Plant biology

Porous Light

Science Signaling  17 Feb 2009:
Vol. 2, Issue 58, pp. ec62
DOI: 10.1126/scisignal.258ec62

Stomata are microscopic pores in the leaf epidermis formed by specialized cells called guard cells. Light causes guard cells to widen the aperture of stomata, allowing more carbon dioxide to enter the plant interior to support increased photosynthesis. However, the factors that affect the development of different proportions of stomata on the leaf surface in response to long-term environmental changes in light are not well understood. Measuring the stomatal index (SI) (the ratio of the number of stomata divided by the total number of stomata and epidermal cells per unit area) of Arabidopsis plants grown under different light conditions, Casson et al. found that plants grown in red light had higher SIs than those grown in white light. Phytochromes are photoreceptors that detect red light, and plants grown in red light that lacked phytochrome B (phyB), but not phyA, phyC, or phyD, had lower SIs compared with wild-type plants. Photoactivated phyB translocates to the nucleus, where it interacts with transcription factors known as phytochrome-interacting factors (PIFs). Mutants defective in pif4, but not those lacking pif3, pif5, or pif6, exhibited reduced SIs when grown in red light. The authors note that phyB deficiency reduced SIs in plants grown in red light to a greater extent than did pif4 deficiency, suggesting that phyB may also regulate stomatal development through pif4-independent mechanisms.

S. A. Casson, K. A. Franklin, J. E. Gray, C. S. Grierson, G. C. Whitelam, A. M. Hetherington, phytochrome B and PIF4 regulate stomatal development in response to light quantity. Curr. Biol. 19, 229–234 (2009). [PubMed]