Influence of pH and plant growth regulators on secondary metabolite production and antioxidant activity of Stevia rebaudiana (Bert)

Background and purpose: Beside being rich with sweet glycosides, Stevia rebaudiana Bertoni is an interesting source of flavonoids and phenols. The current study aimed to assess the potential for increasing total phenols and flavonoids in S. rebaudiana tissue by varying concentrations of plant growth regulators (PGR) and pH levels of media. Materials and methods: The culture was established from seeds and propagated shoots were cultured on media of different pH levels (4.6, 5.8 and 7.4) and PGR. Total polyphenolics and free radical scavenging capability of leaf, callus and root extracts were determined. Shoot height, root length, shoot and root number were also recorded. Results: Shoot elongation and root development was stimulated by singly applied growth regulators though the values of both parameters were also satisfactory in PGR-free media. In the latter media, pH value of 4.6 was a main factor for increasing leaf metabolite levels. A most significant rise in phenols and flavonoids was evident in response to combination of BA either with GA3 or IAA compared to singly applied regulators indicating synergistic effects of PGR (especially of auxins and cytokinins). However, polyphenolics levels and their distribution between different tissues were also influenced by medium pH value. A positive correlation was found between antioxidant activity of S. rebaudiana extracts and phenols and flavonoids. Conclusions: The results show that PGR and medium pH value strongly affect accumulation of secondary metabolites and can lead to significant enhancement in productivity of bioactive polyphenolics in S. rebaudiana plant cultures

Effects of osmotic stress on antioxidative system of duckweed (Lemna minor L)

Background and Purpose: It is known that osmotic stress may cause damage to cells by inducing active oxygen species production or by disrupting detoxification mechanisms. We hypothesize that increased activity of antioxidant enzymes in duckweed (Lemna minor L.) provides a mechanism of tolerance to osmotic stress. Material and Methods: Plants were subjected to NaCl- (50 mM), mannitol- (50 and 100 mM) and polyethylene glycol-mediated osmotic stress (PEG, 50 mM) for a period of 15 days. The responses of antioxidative system including also changes in growth, proline content and the extent of oxidative damage in terms of malondialdehyde, H2O2 and chlorophyll a to chlorophyll b (chl a/b) and chlorophyll a+b to carotenoids (chl a+b/car) ratios were studied. Results and Conclusion: Iso-osmolar concentrations of salt and mannitol significantly reduced relative growth rate compared to control plants while osmotic shockmediated by PEG caused complete cessation of growth. Proline content increased with the severity of osmotic stress showing the highest values in PEG-treated plants. The proline accumulation upon PEG stress was paralleled by equal increase of ascorbic acid pool. Catalase, ascorbate peroxidase and non-specific peroxidase activities showed considerable increase under all osmotic agents, especially PEG. The increased enzyme activities coincided with unchanged H2O2 levels, chl a/b and chl a+b/car under mannitol and salt stress. Despite the highest induction of antioxidative defense, a marked increase in lipid peroxidation and H2O2 level as well as decrease of chl a/b and chl a+b/car accompanied PEG treatment. These results suggested that induction of antioxidant defences is at least one component of the tolerance mechanism of plants to long-term osmotic stress

Odnos između heterozisa i genetske udaljenosti određena SSR markerima kod suncokreta (Helianthus annuus L.)

The objective of this study was to determine the correlation between SSR based genetic distance (GD) of new NS sunflower inbred lines and heterosis for six agronomic traits. Twenty three sunflower inbred lines (20 restorer lines and three female lines used as testers) and their hybrids were examined for plant height, head diameter, thousand seed mass, oil content, seed yield per plant and oil yield per plant. Significant heterosis was observed in hybrid combinations for all examined traits except oil content. Genetic distance between pairs of tested sunflower inbred lines ranged from 0.13 to 0.8. There was no significant positive correlation between genetic distance and mid- and better-parent heterosis, specific combining ability and mean value in any of the examined traits for all 60 hybrids. A highly significant negative correlation was found between GD and mean oil percentage (r=-0.33 p lt 0.01). Although GD was generally a poor predictor of heterosis, better results are obtained if hybrid combinations for each tester and each trait are analyzed separately.Cilj rada je utvrdjivanje odnosa između genetske udaljenosti (GD) koja je određena SSR markerima (mikrosatelitima) kod novih inbred linija suncokreta i heterozisa za šest agronomskih svojstava. Ispitano je dvadeset tri inbred linije (dvadeset restorer linija i tri tester linije majki) i njihovi F1 hibridi za sledeća svojstva: visina biljke, prečnik glave, masa 1000 semena, sadržaj ulja u semenu, prinos semena i ulja po biljci. Zapažen je značajan heterozis kod hibridnih kombinacija za sva ispitivana svojstva sem za sadržaj ulja. Genetska udaljenost između parova ispitivanih inbred linija je bila od 0,13 do 0,8. Između genetske udaljenosti i heterozisa, posebnih kombinacionih sposobnosti i srednjih vrednosti svih ispitivanih svojstava, nije bilo značajne pozitivne korelacije. Jedina značajna vrednost, ali negativna, bila je u odnosu srednje vrednosti ulja i genetske udaljenosti (r=- 0.33 p lt 0.01). Iako se genetskom udaljenosti slabo može predvideti heterozis, bolji će se rezultati dobiti ako se analiziraju hibridne kombinacije za svaki tester i svako svojstvo pojedinačno

Clinical Utility of Red Cell Distribution Width in Alcoholic and Non-alcoholic Liver Cirrhosis

Red blood cell distribution width (RDW) is a measure of the variation of red blood cell width that is reported as a part of standard complete blood count. Red blood cell distribution width results are often used together with mean corpuscular volume (MCV) results to figure out mixed anemia. The aim of our study was to compare the values of RDW in alcoholic and non-alcoholic liver cirrhosis and to determine if RDW follows the severity of disease according to Child-Pugh score. We retrospectively analyzed 241 patients (176 men and 65 women) with liver cirrhosis and anemia, defined as a hemoglobin value <130 g/L in men and <120 g/L in women, which were hospitalized in our Division in a period between 2006 and 2008. Patients were divided in two groups; in first were patients with alcoholic liver cirrhosis, and in second with non-alcoholic cirrhosis. Severity of disease was determined according to Child-Pugh score. Red blood cells distribution width Normal reference range is 11–15%. Alcoholic liver cirrhosis had 204 patients (85%) while non-alcoholic cirrhosis had 37 patients (15%). In group of alcoholic cirrhosis the average RDW was 16.8%. In relation to severity of disease the average RDW for Child-Pugh A was 16.80%, for Child-Pugh B was 16.92%, for Child-Pugh C was 17.10%. In the group of non-alcoholic cirrhosis the average RDW was 16.73% and in relation to severity of disease for Child-Pugh A was 16.25%, for Child-Pugh B 17.01% and for Child-Pugh C was 16.87%. We didn’t find statistically significant difference of RDW between alcoholic and non alcoholic cirrhosis (p>0.05) and we didn’t proved any statistically significant increase of RDW in relation to severity of disease in group of alcoholic cirrhosis (p=0.915) nor in group of patients with non-alcoholic cirrhosis (p=0.697). Our study showed that RDW had not any clinical value in differentiation of anemia neither in alcoholic and non-alcoholic liver cirrhosis nor in severity of liver disease

Physiological and biochemical responses of Fibigia triquetra (DC.) Boiss. to osmotic stress

Water deficit in the soil leads to osmotic stress in plants. The type of stress affects plant water relations, osmolyte accumulation and oxidative stress balance. The present study aimed to investigate the effects of osmotic stress on the Croatian perennial species Fibigia triquetra (DC.) Boiss, adapted to a hot and dry habitat. Plants grown in culture conditions were subjected to isoosmotic concentrations of mannitol and polyethylene glycol (PEG) and certain physiological and oxidative stress parameters were analyzed during a period of 14 days. Dry weight and proline content in Fibigia triquetra shoots increased in response to osmotic stress while the relative water content decreased. After an initial rise, chlorophyll and carotenoid levels in treated plants dropped to untreated plant levels. Oxidative damage to proteins and especially to lipids was evident upon PEG-induced osmotic stress. Superoxide dismutase and ascorbate peroxidase appear to play an essential protective role in stressed plants. Regardless of the osmotic agent, accumulation of heatshock proteins of 70 kDa was noticed under osmotic stress. The tolerance of the plant species to osmotic stress seems to be associated with increased capacity of the antioxidative system and efficient photoprotective system

Differential esterase activity in leaves and roots of Centaurea ragusina L. as a consequence of salinity

Background and Purpose: Centaurea ragusina L. is an endemic Croatian plant species adapted to life in arid and salt-affected environments. Esterase activity (EST) and isoesterase patterns of C. ragusina plants cultured in vitro under saline and osmotic conditions were determined with an aim to evaluate the potential value of esterase activity as a biomarker of salt/osmotic stress as well as physiological significance of EST variations. Material and Methods: Rooted plantlets grown on MS ½ nutrient media supplemented with 150, 300, 450 or 600 mM NaCl or 300 mM mannitolwere investigated after 5, 10 and 15 days. Esterase activity was determined using either 1- or 2-naphthylacetate as substrates. Results and Conclusion: Esterase activities in shoots increased under low saline and mannitol treatments and decreased in response to increased saline treatments. The highest salt and concentration and mannitol stimulated EST activity in roots. In total, twelve and fourteen esterase isoenzymes were resolved in C. ragusina leaves and roots, respectively. Both salt and mannitol induced new esterase isoenzyme (EST11) while mannitol specifically induced two more (EST4-5); otherwise some bands were weakly expressed or even disappeared as a result of salinity in C. ragusina leaves. Two new isosterases (EST10-11) were resolved in mannitol- and salt-treated roots and four (EST2, EST12-14) only in salt-treated roots. Presented results demonstrate that esterase activities and their isoenzymic patterns could serve as useful bioindicators of salinity

Allium test application in biology teaching

Allium-test je jednostavni biotest za određivanje ukupne toksičnosti i genotoksičnosti kojeg učenici uz pomoć nastavnika ili samostalno mogu provesti u školi te njime testirati učinak različitih otopina na modelni organizam Allium cepa L. (obični luk). Allium-test je dobar primjer projekta u nastavi jer se svojim opsegom može prilagoditi dobi učenika, a potiče njihovu kreativnost i samostalnost u provedbi i prezentiranju samog projekta. Sam projekt i rezultati istog potiču učenike na razvijanje svijesti o vodenom okolišu i učinku onečišćenja na svim njegovim razinama.Allium-test is a simple biotest for determining toxicity and genotoxicity which students can perform at school, with the help of teachers or independently, to test the effects of different solutions on the model organism Allium cepa L. (the common onion). The Allium test is a good example of project-based learning because it can be adapted to the age of the students, and it enforces their creativity and independence in the implementation and presentation of the project itself. The project itself and its results encourages students to develop awareness of the aquatic environment and the impact of pollution at all its levels

Effects of osmotic stress on antioxidative system of duckweed (Lemna minor L)

Background and Purpose: It is known that osmotic stress may cause damage to cells by inducing active oxygen species production or by disrupting detoxification mechanisms. We hypothesize that increased activity of antioxidant enzymes in duckweed (Lemna minor L.) provides a mechanism of tolerance to osmotic stress. Material and Methods: Plants were subjected to NaCl- (50 mM), mannitol- (50 and 100 mM) and polyethylene glycol-mediated osmotic stress (PEG, 50 mM) for a period of 15 days. The responses of antioxidative system including also changes in growth, proline content and the extent of oxidative damage in terms of malondialdehyde, H2O2 and chlorophyll a to chlorophyll b (chl a/b) and chlorophyll a+b to carotenoids (chl a+b/car) ratios were studied. Results and Conclusion: Iso-osmolar concentrations of salt and mannitol significantly reduced relative growth rate compared to control plants while osmotic shockmediated by PEG caused complete cessation of growth. Proline content increased with the severity of osmotic stress showing the highest values in PEG-treated plants. The proline accumulation upon PEG stress was paralleled by equal increase of ascorbic acid pool. Catalase, ascorbate peroxidase and non-specific peroxidase activities showed considerable increase under all osmotic agents, especially PEG. The increased enzyme activities coincided with unchanged H2O2 levels, chl a/b and chl a+b/car under mannitol and salt stress. Despite the highest induction of antioxidative defense, a marked increase in lipid peroxidation and H2O2 level as well as decrease of chl a/b and chl a+b/car accompanied PEG treatment. These results suggested that induction of antioxidant defences is at least one component of the tolerance mechanism of plants to long-term osmotic stress

Uticaj suše na razvoj klijanaca kukuruza

Drought stress is one of the most important abiotic stresses influencing performance of crops. Certain stress-related conditions can appear and slow down germination, seedling development and in some cases cause loss of life durability of seed. Assuming that drought in the substrate affects corn seed performance, such conditions were simulated in this study in order to examine their effects on seed germination and length in seven corn hybrids. Polyethylene glycol (PEG) 6000 has been used in laboratory studies for simulation of drought conditions. Different osmotic potentials of PEG solutions were used (control; -0.1, -0.3, -0.6 and -0.9 MPa). Germination percentage decreased as osmotic potential increased at PEG solution.Suša je jedan od najvažnijih abiotskih stresova koji utiču na razvoj ratarskih kultura. Određeni uslovi koji su povezani s pojedinim stresovima mogu dovesti do usporavanja klijanja, razvoja ponika, a u nekim slučajevima i do gubitka životne sposobnosti semena. Pod pretpostavkom da nedostatak vode u supstratu utiče na karakteristike semena kukuruza, simulirani su uslovi suše u ovoj studiji sa ciljem da se ispita njihov uticaj na klijavost semena i razvoj ponika sedam hibrida kukuruza. Polietilen glikol (PEG) se koristi u laboratorijskim istraživanjima za simulaciju uslova suše. Koristili smo različite osmotske potencijale u rastvoru PEG-a (kontrola, -0,1, -0,3, -0,6 i -0,9 MPa). Procenat klijavosti je opadao sa smanjenjem osmotskog potencijala u rastvoru. Osetljivost korena i nadzemnog dela se povećava sa smanjenjem osmotskog potencijala. Na potencijalu od -0,6 i -0,9 MPa, nadzemni deo semena kukuruza nije se razvio