There is an immediate need to increase crop productivity for food and fuel, due to a rapidly increasing global population but there is still a controversy in the scientific community as to which process mainly controls plant growth and hence final crop yield – source or sink capacity.
Source activity refers to photoassimilate production, for example by photosynthesizing leaves. Sink activity is photoassimilate use and storage. Belowground organs of plants (e.g. roots and rhizomes) are sinks during plant growth since they cannot perform photosynthesis. Some organs are both a source and sink. Leaves are sinks when growing and sources when photosynthesizing. Rhizomes are sinks when growing but become sources in the spring when they provide energy for new growth.
A new study by Sonnewwald and Fernie provides a short review of the source vs. sink debate, then focuses on the use of transgenic intervention as a means to influence yield by modifying either source or sink function (or both).
The authors assess of a selection of publications on genetic manipulation source, sink or both. They find that while manipulation of single gene targets have been wholly unsuccessful, the limited work on multi-gene targeting simultaneously manipulating both source and sink has been promising.
Given that “it is clear that a beneficial manipulation of source-sink relationships is far from being something that is facile to predict,” the authors suggest that future manipulations be guided by whole plant modelling. This can better address the inherent complexity of the system while “rapidly simulat[ting] interventions without the need for intervening time lags that going through multiple generations of plants ensues.”