Physiological characterization of photosynthesis, chloroplast ultrastructure, and nutrient content in bracts and rosette leaves from Glaucium flavum

• Published in: Photosynthetica 2010, Vol.48 (4), p.488-493
• Main Authors: Redondo-Gómez, S, Mateos-Naranjo, E, Moreno, F. J
• Format: Article
• Language: English
• Subjects: Biomedical and Life Sciences; carotenoids; chlorophyll content; chlorophyll fluorescence; Life Sciences; Original Papers; photosystem II; Plant Physiology; stomatal conductance
• ISSN: 0300-3604; 1573-9058
• DOI: 10.1007/s11099-010-0065-9

Glaucium flavum is a biennial plant that bears a rosette of leaves, producing a flower stalk, bracteate monochasium, in its second year. The aims of this work were both to investigate the contribution of bracts to gas-exchange activities in this species and to compare this contribution to that of rosette leaves. In addition, we investigated the extent to which its responses can be explained by chloroplast ultrastructure, as well as the possible role of nutrient concentrations in the physiological responses of both leaf types. Gas exchange and plant characteristics regarding chlorophyll fluorescence were examined in a field experiment; we also determined leaf relative water content, tissue concentrations of photosynthetic pigments, chloroplast ultrastructure and nutrient contents. Although bracts indeed contributed to gas-exchange activities of G. flavum, rosette leaves showed higher values of net photosynthetic rate and stomatal conductance to CO₂ for photosynthetic photon flux density above 200 μmol m⁻² s⁻¹. The incongruities in photosynthetic rates between bracts and leaves may be explained by the bigger chloroplasts of rosette leaves, which results in a larger membrane surface area. This agrees with the higher pigment concentrations and quantum efficiency of photosystem II values recorded as well for rosette leaves. On the other hand, bracts showed higher sodium concentrations, which could be a mechanism for salt tolerance of G. flavum.