Fiziološki aspekti potencijala vrba (Salix spp.) u asistiranoj fitoremedijaciji kadmijuma upotrebom limunske kiseline

Abstract

U radu je analiziran uticaj limunske kiseline na morfološke, fiziološke i biohemijske karakteristike odabranih klonova vrba (Salix spp.) gajenih u zemljištu umereno zagađenom kadmijumom (Cd). Definisanjem parametara akumulacije, otpornosti i tolerantnosti različitih klonova vrba na prisustvo kadmijuma u podlozi, kao i uspešnosti primene limunske kiseline kao helatora u procesu asistirane fitoremedijacije, mogao bi se identifikovati klon (ili klonovi) pogodan za dekontaminaciju zemljišta zagađenog kadmijumom. Da bi se postigao cilj istraživanja biljke su gajene u polu-kontrolisanim uslovima tokom 3 meseca. Eksperiment je podeljen u dve faze (dve godine istraživanja),zasnovane na razlikama u metodološkom pristupu. Tokom prve godine limunska kiselina je dodata jednom, dok je tokom druge druge godine aplikacija ovog helatora vršena u tri ponavljanja. U radu je analizaran sadržaj i distribucija Cd u zemljištu i različitim biljnim organima (koren, izdanak, mladi i stari listovi); uticaj Cd i limunske kiseline na morfometrijske parametre: visina i prečnik izdanka, masa i površina listova, broj listova, masa i zapremina korena; na fotosintetičke karakteristike: intenzitet fotosinteze, intenzitet transpiracije, stomatalnu provodljivost, intercelularnu koncentraciju CO2, efikasnost korišćenja vode, koncentraciju fotosintetičkih pigmenata; na mineralnu ishranu i distribuciju makronutrijenata u biljkama (sadržaj azota, fosfora i kalijuma); na sadržaj aminokiseline prolina i cisteina; na aktivnost antioksidativnih enzima (katalaza, askorbat-peroksidaza, gvajakol-peroksidaza), kao neezmiskih antioksidanata poput sadržaja redukovanog glutationa i tiola. Dobijeni rezultati su ukazali na genotipsku specifičnost analiziranih klonova vrba u procesu fitoremedijacije u zavisnosti od primenjenog tretmana, doze Cd i prisustva limunske kiseline. Toksično dejstvo nije bilo jasno uočljivo na morfološkom nivou, dok su primenjeni tretmani signifikantno uticali na fiziološko-biohemijske procese u biljkama. Sa povećanjem sadržaja Cd u biljkama je utvrđena tendencija smanjenja intenziteta fotosinteze, transpiracije, kao i efikasnosti koršćenja vode, dok je primena limunske kiseline ublažila štetan efekat ovog teškog metala, što je registrovano na kombinovanim tretmanima. Kao odgovor na akumulaciju Cd u biljnom tkivu utvrđena je promena aktivnosti antioksidativnih enzima, kao i neezimskih komponenti odbrambenog sistema zaštite. Pored toga, u radu je utvrđeno da primena limunske kiseline utiče na usvajanje, akumulaciju i toleranciju vrba na prisustvo Cd, te rezultati ove studije imaju praktičan značaj u usavršavanju tehnika fitoremedijacije i dekontaminacije zagađenih područja.

The role of citric acid on morphological, physiological and biochemical characteristics of selected willow clones (Salix spp.) grown in soil with moderately polluted cadmium (Cd) was presented. The aim of this study was to determine the Cd accumulation, translocation and tolerance of different willow clones, as well as the influence of citric acid as a chelator in the assisted phytoremediation process. In order to achieve this goal, plants were grown in semi-controlled conditions for 3 months. The experiment was divided into two phases (two years of research), based on differences in the methodological approach, regarding the application of citric acid. During the first-year experiment, citric acid was added once, while in the second year the application of this chelator was performed in three repetitions. The analyses included: the accumulation and distribution of Cd in soil and various plant organs (root, stem, young and old leaves); influence of Cd and citric acid on morphometric parameters: stem hight and diameter, number of leaves, biomass and area of leaves, biomass and volume of the root; on photosynthetic characteristics: net photosynthetic and transpiration rate, water use efficiency, stomatal conductance, intercellular concentration of CO2, concentration of photosynthetic pigments; on mineral nutrition and distribution of macronutrients in plants (nitrogen, phosphorus and potassium content); on the content of the amino acid proline and cysteine; on the activity of antioxidant enzymes (catalase, ascorbate peroxidase, guaiacol peroxidase), as non- enzymatic components such as reduced glutathione and thiol content. The obtained results indicated the genotypic specificity of the analyzed willow clones in the phytoremediation process, depending on the treatment applied, the Cd dose, and the presence of citric acid. The toxic effect was not evident on the morphological level, while the applied treatments showed a significant influence on the physiologicalbiochemical processes in the willows. The net photosynthetic rate, transpiration rate, as well as, water use eficiency showed decreasing with increasing Cd concentration in plant tissue, while the application of citric acid mitigated the harmful effect of this heavy metal, which was registered on combined treatments. In response to the accumulation of Cd in plant tissue, a change in the activity of anti-oxidant enzymes, as well as nonenzymatic components of the defense system has been established. In addition, the application of citric acid showed the promotion role on the absorption, accumulation and tolerance of willows grown in moderately polluted soil cadmium, which has a practical significance in the improvement of phytoremediation techniques and decontamination of polluted soil.