Plant physiology is the study of plant function and behaviour, and it includes all of the dynamic processes of growth, metabolism, defence, reproduction and communication that keep plants alive. It is the first line of defence and the primary means of interaction with the environment and climate. Because the majority of these activities occur at the level of cells, tissues, and organs, there is also a close relationship between plant physiology and plant anatomy, due to the close relationship between structure and function in plants.
Eco Physiology is the study of how a plant's physiology interacts with its environment, both physical and biological. It looks at how temperature and nutrients affect physiological processes in plants and animals, with a focus on how physiological processes scale with organism size. Many environments are stressful and have the potential to disrupt homeostasis, but organisms that live in these habitats are able to develop, mature, and reproduce under these difficult conditions, ecophysiology attempts to understand this mechanism.