羊栖菜幼孢子体对不同N水平生长条件和阳光紫外辐射的响应

探讨了太阳紫外辐射对两种N水平生长条件下羊栖菜幼孢子体光化学特性的影响及其恢复。结果显示,在高的光辐射下羊栖菜藻体的有效光化学效率和相对电子传递速率急剧下降,在全波长太阳辐射条件下它们的下降幅度要比仅在可见光处理下的藻体更大,2种N水平条件下藻体的光化学活性下降趋势相似,但是N加富的生长条件使得藻体具有更高抵御紫外辐射的能力,这可能是与N加富生长条件下的藻体中含有较高含量的紫外吸收物质和类胡萝卜素有关。结果表明羊栖菜的幼孢子体具有比成体更强抵御紫外线的能力,这主要体现在藻体受到紫外辐射损伤后的修复上。

Response of the young sporophytes of Hizikia fusiformis to different N growth conditions and the solar radiation

There are many studies that focused on the effects of changing marine environmental conditions on the adult stage of seaweeds. However, little work has been done to investigate the response of the juvenile stage of them to increasing solar ultraviolet (UV) radiation and coastal eutrophication. Hizikia fusiformis (Harvey) Okamura (Sargassaceae, Phaeophyta) is an important economic brown seaweed, and the culture of young sporophytes through sexual reproduction is a practically feasible approach to the artificial seedlings production of this species. Detailed information derived from physiological experiments is essential for successful controlling and management of growing seedlings in land-based system. In the present work, the effects of solar radiation on the photochemcial properties of photosynthesis were investigated in young sporophytes of Hizikia fusiformis grown at two different N availabilities. The results showed that during culture period, the young sporophytes exhibited a considerable increment of length. However, the relative growth rates were not statistically different between the young sporophytes grown under high N level and the ones grown under normal N level. The contents of Chl a, carotenoids and UV-absorbing compounds (UVAC) were significantly higher in high N-grown algae than the normal N-grown algae. The effective photosynthetic quantum yield and the relative electronic transfer rate (rETR) were drastically reduced in the young sporophytes when exposed to high solar radiation, with the decrease fluctuation being greater in treatment with all spectrum solar radiation (PAB) than the one with solar photosynthetically active radiation (PAR). The decrease trend of the effective photosynthetic quantum yield was similar between the algae grown under normal N level and high N level when the young sporophytes were exposed to PAR or PAB. However, when exposed to PAB, rETR of the thalli grown under high N level was higher than those grown under normal N level. This indicated that the young sporophytes cultured under high N level exhibited higher capacity of defending UV radiation, which might be related with the higher contents of UVAC and carotenoids in the young sporophytes. Our result showed that the young sporophytes of Hizikia fusiformis possessed the higher ability against UV damage than the adult sporophytes, which could be reflected from the recovery of the thalli which was damaged by UV radiation. It is proposed that in artificial seedlings production of Hizikia fusiformis, an appropriate addition of N nutrient in the seawater media would enhance the ability of young sporophytes to resistance the environmental stresses such as solar UV radiation, although the N fertilization had no obvious effect on the growth (length of the young sporophytes).