Chilling response of 'Granny Smith' apple lateral buds inhibited by distalshoot tissues

Apple (Malus x domestica Borkh.) shoots were decapitated before or after ch illing and then forced to budburst to determine the influence of distal inh ibition (paradormancy) on the chilling response of lateral buds. Shoots wer e chilled and forced with the presence or absence of an inhibitory distal d isbudded shoot piece. Endogenous cytokinins were determined from distal and proximal segments of shoots segmented before and after chilling and/or for cing. The isolation of lateral buds from distal inhibition by decapitation before chilling resulted in a dramatic increase in growth rate. This increa se is greater than that observed in terminal buds during the normal develop ment of acrotony on intact shoots. Distal shoot tissues appear to inhibit t he chilling response of lateral buds. On intact shoots cytokinin increased more in the distal shoot tissues, but in decapitated shoots cytokinin incre ased more in the proximal shoot tissues. Increased cytokinin in the proxima l stem segment following decapitation is possibly associated with an increa sed lateral bud growth rate. (C) 2001 Elsevier Science B.V. All rights rese rved.