Effects of Growth Regulators on Abscission of Young Macadamia Fruit

Abstract

Abstract The abscission of young Macadamia integrifolia Maiden & Betche fruit was investigated in vitro with explants consisting of a single fruit attached at the distal end of a segment of the peduncle. A 30% reduction in fruit removal force (FRF) of explants incubated in distilled water was evident within 48 hr after excision and was correlated with increased ethylene production. Pretreatment of explants with 5 and 10 mm ethephon accelerated FRF reduction. Pretreatment with increasing concentrations of silver nitrate (AgNO3) to 1.47 mm or AOA to 0.05 mm, inhibited the reduction in FRF. FRF reduction also was inhibited by 1000 μm NAA and 100 pM 2,4-D. GA3 and BA had no effect. Chemical names used: (2-chloroethyl)phosphonic acid (ethephon); 1-naphthaleneacetic acid (NAA); (2,4-dichloro- phenoxy)acetic acid (2,4-D); gibberellic acid (GA3); N-(phenylmethyl)-H-purin-6-amine (BA); (aminooxy)acetic acid (AOA).