Contribution of Photosynthesis to the Red Light Response of Stomatal Conductance

• Published in: Plant physiology (Bethesda) Vol. 146; no. 2; pp. 737 - 747
• Main Authors: Baroli, Irene, Price, G. Dean, Badger, Murray R, von Caemmerer, Susanne
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01-02-2008; American Society of Plant Physiologists
• Subjects: Antisense Elements (Genetics); Bioenergetics and Photosynthesis; Biological and medical sciences; Carbon Dioxide - metabolism; Cytochromes; Cytochromes f - metabolism; Electric Conductivity; Fundamental and applied biological sciences. Psychology; Guard cells; Irradiance; Leaves; Light; Metabolism; Nicotiana - genetics; Nicotiana - physiology; Photosynthesis; Photosynthesis - genetics; Photosynthesis - physiology; Photosynthesis, respiration. Anabolism, catabolism; Plant Epidermis - physiology; Plant growth; Plant physiology and development; Plant Stomata - physiology; Plant Transpiration; Plants; Plants, Genetically Modified; Ribulose-Bisphosphate Carboxylase - metabolism; Stomata; Stomatal conductance; Transgenic plants; Photosynthesis; Stomatal conductance
• ISSN: 0032-0889; 1532-2548; 1532-2548
• DOI: 10.1104/pp.107.110924

To determine the contribution of photosynthesis on stomatal conductance, we contrasted the stomatal red light response of wild-type tobacco (Nicotiana tabacum 'W38') with that of plants impaired in photosynthesis by antisense reductions in the content of either cytochrome b₆f complex (anti-b/f plants) or Rubisco (anti-SSU plants). Both transgenic genotypes showed a lowered content of the antisense target proteins in guard cells as well as in the mesophyll. In the anti-b/f plants, CO₂ assimilation rates were proportional to leaf cytochrome b₆f content, but there was little effect on stomatal conductance and the rate of stomatal opening. To compare the relationship between photosynthesis and stomatal conductance, wild-type plants and anti-SSU plants were grown at 30 and 300 μmol photon m⁻² s⁻¹ irradiance (low light and medium light [ML], respectively). Growth in ML increased CO₂ assimilation rates and stomatal conductance in both genotypes. Despite the significantly lower CO₂ assimilation rate in the anti-SSU plants, the differences in stomatal conductance between the genotypes were nonsignificant at either growth irradiance. Irrespective of plant genotype, stomatal density in the two leaf surfaces was 2-fold higher in ML-grown plants than in low-light-grown plants and conductance normalized to stomatal density was unaffected by growth irradiance. We conclude that the red light response of stomatal conductance is independent of the concurrent photosynthetic rate of the guard cells or of that of the underlying mesophyll. Furthermore, we suggest that the correlation of photosynthetic capacity and stomatal conductance observed under different light environments is caused by signals largely independent of photosynthesis.