Abstract
Terrestrial plants utilize gravity (1g) as stress and signal factors for growth and morphogenesis. Their gravity-responses have been studied in relation to gravitropism or simulated microgravity conditions. Here we examined possible deteriorative or resistant responses of callus cells to hypergravity originated by centrifugation at 100g. Callus cells obtained from either suspension-cells or root tissues of tomato and broad bean were then grown on MS-agar media in centrifuge tubes. We found that the cell growth was strongly inhibited under 100g conditions for 2-4days. However, the growth was partially recovered after 4days, suggesting that the cells accommodated to the hypergravity conditions with tolerance characteristics developed. Under 100g conditions, cell wall synthesis was strongly inhibited and intracellular levels of soluble sugars, thiols and some enzymatic activities for primary sugar-metabolisms increased temporarily in the earlier hypergravity responses. Following these, growth recovery responses involved the total increase of cell wall contents in the cells.
