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Brassinosteroids (BRs) are steroidal phytohormones that play a multitasking role during the growth and development period as well as stress responses. Plant mutants in BR production or defective signaling result in various physiological as well as phenotypical abnormalities. Presently, various studies have highlighted stress tolerance induction by brassinosteroids in various plant species indicating BRs as a broad spectrum key regulator participating in various molecular processes. The present chapter highlights the studies on BRs regarding their potent role in inducing stress tolerance during viral, fungal, bacterial or nematode attacks in plants. BR's multifaceted role during stress and its potential cross-talk with other phytohormones in adapting and ameliorating the stress have been critically analyzed. The divergence in dosage of BR analogs and their mode of application for management of stress are also discussed which serves as a future area of interest in challenging agriculture, thereby highlighting relevant knowledge gaps.

Pathogen attack in crop plants has negative impacts on plant biology which ultimately causes reductions in crop yield. Hydrogen sulfide (H2S) in addition to its normal plant physiology functions is known for its roles in the regulation of plant physiology under biotic stress. This H2S-mediated regulation of plant biology under biotic stress is modulated by hormonal crosstalk. In this chapter we will discuss how H2S regulates plant growth under biotic stress by interacting with plant hormones like auxins, abscisic acid, ethylene, jasmonic acid, gibberellins, and salicylic acid.

Chromium (Cr) is an element naturally occurring in rocky soils and volcanic dust. It has been classified as a carcinogen agent according to the International Agency for Research on Cancer. Therefore, this metal needs an accurate understanding and thorough investigation in soil–plant systems. Due to its high solubility, Cr (VI) is regarded as a hazardous ion, which contaminates groundwater and can be transferred through the food chain. Cr also negatively impacts the growth of plants by impairing their essential metabolic processes. The toxic effects of Cr are correlated with the generation of reactive oxygen species (ROS), which cause oxidative stress in plants. The current review summarizes the understanding of Cr toxicity in plants via discussing the possible mechanisms involved in its uptake, translocation and sub-cellular distribution, along with its interference with the other plant metabolic processes such as chlorophyll biosynthesis, photosynthesis and plant defensive system.

Brassinosteroids (BRs), a class of steroidal hormones, play diverse roles in plant growth, development, signaling and defense against various biotic and abiotic stresses. It is broad spectrum key regulator in plants that participates in various molecular processes. Exogenous application of BRs vanish various constrains in the path of agricultural development. The present book chapter highlights the interaction and crosstalk of brassinosteroids with other phytohormones such as auxins, gibberellins, jasmonic acid, abscisic acid, salicylic acid, polyamines, ethylene and strigolactones in regulation of various physiological and developmental processes in plants. Various pathways reveal the versatile role of brassinosteroids in various hormonal interactions.

Plant growth and development is under the control of mutual interactions among plant hormones. The five classical categories of plant hormones include auxins, cytokinins, gibberellins, abscisic acid and ethylene. Additionally, newer classes of plant hormones have been recognized like brassinosteroids, jasmonic acid, salicylic acid and polyamines. These hormones play significant roles in regulating the plant growth and development. Various receptors and key signaling components of these hormones have been studied and identified. At genetic level, crosstalk among the various plant hormones is found to be antagonistic or synergistic. In addition, components of signaling pathway of one plant hormone interact with the signaling components of other hormone. Thus, an attempt has been made to review the literature regarding the role of plant hormones in plant physiology and the common molecular players in their signaling and crosstalk.