Sensitivity of Floral Shoot Growth, Fruit Set and Early Fruit Size inActinidia deliciosato Local Carbon Supply

The sensitivity of pre-anthesis shoot growth, fruit set and early fruit size in kiwifruit [ Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson] to cane girdling and defoliation treatments was tested, and the results discussed in terms of shoot carbon balance. The nature and degree of responses obtained was dependent on the time of application. When treatments were applied soon after budbreak, defoliation initially reduced growth, whereas increasingly severe girdling treatments induced responses progressing from stimulation to severe impairment of growth and photosynthetic capability. Similar treatments imposed later in shoot development produced qualitatively different results. The development of floral tissues on the shoot is shown to be sensitive to shoot carbon status during a period close to anthesis, and the significance of this result in relation to fruit heterogeneity at maturity is discussed.