Autochthonous halotolerant plant growth-promoting rhizobacteria promote bacoside A yield of Bacopa monnieri (L.) Nash and phytoextraction of salt-affected soil

Phytoremediation is a promising approach for reclamation of salt-affected soil. Phytoextraction is the most commonly used process, which exploits plants to absorb, immobilize, and accumulate salt in their shoots. In this study, halotolerant plant growth-promoting rhizobacteria (PGPR) were isolated from the rhizosphere of wild grasses growing naturally in salt-affected areas of Lucknow, Uttar Pradesh (India) and were tested for their efficacies of salt-tolerance and plant growth-promoting (PGP) abilities. Based on 16S rRNA sequences, the most efficient halotolerant isolates possessing PGP traits were identified as Pseudomonas plecoglossicida (KM233646), Acinetobacter calcoaceticus (KM233647), Bacillus flexus (KM233648), and Bacillus safensis (KM233652). Application of these isolates as bio-inoculants significantly (P < 0.05) increased the growth and bacoside A yield of a medicinal plant, Bacopa monnieri (L.) Nash, grown on natural salt-affected soil. The phytoremediation of salt-affected soil was evident by the substantial increase in shoot Na⁺:K⁺ ratio of bio-inoculant-treated plants. When compared to un-inoculated control plants, the soil physico-chemical properties of bio-inoculant-treated plants were improved. The shoot and root biomass (fresh and dry weights), soil enzymes, and soil nutrient parameters showed significant positive correlations with the shoot Na⁺:K⁺ ratio. Consequently, the halotolerant PGPR screened in this study could be useful for the reclamation of saline soils concomitant with improved plant growth and bacoside A yield.     

The effect of soil pH and high urea concentrations on urease activity in soil

The rate of hydrolysis of urea in soil over the wide range of concentrations, up to 10 moles N per dm³ soil solution, found in fertilizer practice, was examined in Begbroke sandy loam adjusted to different pH values. On rewetting air-dry soil, urease activity increased rapidly, reached a maximum within the first 24 h and then decreased slowly to level off after about 4 days. Pretreatment of the soil with urea or ammonium had no effect on the urease activity. Urease activity increased with substrate concentration, reached an optimum value and then decreased with rising urea concentration. The results could be explained by substrate inhibition at higher urea concentrations, and the data are well described by a modified Michaelis-Menten equation involving three parameters, V_max, K_m and K_i where K_i is an inhibition constant. K_m decreased linearily with rise in pH whereas K_i increased slightly between pH 4.9 and 7.0 and steeply between 7.0 and 8.4. V_max increased with rise in pH, reached a maximum value at pH 6.0 and then declined at higher pHs. There was a further reaction, reaching a maximum rate at a urea concentration of about 0.2 molar N in the soil solution, that followed Michaelis-Menten kinetics. K_m for this high affinity reaction increased up to pH 7.2 and then decreased at higher pH values; V_max increased up to pH 6.8 and then decreased. The contribution of the high affinity reaction was small except at low concentrations of urea.     

THERMODYNAMICS OF THE EXCHANGE OF NICOTINE ON ALUMINIUM-MONTMORILLONITE

The ion exchange equilibria involving the interaction of nicotine with Almontmorillonite was studied thermodynamically. The exchange isotherms at 30° and 60°C indicated a preference for Al ions by montmorillonite as compared with nicotinium ions. A separation factor supported the conclusion. The enthalpy gain indicated tighter binding of Al. The entropy gain indicated a diffused and disordered arrangement of nicotinium ions in the Goüy layer with Al forming a more ordered arrangement in the Stern layer.     

Benefit-cost analysis of raising Pinus wallichiana seedlings in different capacities/sizes of root trainers in the nursery

Modern nursery methods of seedling production in different sized root trainers,were compared by raising seedlings of Pinus wallichiana involving costs incurred and benefits received. In order to provide a common basis for the comparisons,the study involved the raising of 1000 seedlings annually on a continuous basis for seven years. A relative economic analysis of raising P. wallichiana seedlings in 300,150 and 100 cm3 root trainers was carried out and we estimated that the root trainers of 300 cm3 capacity...     

Phytosequestration of Carbon in Miscanthus × giganteus and Pinus sylvestris L. in Degraded Zinc Smelter and Post-Mining Soils

正Dear Editor,Pinus sylvestris L.is one of the most popular and predominant tree species in Central Europe and Scandinavia.Its cultivation depends on atmospheric conditions,soil fertility,use of fertilizers,and individual characteristics of the trees.Pinus sylvestris L.wood,roots,and needles are used for energy production.Pi-     

Effects of Green Manures and Zinc Fertilizer Sources on DTPA-Extractable Zinc in Soil and Zinc Content in Basmati Rice Plants at Different Growth Stages

Rice is very sensitive to low zinc(Zn) supply in submerged paddy soils and Zn deficiency is one of the major limiting factors in determining rice production in India. A field experiment was conducted during the summer-rainy seasons of 2009 and 2010 at the research farm of the Indian Agricultural Research Institute, New Delhi, to determine the effects of summer green manure crops and Zn fertilizers on diethylenetriaminepentaacetic acid(DTPA)-extractable(available) Zn concentration in soil and total Zn content in Basmati rice cultivar Pusa Basmati 1 at periodic intervals. Summer green manure crops included Sesbania aculeata(Dhaincha),Crotalaria juncea(Sunhemp), and Vigna unguiculata(Cowpea) and the Zn fertilizers used were ethylenediaminetetraacetic acid(EDTA)-chelated Zn, ZnSO_4·7H_2O, ZnSO_4·H_2O, ZnO, and ZnSO_4·7H_2O + ZnO. Beneficial effects of summer green manure crops and Zn fertilizers on DTPA-extractable Zn concentration in soil and total Zn content in dry matter of Basmati rice at periodic intervals were observed, with significant increases in all the determined parameters, in comparison with those in the control(no Zn application or summer fallow). The rate of increase varied among summer green manure crops and Zn fertilizers during both years. Among the summer green manures, incorporation of S. aculeata led to a significant increase in mean Zn content in Basmati rice grain and straw when compared with C. juncea, V. unguiculata, and summer fallow treatments. Among the Zn fertilizers, significant increases in Zn content in Basmati rice dry matter and DTPA-extractable Zn concentration in soil during various growth stages of the plant were recorded with EDTA-chelated Zn application, followed by the application of ZnSO_4·7H_2O, ZnSO_4·H_2O, ZnSO_4·7H_2O + ZnO, ZnO,and no Zn. The highest mean Zn content in Basmati rice grain and straw was recorded with EDTA-chelated Zn application in 2009 and 2010, respectively. The application of ZnSO_4·7H_2O was the second best treatment after EDTA-chelated Zn; however, it was statistically inferior to EDTA-chelated Zn. The lowest values were recorded with the control(no Zn application) during both years of study. The amount of Zn concentration in soil was found to be significantly positively correlated with the Zn content in Basmati rice dry matter during both years. Significantly higher levels of residual fertility in soil after the harvest of Basmati rice were observed with application of EDTA-chelated Zn and incorporation of S. aculeata when compared with those of other Zn sources and summer green manures.     

Progress in breeding for resistance to Ug99 and other races of the stem rust fungus in CIMMYT wheat germplasm

Races belonging to the Ug99 (TTKSK) lineage of the wheat stem rust fungus, carrying complex virulence combinations, and their migration to countries in Africa, Middle East and Asia continue to pose a significant threat to global wheat production. The rapid spread of additional races, e.g., TKTTF or the Digalu lineage, in several countries causing localized epidemics reminds us of the vulnerability of wheat germplasm to stem rust disease, a formidable foe referenced as early as biblical times. A global rust monitoring system reflecting increased surveillance efforts has identified 13 races within the Ug99 lineage in 13 countries and unrelated lineages are emerging, spreading and posing serious threats to wheat production. Race TKTTF has caused localized epidemics in Ethiopia and its variants have been recently implicated in stem rust outbreaks in Europe. Concerted research efforts have resulted in the identification of several new resistance genes and gene combinations for use in breeding. Combining multiple adult plant resistance (APR) genes in high-yielding backgrounds and discovery of new quantitative trait loci conferring stem rust resistance has progressed in the recent years, enhancing the durability of resistance. Effective gene stewardship and new generation breeding materials and cultivars that combine multiple race-specific or minor to intermediate effect APR genes, complemented by active surveillance and monitoring, have helped to limit major epidemics and increase grain yield potential in key target environments.     

Soil Carbon Dynamics Under Changing Climate——A Research Transition from Absolute to Relative Roles of Inorganic Nitrogen Pools and Associated Microbial Processes: A Review

It is globally accepted that soil carbon (C) dynamics are at the core of interlinked environmental problems,deteriorating soil quality and changing climate.Its management remains a complex enigma for the scientific community due to its intricate relationship with soil nitrogen (N) availability and moisture-temperature interactions.This article reviews the management aspects of soil C dynamics in light of recent advances,particularly in relation to the availability of inorganic N pools and associated microbial processes under changing climate.Globally,drastic alterations in soil C dynamics under changing land use and management practices have been primarily attributed to the variation in soil N availability,resulting in a higher decomposition rate and a considerable decline in soil organic C (SOC) levels due to increased soil CO2 emissions,degraded soil quality,and increased atmospheric CO2 concentrations,leading to climate warming.Predicted climate warming is proposed to enhance SOC decomposition,which may further increase soil N availability,leading to higher soil CO2 efflux.However,a literature survey revealed that soil may also act as a potential C sink,if we could manage soil inorganic N pools and link microbial processes properly.Studies also indicated that the relative,rather than the absolute,availability of inorganic N pools might be of key importance under changing climate,as these N pools are variably affected by moisture-temperature interactions,and they have variable impacts on SOC turnover.Therefore,multi-factorial studies are required to understand how the relative availability of inorganic N pools and associated microbial processes may determine SOC dynamics for improved soil C management.     

Shikimate accumulation in nine weedy species following glyphosate application

Glyphosate is commonly used in a variety of weed control scenarios and plants respond biochemically by continuing to attempt to push carbon through the shikimate pathway. The result is an accumulation of shikimate in sensitive plants in the days immediately after application. This research determined shikimate accumulation dynamics in nine problematic plant species from 0 to 6 days after treatment (DAT). Ambrosia artemisiifolia, Trifolium repens and Conyza canadensis showed rising concentrations through 6 DAT to >4000 mg L^?1. Chenopodium album, Xanthium strumarium and Urochloa platyphylla showed concentrations levelling off to a constant of about 2000 mg L^?1. Ambrosia trifida, Amaranthus palmeri and Polygonum pensylvanicum generally showed lower levels of shikimate accumulation and concentrations were decreasing after 3 DAT. No apparent relationships were evident between shikimate accumulation pattern and plant growth rate or speed of glyphosate activity. There also appeared to be no pattern in the shikimate accumulation trends that would allow for an informed decision as to which of these species would be most likely to develop glyphosate resistance. Shikimate concentrations were in agreement between field and glasshouse conditions for C. canadensis, but did not agree with those from A. palmeri.