Phytochrome control of the growth and development of Rumex obtusifolius under simulated canopy light environments*

Studies on the growth and development of Rumex obtusifolius seedlings under simulated shade conditions show that both light quantity and quality contribute to the observed responses. In the shade situation the plants have lower dry matter, lower leaf area and lower net assimilation rates. Petiole elongation occurs under shade conditions only after transfer of the plants from non‐shade environments. The effects of light quality are related to phytochrome photoequilibria set up by the increased relative photon flux in the far‐red found under vegetation canopies.