Comparative phytotoxicity of nitrapyrin and ATC to several leguminous species

Summary The relative toxicity of nitrapyrin 2-chloro-6-(trichloromethyl) pyridine and ATC (4-amino-1, 2, 4-triazole) on the growth of chick peas (Cicer arietinum L.) cow peas (Vigna sinensis L.), green beans (Phaseolus vulgaris L.), green peas (Pisum sativum L.) and mung beans (Phaseolus aureus Roxb.) and their effectiveness as nitrification inhibitor were studied under greenhouse conditions. ATC produced no toxicity symptoms in green peas, whereas resulted in leaf chlorosis in cow peas, chick peas and green beans. However, nitrapyrin toxicity appeared as leaf chlorosis in cow peas, and interveinal chlorosis in chick peas. Moreover, nitrapyrin-treated green beans and peas developed leaf curling and cupping. Although ATC had no significant effect on growth, a suppression in plant growth was associated with nitrapyrin application. Furthermore, green beans was the most resistant and chick peas the most sensitive to nitrapyrin. Nitrapyrin was more effective nitrification inhibitor than ACT, especially at the lower rates.     

绿豆幼苗生长状态对环境羟基自由基水平的影响

为了解植物生长状态对环境羟基自由基水平的影响,研究了相同培养条件下不同生长状态的绿豆(Vigna radiata)幼苗对空气中的羟基自由基水平的影响。结果表明,正常生长的绿豆幼苗周围环境羟基自由基水平显著高于没有植物生长的环境,失活幼苗对周围环境羟基自由水平没有显著影响;渗透胁迫的绿豆幼苗对环境羟基自由基水平影响极显著,渗透胁迫程度不同其影响程度也有所不同;绿豆幼苗对环境羟基自由基水平的影响与其呼吸速率密切相关。这证明绿豆幼苗生长对环境羟基自由基水平有影响,且这种影响依赖于其生理代谢过程及生长状态。     

Sensitivity of the common bean (Phaseolus vulgaris L.) symbiosis to high soil temperature

Summary Experiments were done to test whether N fixation is more sensitive to high soil temperatures in common bean than in cowpea or soybean. Greenhouse experiments compared nodulation, nitrogenase activity, growth and nitrogen accumulation of several host/strain combinations of common bean with the other grain legumes and with N-fertilization, at various root temperatures. Field experiments compared relative N-accumulation (in symbiotic relative to N-fertilized plants) of common bean with cowpea under different soil thermal regimes. N-fertilized beans were unaffected by the higher temperatures, but nitrogen accumulation by symbiotic beans was always more sensitive to high root temperatures (33°C, 33/28°C, 34/28°C compared with 28°C) than were cowpea and soybean symbiosis. Healthy bean nodules that had developed at low temperatures functioned normally in acetylene reduction tests done at 35°C. High temperatures caused little or no suppression of nodule number. However, bean nodules produced at high temperatures were small and had low specific activity. ForP. vulgaris some tolerance to high temperature was observed among rhizobium strains (e.g., CIAT 899 was tolerant) but not among host cultivars. Heat tolerance ofP. acutifolius andP. lunatus symbioses was similar to that of cowpea and soybean. In the field, high surface soil temperatures did not reduce N accumulation in symbiotic beans more than in cowpea, probably because of compensatory nodulation in the deeper and cooler parts of the soil.     

Nitrogen Nutrition and Xylem Transport of Nitrogen in Ureide-producing Grain Legumes

Xylem sap composition was examined in nodulated and nonnodulated cowpea (Vigna unguiculata [L.] Walp.) plants receiving a range of levels of NO₃ and in eight other ureide-forming legumes utilizing NO₃ or N₂ as sole source of nitrogen. A ¹⁵N dilution technique determined the proportions of plant nitrogen derived from N₂ in the nodulated cowpeas fed NO₃. Xylem sap composition of NO₃-fed, nodulated cowpea varied predictably with the relative extents to which N₂ and NO₃ were being utilized. The ratios of asparagine to glutamine (N/N) and of NO₃ to ureide (N/N) in xylem sap increased with increasing dependence on NO₃ whereas per cent of xylem nitrogen as ureide and the ratio of ureide plus glutamine to asparagine plus NO₃ (N/N) in xylem sap increased with increasing dependence on N₂ fixation. The amounts of NO₃ and ureides stored in leaflets, stems plus petioles, and roots of cowpea varied in a complex manner with level of NO₃ and the presence or absence of N₂ fixation. All species showed higher proportions of organic nitrogen as ureide and several-fold lower ratios of asparagine to glutamine in their xylem sap when relying on N₂ than when utilizing NO₃. In nodulated (minus nitrate) cowpea and mung bean (Vigna radiata [L.] Wilczek) the percentage of xylem nitrogen as ureide remained constant during growth but the ratio of asparagine to glutamine varied considerably. The biochemical significance of the above differences in xylem sap composition was discussed.     

Short-term responses of photosynthetic membrane lipids and photochemical efficiency in plants of <Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> and <Emphasis Type="Italic">Vigna unguiculata</Emphasis> submitted to high irradiance

Primary leaves of young plants of common bean (Phaseolus vulgaris cv. Carioca and Negro Huasteco) and cowpea (Vigna unguiculata Walp cv. Epace 10) were exposed to high irradiance (HI) of 2 000 μmol m⁻² s⁻¹ for 10, 20, and 30 min. The initial fluorescence (F₀) was nearly constant in response to HI in each genotype except for Carioca. A distinct reduction of maximum fluorescence (F_m) was clearly observed in stressed genotypes of beans after 20 min followed by a slight recovery for the longer stress times. In common bean, the maximum quantum yield (F_v/F_m) was reduced slowly from 10 to 30 min of HI. In cowpea, only a slight reduction of F_v/F_m was observed at 20 min followed by recovery to normal values at 30 min. HI resulted in changes in the photochemical (q_P) and non-photochemical (q_N) quenching in both species, but to a different extent. In cowpea plants, more efficiency in the use of the absorbed energy under photoinhibitory conditions was related to increase in q_P and decrease in q_N. In addition, lipid peroxidation changed significantly in common bean genotypes with an evident increase after 20 min of HI. Hence the photosynthetic apparatus of cowpea was more tolerant to HI than that of common bean and the integrity of cowpea cell membranes was apparently maintained under HI.     

Interaction between symbiosis and root pathogenesis in green gram (Vigna radiata L. Welczek)

Summary A pot experiment, using cowpea Rhizobium and one percent inoculum ofRhizoctonia botaticola (Taub.) Butler was carried out on green gram (Vigna radiata cv. PS 16) to study the interaction between symbiosis and root rot in terms of plant growth and nitrogen fixation. The microtomy of the infected roots showed distortion of the outer layers of root as a possible cause for antagonistic interaction of these two bio-processes.     

Chromosome Banding Patterns in Some Indian Pulses

By using the Giemsa C-banding technique, chromosome bandingpatterns on the somatic chromosomes of eight important pulsecrops, pea, lentil, guar (cluster bean), chick pea, pigeon pea,mung bean (green gram), urd (black gram) and cowpea have beenstudied. Each species has a characteristic C-banding pattern.The significance of such banding patterns which correlate withthe position of pachytene knobs, in chromosome identification,and in assigning relationships at the cytological level in thepulses of genus Vigna is stressed. Chromosome banding, Giemsa C-banding, pulse crops, Pisum sativum L., garden pea, Lens culinaris Medik, lentil, Cyamopsis tetragonoloba (L.) Taub., guar, Cicer arietinum L., chick pea, gram, Cajanus cajan (L.) Millsp., pigeon pea, Vigna radiata (L.) Wilczek, mung bean, Vigna mungo (L.) Hepper, urd, Vigna unguiculata (L.) Walp, cowpea     

Substrate-dependent auxin production by Rhizobium phaseoli improves the growth and yield of Vigna radiata L. under salt stress conditions

Rhizobium phaseoli strains were isolated from the mung bean nodules, and, the most salt tolerant and high auxin producing rhizobial isolate N20 was evaluated in the presence and absence of L-tryptophan (L-TRP) for improving growth and yield of mung bean under saline conditions in a pot experiment. Mung bean seeds were inoculated with peat-based inoculum and NP fertilizers were applied at 30-60 kg ha-1, respectively. Results revealed that imposition of salinity reduced the growth and yield of mung bean. On the contrary, separate application of L-TRP and rhizobium appeared to mitigate the adverse effects of salt stress. However, their combined application produced more pronounced effects and increased the plant height (28.2%), number of nodules plant-1 (71.4%), plant biomass (61.2%), grain yield (65.3%) and grain nitrogen concentration (22.4%) compared with untreated control. The growth promotion effect might be due to higher auxin production in the rhizosphere and improved mineral uptake that reduced adverse effects of salinity. The results imply that supplementing rhizobium inoculation with L-TRP could be a useful approach for improving growth and yield of mung bean under salt stressed conditions.     

How labile are the egg‐laying preferences of seed beetles?

Abstract.  1. Previous studies have produced conflicting results with respect to the genetic lability of host preference in the seed beetle Callosobruchus maculatus .
2. In this study, replicate lines of an Asian population were kept on an ancestral host (mung bean) or switched to a novel host (cowpea). After 40+ generations, lines were assayed for host preference (in choice tests) and host acceptance (under no-choice conditions), and were compared to African lines chronically associated with cowpea.
3. Host preference diverged in the expected direction. When presented a mixture of cowpeas and mung beans, females from the cowpea lines laid a greater fraction of their eggs on cowpea than did females from the mung bean lines. Preference for cowpea was nearly as strong in the cowpea lines as it was in the cowpea-adapted African lines.
4. In contrast, the experimental host shift did not affect long-term host acceptance. African females laid more eggs if given cowpeas than if given mung beans, but realised fecundities in the cowpea and mung bean lines were similar on the two hosts. Females from all lines laid more eggs if they were reared on cowpea than on mung bean, but rearing host had no effect on either relative host acceptance or host preference.
5. Comparisons with earlier studies suggest that the lability of host preference varies among beetle populations, which precludes generalisation at the species level. Because lines were maintained under no-choice conditions, modification of host preference probably occurred via a lower acceptance threshold for the novel host, without a concomitant change in the long-term acceptance of the ancestral host.     

Nodulation and symbiotic nitrogen fixation of cowpea (Vigna unguiculata (L.) Walp)

Summary Rhizobium strains CIAT 301, CIAT 79 and SLM 602 were tested and found effective in the nodulation and nitrogen fixation of cowpea cv. MI-35 (Vigna unguiculata (L.) Walp) plants in growth chamber experiments. Fresh weight of nodules increased with plant age initially and stabilized in 20–30 days from planting, followed by a secondary flush of nodule growth after 30 days. Apparent nitrogen fixation per gram nodule fresh weight reached a maximum in 20–30 days after planting and then decreased, even though a flush of new nodules was produced.     

Mung bean (<Emphasis Type="Italic">Vigna radiata</Emphasis>) cultivars mediated oviposition preference and development of <Emphasis Type="Italic">Callosobruchus chinensis</Emphasis> (Coleoptera: Chrysomelidae: Bruchinae)

The Azuki bean weevil, Callosobruchus chinensis (L.), is a destructive pest of stored mung bean [Vigna radiata (L.) Wilczek] as well as other leguminous seeds. The development of resistant seeds to manage this pest is of current great interest to plant breeders. In this study, we investigated the oviposition preference and development of C. chinensis on two susceptible mung bean cultivars (Seonhwa and Gyeongseon) and one previously reported resistant cultivar (Jangan), compared to the susceptible cowpea (Vigna unguiculata L.), cultivar (Yeonbun) using both multiple-choice and no-choice tests. In addition, the development of C. chinensis was also examined at four constant temperatures (20, 25, 30, and 35 °C). Both tests found cowpea to be the most suitable seed for oviposition. Total developmental time from oviposition to adult emergence ranged from 27.01 to 38.2 days, being shortest on cowpea and longest on the mung bean, cv. Jangan. However, no successful development of C. chinensis larvae on mung bean, cv. Jangan, occurred at any temperature. The highest rate of adult emergence and the longest adult longevity both occurred on cowpea and certain mung bean cultivars (Seonhwa and Gyeongseon), with the dramatic exception of cv. Jangan. These results suggest that the higher preference and performance of C. chinensis on cowpea (3.3 egg/seed) and least on mung bean, cv. Jangan (0.4 egg/seed). This information may facilitate the exploration of resistant genetic materials and chemicals associated with seeds for successful breeding. Further studies should examine the chemicals associated with mung bean cultivars and its resistant mechanism to develop a control method against bruchines.     

Alleviation of water stress effects in cowpea by Bradyrhizobium spp. inoculation

Experiments were carried out to investigate the effects of different degrees of water stress on cowpea in the presence and absence of Bradyrhizobium spp. inoculation and to evaluate physiological responses to stress. The soil used was Yellow Latosol, pH 6.3 and the crop used was cowpea (Vigna unguiculata (L.) Walp.) cv. ‘IPA 204’. Stress was applied continuously by the control of matric potential (ψ _m ) through a porous cup. The lowered soil ψ _m had a direct effect on the N2 fixation, but the strains Bradyrhizobium introduced by inoculation in the cowpea plants were superior to the indigenous strain demonstrating the importance of inoculation in the stressed plants. At the more negative ψ _m plants inoculated with the strains EI 6 formed associations of greater symbiotic efficiency which helped the cowpea plants to withstand drought stress better than the strain BR 2001 and the uninoculated control. The leghaemoglobin concentration was not inhibited in the drought-stressed plants at ψ _m -70 kPa when inoculated with the strain EI 6, which confered a differential degree of drought resistance in plants. The ψ _w declined in the stressed plants reaching values of -1.0 MPa which was sufficient to cause disturbance in nodulation and biomass production. This revised version was published online in June 2006 with corrections to the Cover Date.     

Antioxidative enzymatic protection in leaves of two contrasting cowpea cultivars under salinity

The aim of this work was to investigate the role of the antioxidant enzymes in salt tolerance comparing the salt-sensitive (Pérola) and a salt-tolerant (Pitiúba) cultivar of cowpea [Vigna unguiculata (L.) Walp.]. Salt stress (100 mM NaCl for 8 d) reduced the leaf growth rate more in the sensitive cultivar. The salt-induced decrease in the relative water content, Na⁺ accumulation and increase in leaf electrolyte leakage was similar in both cultivars. Salt stress induced a higher increase in the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX) and phenol peroxidase (POX) in the tolerant cultivar than in sensitive one.     

Rapid Evolution of Lifespan in a Novel Environment: Sex-Specific Responses and Underlying Genetic Architecture

Animal lifespans can vary substantially among closely related species and even among conspecific populations, but it is often difficult to identify environmental and genetic factors producing such variation. We used experimental evolution to examine how transfer to a novel environment affects adult lifespan and rates of senescence in a seed-feeding beetle. Three replicate lines of Callosobruchus maculatus (F.) were switched to a new host plant (cowpea), and each evolved shorter adult lifespans compared to a line maintained on the ancestral host (mung bean). However, the evolution of lifespan differed between the sexes; female lifespan was reduced by ~11% in all cowpea replicates, whereas male lifespan decreased by an average of only 5.6% and the magnitude of the reduction varied among replicates. Reduced lifespan in lines switched to cowpea mirrored the shorter lifespan observed in a separate population chronically associated with cowpea. We then performed crosses between the mung bean and cowpea lines to estimate the genetic architecture underlying the rapid evolution of a shorter lifespan on cowpea. Dominance (overdominance) contributed substantially to the difference between the cowpea and mung bean lines for female lifespan but not for male lifespan. However, details of the genetic architecture varied among the three replicate crosses, so that the convergent evolution of shorter female lifespan in the different cowpea lines did not arise from identical allelic substitutions. Our study demonstrates that insect lifespan can be predictably modified by a switch to a novel host plant, that both the magnitude of this response and its underlying genetic architecture can be sex-specific, and that convergent evolution of a complex trait such as lifespan can arise from different genetic mechanisms.     

Growth characteristics of mung beans and water convolvuluses exposed to 425‐MHz electromagnetic fields

Effects of high‐frequency, continuous wave (CW) electromagnetic fields on mung beans (Vigna radiata L.) and water convovuluses (Ipomoea aquatica Forssk.) were studied at different growth stages (pre‐sown seed and early seedling). Specifically, the effects of the electromagnetic source's power and duration (defined as power‐duration level) on the growth of the two species were studied. Mung beans and water convolvuluses were exposed to electromagnetic fields inside a specially designed chamber for optimum field absorption, and the responses of the seeds to a constant frequency at various power levels and durations of exposure were monitored. The frequency used in the experiments was 425 MHz, the field strengths were 1 mW, 100 mW, and 10 W, and the exposure durations were 1, 2, and 4 h. Results show that germination enhancement is optimum for the mung beans at 100 mW/1 h power‐duration level, while for water convolvuluses the optimum germination power‐duration level was 1 mW/2 h. When both seed types were exposed at the early sprouting phase with their respective optimum power‐duration levels for optimum seed growth, water convolvuluses showed growth enhancement while mung bean sprouts showed no effects. Water content analysis of the seeds suggests thermal effects only at higher field strength. Bioelectromagnetics 31:519–527, 2010. © 2010 Wiley‐Liss, Inc.     

耐盐碱细菌DQSA1的分离鉴定及盐碱胁迫下对绿豆的促生作用

【背景】近年来,大庆地区土壤盐碱化程度逐渐加剧,而微生物改良盐碱土是当今的研究热点。【目的】从大庆盐碱土中筛选出耐盐碱菌株,验证其促生作用,为改良大庆盐碱土壤提供微生物资源。【方法】采用筛选培养基从大庆盐碱土中获得耐盐碱促生菌,对其进行形态学观察、生理生化和16S rRNA基因鉴定,并测试菌株在盐碱胁迫下对绿豆植株和土壤细菌群落结构的影响。【结果】筛选得到一株耐盐碱促生菌DQSA1,具有固氮、产ACC脱氨酶、产铁载体、产吲哚乙酸(Indole-3-Acetic Acid,IAA)功能;通过生理生化鉴定和系统发育分析,判定该菌株为卓贝尔氏菌属(Zobellella)。在盐碱土中种植绿豆后接种菌株DQSA1,处理后的绿豆较对照相比根系鲜重、根系干重及叶绿素含量分别增加了33%、32%和79%;植株叶部可溶性糖、脯氨酸和可溶性蛋白含量分别升高了10%、80%和73%;根系的脯氨酸及可溶性蛋白含量分别增加了78%和44%。对种植绿豆的土壤细菌进行高通量测序,发现菌株DQSA1可以在盐碱环境下定殖并促进根瘤菌和鞘氨醇杆菌等有益菌的生长。【结论】菌株DQSA1可以在盐碱条件下调节土壤细菌群落结构并促进植物生长,为改良盐碱土地提供了有效的微生物资源。     

Effect of Phytohormone Pretreatment on Nitrogen Metabolism in Vigna radiata Under Salt Stress

Application of NaCl (electrical conductivity 4.0 mS cm^–1) resulted in about 52, 50 and 55 % reduction in total nitrogen contents in mung bean [Vigna radiata (L.) Wilczek] leaf, root and nodule, respectively. In nodule, nitrogenase activity was reduced by about 84 % under stress as compared with the control set. Glutamine synthetase activity was reduced by about 31, 16 and 23 %, glutamate oxoglutarate aminotransferase activity was reduced by 78, 57 and 42 % and glutamate dehydrogenase activity was reduced by 9, 8 and 42 % in leaf, root and nodule, respectively, under salt stress. The pretreatment with indole-3-acetic acid, gibberellic acid and kinetin, each ranging from 0.1 to 10 µM, in restoring the metabolic alterations imposed by NaCl salinity was investigated in mung bean. The three phytohormones used were able to overcome to variable extents the adverse effects of stress imposed by NaCl solution.     

Effects of NaCl and iso-osmotic PEG stress on growth,osmolytes accumulation and antioxidant defense in cultured sugarcane cells

In order to discriminate between the ionic and osmotic components of salt stress, sugarcane (Saccharum officinarum L. cv. Co 86032) calli were cultured on media containing NaCl or polyethylene glycol (PEG) 8000 that exerted the same osmotic pressure (−0.7 MPa). PEG stress exposure for 15 days led to significant growth reduction and loss in water content than salt stressed and control tissues. Osmotic adjustment (OA) was observed in callus tissues grown on salt, but was not evident in callus grown on PEG. Oxidative damage to membranes, estimated in terms of accumulation of thiobarbituric acid reactive substances-TBARS and electrolytic leakage was significantly higher in both the stressed calli than the control however, the extent of damage was more in the PEG stressed calli. The stressed callus tissues showed inhibition of ascorbate peroxidase activity, while catalase activity was increased. These results indicate sensitivity of cells to PEG-mediated stress than salt stress and differences in their OA to these two stress conditions. The sensitivity to the osmotic stress indicate that expression of the stress tolerance response requires the coordinated action of different tissues in a plant and hence was not expressed at the cellular level.     

Effects of salinity and gibberellin on water content,growth and mineral composition of cowpea,calabrese and red radish plants

Salinity had generally little influence on the water content of different parts of cowpea(Vigna sinensis L.), calabrese(Brassica oleracea L. var.botrylis) and red radish(Raphanus salivus L.) plants. Salinity showed a promotive effect on the growth of cowpea, while in calabrese the effect was either promotive or depressive depending upon the concentration of the NaCl, and in red radish plants salinity progressively suppressed growth. Total nitrogen, phosphorus, potassium and sodium contents of cowpea leaves were not affected by salinity treatments, while in calabrese and red radish leaves the contents of N, P and K were generally decreased as the salinity level increased. Gibberellin (GA₃) applied to salt-treated plants had either a stimulatory or inhibitory effect on the growth, water content and contents of N, P, K and Na in the leaves depending upon the plant type, the concentration of GA₃ and level of salinity.     

Nodulation studies in legumes

Summary The influence of combined nitrogen (as ammonium nitrate) on the symbiotic performances of selected bacterial associations of four legumes was examined using sand culture.In barrel medic (Medicago tribuloides Desr.) and vetch (Vicia sativa L. andV. atropurpurea Desf.) bacterial partnerships of a host plant varied greatly in their nodulation responses to a range of amounts of nitrogen applied at sowing. Some bacterial strains exhibited varying degrees of stimulation of nodule number, growth and fixation by low or medium amounts of nitrogen. Higher levels of combined nitrogen depressed symbiosis. Other strain responses showed a severe restriction of symbiosis with any amount of added nitrogen.Seasonal influences conditioned symbiotic responses to combined nitrogen in an association of cowpea (Vigna sinensis End.) With a summer sowing small amounts of ammonium nitrate added at sowing benefited later symbiotic development. No such stimulation was evident in an autumn sowing and symbiotic injury from high levels of nitrogen was greater than in the summer sowing.The developing association of cowpea was found to be most sensitive to ammonium nitrate added just as the first leaves unfolded. Here damage was manifest in a permanent elevation of the top: root ratio with subnormal growth and functioning of nodules. Greatest benefit from added inorganic nitrogen followed applications made as the first nodules appeared on the primary root. In this case added combined nitrogen acted as an investment providing returns in additional fixation equivalent to 5–10 times the amount of nitrogen originally fed to the seedling and representing some 50 per cent greater total fixation than in minus-nitrogen controls.