Abstract
It is well known that there is a positive correlation between ploidy level and cell size. However, it is unknown how endoreduplication induces cell enlargement.
When bean plants grown in low intensity red light for 10 days (cell division in the primary leaves had completed) were transferred to bright white light, cells in the primary leaves rapidly enlarged (Van Volkenburgh and Cleland, 1979). This method was used in the present study with slight modification to induce rapid cell enlargement. After transfer to bright white light, nuclear DNA content in lower epidermal cells remained at the 2C level, whereas it increased to 4C in upper epidermal cells at 4 d after transfer. On the other hand, the size of lower epidermal cells increased by 60% in 5 d and remained unchanged thereafter, whereas upper epidermal cells continuously enlarged for 12d. This suggests that endoreduplication supports cell growth from 5 to 12d.
