Ahmad Naeem Shahzad

Biochar soil amendment on alleviation of drought and salt stress in plants: a critical review

Drought and salt stress negatively affect soil fertility and plant growth. Application of biochar, carbon-rich material developed from combustion of biomass under no or limited oxygen supply, ameliorates the negative effects of drought and salt stress on plants. The biochar application increased the plant growth, biomass, and yield under either drought and/or salt stress and also increased photosynthesis, nutrient uptake, and modified gas exchange characteristics in drought and salt-stressed plants. Under drought stress, biochar increased the water holding capacity of soil and improved the physical and biological properties of soils. Under salt stress, biochar decreased Na+ uptake, while increased K+ uptake by plants. Biochar-mediated increase in salt tolerance of plants is primarily associated with improvement in soil properties, thus increasing plant water status, reduction of Na+ uptake, increasing uptake of minerals, and regulation of stomatal conductance and phytohormones. This review highlights both the potential of biochar in alleviating drought and salt stress in plants and future prospect of the role of biochar under drought and salt stress in plants.

Arsenic uptake, accumulation and toxicity in rice plants: Possible remedies for its detoxification: A review

Arsenic (As) is a toxic metalloid. Serious concerns have been raised in literature owing to its potential toxicity towards living beings. The metalloid causes various water- and food-borne diseases. Among food crops, rice contains the highest concentrations of As. Consuming As-contaminated rice results in serious health issues. Arsenic concentration in rice is governed by various factors in the rhizosphere such as availability and concentration of various mineral nutrients (iron, phosphate, sulfur and silicon) in soil solution, soil oxidation/reduction status, inter-conversion between organic and inorganic As compounds. Agronomic and civil engineering methods can be adopted to decrease As accumulation in rice. Agronomic methods such as improving soil porosity/aeration by irrigation management or creating the conditions favorable for As-precipitate formation, and decreasing As uptake and translocation by adding a inorganic nutrients that compete with As are easy and cost effective techniques at field scale. This review focuses on the factors regulating and competing As in soil-plant system and As accumulation in rice grains. Therefore, it is suggested that judicious use of water, management of soil, antagonistic effects of various inorganic plant-nutrients to As should be considered in rice cultivated areas to mitigate the building up of As in human food chain and with minimum negative impact to the environment.

Impact of copper toxicity on stone-head cabbage (Brassica oleracea var. capitata) in hydroponics

Arable soils are frequently subjected to contamination with copper as the consequence of imbalanced fertilization with manure and organic fertilizers and/or extensive use of copper-containing fungicides. In the present study, the exposure of stone-head cabbage (Brassica oleracea var. capitata) to elevated Cu2+ levels resulted in leaf chlorosis and lesser biomass yield at ≥2 µ M. Root nitrate content was not statistically affected by Cu2+ levels, although it was substantially decreased at ≥5 µ M Cu2+ in the shoot. The decrease in nitrate contents can be related to lower nitrate uptake rates because of growth inhibition by Cu-toxicity. Shoot sulfate content increased strongly at ≥2 µ M Cu2+ indicating an increase in demand for sulfur under Cu stress. Furthermore, at ≥2 µM concentration, concentration of water-soluble non-protein thiol increased markedly in the roots and to a smaller level in the shoot. When exposed to elevated concentrations of Cu2+ the improved sulfate and water-soluble non-protein thiols need further studies for the evaluation of their direct relation with the synthesis of metal-chelating compounds (i.e., phytochelatins).

Foliar Application of Potassium Sulfate Partially Alleviates Pre-anthesis Drought-induced Kernel Abortion in Maize

Reproductive success in cereals is determined primarily by grain setting and grain filling. The kernel abortion in maize during pre-anthesis drought has been widely studied, but the reasons behind this abortion are still largely unknown. The present study investigated the impact of drought stress (control and drought) around pollination and foliar sprays of potassium (K; 0, 1, 2 and 5% K2SO4) on leaf K concentrations and yield determinants of maize under greenhouse and field conditions. Results of both experiments revealed that drought stress before pollination strongly reduced the cob fresh weights, number of grains per cob and hence grain yields. While cob length, cob diameter and grain weights were only slightly affected by drought. Potassium concentrations in cob leaves of drought stressed plants were slightly below the critical threshold values. Foliar spray of 2 and 5% K significantly increased the leaf K concentration, number of grains per cob and grain yield in drought treatments of both experiments. Foliar application of K had little or no significant effect on growth and yield determinants of control plants. It is concluded that potassium deficiency could be one factor associated with poor kernel setting under drought stress. Foliar application of 2 and 5% K2SO4 before silking can significantly improve grain number and grain yield in droughtstressed maize.

Biochar affects growth and biochemical activities of fenugreek ( Trigonella corniculata ) in cadmium polluted soil

Cadmium (Cd) has no defined biological role and may enter the food chain from polluted soils. Biochar has been proposed as an organic amendment to minimize the toxic effects of Cd for plants grown on contaminated soils. In this study, biometric and biochemical attributes of fenugreek (Trigonella corniculata) grown on artificially cadmium (Cd) contaminated soil (0, 25, 50, 75 and 100 mg Cd/kg soil) at three levels of cotton-sticks derived biochar (CSB; 0, 3 and 5 %) were studied. Data show significant decline in the growth, photosynthetic pigments (chlorophyll a, b and total, carotenoids, anthocyanin and lycopene), and physiological attributes (sub-stomatal CO2 concentrations, photosynthetic and transpiration rate) in the presence of high Cd concentrations (50 and 100 mg Cd/kg soil). However, the decline was reduced in the presence of CSB. A steady amplification in lipid peroxidation (assessed via Malondialdihyde (MDA)) and ascorbic-acid assembly was noted with increasing Cd. The concentration of Cd in the root and shoot also decreased with increasing CSB application rates from 3 % - 5 %. Overall, the greater production of protein, amino acids and sugar contents in response to higher application rates of CSB seems to be due to alleviation in Cd toxicity. Thus, cotton-sticks can be safely utilized in the form of biochar as amendment with additional benefit of reducing Cd bioavailability and toxicity to crop plants.

Seed priming improves irrigation water use efficiency, yield, and yield components of late-sown wheat under limited water conditions

* Correspondence: anaeems@gmail.com

Interactive Effect of Boron and Salinity on Growth, Physiological and Biochemical Attributes of Wheat (Triticum aestivum)

A pot experiment was conducted to investigate the interactive effect of salinity (125 mM) and varying concentrations of boron (B) (2, 4 and 6 mM) on the growth and biochemical attributes of wheat. Results showed that application of 4 and 6 mM B along with 125 mM NaCl significantly declined plant biomass and leaf length. The concentration of B in plant leaves was significantly lower in treatments where salinity and B were applied together as compared to individual applications of 2, 4 and 6 mM B. The membrane permeability and protein concentration were significantly increased by the combined application of NaCl and B, whereas the chlorophyll pigments were not influenced. The phenolic compounds and ascorbic acid concentrations were reduced with the individual applied 6 mM B and when combined with application of 125 mM NaCl + 6 mM B. The concentration of Milondialdehyde (MDA) gradually increased by increasing B application and maximum was at the highest level of B and NaCl stress. It is concluded that salinity worsens the deteriorating effect of boron toxicity on wheat growth.