Brassinosteroid enhanced the level of abscisic acid in Chlorella vulgaris subjected to short-term heat stress.

The present study was undertaken to test the influence of exogenously applied 10nM brassinolide (BL) on the abscisic acid (ABA) content in Chlorella vulgaris cultures subjected to short-term (3h) heat stress (30-40 degrees C). We found that BL enhanced the ABA content with increase in temperature. In parallel, under these conditions treatment with BL resulted in growth levels very similar to those of control cell cultures (non-treated). BL had no significant effect on the content of chlorophyll or sugar in Chlorella vulgaris cells. Only a slight effect of BL on the protein content was observed. Under normal growth conditions (25 degrees C), BL showed a minor increase in the ABA content in Chlorella vulgaris cells. The present work also demonstrates that Chlorella vulgaris can synthesize ABA. This is the first evidence of ABA detection in Chlorella vulgaris cells.