Effect of spray volume and time of NAA application on fruit size and cropping of Redchief \u27Delicious\u27

The effect of naphthaleneacetic acid (NAA) thinning sprays on fruit size of Redchief ‘Delicious’ apple was studied in relation to spray application volume and time of application. A constant dose of NAA resulted in similar fruit size at harvest when applied in varying spray volumes from high (near full retention, Vx) to Vx/8. NAA applied as a high volume spray (15 mg l−1) at various stages of fruit development (4.6 to 22.5 mm king fruit diameter, KFD), indicated that the maximum amount of small fruit was produced following applications at about 11 mm KFD. NAA did not consistently affect growth rate of king fruit immediately after treatment when fruit competition was minimized. NAA reduced fruit size at harvest by about 11% when two competing fruits were present on the same spur, but did not significantly reduce fruit size when a single fruit was permitted to develop per spur

The effect of NAA and BA on carbon dioxide assimilation by shoot leaves of spur-type ‘Delicious’ and ‘Empire’ apple trees

The effects of NAA, BA, or Accel on CO2 assimilation of shoot leaves of mature bearing Redchief \u27Delicious\u27 and \u27Empire\u27 apple (Malus X domestica Borkh.) trees were evaluated over two seasons. BA at 50 mg.L-1 did not significantly affect any of the gas-exchange parameters measured. NAA (15 mg.L-1) consistently suppressed CO2 assimilation rate (from approximately 10% to 24% below that of the control). This suppression was NAA-concentration dependent, continued for \u3e15 days after treatment, and was completely overcome in \u27Empire\u27, but only partially or not at all in \u27Delicious\u27 when BA was combined with NAA. These results are discussed in relation to fruit thinning and NAA-induced inhibition of fruit growth in spur-type \u27Delicious\u27