soil-grown plants. It increased the N content of plants grown in perlite-sand culture except at very high levels of S. There was little effect on concentration of N in the shoots. Nitrogen content correlated significantly with leaf area and sugar content, and highly significantly with S concentration in the shoots.