Influence of irradiance and salinity on the growth of carposporelings and juvenile tetrasporophytes in Gracilaria gracilis ( Stackhouse) M. Steentoft, L.M. Irvine & W.F. Farnham ( Rhodophyta; Rhodophyceae; Gracilariales) and agar yield

Abstract

The present study aims to investigate the effects of irradiance and salinity on the growth and agar yield in early stages of development of carposporelings and young tetrasporophytes of Gracilaria gracilis in the laboratory The present study aims to investigate the effects of irradiance and salinity on the growth and agar yield in early stages of development of carposporelings and young tetrasporophytes of Gracilaria gracilis in the laboratory conditions. Three levels of irradiance, photoperiod and salinity were tested. The results showed that the highest growth in basal disc of carposporelings was recorded at 8:16h light/dark, 60 µmol photons m-²s -1, and a salinity of 40 psu after four weeks of culture. The optimal percentage of erect fronds occurred at 16:8 h light/dark, 32 µmol photons.m-² s-1 and a salinity of 30 psu .The highest weight (about 6000mg) of juvenile tetrasporophytes was recorded at 40psu after 228 culture days. The maximum of length was also obtained at 40 psu at the end of the study. The best agar yield was recorded at 8:16 h light/ dark and a salinity of 20 psu. This study proved that Gracilaria may be cultivated using spores in order to obtain mature plants and then extract useful compounds such as gar.