The answer is Body temperature
Circadian rhythm will regulate the daily circle of an organism. There is many biological aspect that could be regulated such as the hormone secretion, blood sugar, body temperature, and sleepiness. The migration of birds would be happen annually, not daily. The female menstrual cycle would be happened monthly too.
The digestion of the food in humans begins in the mouth. In the mouth, the salivary amylase enzyme digests and breaks down a small amount of the starch present in the food. The digestion process begins right in the mouth. and continues till the intestine. The carbohydrates (starch) are the ones whose digestion starts in the mouth.
Hence, the blanks can be filled with 'mouth and amylase' respectively.
Vascular tissue is located inside the pericycle of a root, which I believe would be considered the inner layer.
