Effect of laminaran accumulation on maturation in sporophyte fragments from Ecklonia cava (Phaeophyceae, Laminariales) under various laboratory light and temperature conditions

Abstract

Fragments of Ecklonia cava Kjellman were cultured under controlled laboratory conditions of light irradiance, water temperature, and photoperiod. To clarify the relationship between the maturation of E. cava and the photosynthetic products, laminaran, the content in the fragments was measured with the progress of maturation. The culture conditions ranged from 12.5 to 100 mmol m -2 s -1 , 10-25°C, and 14 : 10 h LD (light : dark) to 10 : 14 h LD. In the case of low light conditions, despite an optimum temperature for maturation, the fragments did not form sori and laminaran was not accumulated during the culture period. In the case of sufficient light and non-optimum temperature conditions, the fragments did not form sori, but laminaran was accumulated. When the fragments were cultured under optimum light and temperature conditions for maturation, laminaran was accumulated in the early stage of maturation, just before or after cortex of the bladelets thickened, and decreased with the progress of maturation, and all fragments matured regardless of the length of the photoperiod. So, these results support the idea that laminaran is used as the main respiratory substrate in the maturation of E. cava.

Comparative Study of Polysaccharides from Reproductive and Sterile Tissues of Five Brown Seaweeds

“…The laminaran content increased in F. evanescens and S. japonica but decreased in S. babingtonii, A. ochotensis, and S. pallidum during sporulation (Table 2). Previously higher laminaran content in fertile plants as compared to the sterile ones was shown for a number of brown algae (Zvyagintseva et al 2005;Iwao et al 2008Iwao et al , 2010Imbs et al 2009). Laminaran was believed to be an important energy source for the formation of zoosporangia and was stored in the zoospores.…”

“…Laminaran was believed to be an important energy source for the formation of zoosporangia and was stored in the zoospores. It may be synthesized mainly to support maturation of the sori at the beginning of the maturation period as one of the major sources of respiratory substrate or as the source of carbon (Iwao et al 2008(Iwao et al , 2010. Then, laminaran is consumed during sporulation, and its content decreases with the progress of maturation of reproductive structures (Iwao et al 2010).…”

“…It may be synthesized mainly to support maturation of the sori at the beginning of the maturation period as one of the major sources of respiratory substrate or as the source of carbon (Iwao et al 2008(Iwao et al , 2010. Then, laminaran is consumed during sporulation, and its content decreases with the progress of maturation of reproductive structures (Iwao et al 2010). The differences in laminaran dynamics observed with changing of sterile algae into fertile ones might be related to different degrees of the reproductive organs' maturation.…”