Hank Greene, an airline pilot, is having difficulty with the sleep-wakefulness portions of his circadian cycle. The pineal gland secretes the hormone , which influences this cycle.

one is through turgidity. this occurs before ground tissue ( collenchyma

and sclerenchyma cells) become well

developed to give structural support to the plant as it grows bigger. the xylem

tissue (composed of rigid tissue) of the young

plant render this support and also maintaining osmotic turgidity of the surrounding

plant cells.