Authors:H. Lepeduš, H. Fulgosi, Mirta Benšić and Vera Cesar
The photosynthetic performance of developing spruce (
L. Karst.) needles was investigated. As revealed by previous reports, the biosynthesis of chlorophylls and carotenoids was not following the characteristic chloroplast ultrastructure building up during needle elongation process. The aim of our study was to investigate photosynthetic capability (evaluated by oxygen evolution and chlorophyll a fluorescence kinetics measurements), the dynamics of chloroplast pigments biosynthesis and the expression of major photosynthetic proteins as well as to find out possible correlation between components of issue. Low amounts of chlorophylls and carotenoids, LHC II and Rubisco LSU were detected in the embryonic shoot of vegetative buds. Although PS II was functional, oxygen production was not sufficient to compensate for respiration in the same developmental stage. The light compensation point of respiration was successively lowered during the needle elongation. Nevertheless the significant increase in photosynthetic pigments as well as the high level of expression of LHC II and Rubisco LSU proteins was observed in the later stages of needle development. Our results suggest that, besides light, some other environmental factors could be critical for producing fully functional chloroplasts in rapidly growing young needles.
Authors:Zorana Katanić, Lejla Atić, Dž. Ferhatović, Vera Cesar and H. Lepeduš
Vegetative buds represent developmental stage of Norway spruce (Picea abies L. Karst.) needles where chloroplast biogenesis and photosynthetic activity begin. We used the analyses of polyphasic chlorophyll a fluorescence rise (OJIP) to compare photosystem II (PSII) functioning in vegetative buds and fully photosynthetically active mature current-year needles. Considerably decreased performance index (PIABS) in vegetative buds compared to needles pointed to their low photosynthetic efficiency. Maximum quantum yield of PSII (Fv/Fm) in buds was slightly decreased but above limited value for functionality indicating that primary photochemistry of PSII is not holdback of vegetative buds photosynthetic activity. The most significant difference observed between investigated developmental stages was accumulation of reduced primary quinine acceptor of PSII (QA−) in vegetative buds, as a result of its limited re-oxidation by passing electrons to secondary quinone acceptor, QB. We suggest that reduced electron transfer from QA− to QB could be the major limiting factor of photosynthesis in vegetative buds.
Authors:Tanja Pfeiffer, Ivna Štolfa, M. Žanić, N. Pavičić, Vera Cesar and H. Lepeduš
Olive is one of the most important cultivated Mediterranean plants. In order to determine the differences in frost resistance of two, two-year-old olive cultivars (Olea europaea cv. Leccino and cv. Oblica) growing on different types of nutrient substrates (soil and coconut fibres), the trees were exposed to low temperature (−5 °C) in the dark. It was shown that low temperature caused an increase in H2O2 concentration, level of lipid peroxidation and carbonyl protein content in both cultivars and on both nutrient substrates, respectively. The CAT and APX activities significantly varied depending on the cultivar, the nutrient substrate type and the time of exposure to low temperature. Cv. Oblica and cv. Leccino growing on coconut fibres showed a better antioxidative response to low temperature probably due to the higher nitrogen and phosphorus concentration established in this type of nutrient substrate. That positive antioxidative response determined on coconut fibres was more pronounced in leaves of cv. Leccino.