Abstract: Effects of extraneous ethylene concentrations on astaxanthin accumulation in H.pluvialis were studied in this paper. After different ethylene concentrations were added into the vegetative green cells respectively, then H.pluvialis were cultivated under unfavorable growth conditions (24 h light cycle, 5000 lux, 25 ℃ and nutrition deficiency) to promote astaxanthin accumulation. In this stage, morphological changes of cells treated by different ethylene concentations were observed with optical microscopy. Astaxanthin content was determined with absorption spectral (OD490). Results showed that the astaxanthin accumulation can be promoted at 0.05 ml/L ethylene in large scale. The 0.05 ml/L treatment can quicken the astaxanthin accumulation 17 days in comparison with blank controls and increase the astaxanthin liquid production reaching 18.6 mg/L or 92.1% higher than blank controls. However, 0.1 ml/L ethylene will on the contrary inhibit H.pluvialis accumulate of astaxanthin. Besides, high content of ethylene (≥0.15 ml/L ethylene) will be fatally lethal to cells.

Key words: Haematoccus pluvialis, astaxanthin content, ethylene, morphological change