Effect of Abscisic Acid on Root and Shoot Growth of Tomato1

Abstract Abscisic acid (ABA) at concentrations between 5 × 10 −7 and 5 × 10 −4 m , was sprayed on seedlings of ‘Sutton's Best of AH’ tomato ( Lycopersicon esculentum Mill). ABA at 5 × 10 −7 and 5 × 10 −6 m significantly enhanced shoot extension growth but did not markedly affect chlorophyll production. Root, but not shoot, fresh and dry weights were significantly reduced by 5 × 10 −5 m ABA. 5 × 10 −6 and 5 × 10 −5 m ABA significantly reduced the root: shoot ratio.