Leaf development in canopy shade (J. Exp. Bot)

Vegetative shade affects the ratio of red (R) and far-red (FR) light; relative to sunlight, the R/FR ratio is decreased due to absorbance of photosynthetically-active R light by other leaves. Low R/FR ratios cause increased elongation of shaded plant stems and petioles, as the plants strive to raise their photosynthetic tissues above those of their competitors. Carabelli, Possentti and Sessa et al. explored the effect of low R/FR on the development of the leaf blade (lamina). Previous work indicated that leaf blade expansion is decreased in low R/FR, and this new study shows that shade leads to a premature exit from the cell cycle, decreasing the number of cells produced. The authors also showed that several HD-Zip II transcription factors contribute to this effect. (Summary by Mary Williams) J. Exp. Bot. 10.1093/jxb/ery331