Acclimation to light and avoidance of photoinhibition in Typha latifolia is associated with high photosynthetic capacity and xanthophyll pigment content.

Tall monocots with long, linear leaves have lower canopy light attenuation than plants with horizontal leaves, yet little is known about their light acclimation and sun-shade responses. The genus Typha, common in nutrient-rich wetlands, is highly productive with dense canopies of such leaves. The objective of this study was therefore to investigate photosynthetic acclimation and pigment content in linear leaves of Typha latifolia L. in response to light availability. This was done in a growth experiment with two light intensities and in the field. In the laboratory, T. latifolia exhibited typical morphological, anatomical and gas exchange sun-shade responses. Net photosynthesis rates in high light were very high for a C3 plant (>40 mmol CO2 m-2 s-1) in both laboratory and field studies, and this was associated with stomatal conductances that were correspondingly high (maximum values >1.0 mol H2O m-2 s-1). The size of the xanthophyll (violaxanthin, antheraxanthin and zeaxanthin; VAZ) pool was also among the top 0.5% of all species. In the field, T. latifolia was able to maintain high net photosynthetic rates (26-41 mmol CO2 m-2 s-1) throughout its canopy and could avoid photoinhibition through high investment in the VAZ pool (0.7-1.3 mmol g-1 DW total VAZ pigments). This pattern of acclimation is likely to be adaptive, explaining why this species is so successful and dominant in high-light, high-nutrient wetland environments. [ABSTRACT FROM AUTHOR]