EFFECTS OF NACL AND KNO(3) CONCENTRATIONS ON THE ABSCISIC-ACID CONTENT OF DUNALIELLA SP (CHLOROPHYTA)

Abscisic acid (ABA) is a hormone which has a number of roles during th e life cycle of a plant. We demonstrated the occurrence of ABA in a ha lotolerant green alga, Dunaliella sp. isolated from a salt pond near A delaide, South Australia, using thin layer chromatography (TLC), high performance liquid chromatography (HPLC) and gas chromatography-mass s pectrometry (GC-MS). The variation of cellular ABA and protein content during the growth of an axenic clonal culture of Dunaliella sp. was i nvestigated under different concentrations of NaCl and KNO3. Experimen tal results can be summarized as follow: (1) ABA content was changed w ith the growth stage of culture: A rapid increase in ABA content was o bserved in the logarithmic phase. After this, the content rapidly decr eased to very low values. (2) ABA content was also affected by the NaC l concentration. The content had a minimum value at the NaCl concentra tion (15%) where growth rate was maximal, and higher values at higher or lower concentrations of NaCl. (3) The ABA content also increased wi th decreasing nitrogen concentration of the medium.