Abstract: Circumnutation of sunflower seedlings was investigated with a self-made-equipment which enabled us to measure the movement track in three dimensions. The results showed that: 1. The tracks of the circumnutation in sunflower seedlings were of three types: elliptic, oscillating and irregular. 2. One seedling might change the circumnutation type in its course of development. Furthermore, seedlings in the same developmental stage also showed different types of tracks of movement. 3. The direction of the autonomous circumnutation could be clockwise or counter-clockwise. An artificial light moving circularly for a certain period of time could change the original direction of the movement. 4. The cireumnutation could not be recorded in the seedling of 1--3 days after sowing in our experiments. It could be measured during 4--8 days after sowing. From the 9th day onwards, the hypocotyls ceased to grow, hence no movement. From the view point of three dimensions, the sphere of the circumnutation generaly increased from the 4th day to the 6th day, and it reduced from the 6th to the 8th day.

Key words: Sunflower, Circumnutation, Three dimension track