AOBPreview originally published online on June 10, 2009
Annals of Botany 2009 104(4):703-713; doi:10.1093/aob/mcp142
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Carbon allocation during fruiting in Rubus chamaemorus
1 Département de biologie
2 Centre de recherche en biologie forestière, Université Laval, Québec City, Québec, G1V 0A6, Canada
3 Centre de recherche Les Buissons, 358 chemin Principal, C.P. 455, Pointe-aux-Outardes, Québec, G0H 1M0, Canada
* For correspondence. E-mail line.lapointe{at}bio.ulaval.ca
Received: 17 December 2008 Returned for revision: 16 February 2009 Accepted: 27 April 2009 Published electronically: 10 June 2009
Background and Aims: Rubus chamaemorus (cloudberry) is a herbaceous clonal peatland plant that produces an extensive underground rhizome system with distant ramets. Most of these ramets are non-floral. The main objectives of this study were to determine: (a) if plant growth was source limited in cloudberry; (b) if the non-floral ramets translocated carbon (C) to the fruit; and (c) if there was competition between fruit, leaves and rhizomes for C during fruit development.
Methods: Floral and non-floral ramet activities were monitored during the period of flower and fruit development using three approaches: gas exchange measurements, 14CO2 labelling and dry mass accumulation in the different organs. Source and sink activity were manipulated by eliminating leaves or flowers or by reducing rhizome length.
Key Results: Photosynthetic rates were lower in floral than in deflowered ramets. Autoradiographs and 14C labelling data clearly indicated that fruit is a very strong sink for the floral ramet, whereas non-floral ramets translocated C toward the rhizome but not toward floral ramets. Nevertheless, rhizomes received some C from the floral ramet throughout the fruiting period. Ramets with shorter rhizomes produced smaller leaves and smaller fruits, and defoliated ramets produced very small fruits.
Conclusions: Plant growth appears to be source-limited in cloudberry since a reduction in sink strength did not induce a reduction in photosynthetic activity. Non-floral ramets did not participate directly to fruit development. Developing leaves appear to compete with the developing fruit but the intensity of this competition could vary with the specific timing of the two organs. The rhizome appears to act both as a source but also potentially as a sink during fruit development. Further studies are needed to characterize better the complex role played by the rhizome in fruit C nutrition.
Key words: Allocation pattern, 14C labelling, carbon translocation, carbon reserves, cloudberry, defoliation, fruit production, gas exchange, Rubus chamaemorus, source–sink relationship, flowering