Coupling of the canopy and the root system through carbon dynamics in tropical trees

Trees in tropical forests are considered the largest component of the terrestrial biosphere carbon cycle. Yet little is known about carbon related coupling between the canopy and the root system. The factors that determine tree carbon assimilation and respiration activities, and thus affecting the dynamics of the carbon cycle, are not yet fully appreciated. Mainly, the mechanisms of the coupling between the activity of the autotrophic and heterotrophic parts of the trees are still in debate. The interrelation between the photosynthesizing canopy, the source of carbohydrates, and the respiring root system, one of the sinks of carbohydrates, is not well understood because of the lack of access to the root system.

This research aims to investigate the canopy-root interrelation using a unique method of directly approaching roots in an aeroponics facility, the Sarah Racine Root Research Laboratory at Tel Aviv University, Tel Aviv, Israel. The Root Laboratory is a temperature controlled greenhouse, divided into compartments, each of which is further divided into an above-ground space of 2.8-4.5 m height and a fully accessible belowground space of 6 m depth. By flux measurements and carbon isotope labeling the type and velocity of coupling between canopy activity and root response can be studied. Two possible mechanisms couple plant photosynthetic activity with root respiration. Firstly, the direct transport of assimilates from leaves through the phloem to the roots. Secondly, the indirect physiochemical effect on root activity through pressure-concentration waves, which increases the turgor in the phloem. The latter mechanism has been suggested on theoretical grounds, but has yet to be shown in plants.

Eshel A, Grünzweig JM. 2013. Root-shoot allometry of tropical forest trees determined in a large-scale aeroponic system. Annals of Botany 112, 291-296.

Nina Buchmann, ETH Zurich, Switzerland

Israel Oren (PhD student)

Partner organizations:
ETH Zurich, Switzerland

canopy   canopy