EFFECTS OF ABSCISIC-ACID ON EX-VITRO ACCLIMATIZATION OF ARONIA-ARBUTIFOLIA (L) PERS

The use of abscisic acid (ABA) as an in vitro prehardening treatment t o enhance ex vitro acclimatization of Stage III Aronia arbutifolia pla ntlets was explored. Effects of ABA (0-4 mg . liter(-1)) pretreatment on ex vitro shoot growth, leaf carbon assimilation (LCA) and nonstruct ural carbohydrate content were evaluated during plantlet acclimatizati on under two photosynthetic photon flux (PPF) levels (450 and 650 mu m ol . m(-2). s(-1)). Stage III plantlets rooted in the presence of ABA exhibited both shoot growth inhibition and transient negative LCA rate s at time of transfer ex vitro. Regardless of treatment, maximum LCA r ates were achieved by day 20 post-transplant. Pretreatment with AEA ha d no effect on stem or leaf starch content at time of transplant, howe ver, leaf and stem soluble sugar content was higher in ABA treated pla ntlets than controls. Further suppression of shoot growth and alterati on in the pattern of stem starch utilization occurred at the higher ir radiance level. These results indicate that ABA pretreatments provide no physiological advantage that would facilitate ex vitro acclimatizat ion of Aronia plantlets.