© 2004 Heron Publishing—Victoria, Canada
Does variability in shoot carbon assimilation within the tree crown explain variability in peach fruit growth?
A. S. Walcroft (1, 2, 3), F. Lescourret (4), M. Génard (4), H. Sinoquet (1), X. Le Roux (1, 5) and N. Donès (1)
1. UMR 547 PIAF, INRA-Université Blaise Pascal, Domaine de Crouelle, 234 avenue du Brezet, 63039 Clermont-Ferrand Cedex 2, France / 2. Landcare Research, Private Bag 11052, Palmerston North, New Zealand / 3. Corresponding author (walcrofta@landcareresearch.co.nz) / 4. INRA - PSH, Domaine St. Paul, site Agroparc, 84914 Avignon Cedex 9, France / 5. Laboratoire d’Ecologie Microbienne (UMR 5557 CNRS-Université Lyon I, USC INRA), bat 741, 43 bd du 11 novembre 1918, 69622
Villeurbanne, France / Received May 9, 2003; accepted July 20, 2003; published online January 2, 2004
Summary
A three-dimensional model of radiative transfer and leaf gas exchange was used to quantify daily carbon (C) assimilation of
all fruit-bearing shoots (FBS) in an early maturing 6-year-old peach tree (Prunus persica L. Batsch) with a heavy crop load. For a sample of FBS (n = 36), growth of fruit and leafy shoots was measured every 1–2 weeks from 24 days after bloom (DAB) until harvest, between
93–101 DAB. The objective was to relate shoot C assimilation with harvested fruit mass for each shoot to test the hypothesis
that variation in C supply contributes significantly to variation in fruit growth within and among FBS. Mean C assimilation
of the sampled shoots was 0.07 g C fruit–1 day–1, but varied between 0.014 and 0.32 g C fruit–1 day–1. This indicates that C availability for fruit growth would have varied significantly among individual FBS if they were autonomous.
Mean fruit dry mass on each FBS varied between 0.716 and 7.68 g C at harvest, and most of the variation originated among,
not within, individual FBS. However, there were no correlations between the mean and standard deviation of fruit mass and
fruit relative growth rate when each was plotted against shoot C assimilation, indicating that factors such as those regulating
C demand of fruit, or C transfer among individual FBS, may be more important in controlling variability in fruit growth than
intra-crown variability in shoot C assimilation. Under the study conditions, FBS were non-autonomous for C, because a model
of fruit and leafy shoot growth was unable to reproduce the observed growth without supplementary contribution of C from shoots
without fruit.
Keywords:
branch autonomy, photosynthesis, radiative transfer, three-dimensional modeling.
