“It is the type of coordination present between the cells or different organs within the body of multicellular organisms. In this kind of coordination, a group of cells releases specific chemicals, which regulates the activities of other cells of the body.” Chemical coordination occurs in plants with the help of fluids secreted in plants known as phytohormones or plant hormones. For example, auxin is responsible for the growth of the plants, and cytokinin helps in cell division in the fast-growing part of the plant such as plant hormones. External stimuli greatly influence the synthesis and action of phytohormones. Plants respond to the photo-periodic stimulus by specialized pigment present in the minimal quantity called phytochrome.