ISHS Acta Horticulturae 636: XXVI International Horticultural Congress: Key Processes in the Growth and Cropping of Deciduous Fruit and Nut Trees
POSSIBLE ROLES OF SUGAR CONCENTRATION AND ITS METABOLISM IN THE REGULATION OF FLOWER BUD INFORMATION IN JAPANESE PEAR (PYRUS PYRIFOLIA) |
| Authors: | A. Ito, H. Hayama, Y. Kashimura |
| Keywords: | carbohydrate, sorbitol, sucrose, sugar catabolism, enzyme activity, sugar concentration |
| DOI: | 10.17660/ActaHortic.2004.636.44 |
| Abstract:
In order to elucidate the role of carbohydrate in flower bud formation, the relationship between bud growth rate and sugar concentrations/sugar catabolizing enzyme activities were investigated during flower bud development using untreated and shaded buds of ‘Kosui’, and untreated buds of ‘Chojuro’ Japanese pears (Pyrus pyrifolia). Concentrations of fructose, glucose, sorbitol and sucrose were measured, as were the activities of NAD-dependent sorbitol dehydrogenase (NAD-SDH), NADP- dependent SDH (NADP-SDH), sucrose synthase (SS) and acid invertase (AI) in the buds. When comparing untreated ‘Kosui’ and ‘Chojuro’ buds, bud weight increment was larger in ‘Chojuro’ than in ‘Kosui’, and activities of all enzymes measured here were higher in ‘Chojuro’ than in ‘Kosui’. Sorbitol and sucrose concentrations were higher in ‘Kosui’ than in ‘Chojuro’. On the other hand, early three-week shadings (shading between May 24th to July 28th) decreased the concentrations of sorbitol, glucose and fructose in the buds and simultaneously decreased the increment of bud fresh weight as compared with the non-treated buds, but later shadings (between July 28th to September 2nd) did not. Activities of NAD-SDH, NADP-SDH, AI (soluble form) and SS became higher in the shaded bud than in the non-treated bud. When considering the data of untreated ‘Kosui’ and ‘Chojuro’ buds, bud growth rate correlated positively with the activities of NAD-SDH and AI (soluble) whereas it correlated with no type of sugar concentration. On the other hand, when considering the data of untreated and shaded ‘Kosui’ buds, bud growth rate correlated with fructose, glucose and sorbitol concentrations whereas it correlated with no type of enzyme activity. We postulate that the higher activities of sugar catabolizing enzymes should enhance the capacity of buds to attract assimilates thereby accelerating bud growth. However, when carbohydrate supply to the bud is severely limited, sugar concentration should be the limiting factor of bud growth. | |
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