Identification of (+)-abscisic acid in strawberry leaves

The acidic ether extract of leaves collected in October from dormant strawberry plants outdoors at Invergowrie inhibited coleoptile growth in germinating wheat embryos. On paper chromatograms developed either with isopropanol: ammonium hydroxide: water (10:1:1) or isopropanol: 1% ammonium hydroxide (4:1), the zones possessing inhibitory activity had Rf's 0.6-0.7 and 0.6-1 respectively. Fractions possessing comparable activity were eluted from granular animal charcoal columns by 10% and 20% acetone in water, and, on further purification, eluted only by 10% ethyl acetate in chloroform from columns of celitesilicic acid (2:1). The inhibitor in this fraction was identified as (+)-abscisic acid (abscisin II, dormin) by spectropolarimetry.