We examined the response of rhizome growth to red light-break under different short daylengths in lotus (Nelumbo nucifera) seedlings. Maximum inhibitory response of rhizome enlargement to light-break under 10, 8 and 4 hr daylengths occurred 10, 8-10 and 12-14 hrs after the beginning of the dark period, respectively. It was found that rhythmic response to light-break is involved in rhizome growth of lotus.