Uticaj delimičnog isušivanja korenova na ekspresiju NCED, TAO1 i EIL1 gena i rastenje divljeg tipa i flacca mutanta paradajza (Lycopersicon esculentum Mill.)

Abstract

Cilj ovog istraţivanja je bio karakterizacija fizioloških procesa koji su u osnovi regulacije rastenja i razvića biljaka paradajza pod dejstvom delimiĉnog isušivanja korenova (Partial root-zone drying -PRD), ali i regulisanog deficita navodnjavanja (Regulated deficit irrigation - RDI). Cilj je bio i da se u ova ispitivanja ukljuĉe i molekularna istraţivanja, koja bi, uz analizu procesa rastenja i drugih fizioloških procesa (vodnog reţima, razmene gasova, akumulacije i distribucije stres hormona ABA, kao i usvajanja i distribucije jona), znaĉajno doprinela razumevanju PRD i RDI efekata na paradajz. Zato je praćena ekspresija gena ukljuĉenih u biosintetski put ABA (TAO1 i NCED1) i transdukciju signala etilena (EIL1). Eksperimentalni model u ovim istraţivanjima je bio paradajz (Lycopersicon esculentum Mill.), kao kultura koja ima znaĉajne potrebe za vodom i kod koje suša moţe da izazove znaĉajne efekte na rastenje i razviće. Odabrani su divlji tip (WT), sorta Ailsa Craig, i mutant flacca koji se odlikuje smanjenom sintezom hormona ABA. Biljke paradajza divljeg tipa i mutanta flacca su nakon proklijavanja presaĊene u posebno dizajnirane saksije, koje su podeljene na dve polovine plastiĉnom ploĉom, ĉime je omogućeno razdvajanje korenovog sistema u dva hidrauliĉno izolovana kompartmenta. Biljke su gajene u komercijalnom supstratu (Klasmann Potground H) u uslovima fitotronske komore (temperatura dan/noć 26/17 oC, relativna vlaţnost vazduha 60%, osvetljenost (PAR) 250 μmolm-2s-1 i duţina fotoperioda od 14 h). Koliĉina vode u supstratu je merena pomoću TDR proba (Time domain reflectometer, TRASE, Soil Moisture Equipment Corp., USA). Primenjivana su tri razliĉita tretmana zalivanja. Optimalno navodnjavanje (Full irrigation - FI) - supstrat u celoj rizosferi je svaki dan zalivan do optimalnog vodnog kapaciteta, odnosno, sadrţaja vode u supstratu od 36%. Delimiĉno isušivanje korenovog sistema (PRD) - supstrat u polovini korenovog sistema je zalivan do optimalnog vodnog kapaciteta, dok u drugoj polovini nije zalivan sve dok se sadrţaj vode u supstratu nije spustio na 18- 20%, kada je vršena inverzija strana zalivanja. Regulisani deficit navodnjavanja (RDI) - biljke su zalivane do vrednosti vode u supstratu od 18%. Vodni potencijal listova i otvorenost stoma su mereni u danu PRD okreta (promene strane zalivanja korena)...

The aim of presented PhD thesis was to investigate the physiological mechanisms that are in the base of tomato growth and development under partial root-zone drying (PRD) and regulated deficit irrigation (RDI). Investigations included plant growth, water regime, gas exchange, abscisic acid (ABA) content in the leaves of tomato and ions content in different tomato plant organs. The aim of presented PhD thesis was, also, to assess the expression of TAO1, NCED and EIL1 genes in the leaves of tomato under drought treatments of PRD and RDI. The investigated genes are involved in the biosynthesis and signaling pathways of abscisic acid (ABA) and ethylene as key hormones in the reactions of plants to drought. Experiments were done with tomato plants (Lycopersicon esculentum Mill.), wild type (Ailsa Craig) and flacca mutant. Tomato was chosen because of its significant needs for water and because drought may have significant effects on its growth and development. Tomato mutant flacca, which is chosen for investigation, is defective in the last step of ABA biosynthesis. As a consequence, the endogenous level of ABA in flacca tissues is significantly lower than in wild type. Tomato plants wild type (WT) and flacca mutant were raised from seed and transplanted into 10 L pots (one plant per pot) filled with commercial compost (Klasmann Potground H) in a growth chamber (photoperiod was 14 h; light intensity at plant level 250 μmolm-2s-1, temperature 26/17 oC and relative humidity 60%). For PRD experiments the pots were specially designed in such a way that they were separated with plastic sheets into two equally sized compartments. Washed roots of the seedlings were divided into approximate halves and repotted into these two hydraulically separated compartments. The volumetric soil water content (θ) of both compartments of each pot was measured daily using TDR probes (time domain reflectometer, TRASE, Soil Moisture Equipment Corp., USA After transplantation, plants were subjected to following irrigation treatments: full irrigation (FI), in which the whole root system was irrigated to full substrate holding capacity (θ of 36%); ) partial root-zone drying (PRD), where one half of the root was irrigated to reach θ of 36% while the other half was allowed to dry, and the irrigation was shifted when θ of the dry side had decreased to 18-20%. deficit irrigation (RDI), in which water was evenly applied to the whole root system to rich θ of 18%. Leaf water potential and stomatal conductance were measured in day when PRD shift occurred...