ISHS Acta Horticulturae 329: VII International Symposium on Plant Growth Regulators in Fruit Production
LONG-TERM EFFECTS OF PACLOBUTRAZOL ON LONGEVITY OF SWEET CHERRY SPURS |
| Author: | P.E. Lauri |
| Abstract:
The action of paclobutrazol (PB) in reducing long shoot growth and enhancing flowering has been documented for more than ten years. Studies on some stone and pome fruit trees have also demonstrated its two to more than three year persistency, especially with soil applications. Little information is available on the long-term effects of PB treatment on spur longevity and on the evolution of their ability to fructify. This study on 'Van' sweet cherry trees was designed to investigate how an overall foliar PB application (500 mg / 1 a.i. ; 1.5 1 per tree) affects spur behavior during the year of treatment and the following two years. For each year, the percentage number of spurs per number of long shoot nodes is given as well as the distribution of spurs along the annual unit of extension. These results suggest that paclobutrazol acts at two different levels: firstly, by increasing the initial percentage of leafy spurs (80% versus 60%); secondly, by slowing down the percentage decrease of leafy spurs which characterized the untreated shoots as spurs aged (60% versus 20% for three year old spurs). The longevity of fruiting spurs was also highly correlated with PB treatment. The maximal percentage of fruiting spurs was observed for two year old spurs on control shoots (20%), with a decrease for three year old spurs, whereas the percentage of fruiting spurs increased steadily as spurs aged on treated shoots (reaching 50% at three years old). A twofold action hypothesis is proposed that PB may intrinsically affect spur behavior since it has a direct effect by persisting for at least three years in spur tissues and this action could be a side-effect of its known reduction of long shoot growth which leads to better light penetration within the crown. | |
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