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The effect of girdling on flowering and leaf net photosynthesis in mango cv. Cogshall

Urban L., Lechaudel M., Alphonsout L.. 2009. In : Oosthuyse Steve A. (ed.). Proceedings of the eighth international mango symposium, Sun City, South Africa, February 5-10, 2006. Louvain : ISHS [Belgique], p. 251-257. (Acta Horticulturae, 820). International Mango Symposium. 8, 2006-02-05/2006-02-10, Sun City (Afrique du Sud).

Girdling has been suggested as a way to improve earliness and intensity of flowering in mango. However, the accumulation of carbohydrates associated to girdling may result in a decrease in photosynthesis. The general objective of this trial was to get a preliminary view about the effect of girdling on flowering and leaf net photosynthesis (Anet) in mango, cv. Cogshall. The trial was performed on three-year old mango trees in la Réunion island. 18 branches were selected for being homogeneous in terms of light exposure and initial stem diameter. 7 branches were girdled on April 1, 2004, and 11 left untreated. Measurements of leaf gas exchanges and chlorophyll fluorescence parameters were performed each month from March to August 2004 on recently matured leaves, experiencing similar light exposure. Flowering occurred 15 days earlier in the girdled than in the non-girdled treatment. Anet was reduced by 77% within 28 days from girdling and remained at about 2 µmol m-2 s-1 until the beginning of flowering, then it started to recover. Differences in Anet between treatments and temporal variations in Anet were paralleled by differences and variations in stomatal conductance (gs) of similar magnitude. The negative effect of girdling on Anet was not due to a gs-associated decrease in the intercellular concentration in CO2 (Ci). But the negative effect of girdling on Anet appears attributable at least partly to a decrease in photosynthetic capacity in the first place, and on apparent photosynthetic light use efficiency ([alpha]) secondly. Although the negative effect of girdling on Anet is reversible, and although girdling small branches has probably exacerbated the rate and magnitude of carbohydrate accumulation and photosynthesis reduction, our results urge us to evaluate the effect of girdling on flowering in the light of its negative side-effect on photosynthesis.

Mots-clés : mangifera indica; réunion; france

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