Effects of light conditions on the growth of commercial seaweed Undaria pinnatifida

Abstract

The artificial lighting conditions which promoted growth of the gametophytes and sporophytes of brown alga Undaria pinnatifida were examined. The seaweed was subjected to continuous or intermittent white, blue, or red light. There were notable, but not significant, differences in gametophyte and sporophyte growth between continuous and intermittent (104 Hz) white light conditions. Gametophyte growth was promoted most notably by white, followed by blue light. Sporophyte growth length was promoted most notably under intermittent white light, while body length and blade area were promoted notably under continuous white light. Sporophytes under blue or red light withered considerably. The results showed that white light is more beneficial for growth of both U. pinnatifida gametophytes and sporophytes compared with blue or red light. Male and female gametophyte grew more robustly under white light regardless of whether the pattern was intermittent or continuous light. However, the results further indicated that overall continuous white light promoted growth to a greater degree than did intermittent white light. Finally, white light promoted U. pinnatifida sporophyte growth to a greater degree than blue or red light.   Key words: Light wavelength, intermittent light, Undaria pinnatifida, seaweed culture, sporophyte growth.