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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Plant Sci. | doi: 10.3389/fpls.2019.01039

Fruit and Leaf Response to different Source-Sink ratios in Apple, at the scale of the Fruit-bearing Branch.

  • 1INRA Plantes et Système de cultures Horticoles, France
  • 2Agrocampus Ouest, France

Apple fruit growth is the result of several factors: inherent demand (relative sink strength) of the fruit (defined by the demands for cell division and expansion growth etc.), carbon assimilation by the source leaves (source strength), and the resulting allocation to the organ in question. It is thus a complex process involving source-sink interactions. In the present study, we designed an experimental system in which parts of fruit-bearing branches of two apple cultivars (‘Fuji’ and ‘Ariane’) were isolated from the rest of the tree by girdling and then subjected to specific pruning and fruit removal treatments in order to create a wide range of global (branch-level) source-sink ratios. We monitored fruit kinetics but also photosynthesis as a response to light in leaves of the three different shoot types (i.e. the rosette, the bourse and the vegetative shoots) in order (1) to study the impact of source-sink distance on carbon partitioning between fruits within the same branch and (2) to investigate the impact of source/sink ratio on fruit growth and leaf photosynthetic activity. Our results indicate (1) no significant differences among lateral fruits belonging to different ranks, and this independent of source availability; (2) that a modification of the source/sink ratio seems to be compensated by an alteration of the photosynthetic rate of leaves, with stronger and weaker values obtained for lower and higher ratios, respectively. Moreover, our results seem to suggest that two growing sinks together will upregulate photosynthesis rate more strongly than one growing sink does on its own, and this with the same leaf area per fruit. These results are discussed and some hypotheses are put forward to explain them.

Keywords: Malus domestica (Bork.), apple, branch, Source-sink ratio, Photosynthesis, defoliation, FSPM, fruit growth

Received: 30 Dec 2018; Accepted: 25 Jul 2019.

Copyright: © 2019 Baïram, Le Morvan, Delaire and Buck-Sorlin. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence:
Dr. Emna Baïram, INRA Plantes et Système de cultures Horticoles, Avignon, France, emna.bairam@gmail.com
Prof. Gerhard Buck-Sorlin, Agrocampus Ouest, Rennes, 35042, Brittany, France, gerhard.buck-sorlin@agrocampus-ouest.fr