Abstract
Involvement of phytohormones in the formation of double pistils in sweet cherry (Prunus avium L.) was investigated. 1) ‘Satohnishiki’ spurs were sprayed with naphthaleneacetic acid (NAA), abscisic acid (ABA), gibberellin A3 (GA3), benzyleadenine (BA) and ethephon at 100 ppm. BA and ethephon treatments increased the percentage of flowers with double pistils. However, the frequency of double pistils was low in NAA, ABA and GA3 treatments. 2) Spurs of ‘Satohnishiki’ and ‘Napoleon’ were sprayed with 50 and 200 ppm BA. BA hastened the progression of flower differentiation and increased the occurrence of double pistils. 3) ‘Satohnishiki’ spurs were sprayed with 100 and 200 ppm ethephon. Ethephon also increased the frequency of double pistils, but delayed flower differentiation. 4) Ethylene production by spurs of the trees grown in sunlit growth chambers controlled at 20°C, 30°C, 35°C, increased with the temperature. These findings showed that BA and ethephon induce the formation of double pistils in sweet cherry. Since ethephon delayed the progression of flower differentiation similar to that due to high temperature and high temperature increased ethylene production by spurs, it is suggested that ethylene could be involved in the formation of double pistils induced by high temperature. However, BA accelerated flower differentiation in contrast to high temperature, indicating that the mechanism of pistil doubling induced by BA differs from that induced by high temperature.
