Autumn photosynthesis of 'Golden Delicious' apple trees - the effects of picking and fertilisation treatment

摘要

The influence of the foliar application of the mineral nutrients phosphorus and potassium on the photosynthesis and leaf and bark carbohydrates (sorbitol, sucrose, fructose and glucose) was studied in Malus domestica cv. 'Golden Delicious'. The research was done on 12-year old trees on M9 rootstocks (unpicked or picked trees either sprayed or not with the PK fertilizer Hascon M 10 AD) in the year 2000. Measurements of photosynthesis showed high photosynthetic activity (A(350)) and photosynthetic capacity (A(2000)) of apple trees in the late season. Results of the measurements of photosynthetic activity indicate that sink regulation of apple leaf photosynthesis was dependent on the fertilisation treatment. Photosynthesis measured at 350 ppm was the highest in the PK sprayed unpicked trees and the lowest in the PK sprayed trees without the crop. The sink removal effect was not observable two days after fruit picking, but was significant 5 and 20 days later. All trees showed a high photosynthetic capacity which decreased slowly until the end of October. The onset of senescence could be seen also from the foliar phosphorus content. Eight days after fruit removal trees without fruits showed significantly higher contents of sorbitol, sucrose, and fructose in the leaves. Sink dependent translocation of carbohydrates can be seen from the analyses of bark carbohydrates as well. The unpicked trees sprayed with PK had a significantly lower content of sorbitol and high photosynthetic rate when compared to the sprayed and picked trees. Nutritional dependency on sink/source effect could not be supported by foliar analyses.