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)
Abstract:
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-transplantexperimentSource:
University of Belgrade, Faculty of Biology, 2013, 1-181Funding / projects:
- Evolution in the laboratory and adaptations in the wild (RS-MESTD-Basic Research (BR or ON)-173007)
- Fiziološki i evolucioni aspekti stresnog odgovora u prirodnim i laboratorijskim populacijama (RS-143033)
URI
http://eteze.bg.ac.rs/application/showtheses?thesesId=1257https://fedorabg.bg.ac.rs/fedora/get/o:8227/bdef:Content/download
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http://nardus.mpn.gov.rs/123456789/2093
https://radar.ibiss.bg.ac.rs/handle/123456789/2432