Abstract:

To explore the effects of fruit bagging on apple quality, eight-year-old red ‘Fuji’ apple trees (‘Tianhong 2’/‘M26’/Malus× robusta) were used as experimental materials, and five treatments (no-bagging, bagging 1/3 of all fruits, bagging 1/2 of all fruits, bagging 2/3 of all fruits and bagging all fruits) were set up. The Kobayashi fruit bags (double layer paper bag, inner red and outer brown) were used in all treatments. The effects of different fruit bagging densities on photosynthetic characteristics of tree leaves were studied before fruit bagging (June 19), 2 days after bagging (June 21), during bagging (August 22 and September 27), 2 days after bag removal (October 9) and 1 day after harvest (November 3). The results showed that bagging not only decreased the light intensity within the apple tree canopy, but also significantly reduced the photosynthetic rate of the leaves, while the net photosynthetic rate within the apple tree canopy significantly decreased with the increase of fruit bagging density, especially in August and September. The changes of the light intensity in the canopy, stomatal conductance, chlorophyll content, carotenoid content and specific leaf weight of leaves in the five treatments were basically consistent with the change of net photosynthetic rate, suggesting that fruit bagging could lower the leaf photosynthetic performance. Our experiments also indicated that the decrease of photosynthetic rate was caused by the decrease of stomatal conductance and this might be associated with the decrease of light intensity, while in September, the decrease of photosynthetic rate might also be related to high temperature and weak light intensity, and non-stomatal limitation in leaves of bagged apples.

Key words: apple trees, bagging, tree canopy, photosynthesis, chlorophyll, light intensity, stomatal limitation