ISHS Acta Horticulturae 800: X International Pear Symposium
TRANSLOCATION OF NUTRIENTS IN JAPANESE PEAR 'KOSUI' GRAFTED BY THE 'TREE JOINT' METHOD |
| Authors: | T. Seki, K. Kawashima, K. Shibata, H. Inoue, Y. Umemiya |
| Keywords: | 13C, 15N, stable isotope, sap flow, flow rate |
| Abstract:
We investigated the translocation of 13C photosynthates and 15N synthates in order to elucidate the mechanism of nutrient translocation in Japanese pear (Pyrus pyrifolia Nakai) 'Kosui' trees grafted by the ‘tree joint’ method. Young 'Kosui' trees were potted in 2003 and 2004, and two or three trees were grafted together by the ‘tree joint’ method. In 2003, 13CO2 was applied on September 9 to the leaves of two jointed 'Kosui' trees. Plants were sampled on September 12. In 2004, 15N-Ammonium Sulfate was applied to two jointed trees on July 6, and then sampled on August 10 and September 13. The translocation rate (translocated assimilate/total assimilate) of 13C and 15N were 3.8–7.0% and 1.1–4.4%, respectively. 13C was translocated more to the top part of the tree along the main stem than the bottom. When 13C assimilation was conducted to either one of two jointed trees, very little was distributed into the root and rootstock of the other. Distribution rate to the main stem was the highest. This translocation of assimilate between grafted trees might be destined for reserve organs in the period of reserve nutrient accumulation. 15N translocation from the top of the tree to the bottom was observed most in leaves and current shoots on August 10. This suggested that the grafting point and leaves of an adjacent tree were so close that translocation to these leaves and current shoots occurred. On the other hand, translocation of nitrogen from the bottom of trees to the top was observed much in roots or rootstocks of the top trees on August 10, followed by much translocation rate in leaves and current shoots on September 13. It is suggested that once the translocation from the grafting point towards the root system had occurred, then nitrogen assimilate was translocated to leaves and current shoots. The effect of cutting off the stem of the central tree on three 'Kosui' jointed trees was investigated on October 13, 2006. Photosynthesis and stomatal conductance was reduced but no difference was detected between the cut and non-cut treatments. It is suggested that there might be very little short term effect of cutting off the stem. The transpiration flow rate of jointed trees after cutting the stem off was investigated on November 2. Slight changes were observed in the stem and the scaffold branches of the central tree for three hours after the cutting, but very little change was seen in the top tree and the bottom one, showing that the short term effect on water status by cutting the stem off of the central tree occurs only in the central tree, not in the adjacent trees. | |
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