Browsing by Author "Loulakakis, Konstantinos"

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    Effect of heavy metal stress in plant metabolism of solanaceous plant species with emphasis on nitrogen assimilation
    (Cranfield University, 2011-02) Christofaki, Maria Ioannou; Loulakakis, Konstantinos; Primikirios, Nikolaos; Aldred, David
    Several plant species are able to accumulate and withstand large quantities of heavy metals in their tissues without dramatic alterations in their growth usually observed in plants. Such metal accumulating plants are tested and used for remediation of contaminated soils and waters. Although the literature provides extensive information on the effect of heavy metals in growth and development of several metal-accumulating and non accumulating plants, nitrogen metabolism and the regulation of related enzymes have not been widely studied. In an effort to better understand the responses of plants species under heavy metal stress, a comparative study was held between two solanaceous species, Nicotiana tabacum and Nicotiana glauca, plants with promising properties for phytoremediation. Plants of the two species were grown in the presence of different concentrations of the heavy metals zinc (Zn), nickel (Ni) and cadmium (Cd) in the following experimental systems in the greenhouse: in pots containing artificial substrate for 6 weeks and hydroponically for 8 days. In order to get a global picture for the heavy metal –induced variations concerned the examined species, the accumulation and distribution of metals in various plants tissues (lower and upper leaves, lower and upper shoots, roots) was determined. Also, several morphological parameters related with plants growth, physiological related with light and dark reactions of photosynthesis and water balance, biochemical related with nitrogenous compounds metabolism and the enzymes involved in ammonia assimilation, were followed. The presence of the referenced metals in the culture medium induced alterations, in all the parameters examined. In particular, strong positive correlations exhibited between the accumulation of Zn, Ni and Cd in the examined tissues and the supplied metals concnentrations. Our data revealed different accumulation patterns for each examined metal at tissue and species level. Furthermore, both growth and physiological parameters were negatively affected at least by the higher concentration of the three metals tested. However, differential responses were observed between N. tabacum and N. glauca, where the latter seemed to be more sensitive at the higher concentration of the metals, especially for Ni and Cd, showing heavier symptoms. In addition, proline accumulation was positively affected over the range of the three metals concentrations. Alterationsinduced in quantitive and qualitive profile of soluble proteins corresponding to Zn, Ni and Cd treatments. Furthermore, the concentration of Zn, Ni and Cd differentially affected the specific activities and the protein levels of ammonia assimilating enzymes glutamine synthetase (GS), glutamate synthase (Fd-GOGAT) and glutamate dehydrogenase (GDH).
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    Effect of Milsana concentration in metabolism of solanum lycopersicum plants grown under salinity stress
    (Cranfield University, 2013) Christoulaki, Maria Eirini; Loulakakis, Konstantinos; Aldred, David
    Salinity is a major abiotic factor that causes serious problems in agriculture around the world which leads to reduced crop production. Scientists all over the world are looking for natural, environment friendly compounds against biotic and abiotic factors. Milsana, a formulated plant extract from Reynoutria sachalinensis, is widely used to elicit plant defences against biotic stress. In addition Milsana has been found to act by enhancing the flavonoid metabolic pathway. Considering the about the effect of Milsana concentration on tomato plants under physiological conditions and under NaCl stress was examined. The experimental approach included the study of the effect of various concentrations of Milsana (0/5%, 1.0% and 2.0%) on untreated plants and plants under salinity stress (70mM and 140mM NaCl). Plant height, fruit quality, antioxidant and photosynthetic capacity were used to determine the response of tomato plants to Milsana, NaCl stress, and their combination. The effect of Milsana was tested in two different sets of experiments, one carried out in growth chambers under controlled conditions and the other carried out in a greenhouse. Milsana led to enhanced growth, when applied to non saline stressed plants. Furthermore the negative effect of NaC1 on photosynthesis, ROS homeostasis, and fruit quality traits was counteracted by the application of Milsana.
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    Essential oils from Dittany of Crete for the control of botrytis cinerea on tomato, eggplant and pepper fruits
    (Cranfield University, 2014) Stavropoulou, Andriana; Magan, Naresh; Loulakakis, Konstantinos; Tzortzakis, Nikolaos
    The degree of postharvest losses of fruit and vegetables due to attack by microorganisms worldwide is significant. In addition, the use of chemicals increases consumer concerns regarding food safety. Recent studies indicate that exploitation of natural compounds such as essential oils (EOs) may provide an alternative and friendlier way for the preservation of fresh produce. In this research project the efficacy of Origanum dictamnus L. essential oils (EOs) (a medicinal-aromatic plant of Crete) for the control of B. cinerea, a common postharvest pathogen of three economically important Cretan vegetables, tomato, pepper and eggplant was examined. Pathogen development in culture medium or on fruits was evaluated after treatment with dittany EO (0, 50, 100, 250 ppm) in vitro and in situ when stored at 12°C and 95% RH during or following exposure to EO volatiles. The impacts of short term exposure of B. cinerea to volatiles on growth and sporulation were also studied. Fungal development in vitro was completely inhibited by the continued application of 100 or 250 ppm of EO volatiles while inhibitory effects were also marked by lower EO concentration and short time of exposure. In inoculated fruits the 50 ppm of EO application resulted in suppressed disease development by reduced lesion growth and fungal sporulation, where increasing EO concentration led to greater effects. Pre-exposure of fruits to volatiles before fungal inoculation revealed reduced lesion growth, indicating that dittany EO probably caused induced resistance of fruits against the pathogen. Moreover, EO application did not affect quality-related characteristics of fruits while skin lightness and pulp lightness of eggplant fruits was improved under the presence of dittany volatiles. Overall, the results suggest that dittany EO volatiles may be considered as an alternative food preservative treatment, significantly reducing or eliminating B. cinerea infection during fruit storage and perhaps also in transit.