Muhammad Sajid Aqeel Ahmad

Essential Roles and Hazardous Effects of Nickel in Plants

With the worlds ever increasing human population, the issues related to environmental degradation of toxicant chemicals are becoming more serious. Humans have accelerated the emission to the environment of many organic and inorganic pollutants such as pesticides, salts, petroleum products, acids, heavy metals, etc. Among different environmental heavy-metal pollutants, Ni has gained considerable attention in recent years, because of its rapidly increasing concentrations in soil, air, and water in different parts of the world. The main mechanisms by which Ni is taken up by plants are passive diffusion and active transport. Soluble Ni compounds are preferably absorbed by plants passively, through a cation transport system; chelated Ni compounds are taken up through secondary, active-transport-mediated means, using transport proteins such as permeases. Insoluble Ni compounds primarily enter plant root cells through endocytosis. Once absorbed by roots, Ni is easily transported to shoots via the xylem through the transpiration stream and can accumulate in neonatal parts such as buds, fruits, and seeds. The Ni transport and retranslocation processes are strongly regulated by metal-ligand complexes (such as nicotianamine, histidine, and organic acids) and by some proteins that specifically bind and transport Ni. Nickel, in low concentrations, fulfills a variety of essential roles in plants, bacteria, and fungi. Therefore, Ni deficiency produces an array of effects on growth and metabolism of plants, including reduced growth, and induction of senescence, leaf and meristem chlorosis, alterations in N metabolism, and reduced Fe uptake. In addition, Ni is a constituent of several metallo-enzymes such as urease, superoxide dismutase, NiFe hydrogenases, methyl coenzyme M reductase, carbon monoxide dehydrogenase, acetyl coenzyme-A synthase, hydrogenases, and RNase-A. Therefore, Ni deficiencies in plants reduce urease activity, disturb N assimilation, and reduce scavenging of superoxide free radical. In bacteria, Ni participates in several important metabolic reactions such as hydrogen metabolism, methane biogenesis, and acetogenesis. Although Ni is metabolically important in plants, it is toxic to most plant species when present at excessive amounts in soil and in nutrient solution. High Ni concentrations in growth media severely retards seed germinability of many crops. This effect of Ni is a direct one on the activities of amylases, proteases, and ribonucleases, thereby affecting the digestion and mobilization of food reserves in germinating seeds. At vegetative stages, high Ni concentrations retard shoot and root growth, affect branching development, deform various plant parts, produce abnormal flower shape, decrease biomass production, induce leaf spotting, disturb mitotic root tips, and produce Fe deficiency that leads to chlorosis and foliar necrosis. Additionally, excess Ni also affects nutrient absorption by roots, impairs plant metabolism, inhibits photosynthesis and transpiration, and causes ultrastructural modifications. Ultimately, all of these altered processes produce reduced yields of agricultural crops when such crops encounter excessive Ni exposures.

Alleviation of waterlogging stress in upland cotton (Gossypium hirsutum L.) by exogenous application of potassium in soil and as a foliar spray

The effectiveness of exogenous application of K in ameliorating the adverse effects of waterlogging on cotton plants was assessed under greenhouse conditions. Forty-day-old plants were subjected to continuous flooding for 1 week and then K (60 kg ha–1) was applied either as soil application, foliar spray, or in combination. The waterlogging treatment significantly reduced plant height and fresh and dry biomass, photosynthetic pigments, gas exchange parameters and nutrient accumulation (N, K+, Ca2+) in stem, root and leaves of cotton plants, Although Mg2+ content in roots increased significantly due to waterlogging, it was not affected in stem or leaves. In contrast, Mn2+ and Fe2+ contents generally increased under waterlogged conditions. All water relation parameters were also significantly influenced by waterlogging stress. Waterlogged plants supplemented with K showed a significant improvement in growth, photosynthetic pigments and photosynthetic capacity. Potassium supplementation also improved nutrient uptake of waterlogged plants and resulted in significantly higher accumulation of K+, Ca2+, N, Mn2+ and Fe2+ than those plants not supplied with K. Although all modes of K application were effective in mitigating the inhibitory effects of waterlogging, the combined application through soil + foliar spray yielded the best results and the foliar application (alone) being the least effective.

Patterns of ion excretion and survival in two stoloniferous arid zone grasses

Desert plants show specific mechanisms to thrive under prevailing harsh conditions. To study the survival mechanism(s) in native desert plant species, Lesser Cholistan desert in Pakistan was surveyed and two potential salt secretory grass species, Aeluropus lagopoides and Ochthochloa compressa, were selected from five saline sites. Both these grasses responded differentially to saline environments by showing specialized mechanisms of survival including excretion of toxic ions through trichomes, vesicular and glandular hairs through leaf surface. In A. lagopoides, salt tolerance was associated with excreted Na(+) concentration through leaf surface and accumulation of useful ions like Ca(2+) and K(+) in the shoot. Contrarily, O. compressa excreted all the ions through leaves without discriminating among toxic or beneficial ions. Results suggested that A. lagopoides was more successfully adapted to saline desert environments than O. compressa by excretion of excessive toxic ions and retention of Ca(2+) and K(+) in the shoot. This appears to be an adaptive character of the former species to successfully thrive in harsh desert conditions.

Phytotoxic effects of nickel on yield and concentration of macro- and micro-nutrients in sunflower (Helianthus annuus L.) achenes

The phytotoxic effects of varying levels of nickel (0, 10, 20, 30, and 40 mg L(-1)) on growth, yield and accumulation of macro- and micro-nutrients in leaves and achenes of sunflower (Helianthus annuus L.) were appraised in this study. A marked reduction in root and shoot fresh biomass was recorded at higher Ni levels. Nickel stress also caused a substantial decrease in all macro- and micro-nutrients in leaves and achenes. The lower level of Ni (10 mg L(-1)) had a non-significant effect on various yield attributes, but higher Ni levels considerably decreased these parameters. Higher Ni levels decreased the concentrations of Ca, Mn and Fe in achenes. In contrast, achene N, K, Zn, Mn and Cu decreased consistently with increasing level of Ni, even at lower level (10 mg L(-1)). Sunflower hybrid Hysun-33 had better yield and higher most of the nutrients in achenes as compared with SF-187. The maximum reduction in all parameters was observed at the maximum level of nickel (40 mg L(-1)) where almost all parameters were reduced more than 50% of those of control plants. In conclusion, the pattern of uptake and accumulation of different nutrients in sunflower plants were nutrient- and cultivar-specific under Ni-stress.

Crop Production for Agricultural Improvement

Crop improvement through different means: Challenges and prospect, Muhammad Ashraf, Muhammad Sajid Aqeel Ahmad, Munir Ozturk and Ahmad Aksoy PART I. Breeding for crop improvement Bridging genomic and classical breeding approaches for improving crop productivity, Mehboob-ur-Rahman, Tayyaba Shaheen, Muhammad Ashraf, Yusuf Zafar Breeding for improved drought tolerance, Abazar Rajabi, Eric Schmieder Ober Breeding for biotic stress resistance/tolerance in plants, Carlotta Balconi, Piergiorgio Stevanato, Mario Motto The American halophyte Prosopis strombulifera, a new potential source to confer salt tolerance to crops, Mariana Reginato, Veronica Sgroy, Analia Llanes, Fabricio Cassan, Virginia Luna Breeding for Biotic Stress Tolerance in Plants, L.F. De Filippis Breeding Wheat for Salt Tolerance and Stem Rust Resistance, Makhdoom Hussain, Aziz ur Rehman, Imran Habib, Mumtaz Hussain, Nadeem Ahmad, Muhammad Arif Khan, Muhammad Hussain and Faqir Muhammad The potential of breeding okra (Abelmoschus esculentus L.) for water stress tolerance, Abdul Naveed, Asif Ali Khan, Saeed Rauf PART II. Biotechnology , Molecular Biology and Genetics Biotechnology as an aid for crop improvement to overcome food shortage, Khalid ul Rehman Hakeem, Munir Ozturk, Parvaiz Ahmad, Abdul Razaque Memon Plant Genetic Engineering: Problems and Applications, Bushra Rashid, Tayyab Husnain, Sheikh RiazuddinAgrobacterium tumefaciens and its Use in Plant Biotechnology, Ibrahim Ilker Ozyigit Progress and prospects for efficient micropropagation of woody plants, Faheem Aftab Novel Methods in Micropropagation of Pistachio, Engin Tilkat, Yelda Ozden Ciftci, Hulya Akdemir, Ahmet Onay, Emine Ayaz Crop productivity and water use efficiency: The role of carbon isotope discrimination technique, Javed Akhter and Philippe Monneveux Behaviour of Plant Pathogens for Crops under Stress during the Determination of Physiological, Biochemical, and Molecular Approaches for Salt Stress Tolerance, Murat Dikilitas and Sema Karakas Biochemical and molecular aspects of drought tolerance in wheat Triticum L. Genotypes, Rada Mammad Huseynova, Samira Mahammadrahim Rustamova, Saftar Yusif Suleymanov, Jalal Alirza Aliyev Molecular basis of disease resistance in cereal crops: An overview, Hadi Bux, Muhammad Ashraf, Awais Rasheed, Dipak Sharma Poudyal, Alvina Gul Kazi, Muhammad Afzaal Polyamines: Role in plants under abiotic stress, Parvaiz Ahmad, Ashwani Kumar, Aditi Gupta, Xiangyang Hu, Khalid ul Rehman Hakeem, Satyawati Sharma PART III. Crop Management Practices in Saskatchewan, Canada, Ahmet Ruhi Mermut Invasive weed species: A threat to sustainable agriculture, Ghazala Nasim, Asad Shabbir An overview of plant growth promoting rhizobacteria (PGPR) for sustainable agriculture, Rifat Hayat, Iftikhar Ahmed, Rizwan Ali Sheirdil Arbuscular mycorrhizae for sustainable agriculture, Ghazala Nasim A site-specific potassium fertilization approach to overcome sporadic response of crops, Abdul Hannan, Muhammad Arif, Muhammad Arif, Muhammad Waqas Optimal Supply of Micronutrients Improves Drought Tolerance in Legumes, Muhammad Yasin Ashraf, Khalid Mahmood, Muhammad Ashraf, Javed Akhter, Faqir Hussain Potential of Rhizobia for Sustainable Production of Non-legumes, Ijaz Mehboob, Muhammad Naveed, Zahir Ahmad Zahir and Muhammad Ashraf Effect of Drip and Subsurface Drip Irrigation with Saline Water on Tomato Crop, Besma Kahlaoui, Mohamed Hachicha, Saloua Rejeb, Mohamed Nejib Rejeb Lipid and carbohydrate metabolism of cowpea (Vigna unguiculata L. walp) cultivars in relation to temperature stress, Shahidul Islam, Carmen Rafaela Carvajal Rebanales, James Otis Garner, Jr. Transcriptomics and proteomics analysis of root nodules of model legume plants, Abdul Razaque Memon A Review on Barley Yellow Dwarf Virus, Syed Jawad Ahmad Shah, Muhammad Bashir, Naheed Manzoor Agrobacterium tumefaciens and its Use in Plant Biotechnology, Ibrahim Ilker Ozyigit Progress and prospects for efficient micropropagation of woody plants, Faheem Aftab Novel Methods in Micropropagation of Pistachio, Engin Tilkat, Yelda Ozden Ciftci, Hulya Akdemir, Ahmet Onay, Emine Ayaz Crop productivity and water use efficiency: The role of carbon isotope discrimination technique, Javed Akhter and Philippe Monneveux Behaviour of Plant Pathogens for Crops under Stress during the Determination of Physiological, Biochemical, and Molecular Approaches for Salt Stress Tolerance, Murat Dikilitas and Sema Karakas Biochemical and molecular aspects of drought tolerance in wheat Triticum L. Genotypes, Rada Mammad Huseynova, Samira Mahammadrahim Rustamova, Saftar Yusif Suleymanov, Jalal Alirza Aliyev Molecular basis of disease resistance in cereal crops: An overview, Hadi Bux, Muhammad Ashraf, Awais Rasheed, Dipak Sharma Poudyal, Alvina Gul Kazi, Muhammad Afzaal Polyamines: Role in plants under abiotic stress, Parvaiz Ahmad, Ashwani Kumar, Aditi Gupta, Xiangyang Hu, Khalid ul Rehman Hakeem, Satyawati Sharma PART III. Crop Management Practices in Saskatchewan, Canada, Ahmet Ruhi Mermut Invasive weed species: A threat to sustainable agriculture, Ghazala Nasim, Asad Shabbir An overview of plant growth promoting rhizobacteria (PGPR) for sustainable agriculture, Rifat Hayat, Iftikhar Ahmed, Rizwan Ali Sheirdil Arbuscular mycorrhizae for sustainable agriculture, Ghazala Nasim A site-specific potassium fertilization approach to overcome sporadic response of crops, Abdul Hannan, Muhammad Arif, Muhammad Arif, Muhammad Waqas Optimal Supply of Micronutrients Improves Drought Tolerance in Legumes, Muhammad Yasin Ashraf, Khalid Mahmood, Muhammad Ashraf, Javed Akhter, Faqir Hussain Potential of Rhizobia for Sustainable Production of Non-legumes, Ijaz Mehboob, Muhammad Naveed, Zahir Ahmad Zahir and Muhammad Ashraf Effect of Drip and Subsurface Drip Irrigation with Saline Water on Tomato Crop, Besma Kahlaoui, Mohamed Hachicha, Saloua Rejeb, Mohamed Nejib Rejeb Lipid and carbohydrate metabolism of cowpea (Vigna unguiculata L. walp) cultivars in relation to temperature stress, Shahidul Islam, Carmen Rafaela Carvajal Rebanales, James Otis Garner, Jr. Transcriptomics and proteomics analysis of root nodules of model legume plants, Abdul Razaque Memon A Review on Barley Yellow Dwarf Virus, Syed Jawad Ahmad Shah, Muhammad Bashir, Naheed Manzoor

Toxins and Their Phytoremediation

The agricultural and industrial revolutions in the last few decades have resulted in increased concentration of toxins in our environment that are now-a-days a major cause of toxicity in plants and animals. Among different toxins, increasing levels of salts, heavy metal, pesticides and other chemicals are posing a threat to agricultural as well as natural ecosystems of the world. These contaminants result in soil, air and water pollution, and loss of arable lands as well as crop productivity. They also cause changes in species composition and loss of biodiversity by bringing about changes in the structure of natural communities and ecosystems. In this situation, different approaches are being adopted to reclaim polluted environments. Among these, phytoremediation has a potential in removing these toxins from the environment. This approach is based on the use of natural hyperaccumulator plant species that can tolerate relatively high levels of pollutants in the environment. Pollutants accumulated in stems and leaves of high biomass producing and tolerant plants can be harvested and removed from the site. Therefore, this approach has a potential to remove large amounts of toxins by harvesting the above-ground biomass. However, the effectiveness of phytoremediation approach can be increased if we have better knowledge of physiological, biochemical, molecular and genetic bases of plant resistance to natural and anthropogenic induced toxins. All these aspects of toxicity mechanisms and their removal techniques are comprehensively reviewed in this book.

Structural and Functional Adaptations in Plants for Salinity Tolerance

Salt tolerance in plants is a multifarious phenomenon involving a variety of changes at molecular, organelle, cellular, tissue as well as whole plant level. In addition, salt tolerant plants show a range of adaptations not only in morphological or structural features but also in metabolic and physiological processes that enable them to survive under extreme saline environments. Morpho–anatomical adaptations include xeromorphic characteristics like thick epidermis and sclerenchyma, well developed bulliform cells, increased density of trichomes and increased moisture retaining capacity by increasing cell size and vacuolar volume. Development of excretory structures like vesicular hairs and salt glands is another major structural adaptation and very crucial for salt tolerance. Physiological adaptations include restricted toxic ion uptake, increased succulence, osmotic adjustment and exclusion of toxic Na+ and Cl–.

Interaction of callus selection media and stress duration for in vitro selection of drought tolerant callus of wheat

Callus culture is a novel approach addressing cultured cells as selection units independent of whole plant. Natural variations for drought tolerance existing among cell lines can be exploited in vitro in the presence of suitable concentration of osmoticum and stress duration. The study was aimed to standardized callus selection media and culture duration to select drought tolerant cell line (callus) of wheat. Calli were induced from immature embryos on Murashige and Skoog (MS) based medium supplemented with 4 mg/L of 2,4-dichlorophenoxyacetic acid (2,4-D). Proliferated calli were cultured on various callus selection medias (MS based media + 30 g/L sucrose + 6 g/L agar + 4 mg/L 2,4-D + various levels of polyethylene glycol-600 (PEG-6000) induced osmotic stress including -0.3, -0.6, -0.9 or -1.2 MPa along with control, that is, 0.0 MPa) for two, three or four weeks. Callus health, callus growth rate, callus survival (%) and regeneration (%) declined significantly on media supplemented with higher levels of PEG-6000 induced osmotic stress and with increasing stress duration. Not a single callus could survive nor regenerate on selection media comprising PEG-6000 induced osmotic stress of -1.2 MPa imposed for four weeks. The highest callus growth rate (CGR) was recorded on PEG-6000 free media when calli were cultured for four weeks (-7.32%) on the media supplemented with PEG-6000 induced osmotic stress of -1.2 MPa. Callus selection media comprising PEG-6000 which induced osmotic stress of -0.9 MPa for four weeks was found selective and sub-lethal for wheat calli with 8.63% CGR, 26.62% callus survival and 21.50% regeneration; and seemed ideal for screening drought tolerant somaclonal cell lines of wheat.

Crop Improvement Through Different Means: Challenges and Prospects

In the recent years, the looming food scarcity problem has transformed plant sciences as an emerging discipline committed to devise new strategies for enhanced crop productivity. The major factors causing food scarcity are biotic and abiotic stresses such as plant pathogens, salinity, drought, flooding, temperature extremes, nutrient deficiency or excess, etc. which substantially limit crop productivity world-wide. In this scenario, such strategies should be adopted which may be employed to achieve maximum productivity and economic crop returns under such adversaries. Major strategies include pathogen/pest management practices, breeding of new crop varieties, screening and selection of existing crop gene pool, production of genetically modified (GM) crops, exogenous use of osmoprotectants and plant hormones, agronomic and soil reclamation practices, sustainable use of available water supplies, etc. In this book, we have mainly focused on physiological, biochemical, molecular and genetic tools for crop improvement under environmental adversaries. In addition, the adverse effects of different biotic (diseases, pathogens, etc.) and abiotic (salinity, drought, high and low temperatures, metals, etc.) stresses on crop development and the potential strategies to enhance crop productivity under such stressful environments have been critically discussed. Moreover, the role of nutrient, water and soil management in improving crop efficiency is also a part of this book.

Nitrate and Nitrogen Oxides: Sources, Health Effects and Their Remediation

Increased use of nitrogenous (N) fertilizers in agriculture has significantly altered the global N-cycle because they release nitrogenous gases of environmental concerns. The emission of nitrous oxide (N2O) contributes to the global greenhouse gas accumulation and the stratospheric ozone depletion. In addition, it causes nitrate leaching problem deteriorating ground water quality. The nitrate toxicity has been reported in a number of studies showing the health hazards like methemoglobinemia in infants and is a potent cause of cancer. Despite these evident negative environmental as well as health impacts, consumption of N fertilizer cannot be reduced in view of the food security for the teeming growing world population. Various agronomic and genetic modifications have been practiced to tackle this problem. Some agronomic techniques adopted include split application of N, use of slow-release fertilizers, nitrification inhibitors and encouraging the use of organic manure over chemical fertilizers. As a matter of fact, the use of chemical means to remediate nitrate from the environment is very difficult and costly. Particularly, removal of nitrate from water is difficult task because it is chemically non-reactive in dilute aqueous solutions. Hence, the use of biological means for nitrate remediation offers a promising strategy to minimize the ill effects of nitrates and nitrites. One of the important goals to reduce N-fertilizer application can be effectively achieved by choosing N-efficient genotypes. This will ensure the optimum uptake of applied N in a balanced manner and exploring the molecular mechanisms for their uptake as well as metabolism in assimilatory pathways. The objectives of this paper are to evaluate the interrelations which exist in the terrestrial ecosystems between the plant type and characteristics of nutrient uptake and analyze the global consumption and demand for fertilizer nitrogen in relation to cereal production, evaluate the various methods used to determine nitrogen use efficincy (NUE), determine NUE for the major cereals grown across large agroclimatic regions, determine the key factors that control NUE, and finally analyze various strategies available to improve the use efficiency of fertilizer nitrogen.