**1. Introduction**

#### **1.1 The meaning of a plant hormone**

Plants need sunlight, water, oxygen, minerals for their growth and development. These are. Apart from external factors there are some intrinsic factors that regulate the growth and development of plants [1]. These are called plant hormones or "Phytohormones". The term "hormone" was originally used narrowly to refer to secretory substances generated by particular organs, glands, tissues, or cells in

animals that were transported by veins (or other comparable tissues) to more or less specific tissues and had some effect on their metabolism [2]. However, the terminology is now always used to refer to the mobile signals of living creatures and is frequently used with a heading to indicate the type of living things, such as animal hormones, plant hormones, insect hormones, etc. Every living species has hormones that are frequently exclusive to that species and reflect the traits of its biological occurrences. The peculiar growth phenomenon known as developmental plasticity, in which a plant continuously forms new organs and tissues throughout its life cycle, can be attributed, at least in part, to the features of plant hormones [3]. Plant hormones are a group of organic, naturally occurring chemicals that, when present in small amounts, affect physiological functions. Growth, differentiation, and development are the primary processes impacted, while other processes, such stomatal movement, may also be impacted. Although the term "phytohormones" is not commonly used, plant hormones have also been referred to as such [4].


Plant hormones control every phase of the life cycle of the plant. In general, more than one hormone influences plant biological activity, therefore the biological phenomena frequently represents the combined interactions of multiple distinct hormones [5]. When plants confront biotic and abiotic pressures, they can only survive by altering various biological processes, unlike animals that may flee from harsh situations. In these circumstances, plant hormones also work together to alter biological reactions for the establishment and maintenance of plant stress tolerance. Transducing extracellular or intracellular signals into cellular responses is a process known as signal transduction. The processes of signal transduction are involved in hormones functioning. Hormones are compounds that function at low concentrations that circulate through some or all living creatures to signal and regulate the response, growth, and development of those organisms [6].
