Source-sink relation in plants

Plant performance -how does a plant grow under various conditions- depends on the acquisition of raw material (carbon fixation and mineral uptake), the allocation of this material over the plant organs, and the ability to cope with environmental stresses.

Although the above is a gross oversimplification, it provides a useful scheme to approach plant performance. For total biomass production, photosynthetic carbon dioxide fixation is by far the most important process. However, mineral nutrition, although contributing a much smaller proportion in terms of weight, is also essential for plant growth.

Functionally a plant can be divided into source and sink, sources being the parts where net fixation of carbon dioxide occurs, and sinks being the sites where assimilates are stored or used. Allocation of assimilates between plant parts occurs via transport in the phloem.

Much of the present research uses the model species Arabidopsis thaliana, because of its obvious advantages: small size, sequenced genome, availability of mutants, etc. However, in other projects we try to exploit the knowledge, as obtained in Arabidopsis, to other species, e.g. tomato and potato.

Our approach:

The understanding of source-sink relations implies research on primary metabolism, i.e. mainly carbohydrate metabolism. Therefore, we focus on metabolites and enzymes involved in this process, including cellular and tissue localization.

To understand the regulation of plant growth and allocation of reserves, insight into the genetic components is essential. QTL analysis, which makes use of existing natural variation within a species, offers such an approach. This approach will be used to gain insight into the various aspects of plant performance, to be studied at the level of primary production, allocation of assimilates, and interaction between mineral nutrition and carbohydrate metabolism.

Plants often have to cope with adverse environmental conditions (stress) and the effect of sub-optimal condition (e.g. drought or salt stress) is studied in several projects.