Rhizobium sp. exopolysaccharide production,nodulation, and acetylene reduction activity (N2-fixation) in pigeon pea (Cajanus cajan L.)

Summary There was no correlation between the quantity of exopolysaccharide produced and acetylene reduction activity by Rhizobium spp. or by Bradyrhizobium spp. (Cajanus). The exopolysaccharide-defective mutants of Rhizobium sp. strain P 116 either failed to nodulate or showed a decrease in effectiveness. The deficiency in exopolysaccharide production was corrected by the addition of purified exopolysaccharide from the parent strain, or from Bradyrhizobium sp. strain P 149 or S24 isolated from pigeonpea (Cajanus cajan) and mungbean (Vigna radiata), respectively. However, the nodules so formed were not fully effective compared to those formed by the parent strain.     

Identification and Characterization of Slow Rusting Components in Pea (Pisum sativum L.)

Three hundred and forty five accessions of pea of diverse origin, height, leaf types and disease reaction were screened for rust disease severity and area under disease progress curve (AUDPC). The frequency of slow rusting types in the tall, dwarf, early and late groups appeared comparable. Of the 345 accessions, forty-four genotypes were evaluated for disease intensity, which was converted into AUDPC, number of pustules/leaf and pustule size. Wide range of variation was found for these traits. The slow rusting attribute of 16 genotypes was further confirmed by testing these under unprotected (inoculated) and protected (fungicidal spray) conditions for two successive years for disease intensity by assessing the AUDPC, seed yield/plot, and 100-seed weight. The fast rusting genotypes exhibited lower AUDPC, accompanied with increased seed yield and seed weight when grown under the protected condition, as compared to those raised under the unprotected condition. The genotypes Pant P 11, FC 1, HUDP 16, JPBB 3 and HUP 14 appeared as slow rusting genotypes.     

Soil physical and hydraulic properties in a rice-wheat cropping system in India: effects of rice-straw management

Abstract. The effects of rice-straw management (incorporation, burning or removal) on soil organic carbon content and physical and hydraulic properties were determined after five years of rice–wheat cropping in a sandy loam soil in northwest India. Soil organic carbon content was greater with straw incorporation and straw burning than with straw removal, and aggregation status, total porosity, pore-size distribution, bulk density, dispersion ratio and soil strength were correspondingly improved. The treatment effects were confined mainly to the 0–5 cm depth. Water retention was less with straw burning than straw removal, owing to increased water repellency of the soil surfaces. Cumulative infiltration and its rate after five hours were greater with straw incorporation than straw burning or removal. Air entry values were unaffected by straw management; however, the values were greater after rice harvest than after wheat harvest.     

Seasonal pattern of total soil respiration in undisturbed and disturbed ecosystems of Central Himalaya

Summary The rates of CO₂ efflux were measured by an alkali absorption method (using 20 ml 0.5 N NaOH) from soils in four undisturbed sites [two evergreen oak forests, Quercus floribunda Lindl. (tilonj oak), Quercus leucotrichophora A Camus (banj oak), and two evergreen conifer forests, Cedrus deodara Loud. (deodar forest) and Pinus roxburghii Sarg. (chir pine forest)] and three disturbed sites. The sites were located between elevations of 1850 and 2360 m in the Central Himalaya. The seasonal pattern of soil respiration was similar in all the sites with a maximum during the rainy season, intermediate rates during the summer season and the lowest level of activity in winter. The rate of CO₂ efflux was higher in broadleaf than in conifer forests, and it was lowest in the disturbed sites. Among the edaphic conditions, soil moisture, N, organic C, pH, soil porosity, and root biomass positively affected total soil respiration. The proportion of root respiration to total soil respiration was higher in the disturbed sites than the undisturbed sites in winter. Conditions in the winter season were less favourable for microbial respiration than for root respiration.     

Physiological and biochemical effects of salicylic acid on Pisum sativum exposed to isoproturon

In the present study, attenuation of isoproturon (IPU) toxicity by salicylic acid (SA) was observed. Seven-day-old seedlings of pea (Pisum sativum L. cv. Azad P-1) were treated with 10 mM IPU. IPU influenced physiological and biochemical parameters. IPU significantly inhibited growth variables like shoot and root height, fresh and dry biomass of the pea. The contents of carotenoids, chlorophylls, protein and activity of nitrate reductase were inhibited significantly. IPU enhanced the accumulation of H₂O₂, ion leakage and lipid peroxidation due to induction of oxidative stress in pea. The activities of antioxidant enzymes, namely superoxide dismutase, catalase and ascorbate peroxidase increased while the activities of guaiacol peroxidase decreased. However, exogenous SA regulated the toxic effects of IPU. The indices of oxidative stress appeared to be alleviated by SA. Pigment content and activities of enzymes increased approximately up to the level of control. IPU caused non-target phytotoxicity to P. sativum. The natural growth regulator/allelochemical has potential to overcome the adverse effects caused by IPU.

Abbreviations: CAT: catalase; EL: electrolyte leakage; IPU: isoproturon; LP: lipid peroxidation; MDA: malondialdehyde; NR: nitrate reductase; POD: guaiacol peroxidase; SOD: superoxide dismutase; TCA: trichloroacetic acid     

Sorption behavior of triazole fungicides in Indian soils and its correlation with soil properties

Adsorption-desorption of triazole fungicides, hexaconazole [2-(2,4-dichlorophenyl)-1-(1H-1,2,4,-triazol-1-yl) hexan-2-ol], triadimefon [1-(4-chlorophenoxy)-3,3-dimethyl-1-(1H-1,2,4-triazol-1-yl) butan-2-one], and penconazole[1-(2,4-dichloro-beta-propyl phenethyl)-1H-1,2,4-triazole] was studied in five Indian soils using batch method. The adsorption isotherms fitted very well to the Freundlich equation. Adsorption of various triazole fungicides increased in this order: triadimefon > hexaconazole > penconazole. The product of the Freundlich adsorption constants, K(f)(1/n), showed good correlation with the soil organic carbon (OC) content, suggesting that soil OC is the main controlling factor for triazoles adsorption. Clay and silt content of the soil also affected the adsorption constants. Adsorption of hexaconazole and triadimefon was nearly reversible in two low OC soils (soil 3, soil 5) where 90-100% of the sorbed fungicides was released in a single washing step. Otherwise, desorption of triazole fungicides showed hysteresis, and 30-60% of the triazole fungicides were retained by the soil after single washing. IR spectra showed that H-bonds and charge-transfer bonds between humic acid and fungicides probably operated as mechanisms of adsorption.     

Effects of soil-cation composition on reactions of four herbicides in a candler fine sand

Sorption, persistence and transport of herbicides in soils depend on the relative saturation of soils with cations from various soil amendments. Current research was conducted to study the effect of preequilibration of a Candler fine sand (Hyperthermic uncoated typic Quartzipsamments; 0–30 cm depth) with AlCl₃, CaCl₂, CuCl₂, FeCl₃, or KCl salt solutions on sorption in bromacil, simazine, norflurazon, and diuron herbicides commonly used in Florida citrus groves. Preequilibration of the soil with either FeCl₃, or AlCl₃ significantly decreased the sorption and therefore increased internal leaching potential, of all four herbicides as compared to their sorption in untreated soil. This decrease in sorption was much greater for bromacil and simazine (24 to 35%) than for norflurazon and diuron (7 to 8%). The desorption of bromacil and diuron in 1M NH₄OAc was also significantly lower in soils preequilibrated with FeCl₃ or AlCl₃ than the untreated soil. However, the reverse was true in the case of simazine and norflurazon. Preequilibration of the soil with CuCl₂, KCl, and CaCl₂ resulted in a significant decrease in sorption of norflurazon, diuron, and simazine but did not affect bromacil sorption. Accordingly, the species of adsorbed cation had varying effects on the sorption/desorption of each of the herbicides and varied their leaching potential.     

Effect of green manuring,blue-green algae and neem-cake-coated urea on wetland rice (Oryza sativa L.)

Summary A field trial was set up to examine the effect of green manuring, blue-green algae, and neem-cake-coated urea on a rice crop. Summer green manuring using Sesbania aculeata increased the crop yield. Inoculation of blue-green algae increased the rice grain yield when 60 kg N ha^-1 was applied as prilled urea, but the increase in grain yield was greater when 60 kg N ha^-1 was applied as neem-cake-coated urea. The results of the present study show that applications of green manure, neem-cake-coated urea, and blue-green algae are complementary and that the three treatments can be used together in the rice ecosystem. The green manure and the fertilizer treatments had no effect on the algal flora of the soil.     

Potential therapeutic applications of some antinutritional plant secondary metabolites

Plant-based formulations have been used since ancient times as remedial measures against various human and animal ailments. Over the past 20 years interest in traditional medicines has increased considerably in many parts of the world. Whereas modifications in lifestyles, including diet, have had a profound effect on the increased risks of various diseases, there is considerable scientific evidence, both epidemiological and experimental, regarding vegetables and fruits as key features of diets associated with reduced risks of diseases such as cancers and infections. This has led to the use of a number of phytometabolites as anticarcinogenic and cardioprotective agents, promoting a dramatic increase in their consumption as dietary supplements. There are changing perceptions regarding the therapeutic potential of various plant secondary metabolites (PSMs), some of which have also been known to possess certain antinutritional qualities. The knowledge gained at the cellular and molecular levels, and biological activities of PSMs including tannin-polyphenols, saponins, mimosine, flavonoids, terpenoids, and phytates, would be useful in planning for future epidemiological studies and human cancer prevention trials, especially when a large pure dosage is not the option to deliver the active compounds to many tissues. It is well observed that alteration of cell cycle regulatory gene expression is frequently found in tumor tissues or cancer cell lines, and studies have suggested that the herbal-based or plant-originated cell cycle regulators might represent a new set of potential targets for anticancer drugs. The recent upsurge of interest in this area of research and advances made therein indicate that the impact of a number of diseases affecting humans and animals may be lessened, if not prevented, by simple dietary intake of PSMs with putative therapeutic properties.