Search

The net photosynthesis of the Mediterranean brown seaweedCystoseira barbata f.repens is measured according to irradiance, temperature and salinity. There is not only, a good utilization of low light intensities (light-shade adaptation), but also a specific ability to use a broad range of irradiance, which corresponds in the photosynthesis-irradiance curves to a high initial slope and an extended light saturation level from 300 to 1500 μmol photon m−2 s−1; only very high irradiances induce photoinhibition. Maximum net photosynthesis occurred at temperatures ranging from 20 °C to 30 °C. The alga tolerates not only a low level of salinity, but also a slight increase in salinity; however, at more than 47.5 g 1−1 NaCl, oxygen exchange is significantly reduced.

Apical segments of Cystoseira barbata f. aurantia were grown in the laboratory under various light conditions: white light (as reference) or broad band isoquantic red light (600-700 nm, peak transmission: 660 nm) or blue light (400-580 nm, peak transmission: 430 nm). Growth of apices was higher under blue light than in other conditions. Morphogenesis of cultivated thalli under white or red light was different from field plants with high growth of primary axis and low level of ramifications. Under blue light, morphogenesis of thalli was similar to those harvested in nature. Net photosynthesis was measured and P VS I curves were established under white light. Maximum net photosynthetic rates and initial slope were higher for thalli cultivated under blue light and lower under white and red light (...)