EFFECT OF RADIATION QUALITY ON GROWTH, NITROGEN UPTAKE, AND HCO3-, CO2 AND PH INTERACTIONS IN ULVA-PERTUSA

A floating sterile mutant of Ulva pertusa, which grows faster than the wild type and also during summer periods, was grown in the laboratory under ''white light'' (WR as reference), broad band isoquantic red (6 00-700 nm, KR) and blue (400-500 nm, BR) radiation. The observed speci fic growth rates at WR, BR, and RR were 8.6, 2.15, and 1.2 %, respecti vely. A stimulatory effect of BR on the growth at low irradiance (60 m u mol m(-2) s(-1)) was observed during the 15 d of culture. Around 42. 1 % of total nitrogen was used by Ulva mutant in WR, but under BR and RR it was around 27.0 and 16.7 %, respectively, However, the utilizati on of nitrogen under BR was significantly higher than under RR, Consid erable CO2 fluctuation in the light and dark periods was observed in a ll the cultures, and it was higher under WR, followed by BR and RR. Th e possible growth promoting effect of BR includes nitrogen uptake and the consumption of HCO3- which in turn leads to reduced air CO2 concen tration in the medium.