Plant growth regulators : signalling under stress conditions Agriculture faces many challenges to fulfil the growing demand for sustainable food production and ensure high quality nutrition for a rapidly growing population. To guarantee adequate food production it is necessary to increase the yield per area of arable land. A method for achieving this goal has been the application of growth regulators to modulate plant growth. Plant growth regulators (PGRs) are substances in specific formulations which when applied to plants or seeds have the capacity to promote inhibit or modify physiological traits development and or stress responses. They maintain proper balance between source and sink for enhancing crop yield. PGRs are used to maximize productivity and quality improve consistency in production and overcome genetic and abiotic limitations to plant productivity. Suitable PGRs include hormones such as cytokinins and auxins and hormone like compounds such as mepiquat chloride and paclobutrazol. The use of PGRs in mainstream agriculture has steadily increased within the last 20 years as their benefits have become better understood by growers. Unfortunately the growth of the PGR market may be constrained by a lack of innovation at a time when an increase in demand for new products will require steady innovation and discovery of novel cost competitive specific and effective PGRs. A plant bio stimulant is any substance or microorganism applied to plants with the aim to enhance nutrition efficiency abiotic stress tolerance and or crop quality traits regardless of its nutrients content. Apart from traditional PGRs which are mostly plant hormones there are a number of substances molecules such as nitric oxide methyl jasmonate brassinosteroids seaweed extracts strigolactones plant growth promoting rhizobacteria etc. which act as PGRs. These novel PGRs or bio stimulants have been reported to play important roles in stress responses and adaptation. They can protect plants against various stresses including water deficit chilling and high temperatures salinity and flooding. This book includes chapters ranging from sensing and signalling in plants to translational research. In addition the cross talk operative in plants in response to varied signals of biotic and abiotic nature is also presented. Ultimately the objective of this book is to present the current scenario and the future plan of action for the management of stresses through traditional as well as novel PGRs. We believe that this book will initiate and introduce readers to state of the art developments and trends in this field of study. Preface Prospective Role of Plant Growth Regulators for Tolerance to Abiotic Stresses Accumulation Partitioning and Bioavailability of Micronutrients in Plants and their Crosstalk with Phytohormones An insight into role of plant growth regulators in stimulating abiotic stress tolerance in some medicinally important plants Hormonal Regulation in cell culture of Artemisia annua L. plant Medicinal and Aromatic Plants under Abiotic Stress: A Crosstalk on Phytohormones’ Perspective Cytokinin mediated signaling during environmental stress in plants Leaf senescence and ethylene signaling Methyl Jasmonate and Brassinosteroids: Emerging Plant growth regulators in Plant abiotic stress tolerance and Environmental Changes Brassinosteroids signalling pathways in plant defense and adaptation to stress Roles of hydrogen sulfide in regulating temperature stress response in plants Physiological biochemical and molecular mechanism of nitric oxide mediated abiotic stress tolerance Melatonin: Role in abiotic stress resistance and tolerance Strigolactones A Novel Carotenoid Derived Phytohormone: Biosynthesis Transporters Signalling and Mechanisms in Abiotic Stress Role of soluble sugars in metabolism and sensing under abiotic stress Natural Polysaccharides: Novel Plant Growth Regulators Role of AM fungi and PGPR in alleviating stress responses and inducing defense mechanism Arbuscular Mycorrhizal Fungi: A Natural Biotechnological Tool for Sustainable Crop Production under Saline Soils in the Modern Era of Climate Change PGPR assisted bioremediation and plant growth: A sustainable approach for crop production using polluted soils Rhizobia: A Potent Tool for Amelioration of Drought Stress in Legumes Understanding the role of bacterial fertilizers in stressed agriculture: actions mechanisms and future prospects Bioreactor upscaling of different tissue of medicinal herbs for extraction of active phytomolecules: a step towards industrialization and enhanced production of phytochemicals Index.