Chilling effects on primary photosynthetic processes in Medicago sativa: Acclimatory changes after short- and long-term exposure to low temperatures
|Článek v odborném periodiku
|Časopis / Zdroj
|Fakulta / Pracoviště MU
|Alfalfa; Chlorophyll fluorescence; Photosystem II
|Two cutivars (cv.) of alfalfa (Medicago sativa L.) were used to study the influence of chilling on chlorophyll fluorescence parameters related to the photosynthetic performance of photosystem II (PS II). Potted plants were exposed to two chilling treatments (10 and 5 degrees C) for 15 and 22 days, respectively. After the chilling, basic chlorophyll fluorescence parameters (F-V/F-M, phi(PSII), qN) and chlorophyll fluorescence signals emitted from light-harvesting complexes (F-0 - backgroung chlorophyll fluorescence) were measured by slow Kautsky kinetics supplemented by quenching analysis. Short-term effect of 5 degrees C was evaluated by fast chlorophyll fluorescence transients (OJIPs). Chilling did not lead to any change in F-V/F-M and phi(PSII) in both cultivars, indicating their chilling tolerance. Background chlorophyll fluorescence showed a chilling-induced increase in the cv. Zuzana but not the cv. Holyna. The F-0 increase was attributed to functional detachment of light-harvesting complexes from core PS II. In both cultivars, chilling treatment led to a decrease in non-photochemical quenching (qN). This decrease was attributed to a long-term acclimation of plants to low temperatures and the adjustment of PS II processes and photosynthetic performance. The shape of OJIP curves and OJIP-derived chlorophyll fluorescence parameters were found to be temperature-dependent after a short-term exposition to 5 degrees C. Both alfalfa cultivars showed chilling tolerance; however, the results suggest that the cv. Holyna may be more chilling-tolerant than the cv. Zuzana.