This chapter introduces central topics in physiological processes that control plant growth, development, and responses to environmental factors. It will cover transport, phytohormones, and photosynthesis, the most important reaction in the biosphere. Plant growth and development are regulated by physiological processes. Xylem transport ensures the movement of water and dissolved minerals from roots to aerial parts, supporting transpiration and nutrient distribution. Plant responses to biotic (e.g., pathogens) and abiotic (e.g., drought, salinity, temperature) factors are mediated through signaling networks. These responses enable plants to adapt and survive in changing environments. Phytohormones such as auxins, gibberellins, cytokinins, ethylene, and abscisic acid regulate plant growth and developmental processes, including cell division, elongation, seed germination, flowering, and fruit ripening. For example, auxins influence tropisms and root development, while abscisic acid mediates drought tolerance by controlling stomatal closure. Understanding plant physiological processes provides insights into how plants integrate internal and external cues to optimize plant growth and reproduction and develop sustainable practices to meet global food security.