Fiziološke, biohemijske i molekularne osnove tolerantnosti na sušu i osmotski stres u ranim vegetativnim fazama razvoja odabranih genotipova roda Pisum

Drought and osmotic stress, in addition to the effects on plant growth and development, lead to oxidative stress and the production of a large quantity of reactive oxygen species (ROS). Plants have developed antioxidant defense mechanisms in order to neutralise the damaging effects of ROS. The aim of this dissertation was to investigate the physiological and biochemical processes which are in the base of field pea reaction to drought and osmotic stress. The aim was also to include molecular research in the study, along with the analysis of growth and other physiological processes (activity of antioxidant enzymes, accumulation, and distribution of plant stress hormons abscisic acid), which would significantly improve understanding of not only osmotic and drought stresses, but also about the effects of oxidative stress on field pea plants. Studies were conducted on seven selected genotypes of the genus Pisum from the collection of the Institute of Field and Vegetable Crops, Novi Sad. Treatments consisted of two experimental systems: osmotic and drought stresses and drought in the environmental test chamber. For induction of osmotic stress different concentrations of osmotic solutions PEG 6000 (-0.1MPa and -0.2MPa) were used in a shorter (10 days) and longer time interval (15 days). Water without PEG 6000 was used as control. The drought experiment was conducted in control conditions (phytotron chamber) in a such waz that the plants were irrigated at the optimal soil water content until the third pair of leaves began emergence, after which soil drought was induced by termination of irrigation up to 18% (moderate drought), and 9% substrate water content (severe drought). Control plants were irrigated at the optimal level of soil water regime (36% substrate water content). In osmotic stress experiment in the germination stage physiological tests included measurements of germination percentage and Mean Germination Time, while in the seedling stage was performed testing of the length and biomass of plant shoot and root, as well as shoot dry weight and root dry weight ratio (shoot/root ratio) and calculation of the tolerance indexes for the shoots and roots...Suša i osmotski stres, pored efekata na rastenje i razviće biljaka, dovode i do oksidativnog stresa i nastajanja velike količine reaktivnih kiseoničnih vrsta (ROS). Kako bi neutralisale štetne efekte ROS, biljke su razvile antioksidativne sisteme zaštite. Cilj istraživanja ove disertacije je bio da se detaljno prouče fiziološki i biohemijski procesi koji su u osnovi reakcija biljaka stočnog graška na sušu i osmotski stres. Cilj je bio i da se u ova ispitivanja uključe i molekularna istraživanja, koja bi, uz analizu procesa rastenja i drugih fizioloških procesa (aktivnost antioksidativnih enzima, akumulacije i distribucije stres hormona abscisinske kiseline), značajno doprinela razumevanju efekata, ne samo osmotskog i stresa suše, već i oksidativnog stresa na biljke stočnog graška. Istraživanja su vršena na 7 odabranih genotipova roda Pisum iz kolekcije Instituta za ratarstvo i povrtarstvo iz Novog Sada. Tretmani su obuhvatili dva eksperimentalna sistema: osmotski stres i sušu. Za indukciju osmotskog stresa su korišćene različite koncentracije rastvora osmotikuma PEG 6000 osmotskog potencijala (od -0,1MPa i -0,2MPa) primenjene u kraćem (10 dana) i dužem vremenskom intervalu (15 dana) kod klijanaca i ponika biljaka. Kao kontrolna varijanta je korišćena voda bez dodatka PEG 6000. Eksperiment suše je obavljen kod biljaka gajenih u kontrolisanim uslovima (u fitotronskoj komori) i to tako da su biljke zalivane optimalno do pojave trećeg para listova, a potom je suša u zemlištu izazvana prekidanjem zalivanja biljaka do 18% (umerena suša) i 9% sadržaja vode u spustratu (jaka suša). Biljke u kontroli su zalivane do optimalnog vodnog režima zamljišta (36% sadržaja vode u supstratu). U ogledu osmotskog stresa u fazi klijanja su obavljena fiziološka ispitivanja uticaja osmotskog stresa na % klijavosti i srednje vreme klijanja ili Mean Germination Time, dok su u fazi ponika obavljena ispitivanja dužine i biomase nadzemnog dela i korena, kao i odnosa suve mase nadzemnog dela i korena, a izračunat je i indeks tolerantnosti za nadzemni deo i koren..