Auxin induced stress tolerance in algae.

IAA effect on responses of West African algae Caloglosa, Bostrychia, Rhizoclonium and the fresh water alga Pithophora to different growth conditions was examined in growth chamber experiments. The auxin (2.28 x 10(-5) M) caused growth increase of 2.3- and 2.6-fold in Caloglossa and 1.6 and 1.7 in Rhizoclonium, respectively, in sea water and 1:1 diluted sea water/Erdschreiber medium. In Bostrychia pronounced deterioration of growth was noticed in the control samples between 16 and 32 days in culture. The cultures maintained an active growth, however, in the presence of IAA. IAA also allowed Pithophora to withstand salinity: Compared to growth in fresh water, a 65% growth inhibition was recorded in 1:1 diluted sea water in the absence of auxin and a slight growth stimulation when the auxin was present. Pithophora and Rhizoclonium also maintained higher rates of growth in extremal temperatures of 10 and 45 degrees C when the auxin was present.