Muhammad Javed Akhtar

Effect of substrate-dependent microbial ethylene production on plant growth

Various compounds have been identified as precursors/substrates for the synthesis of ethylene (C2H4) in soil. This study was designed to compare the efficiency of four substrates, namely L-methionine (L-MET), 2-keto-4-methylthiobutyric acid (KMBA), 1-aminocyclopropane-1-carboxylic acid (ACC), and calcium carbide (CaC2), for ethylene biosynthesis in a sandy clay loam soil by gas chromatography. The classic “triple” response in etiolated pea seedling was employed as a bioassay to demonstrate the effect of substrate-dependent microbial production of ethylene on plant growth. Results revealed that an amendment with L-MET, KMBA, ACC (up to 0.10 g/kg soil) and CaC2 (0.20 g/kg soil) significantly stimulated ethylene biosynthesis in soil. Overall, ACC proved to be the most effective substrate for ethylene production (1434 nmol/kg soil), followed by KMBA, L-MET, and CaC2 in descending order. Results further revealed that ethylene accumulation in soil from these substrates caused a classic “triple” response in etiolated pea seedlings with different degrees of efficacy. A more obvious classic “triple” response was observed at 0.15, 0.10, and 0.20 g/kg soil of L-MET, KMBA/ACC, and CaC2, respectively. Similarly, direct exposure of etiolated pea seedlings to commercial ethylene gas also modified the growth pattern in the same way. A significant direct correlation (r = 0.86 to 0.97) between substrate-derived C2H4 and the classic triple response in etiolated pea seedlings was observed. This study demonstrated that the presence of substrate(s) in soil may lead to increased ethylene concentration in the air of the soil, which may affect plant growth in a desired direction.

Precursor (L-tryptophan)-Inoculum ( Azotobacter ) Interaction for Improving Yields and Nitrogen Uptake of Maize

ABSTRACT Auxins produced in the rhizosphere as a result of precursor-inoculum interaction may affect plant growth. Auxin production by Azotobactercultures was measured {in vitro} in the presence and absence of L-tryptophan and the most prolific auxin-producing culture (Z4) was then selected. A field experiment was conducted to evaluate the effect of L-tryptophan (an auxin precursor) and Azotobacterapplication on the growth, yield, and nitrogen (N) uptake of maize crop. Five levels of L-tryptophan (10− 3–10− 7 M) were tested with and without Azotobacter inoculation in a fertilized (NPK: 150–100–100 kg ha− 1, respectively) field. Results revealed that application of L-tryptophan (L-TRP) or Azotobacter inoculation alone significantly affected the maize crop; however, their combined application produced more pronounced effects as compared with their separate application. Combined application of 10− 4 M L-TRP and Azotobacter significantly increased the grain yield (18.4%), fresh biomass (16.7%), 1000-grain weight (14.5%), and total nitrogen uptake (40%) compared with an untreated and uninoculated control. It is highly likely that the physiological response evoked is due to the presence of auxins produced in the rhizosphere of maize as a result of precursor-inoculum interaction.

Judicious use of kinetin to improve growth and yield of rice in nickel contaminated soil.

ABSTRACT The present study was conducted to evaluate the effect of kinetin on growth and yield of rice in the presence and absence of nickel contamination. Rice seedlings were dipped in kinetin solution (10−3, 10−4 and 10 M−5) for 2 hours and transplanted in pots having soil contaminated with nickel sulfate @ 130 mg kg−1. Experiment was laid out according to completely randomized design with four replications. Results revealed that kinetin significantly improved growth and yield of rice grown in nickel contamination. Kinetin @ 10−4 M showed maximum improvement in plant height, paddy yield, 1000 grain weight, number of tillers and panicles up to 9.76, 15.72, 11.77, 11.87, and 10.90%, respectively, as compared to plants grown in contaminated soil without kinetin. Kinetin also improved the uptake of nutrients (NPK) in straw and grain of plants grown in Ni contaminated soil. Plants treated with kinetin had more concentration of Ni in shoot but less in grain compared to plants grown in Ni contaminated soil without application of kinetin. The application of kinetin can reduce stress effect on plants through improvement in the biomass of plant. This strategy could be used to increase the phytoextraction of Ni from the contaminated soil.

Combined application of compost and Bacillus sp. CIK-512 ameliorated the lead toxicity in radish by regulating the homeostasis of antioxidants and lead

Lead (Pb) contamination is ubiquitous and usually causes toxicity to plants. Nevertheless, application of compost and plant growth promoting rhizobacteria synergistically may ameliorate the Pb toxicity in radish. The present study assessed the effects of compost and Bacillus sp. CIK-512 on growth, physiology, antioxidants and uptake of Pb in contaminated soil and explored the possible mechanism for Pb phytotoxicity amelioration. Treatments comprised of un-inoculated control, compost, CIK-512, and compost + CIK-512; plants were grown in soil contaminated with Pb (500mgkg-1) and without Pb in pot culture. Lead caused reduction in shoot dry biomass, photosynthetic rate, stomatal conductance, relative water contents, whereas enhanced root dry biomass, ascorbate peroxidase, catalase, malondialdehyde and electrolyte leakage in comparison with non-contaminated control. Plants inoculated with strain CIK-512 and compost produced significantly higher dry biomass, photosynthetic rate and stomatal conductance in normal and contaminated soils. Bacterial strain CIK-512 and compost synergy improved growth and physiology of radish in contaminated soil possibly through homeostasis of antioxidant activities, reduced membrane leakage and Pb accumulation in shoot. Possibly, Pb-induced production of reactive oxygen species resulted in increased electrolyte leakage and malondialdehyde contents (r = 0.88-0.92), which led to reduction in growth (r = -0.97) and physiology (r = -0.38 to -0.80), however, such negative effects were ameliorated by the regulation of antioxidants (r = 0.78-0.87). The decreased activity of antioxidants coupled with Pb accumulation in aerial part of the radish indicates the Pb-phytotoxicity amelioration through synergistic application of compost and Bacillus sp. CIK-512.

Petroleum Hydrocarbons-Contaminated Soils: Remediation Approaches

Petroleum, the backbone of today’s mechanized society, now has become a threat to environment due to extraction and transportation. Accidental oil spills occur regularly at many locations throughout the world. Contamination of soil and water resources with petroleum oil and its products has become a serious problem due to carcinogenic and mutagenic compounds. Efforts are now focused on seeking potential remediation techniques for cleanup of petroleum hydrocarbons-contaminated soils in a cost effective and eco-friendly way. Various physical, chemical and biological remediation strategies have been used to restore contaminated soils. However, plant assisted bioremediation of petroleum hydrocarbons-contaminated soil is getting more attention as compared to sole use of either microorganisms or plants. The challenging task for such efforts to be successful is not only the survival of microorganisms upon their inoculation into hostile contaminated environment but also positive plant-microbe interactions. Bacteria having ACC-deaminase enzymes are considered helpful for plants in stressed environment. We have discussed that use of bacteria equipped with dual traits of bioremediation potential and ACC-deaminase activity in association with plants can be a good approach for remediation of petroleum hydrocarbons-contaminated soil.

Optimizing Available Phosphorus in Calcareous Soils Fertilized with Diammonium Phosphate and Phosphoric Acid Using Freundlich Adsorption Isotherm

In calcareous soils, phosphorus (P) retention and immobilization take place due to precipitation and adsorption. Since soil pH is considered a major soil variable affecting the P sorption, an acidic P fertilizer could result in low P adsorption compared to alkaline one. Therefore, P adsorption from DAP and phosphoric acid (PA) required to produce desired soil solution P concentration was estimated using Freundlich sorption isotherms. Two soils from Faisalabad and T. T. Singh districts were spiked with 0, 10, and 20 % CaCO3 for 15 days. Freundlich adsorption isotherms (P = aC b/a) were constructed, and theoretical doses of PA and DAP to develop a desired soil solution P level (i.e., 0.20 mg L−1) were calculated. It was observed that P adsorption in soil increased with CaCO3. Moreover, at all the levels of CaCO3, P adsorption from PA was lower compared to that from DAP in both the soils. Consequently, lesser quantity of PA was required to produce desired solution P, 0.2 mg L−1, compared to DAP. However, extrapolating the developed relationship between soil CaCO3 contents and quantity of fertilizer to other similar textured soils needs confirmation.

Phosphorus-Mobilizing Rhizobacterial Strain Bacillus cereus GS6 Improves Symbiotic Efficiency of Soybean on an Aridisol Amended with Phosphorus-Enriched Compost

Abstract Legume plants are an essential component of sustainable farming systems. Phosphorus (P) deficiency is a significant constraint for legume production, especially in nutrient-poor soils of arid and semi-arid regions. In the present study, we conducted a pot experiment to evaluate the effects of a phosphorus-mobilizing plant-growth promoting rhizobacterial strain Bacillus cereus GS6, either alone or combined with phosphate-enriched compost (PEC) on the symbiotic (nodulation-N2 fixation) performance of soybean (Glycine max (L.) Merr.) on an Aridisol. The PEC was produced by composting food waste with addition of single super phosphate. The bacterial strain B. cereus GS6 showed considerable potential for P solubilization and mobilization by releasing carboxylates in insoluble P (rock phosphate)-enriched medium. Inoculation of B. cereus GS6 in combination with PEC application significantly improved nodulation and nodule N2 fixation efficiency. Compared to the control (without B. cereus GS6 and PEC), the combined application of B. cereus GS6 with PEC resulted in significantly higher accumulation of nitrogen (N), P, and potassium (K) in grain, shoot, and nodule. The N:P and P:K ratios in nodules were significantly altered by the application of PEC and B. cereus GS6, which reflected the important roles of P and K in symbiotic performance of soybean. The combined application of PEC and B. cereus GS6 also significantly increased the soil dehydrogenase and phosphomonoesterase activities, as well as the soil available N, P, and K contents. Significant positive relationships were found between soil organic carbon (C) content, dehydrogenase and phosphomonoesterase activities, and available N, P, and K contents. This study suggests that inoculation of P-mobilizing rhizobacteria, such as B. cereus GS6, in combination with PEC application might enhance legume productivity by improving nodulation and nodule N2 fixation efficiency.

Increasing beta cell mass to treat diabetes mellitus.

Finding a radical cure for diabetes has reached paramount importance in medicine due to the widespread prevalence of the disease. A substantial reduction in insulin-secreting beta cells is evident in diabetes. The failure of cyclin-dependent kinases (CDKs) and cyclins to access the nucleus is responsible for quiescence or senescence in human and rodent beta cells. The augmentation of beta cell proliferation is supposed to reverse diabetes. This concept has inspired the discovery of newer drugs that encourage the proliferation of beta cells. Although it is a rational step towards a cure for diabetes, the differences in biochemical pathways in rodents and human beta cells pose difficulty in promoting the proliferation of human beta cells. Primarily, it is mandatory to clearly understand the intracellular pathways involved in the proliferation of beta cells so as to pave the way for therapeutic interventions. There are several intrinsic factors that trigger the proliferation of beta cells. Furthermore, it is also obvious that the early death of beta cells due to oxidative stress-related upregulation of pro-apoptotic genes also predisposes individuals to diabetes mellitus. Polyphenols, exendin 4, histone deacetylase inhibitors, glucagon-like peptide 1, phenyl pyruvic acid glucoside, and several flavonoids reduce the early apoptosis of beta cells partly through their role in the reduction of oxidative stress. A better understanding of intracellular pathways, the identification of specific mitogens, the induction of beta cell proliferation, and the inhibition of apoptosis may help us treat diabetes mellitus through an increase in beta cell mass.

Simultaneous use of plant growth promoting rhizobacterium and nitrogenous fertilizers may help in promoting growth, yield, and nutritional quality of okra

ABSTRACT This study was conducted to evaluate the simultaneous use of plant growth promoting rhizobacterium (QS1) and different combinations of urea-nitrogen and biogas slurry-nitrogen for improving growth, yield, and nutritional quality of field grown okra. The isolate QS1 was identified as Bacillus sp. QS1 based on its ribosomal ribonucleic acid (rRNA) sequence analysis. Results revealed that among the combinations, the application of 50% urea-nitrogen + 50% biogas slurry-nitrogen was optimal for improving crop performance. This combination significantly (p ≤ 0.05) promoted okra growth viz. plant height (69.63–80.03 cm), no of branches per plant (14–18), shoot fresh weight (86.66–136.25 g/plant), root fresh weight (22.5–26.58 g/plant), and fruit yield (8.5–13.5 kg/plot) compared to the plants receiving 100% urea-nitrogen. The interactive effective of this nitrogen combination and QS1 inoculation produced the highest growth and yield response. Similarly, the same treatment improved nitrogen, phosphorus, potassium, and protein contents in shoot and fruit of okra compared to other treatments.

Reversible Tuning of Ferromagnetism and Resistive Switching in ZnO/Cu Thin Films

Systematic magnetic, electronic, and electrical studies on the Cu0.04Zn0.96O/Ga0.01Zn0.99O cell structure grown on (001) sapphire by the pulsed laser deposition technique show that the Cu multivalent (CuM+) ions modulate magnetic and resistive states of the cells. The magnetic moment is found to be reduced by ∼30% during the high resistance state (HRS) to low resistance state (LRS) switching. X-ray photoelectron spectroscopy results reveals an increase of the Cu+/Cu2+ oxidation state ratio (which has been determined by the relative positions of the Fermi level and the Cu acceptor level) during the HRS to LRS transition. This decreases the effective spin-polarized Cu2+–Vö–Cu+ channels and thus the magnetic moment. A conduction mechanism involving the formation of conductive filaments from the coupling of the CuM+ ions and Vö has been suggested.