Evoluciona ekofiziologija stresa: uloga enzimskih i neenzimskih antioksidanata u prirodnim populacijama Iris pumila L. (Iridaceae)
Evolutionary ecophysiology of stress: the role of enzymatic and non-enzymatic antioxidants in natural populations of Iris pumila L. (Iridaceae)
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In evolutionary biology, environmental stress is defined as a mechanism that leads to adaptation and evolution in a variable environment and includes properties of stress, as an environmental component, and stressed, as the biological component. During the evolution higher plants, as sessile and modular organisms, have developed a number of biochemical, physiological and morpho-anatomical mechanisms that enable them to increase individual fitness under unstable environmental conditions. Short-term, in ecological time scale, plants adjust to varying biotic and abiotic factors in their habitat by phenotype flexibility, which may include all levels of biological organization - from the molecular to the morphological. For natural populations of plants, light is the most heterogeneous abiotic factor, both spatially and temporally, and at the same time, one of the most important environmental resources. In this context, antioxidative enzymes and non-enzymatic antioxidants, as specific biochemical mechanisms, are of grat importance for plants protection against oxidative stress. The aims of this doctoral dissertation were: (I) to investigate the size and patterns of seasonal phenotypic plasticity of biochemical (specific activities of antioxidative enzymes superoxide dismutase - SOD; ascorbate peroxidase – APX, catalase – CAT, gluthatione reductase - GR, class III peroxidase – POD; content of non-enzymatic antioxidants, anthocyanins - Anth and phenolics - Phen), morpho-anatomical (specific leaf area - SLA, stomatal density - SD) and physiological leaf traits (leaf dry matter content - LDMC, leaf water content - LWC, relative leaf water content - RWC, succulence – SU, concentration of photosynthetic pigments: chlorophyll a - Chl a, chlorophyll b - Chl b and carotenoids - Cars) in two I. pumila populations, one inhabiting open site (“Dune” population) and the other one from woodland understory (“Wood” population) in Deliblato sand; (II) testing the local adaptation hypothesis of I.pumila to abiotic conditions at the open and shaded habitat, using reciprocal transplant experiment in nature (III) to determine the variation of degree (relative variance of eigen-value, rVE) and patterns of phenotypic integration (CPC analysis) of functionally linked traits in the I.pumila leaves, induced by heterogeneous environment. The seasonal variation pattern of functional leaf traits of I.pumila from two populations, Dune and Wood, was specific for each trait, as well as for the population tested. Specific activities of antioxidative enzymes and content of non-enzymatic antioxidants were the highest during the most stressful, summer period, with high light intensities, elevated atmospheric temperature and water deficit, in comparison to other seasons, such as spring or autumn. During the whole vegetation period, plants from the Wood population had higher antioxidative enzymes activities than those from the Dune population, while an opposite trend was observed for non-enzymatic antioxidants, especially anthocyanins, whose content was, in general, higher in the leaves of plants from the open habitat. Besides the variation in the activities and contents of antioxidants, a decrease in the chlorophyll concentration was observed in plants from Dune population, which could be a means for regulating reactive oxygen species generation in the chloroplasts of these plants. Testing the adaptability of the biochemical, physiological and morphoanatomical leaf traits in the I. pumila showed that average values for most of the traits investigated did not differ significantly between the Dune and Wood population, neither in the open nor in the shaded habitat. No statistically significant differences among I. pumila populations at the same habitat implicate there was no genetic differentiation between Dune and Wood populations due to local selection in their light environments. Therefore, as the pattern of variation of tested leaf traits (induced by different intensities of ambient light) increases the performance of I. pumila under the given environmental conditions, this type of phenotypic changes could be defined as adaptive plasticity. The size of light-induced phenotypic plasticity, estimated by the plasticity index, was specific for each type of leaf traits considered. Antioxidants and photosynthetic pigments showed higher phenotypic plasticity compared to morpho-anatomical and physiological traits. The absence of statistical significance in the plasticity of the most of the leaf traits analyzed indicates that I. pumila genotypes of different origin respond to light intensity variation by forming similar, adaptive phenotypes, thus preventing the effect of local selection on phenotypic plasticity of the investigated leaf trait. According to the literature data, increased environmental stress intensity can be followed by an increase in the integrity of functionally related traits or organism modules, which was also confirmed in I.pumila. The highest number of correlation between analyzed leaf traits was obtained in the least favourable, summer period in the plants from both populations, that is, under increased intensity of abiotic stress. The size and number of phenotypic correlation coefficients were the highest in the group of antioxidants, as well as in the group of traits related to photosynthetic pigments, leading to the conclusion that these two groups of traits could be treated as separate leaf functional modules.
Keywords:Iris pumila; SOD; CAT; APX; GR; POD; Natural plantpopulations; Environmental stress; Phenotypic plasticity; Reciprocal-transplantexperiment
Source:University of Belgrade, Faculty of Biology, 2013, 1-181
- Evolution in the laboratory and adaptations in the wild (RS-173007)
- Fiziološki i evolucioni aspekti stresnog odgovora u prirodnim i laboratorijskim populacijama (RS-143033)