Pigment contents of chloroplasts and net photosynthetic rate were dramatically reduced in maize leaves suffering from iron deficiency. However, the reduction in photosynthesis was probably not caused by decreased contents of chlorophylls and carotenoids and by photon absorption; the primary limiting factor for photosynthesis may rather be the decrease of electron transport activity in photosystem 1. Iron-deficient leaves suffered serious acceptor-side photoinhibition, and more than 60 % of absorbed photons were dissipated, while less than 40 % was used in photochemical reaction. Thermal energy dissipation depending on xanthophyll cycle and D1 protein turnover was enhanced when acceptor-side photoinhibition occurred in iron-deficient maize leaves. and Chuang-Dao Jiang, Hui-Yuan Gao, Qi Zou.
We checked the hypothesis that the transient presence of anthocyanins in young leaves serves a photoprotective function. For this purpose, Rosa sp. and Ricinus communis L., whose young leaves are red to become green upon maturation, were used. Thus, young leaves with high and mature leaves with low anthocyanin contents were analysed concerning their carotenoid (Car) composition and susceptibility to photoinhibition. Cars, including the components of the xanthophyll cycle, had similar contents in young and mature leaves, when expressed on a chlorophyll basis. Yet, when expressed on a leaf area basis or on the assumed photon absorptive capacity of leaves, Cars contents were considerably lower in anthocyanic young leaves. Although this may indicate a low photodissipative potential, red young leaves were considerably less susceptible to photoinhibitory damage. The results are compatible with a photoprotective function of anthocyanins, indicating also that their presence may compensate for a low capacity in the xanthophyll cycle-dependent harmless dissipation of excess excitation energy. and Y. Manetas, A. Drinia, Y. Petropoulou.
Soil metal contamination leads to a decrease in a yield of crops and is a threat to human health. In the present study, the properties (i.e., photosynthetic pigments, gas-exchange parameters, chlorophyll fluorescence, biomass, leaf area, leaf mass per area) of three green vegetables (i.e., Brassica chinensis, Chrysanthemum coronarium, Brassica alboglabra) grown under various Cu treatments [0, 200, 400, and 600 mg(Cu) kg-1] were measured and analysed. The results showed that soil Cu contamination resulted in the damage of photosynthetic pigments, negative effects on gas exchange, and hampered growth of all three vegetables. However, it did not significantly influence PSII functions of the three vegetables. It indicates that soil Cu contamination negatively affected photosynthesis particularly due to stomatal factors, but not due to the damage of photosynthetic apparatus., M.-Z. Lin, M.-F. Jin., and Obsahuje bibliografii
A theory of spectra and excitation dynamics in antenna based on the notion of exciton interactions in the cyclic structures of light-harvesting pigments is reported. The theory provides an explanation for the picosecond absorbance difference spectra, the induced absorption anisotropy decay, the anomalously high bleaching valné, as well as for the fluorescence spectra, kinetics and depolarizatio