Abstract: The embryo spores of Laminaria japonica were cultured in artificial se
awater with different N/P ratio to observe their early development. 80 percent o
f the spores cultivated in whole-ingredient artificial seawater developed norma
lly, but the time of spore germination and gametophyte formation was lagged sign
ificantly  and the amount of female gametes was significantly hig
her than that of male gametes (P<0001), as compared to the control cultiva
ted in natural seawater. Artificial seawater with different N/P ratio showed dif
ferent effects on the spore germination rate. The artificial seawater with N/P＞
15 decreased the spore germination rate, while that without N or P inhibited the
 spore germination significantly (P<0001). It was concluded that
L. japonica spores could develop normally in artificial seawater, but their
germination rate was affected by the seawater N/P. The deficiency of N or P in a
rtificial seawater would lag the time of gametophyte formation and affect the di
fferentiation ratio of female-male gametes.

Key words: artificial seawater, N/P ratio, embryo spore, early development, Laminaria japonica, runoff efficiency, alfalfa, soil water storage, hay yield.