PARENT SESSION
Posters P3B Photosynthetic acclimation: Ecophysiology, diverse environments. Abstracts (479-522)

Effects of K⁺ limitation on chl a fluorescence and photosynthetic efficiency on barley. Martine Dorais^*,1, Bouchra Yaakoubd¹, ¹ Agriculture and Agri-Food Canada, Ste-Foy, Quebec, Canada

ABSTRACT- Potassium is the most abundant cation in the cytoplasm. It is essential for many processes in plants, including proteins synthesis, enzyme activation, membrane transport processes, charge balancing, and the generation of turgor. In the photosynthetic process, K⁺ is the main counterion to the light-induced H⁺ flux across the thylakoid membranes and for the establishment of the pH gradient essential for the ATP synthesis. K⁺ is also closely related to CO₂ fixation. Although the effects of K⁺ on plant metabolism have been extensively studied, details of the events linking the physiological and biochemical roles of K⁺ and the growth response have not been well established. One reason for this is the fact that different but interrelated metabolic processes affected by K⁺ are rarely examined simultaneously in the same system. In order to achieve a better understanding of the processes involved under potassium limited growing conditions, we have determined response of photosynthetic apparatus and chlorophyll a fluorescence parameters of barley (Hordeum vulgare L.) leaves cultivated hydroponicaly under different levels of K⁺. Our results show a close variation between K⁺ concentration and some gas exchange and Chl a fluorescence parameters. Results will also be discussed in terms of mechanisms involved in the osmotic response under inadequate K⁺ supply.

KEY WORDS: fluorescence, potassium, chlorophyll a, photosynthetic efficiency