Environmental control of gametogenesis in Laminaria saccharina. II. Correlation of nitrate and phosphate concentrations with gametogenesis and selected metabolites

Abstract

The gametophyte growth, morphology, gametogenesis, and metabolites of Laminaria saccharina (L.) Lamouroux were studied in different cyncentrations of nitrate and phosphate in axenic culture, using a synthetic seawater medium under optimal light and temperature conditions.Nitrate and phosphate were required for the various stages of gametophyte development and gametogenesis. Under nitrate and phosphate concentrations optimal for growth and gametogenesis, maximum quantities of DNA, RNA, protein, and carbohydrate, and low quantities of lipid were produced. Further, nutrient concentrations which gave rise to the greatest fertility also gave rise to the highest ratios of RNA/DNA and protein/RNA.Antheridial production occurred over a wider range of nitrate and phosphate concentrations than oogonial production. Further, percentage fertility was greater for the male gametophyte. This indicated that the female gametophyte was the limiting agent in sexual fusion.