PHYSIOLOGICAL RESPONSES OF BARLEY (HORDEUM VULGARE L.) SEEDLINGS TO SHORT-TERM SALT STRESS

Abstract

Zaslanjivanje tla predstavlja abiotički stres koji uvelike ograničava poljoprivrednu proizvodnju. Cilj ovoga rada bio je istražiti utjecaj solnog stresa na klijance ječma (Hordeum vulgare L.) te utvrditi koji se pokazatelji solnog stresa primarno aktiviraju kao mehanizmi tolerancije u ranoj fazi razvoja klijanaca. Sedam dana stare biljke uzgajane u kontroliranim uvjetima uzgojne komore izložene su različitim koncentracijama natrijevog klorida (50, 100, 200, 400 mM). Utjecaj solnog stresa praćen je nakon 3, 6, 12 i 24 sata. Fiziološka i biokemijska mjerenja izvršena su na prvim potpuno razvijenim listovima i korijenju klijanaca ječma. Porastom razine stresa povećao se sadržaj prolina i relativni sadržaj vode (RWC), ukazujući na važnost osmotske prilagodbe klijanaca te njihove otpornosti na moguću dehidraciju uslijed osmotskog stresa. Smanjenje razine malondialdehida ukazalo je na smanjenje oksidacijskog oštećenja staničnih lipida što je odlika stres tolerantnih biljaka, no osjetljivost na oštećenje u uvjetima solnog stresa ipak se povećava na što je ukazalo smanjenje koncentracije fotosintetskih pigmenata: klorofila a, klorofila b i karotenoida. Parametri fluorescencije klorofila a (L- i K-stupanj; indeks vitalnosti - PIABS) potvrdili su izrazito dobru funkcionalnost fotosintetskog aparata u klijanacima ječma u uvjetima kratkotrajnog solnog stresa. Rezultati istraživanja mogu pridonijeti razumijevanju mehanizama osmotske komponente solnog stresa i razvoju alata za poboljšanje tolerancije komercijalno značajnih žitarica u svrhu održanja stabilnog prinosa.Soil salinization is an abiotic stress factor seriously limiting agricultural production. This study aimed to investigate the impact of salt stress on barley seedlings (Hordeum vulgare L.) and to determine which salt stress indicators are primarily activated as tolerance mechanisms in the early stages of seedling development. Seven-day-old plants, grown under controlled conditions of the growth chamber, were exposed to different sodium chloride concentrations (50, 100, 200, 400 mM). The effect of salt stress was monitored after 3, 6, 12, and 24 hours. Physiological and biochemical measurements were performed on the first fully developed leaves and roots of barley seedlings. As stress levels increased, proline content and relative water content (RWC) also increased, indicating the importance of osmotic adaptation of seedlings and their resistance to possible dehydration due to osmotic stress. Decreased malondialdehyde levels showed a decrease in oxidative damage of cellular lipids, which is a feature of stress-tolerant plants. Sensitivity to damage in salt stress conditions still exists as indicated by decreased levels of photosynthetic pigments: chlorophyll a, chlorophyll b, and carotenoids. Chlorophyll a fluorescence parameters (L- and K-band; vitality index - PIABS) confirmed very good functionality of the photosynthetic apparatus of barley seedlings after short-term salt stress induction. This research could contribute to understanding the mechanisms of the osmotic component of salt stress. The results could also be useful for developing tools to improve the tolerance of commercially important cereals to maintain yield stability under increased salinity