OPEN ACCESS ARTICLE

This Article Free via Open Access: OA OA Full Text Full Text (PDF) Supplemental Data OA All Versions of this Article: 150/2/1083    most recent pp.109.135509v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Boccalandro, H. E. Articles by Casal, J. J. Search for Related Content PubMed PubMed Citation Articles by Boccalandro, H. E. Articles by Casal, J. J. Agricola Articles by Boccalandro, H. E. Articles by Casal, J. J.

WHOLE PLANT AND ECOPHYSIOLOGY

Phytochrome B Enhances Photosynthesis at the Expense of Water-Use Efficiency in Arabidopsis^1,[W],[OA]

IFEVA, Facultad de Agronomía, Universidad de Buenos Aires, and Consejo Nacional de Investigaciones Científicas y Técnicas, 1417–Buenos Aires, Argentina (H.E.B., M.L.R., J.E.M., M.J.Y., J.J.C.); Cátedra de Cultivos Industriales, Departamento de Producción Vegetal, Facultad de Agronomía, Universidad de Buenos Aires, 1417–Buenos Aires, Argentina (E.L.P.); and Facultad de Ciencias Ambientales and Instituto de Ciencias Ambientale, Universidad de Castilla-La Mancha, E–45071 Toledo, Spain (L.S.)

In open places, plants are exposed to higher fluence rates of photosynthetically active radiation and to higher red to far-red ratios than under the shade of neighbor plants. High fluence rates are known to increase stomata density. Here we show that high, compared to low, red to far-red ratios also increase stomata density in Arabidopsis (Arabidopsis thaliana). High red to far-red ratios increase the proportion of phytochrome B (phyB) in its active form and the phyB mutant exhibited a constitutively low stomata density. phyB increased the stomata index (the ratio between stomata and epidermal cells number) and the level of anphistomy (by increasing stomata density more intensively in the adaxial than in the abaxial face). phyB promoted the expression of FAMA and TOO MANY MOUTHS genes involved in the regulation of stomata development in young leaves. Increased stomata density resulted in increased transpiration per unit leaf area. However, phyB promoted photosynthesis rates only at high fluence rates of photosynthetically active radiation. In accordance to these observations, phyB reduced long-term water-use efficiency estimated by the analysis of isotopic discrimination against ¹³CO₂. We propose a model where active phyB promotes stomata differentiation in open places, allowing plants to take advantage of the higher irradiances at the expense of a reduction of water-use efficiency, which is compensated by a reduced leaf area.

² These authors contributed equally to the article.

³ Present address: Cátedra de Química Orgánica y Biológica, Facultad de Ciencias Agrarias and Instituto de Ciencias Básicas, Universidad Nacional de Cuyo, 5505–Mendoza, Argentina.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Jorge J. Casal (casal{at}ifeva.edu.ar).

^[W] The online version of this article contains Web-only data.

^[OA] Open Access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.109.135509

^* Corresponding author; e-mail casal{at}ifeva.edu.ar.

Received January 9, 2009; accepted April 7, 2009; published April 10, 2009.

This article has been cited by other articles:

				F.-F. Wang, H.-L. Lian, C.-Y. Kang, and H.-Q. Yang Phytochrome B Is Involved in Mediating Red Light-Induced Stomatal Opening in Arabidopsis thaliana Mol Plant, November 24, 2009; (2009) ssp097v1. [Abstract] [Full Text] [PDF]

				K. A. Franklin and P. H. Quail Phytochrome functions in Arabidopsis development J. Exp. Bot., October 8, 2009; (2009) erp304v1. [Abstract] [Full Text] [PDF]

				C.-Y. Kang, H.-L. Lian, F.-F. Wang, J.-R. Huang, and H.-Q. Yang Cryptochromes, Phytochromes, and COP1 Regulate Light-Controlled Stomatal Development in Arabidopsis PLANT CELL, September 1, 2009; 21(9): 2624 - 2641. [Abstract] [Full Text] [PDF]