Fundamental processes such as photosynthesis , respiration , plant nutrition , plant hormone functions , tropisms , nastic movements , photoperiodism , photomorphogenesis , circadian rhythms , environmental stress physiology , seed germination , dormancy and stomata function and transpiration , both parts of plant water relations , are studied by plant physiologists .
The main topics of plant physiology are photosynthesis , respiration , plant nutrition , plant hormones , tropisms , nastic movements , photoperiodism , photomorphogenesis , circadian rhythms , environmental stress physiology , seed germination , dormancy , stomata function and transpiration .