Responses of carbon acquisition traits to irradiance and light quality in Mercurialis annua (Euphorbiaceae): evidence for weak integration of plastic responses.

It is often suggested that traits will be integrated, either because of pleiotropy or because natural selection may favor suites of integrated traits. Plant responses to different environments can provide evidence of such integration. We grew Mercurialis annua plants in high-density stands in high irradiance, in neutral shade, and in high red to far-red (R:FR) shade, resulting in environments of high irradiance, low R:FR; low irradiance, low R:FR; and low irradiance, high R:FR.