Responses of the photosynthetic electron transport system of chloroplasts to exogenous proline application were evaluated in young and mature leaves of Arabidopsis thaliana plants under optimal growth conditions. Exogenous proline application (10 mM) during the 4th week of growth increased proline accumulation in young leaves more than in mature leaves, and possibly due to its degradation producing NADPH, decreased significantly the ratio of NADP+/NADPH in both leaf types compared with controls (without proline). However, the ratio of NADP+/NADPH remained significantly higher in the young leaves, suggesting lower proline degradation which resulted in less reduced plastoquinone pool than that in the mature leaves, under both low light [130 μmol(photon) m-2 s-1] and high light [1,200 μmol(photon) m-2 s-1] treatments. The young leaves seemed to adjust nonphotochemical fluorescence quenching in order to maintain a better PSII quantum yield. We concluded that under optimal growth conditions exogenous proline results in overreduction of the plastoquinone pool and blockage of photosynthetic electron flow due to accumulation of NADPH. We suggest that optimum concentrations of proline are required for optimal PSII photochemistry., I. Sperdouli, M. Moustakas., and Obsahuje seznam literatury
Let $S$ be topological semigroup, we consider an appropriate semigroup compactification $\widehat{S}$ of $S$. In this paper we study the connection between subgroups of a maximal group in a minimal left ideal of $\widehat{S}$, which arise as equivalence classes of some closed left congruence, and the minimal flow characterized by the left congruence. A particular topology is defined on a maximal group and it is shown that a closed subgroup under this topology is precisely the intersection of an equivalence class with the maximal group for some left congruence on $\widehat{S}$.