When growth controls photosynthesis

In this article I summarize a number of principles that control plant growth under natural growth condition. The main message is that under most environmental conditions, photoassimilate provision is less constrained than structural carbon investment. This means that the controls of carbon investment need to be modeled as a priority over carbon acquisition (photosynthesis). The dominance of carbon sink control over carbon source control is particularly pronounced under drought and low temperature. The fine tuning between C-sink and C-source activity makes it difficult to show which is the dominant driver. Experimental research (manipulation of plant and environmental conditions) and studies along environmental gradients show that, except for shade condition, C is rarely a limiting resource at current atmospheric CO2 concentrations. Mutual shading in dense plant stands has to be viewed in an evolutionary, rather a leaf carbon balance context only.