Changes in Antioxidative Protection in Bean Cotyledons During Natural and Continuous Irradiation-Accelerated Senescence

We employed continuous irradiation (CL) for induction of premature senescence caused by enhanced production of reactive oxygen species. As a model plant we used bean (Phaseolus vulgaris L. cv. Jantar) cotyledons because they have well defined and a quite short life span. Senescence of bean cotyledons induced by CL progressed more rapidly than natural senescence: the life span of CL cotyledons was 13 d compared to 16 d in controls (C). Chl content was significantly lower in 10- and 13-d-old CL plants than in C plants and the change with age was not statistically significant. Activities of all antioxidative enzymes declined either with senescence onset or during whole life span. Activity of antioxidative enzymes, except ascorbate peroxidase, was lower in CL plants compared to C plants. On the contrary, contents of non-enzymatic antioxidants -carotene and ascorbate were higher in CL plants than in C plants. No significant difference, except in the youngest cotyledons, was observed in glutathione content.     

Effect of NaCl and Proline on Bean Seedlings Cultured in vitro

Effects of NaCl (150 mM), proline (10 mM) and their combination on growth and contents of chlorophyll, proline and protein of bean (Phaseolus vulgaris cv. Kizilhaç) seedlings in vitro were investigated. NaCl decreased seedling growth. Proline added to control seedlings did not change seedling growth but decreased chlorophyll and increased protein contents. When proline added to NaCl-treated seedlings growth was increased in comparison with NaCl-treated only. Thus, proline alleviated salinity stress in bean seedlings.     

Interaction of Cytokinins and Abscisic Acid During Regulation of Stomatal Opening in Bean Leaves

Effects of benzyladenine (BA) and abscisic acid (ABA) applied separately or simultaneously on parameters of gas exchange of Phaseolus vulgaris L. leaves were studied. In the first two experimental sets) 100 M ABA and 10 M BA were applied to plants sufficiently supplied with water. Spraying of leaves with ABA decreased stomatal conductance (g _s) and in consequence transpiration rate (E) and net photosynthetic rate (P _N) already 1 h after application, but 24 h after application the effect almost disappeared. 10 M BA slightly decreased gas exchange parameters, but in simultaneous application with ABA reversed the effect of ABA. Immersion of roots into the same solutions markedly decreased gas exchange parameters and 24 h after ABA application the stomata were completely closed. The effect of ABA was ameliorated by simultaneous BA application, particularly after 1-h treatment. In the third experimental set, plants were pre-treated by immersing roots into water, 1 M BA, or 100 M ABA for 24 h and then the halves of split root system were dipped into different combinations of 1 M BA, 100 M ABA, and water. In plants pre-treated with ABA all gas exchange parameters were small and they did not differ in plants treated with H₂O+H₂O, H₂O+BA, or BA+BA. In plants pre-treated with BA or H₂O, markedly lower values of P _N were found when both halves of roots were immersed in ABA. Further, the effects of pre-treatment of plants with water, 1 M BA, 100 M ABA, or ABA+BA on the development of water stress induced by cessation of watering and on the recovery after rehydration were followed. ABA markedly decreased gas exchange parameters at the beginning of the experiment, but in its later phase the effect was compensated by delay in development of water stress. BA also delayed development of water stress and increased P _N in water-stressed leaves. BA reversed the effect of ABA at mild water stress. Positive effects of BA and ABA pre-treatments were observed also after rehydration.     

Effects of NaCl and Proline on Polyphenol Oxidase Activity in Bean Seedlings

In this work, the effects of NaCl (0, 50, 100, and 150 mM), proline (0, 5 and 10 mM) and NaCl + proline in combinations on activity of polyphenol oxidase (PPO; E.C. 1.10.3.1) and soluble protein content have been investigated in the root, stem and leaf tissues of bean (Phaseolus vulgaris L.) seedlings grown in embryo culture. PPO activities were higher in all the tissues treated with NaCl, proline and NaCl + proline combinations those that of the control tissues. The protein content was very high in tissues exposed to proline and NaCl + proline combination, but NaCl alone decreased protein contents in root and leaf tissues. The results suggest that proline may play a role as an enzyme-stabilizing agent in salt stress.     

Effect of Benzyladenine and Hydroxybenzyladenosine on Gas Exchange of Bean and Sugar Beet Leaves

Using bean seedlings, the effects of benzyladenine (BA) on stomatal conductance (g_s), transpiration rate (E), and net photosynthetic rate (P_N) were examined in order to find out dose and time responses. In bean seedlings, BA appli roots in concentrations of 1, 5, 10, and 20 µM increased g_s and P_N of leaves already 1 h after application. E was not markedly affected and water use efficiency (WUE) was increased. However, the effects were mostly transient and after 24 h P_N only at 1 and 5 µM BA was increased, and other parameters were not affected or even decreased. In sugar beet seedlings, the effects of hydroxybenzyladenosine (HBA) in addition to those of BA on the same parameters were determined. The both cytokinins were applied in 1, 5, 10, and 20 µM concentrations either to roots or sprayed on leaves However, the effects were inconsistent and the positive effect was observed only after 24 h on P_N in plants with roots immersed in 5 and 10 µM BA, or 10 µM HBA, and on E in plants sprayed with 5 µM BA or 10 µM HBA. Thus the stimulation of gas exchange by exogenously applied cytokinins is rather exceptional than general.     

Bean lectins IV: genetic variation in the non-denatured structure of lectins from different Phaseolus vulgaris L. cultivars

Summary Variation in the native conformation of bean lectins was examined using electrophoresis of non-denatured total protein extracts and purified albumin and globulin lectin. The observed variation was related to the genetic variation reported previously for lectin polypeptide composition as revealed by two-dimensional isoelectricfocusing-sodium dodecyl sulfate polyacrylamide gel electrophoresis (IEF-SDS/PAGE). When eleven cultivars with different IEF-SDS/PAGE lectin polypeptide compositions were compared, eight had unique non-denatured lectin patterns and three had identical patterns. For some cultivars differences in non-denatured lectin patterns were observed between the purified albumin and globulin lectin preparations.     

Influence of Drought,High Temperature,and Carbamide Cytokinin 4-PU-30 on Photosynthetic Activity of Bean Plants. 1. Changes in Chlorophyll Fluorescence Quenching

Fifteen-day-old bean plants (Phaseolus vulgaris L.) grown in a climatic chamber were exposed to water deficit (WD) and high temperature (HT) stresses applied separately or in combination. Changes in chlorophyll fluorescence quenching were investigated. Bean plants that endured mild (42 °C, 5 h for 2 d) WD separately or in combination with HT did not change their q_P and q_N quenching (measured at 25 °C) compared with those of the control. After 5 min testing at 45 °C, q_P in control and droughted plants strongly decreased, while q_P of plants that experienced combined WD+HT stress was insignificantly influenced, suggesting the acclimation effect of HT treatments. At more severe stresses (after 3 d-treatment), q_P measured at 25 °C was the lowest in WD+HT plants and q_N values were the highest. But when measured at 45 °C, q_P of WD+HT plants had practically the same values as at 25 °C. Under these conditions q_P of WD plants also showed an adaptation to HT. Twenty-four hours after recovery, the unfavourable effects of the stresses were strongly reduced when measured at 25 °C, but they were still present when measured at 45 °C. Positive effect of the carbamide cytokinin 4-PU-30 was well expressed only in droughted plants. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effect of Benzylaminopurine on Rehydration of Bean Plants after Water Stress

The possibility of improving the recovery of plant photosynthesis after water stress by cytokinin-induced stimulation of stomatal opening or delay of leaf senescence was tested. The 6-benzylaminopurine (BAP) in concentrations 1 and 10 M was applied to the substrate (sand + nutrient solution) or sprayed on primary leaves of 14-d-old Phaseolus vulgaris L. plants sufficiently supplied with water or water-stressed for 4 d. The later ones having relative water content decreased to 69 % were fully rehydrated during the following three days. Parameters of photosynthesis and water relations were measured in primary leaves of 7-, 10-, 14-, and 17-d-old plants. Application of 1 M BAP slightly delayed leaf senescence: in 17-d-old control plants, net photosynthetic rate (P_N) and chlorophyll (Chl) content, and when sprayed on leaves also some of Chl a fluorescence kinetic parameters of BAP-treated leaves were slightly higher than those of untreated leaves. Both types of application of 1 M BAP slightly improved recovery of plants during rehydration after water stress in terms of increased g_ad, g_ab and P_N, i.e., parameters which were markedly decreased by mild water stress. However, contents of Chl a, Chl b and carotenoids and parameters of Chl a fluorescence kinetic were not markedly affected by mild water stress and after rehydration were not stimulated by 1 M BAP. 10 M BAP had mostly negative effects on the parameters measured.     

Comparison of resistance to drought of three bean cultivars

The aim of the present work was to evaluate oxidative stress and plant antioxidant system of three contrasting bean (Phaseolus vulgaris L.) genotypes in the response to drought. Drought was imposed 14 d after emergence, by withholding water, until leaf relative water content reached 65 %. Water stress increased lipid peroxidation (LPO), membrane injury index, H₂O₂ and OH^⋅ production in leaves of stressed plants. Activities of the antioxidative enzymes superoxide dismutase (SOD) and ascorbate peroxidase (APOX) increased significantly under water stress in all the studied cultivars, while catalase (CAT) increased in cvs. Plovdiv 10 and Prelom, but decreased in cv. Dobrudjanski ran. Furthermore cv. Plovdiv 10 which had the highest APOX and CAT activities also showed the lowest increase in H₂O₂ and OH^⋅ production and LPO while cv. Dobrudjanski ran showed the lowest increases (and often the lowest values) in the antioxidant enzyme activities and the highest increases of H₂O₂ and OH^⋅ production, and LPO. On the basis of the data obtained we could specify cv. Plovdiv 10 and cv. Prelom as drought tolerant and cv. Dobrudjanski ran as a drought sensitive.     

Proline metabolism in response to nitrogen deficiency in French Bean plants (Phaseolus vulgaris L. cv Strike)

The objective of the present work was to determine the impact ofnitrogen deficiency on proline metabolism in French Bean plants(Phaseolus vulgaris L. cv. Strike). The nitrogen wasapplied to the nutrient solution in the form of NH₄NO₃ at1.45 mM (N1), 2.90mM (N2) and 5.80mM (N3, optimal level). Our results indicateNdeficiency is characterised by a decline in proline accumulation both in theroot and leaves, fundamentally because proline degradation is encouraged by thestimulation of the enzyme proline dehydrogenase. By contrast, under conditionsof adequate N (N3), proline levels rise due to the action of ornithine,suggesting predominance of the ornithine pathway over the glutamine pathway, inaddition to the inhibition of proline dehydrogenase activity.     

Changes Induced by Low Oxygen Concentration in Photosynthetic and Respiratory CO2 Exchange in Phosphate-Deficient Bean Leaves

Effect of phosphorus deficiency on photosynthetic and respiratory CO₂ exchanges were analysed in primary leaves of 2-week-old bean (Phaseolus vulgaris L. cv. Golden Saxa) plants under non-photorespiratory (2 % O₂) and photorespiratory (21 % O₂) conditions. Low P decreased maximum net photosynthetic rate (P_Nmax) and increased the time necessary to reach it. In the leaves of P-deficient plants the relative decrease of P_Nmax at 2 % O₂ was larger than at 21 % O₂. The results suggested the influence of photorespiration in the cellular turnover of phosphates.     

Effects of Brassmosteroids on Growth, Nodulation, Phytohormone Content and Nitrogenase Activity in French Bean Under Water Stress

Effect of pre-treatments of 1 and 5 M epibrassinolide or homobrassinolide prior to water stress induction on changes in root nodulation and contents of endogenous abscisic acid (ABA) and cytokinin trans-zeatin riboside (ZR), and nitrogenase activity was investigated in the nodulated roots of Phaseolus vulgaris L. cv. Arka Suvidha. Brassinosteroids in the unstressed plants increased root nodulation, ZR content and nitrogenase activity, and also ameliorated their stress-induced decline in the nodulated roots. The ABA contents in the nodules of control or stressed plants were not altered by brassinosteroids treatment. There was an increase in pod yield by brassinosteroids treatment (5 M) in the irrigated control as well as stressed plants without influencing pod number or pod length. Among the brassinosteroids, epibrassinolide was relatively more effective.     

Role of bean lectins inRhizobium phaseoli-Phaseolus vulgaris interactions. Some properties of lectins from two bean cultivars

Lectins from twoPhaseolus vulgaris L. cultivars were isolated and purified by salt fractionation, affinity chromatography and gel permeation chromatography. The cultivars used were: alubia, with a low-nodulating ability, and Bat 76 with a good symbiotic aptitude. Differences in properties of the two lectins were noted: alubia lectin gave only one peak with haemagglutinating activity following gel permeation chromatography while Bat 76 yielded two active peaks, although both lectins had several bands of about 30 kDa following gel electrophoresis, Bat 76 lecting had three bands of about 50 kDa which were not present in alubia and red kidney bean lectins. Peptide-mapping, by limited proteolysis and two dimensional gel electrophoresis, also showed differences between the lectins which are therefore judged to be different.     

Ferredoxin and ferredoxin-NADP-oxidoreductase in leaves ofPhaseolus vulgaris L.

During light-induced greening of 10-dayold etiolated bean seedlings a strong increase is observed of ferredoxin (Fd) and of ferredoxin-NADP-oxidoreductase (FNR; E.C. 1.6.99.4) activity, both known to reside in chloroplasts. The production of Fd starts immediately upon illumination and proceeds almost linearly for at least the next 72 h. It is inhibited by chloramphenicol (CAP) but not by cycloheximide (CHI), beit that in the presence of the latter Fd synthesis was impaired after 48 h of illumination. We conclude that for the elaboration of functional Fd in greening chloroplasts protein synthesis on chloroplast ribosomes is required. The increase of FNR activity shows a lag of about 24 h and is blocked by both CAP and CHI. When CAP is applied at 24 h after the illumination started it has no effect. We suggest that the synthesis of FNR on cytoplasmic ribosomes requires prior synthesis of protein(s) on chloroplast ribosomes.The nature of possible interactions between chloroplasts and cytoplasm is discussed.Abbreviations CAP D-threo-chloramphenicol - CHI cycloheximide - DCIP dichlorophenol-indophenol - DEAE diethylaminoethyl - Fd Ferredoxin - FNR ferredoxin-NADP-oxidoreductase - NAR nitrate reductase - NIR nitrite reductase     

Interaction of Uromyces phaseoli and Meloidogyne incognita on Bean

Uromyces phaseoli, the causal agent of bean rust, suppressed shoot and root growth of three bean cultivars, reducing root weight more than shoot weight. The greatest suppression of root weight was on the cultivar that appeared most susceptible by visual ratings of shoot symptoms. Meloidogyne incognita suppressed shoot and root growth of all test cultivars; root weight reductions differed among cultivars identical in susceptibility to this pathogen in root-gall rating tests. Infection of plants with both pathogens suppressed plant weights significantly more than did infection by either pathogen alone, evidencing an additive effect. U. phaseoli and M. incognita on the same plant influenced the reproduction of one another, presumably through effects on the host. Fungal uredia were reduced in size and sporulation capacity; M. incognita produced fewer root galls, and fewer eggs per egg mass.     

Responses of Ribulose-1,5-Bisphosphate Carboxylase,Protein Content,and Stomatal Conductance to Water Deficit in Maize,Tomato, and Bean

We compared responses of maize, tomato, and bean plants to water stress. Maize reached a severe water deficit (leaf water potential –1.90 MPa) in a longer period of time as compared with tomato and bean plants. Maize stomatal conductance (g _s) decreased at mild water deficit. g _s of tomato and bean decreased gradually and did not reach values as low as in maize. The protein content was maintained in maize and decreased at low water potential (_w); in tomato it fluctuated and also decreased at low _w; in bean it gradually decreased. Ribulose-1,5-bisphosphate carboxylase/oxygenase activity remained high at mild and moderate stress in maize and tomato plants; in bean it remained high only at mild stress.     

Resistance Gene Analog Polymorphism (RGAP) Markers Co-Localize with Disease Resistance Genes and QTL in Common Bean

Resistance (R) genes containing nucleotide-binding site (NBS)-leucine rich repeats (LRR) are the most prevalent types of R gene in plants. The objective of this study was to develop PCR-based R-gene analog polymorphism (RGAP) markers for common bean (Phaseolus vulgaris L). Twenty degenerate primers were designed from the conserved kinase-1a (GVGKTT) and hydrophobic domains (GLPLAL) of known NBS-LRR type R-genes and from EST databases. Sixty-six of the 100 primer combinations tested yielded polymorphism. Thirty-two RGAP markers were mapped in the BAT 93/Jalo EEP558 core mapping population for common bean. The markers mapped to 10 of 11 linkage groups with a strong tendency for clustering. In addition, the RGAP markers co-located, on six linkage groups, with 15 resistance gene analogs (RGAs) that were previously mapped in other populations of common bean. The distance between the priming sites in NBS-LRR type R-genes is around 500 bp. Of the 32 RGAP markers, 19 had sizes larger and 13 less than 500 bp. RGAP markers mapped close to known R-genes on B11, and to QTLs for resistance on B1, B2, B6, B7, B8, B10, and B11. RGAP appears to provide a useful marker technique for tagging and mapping R-genes in segregating common bean populations, discovery of candidate genes underlying resistance QTL, and future cloning of R-genes in common bean.     

Five primary trisomics from translocation heterozygote progenies in common bean,Phaseolus vulgaris L.

Summary Twelve distinct phenotypic groups of plants were isolated from nondisjunction progenies of 11 translocation heterozygote stocks. All the plants in these phenotypic groups originated in the light weight seed class. Five of the 12 phenotypic groups of plants have been verified as primary trisomics. They are all phenotypically distinguishable from each other and from disomics. One of the five primary trisomic groups, puckered leaf, was directly recovered as a primary trisomic from the original translocation heterozygote progenies. Three of the five trisomics — weak stem, dark green leaf, and convex leaf — originated first as tertiary trisomics. The related primary trisomics were isolated later from progenies of selfed tertiary trisomics. The fifth group, chlorotic leaf, originated at a low frequency among the progenies of three other trisomics: puckered leaf, convex leaf, and dark green leaf. The chlorotic leaf did not set seed under field conditions. The remaining four groups — puckered leaf, dark green leaf, convex leaf, and weak stem — are fertile, though sensitive to high temperature conditions. The transmission rate of the extra chromosome on selfing ranges from 28% to 41%. Physical identification of the extra chromosome has not been achieved for any of the five trisomic groups. Two trisomic groups, dark green leaf and convex leaf, have produced tetrasomics at low frequency. The phenotypes of these two tetrasomics are similar to the corresponding trisomics but more exaggerated.Fla. Agr. Expt. Stn. Journal Series No. 7137     

Molecular composition and surface properties of storage lipid particles in wax bean (Phaseolus vulgaris)

Lipid particles have been isolated from seeds of wax bean (Phaseolus vulgaris), a species in which starch and protein rather than lipid are the major seed storage reserves. These lipid particles resemble oil bodies present in oil-rich seeds in that > 90% of their lipid is triacylglycerol. Moreover, this triacylglycerol is rapidly metabolized during seed germination indicating that it is a storage reserve. The phospholipid surfaces of oil bodies are known to be completely coated with oleosin which prevents their coalescence, particularly during desiccation of the developing seed. This would appear to be necessary since lipid is the major storage reserve in oil seeds, and there are very few alternate types of storage particles in the cytoplasm of oil seed endosperm to provide a buffer against coalescence of oil bodies by isolating them from one another. The present study indicates that the surfaces of lipid particles from wax bean are not completely coated with oleosin and feature regions of naked phospholipid. This finding has been interpreted as reflecting the fact that lipid particles in wax been seeds are less prone to coalescence than oil bodies of oil-rich seeds. This arises because the individual lipid particles are interspersed in situ among highly abundant protein bodies and starch grains and hence less likely to come in contact with one another, even during desiccation of the developing seed.     

Effect of Cytokinins and Cytokinin Antagonists on in vitro Cultured Gypsophila paniculata L.

This study deals with the effects of two cytokinins [kinetin (Kin) and N-(2-chloro-4-pyridyl)-N-phenylurea (CPPU)] and cytokinin antagonists [2-chloro-4-cyclobutyl-amino-6-ethylamino-1,3,5-triazine (ACK1) and N-(4-pyridyl)-O-(4-chlorophenyl)carbamate (ACK2)] in concentration of 1 μM on in vitro cultured Gypsophila. The application of Kin and CPPU stimulated bud opening and increased fresh and dry masses. Cytokinin antagonists reduced the number of sprouted buds and bud fresh and dry masses. In plants treated with CPPU the chloroplasts possessed well developed membrane system, which covered almost the entire chloroplasts volume. In ACK2 treated plants, the plastid apparatus in each cell was represented by two types of chloroplast in which the inner membrane system was differently organized. Cell wall adjacent chloroplasts possessed structure similar to the controls. In inner located chloroplasts part of thylakoids were semi-concentrically arranged and partially destructed. This revised version was published online in July 2006 with corrections to the Cover Date.