Uticaj teških metala na morfo-anatomske i fiziološke karakteristike klonova topola (Populus spp.)

Abstract

<p>Pored usvajanja neophodnih nutrijenata, biljke su sposobne da usvajaju i<br />nakupljaju druge elemente, uključujući i one koji ne učestvuju u metaboličkim<br />procesima. Kadmijum (Cd) je te&scaron;ki metal koji ulazi u sastav neživog dela biosfere, i u<br />prirodi se sreće u zemlji&scaron;tu i biljkama. Nikl (Ni) je mikroelement koji ulazi u sastav<br />enzima ureaze, i uključen je u proces usvajanja gvož&ntilde;a iz zemlji&scaron;ta. Sa izuzetkom<br />hiperakumulatoskih biljnih vrsta, visoke koncentracije Cd i Ni u podlozi mogu ispoljiti<br />toksično dejstvo na biljke. Velika produkcija biomase, brz rast i visok intenzitet<br />transpiracije su karakteristike topola koje ih čine pogodnim test-biljkama u<br />ispitivanju efikasnosti u uklanjanju toksičnih te&scaron;kih metala iz zemlji&scaron;ta, u procesu<br />nazvanom fitoremedijacija. Stoga je cilj rada bilo ispitivanje uticaja Ni i Cd na morfoanatomske i fiziolo&scaron;ke karakteristike taksonomski udaljenih klonova topola. Rast<br />biljaka, nakupljanje suve materije, koncentracija fotosintetičkih pigmenata,<br />intenziteti fotosinteze i disanja, aktivnost enzima nitrat-reduktaze, gra&ntilde;a listova i<br />korena, mineralna ishrana i nakupljanje kadmijuma i nikla u pojedinim organima<br />proučavani su kod biljaka gajenih u prisustvu različitih koncentracija te&scaron;kih metala.<br />Biljke su gajene metodom vodenih kultura koristeći Hoagland-ov hranljivi rastvor koji<br />je sadržavao 10-4 ili 10-5 M Cd ili Ni. Dobijeni rezultati ukazuju na postojanje<br />genetske specifičnosti ispitivanih parametara, kao i izražene me&ntilde;uklonske<br />varijabilnosti u prisustvu te&scaron;kih metala. Efekti toksičnog dejstva te&scaron;kih metala<br />(inhibicija rasta, hloroza) konstatovani su kod svih klonova topola, a njihov intenzitet<br />je zavisio od vrste metala i primenjene koncentracije. Uticaj na visinu biljaka, masu i<br />povr&scaron;inu listova, masu stabla i korena, fotosintetičke karakteristike, usvajanje i<br />distribuciju makro- i mikroelemenata i gra&ntilde;u listova i korena varirao je me&ntilde;u<br />klonovima u zavisnosti od tretmana. Na svim tretmanima, biljke topola su<br />akumulirale najveće količine kadmijuma i nikla korenu. Ukoliko se produkcija<br />biomase uzme kao indikator tolerantnosti prema ispitivanim te&scaron;kim metalima, može<br />se uočiti najmanja osetljivost klona M-1 prema primenjenim koncentracijama nikla, i<br />najveća tolerantnost klona B-81 prema primenjenim koncentracijama kadmijuma.</p>

<p>Beside the ability to take up essential nutrients, plants are able to absorb and<br />accumulate other metals, even those with unknown metabolic function. The presence<br />of heavy metals in excess amounts in the environment is a global problem,<br />threatening the health of vegetation, wildlife and humans. Cadmium (Cd) is a heavy<br />metal constituting a nonliving component of the biosphere, and occurs naturally in<br />soils and plants. Nickel (Ni) is micronutrient needed to form urease, and also<br />involved in iron uptake from the soil. With exception of some species called<br />hyperaccumulators, high concentrations of Ni and Cd in the growing substrate could<br />be toxic for plants. Because of their fast growth, high biomass production and<br />transpiration rate, poplars are good test plants for studying efficacy of removal of<br />toxic metals from contaminated soils, in the process termed &ldquo;phytoremediation&rdquo;.<br />Therefore, the aim of our study was to evaluate the impact of Ni and Cd on morphoanatomical<br />and physiological characteristics of taxonomically distant poplar clones.<br />Plant growth, dry matter accumulation, photosynthetic pigments concentration, rates<br />of dark respiration and photosynthesis, nitrate reductase activity (NRA), structure of<br />leaves and roots, mineral nutrition, and accumulation of cadmium and nickel in plant<br />organs were studied. Plants were grown hydroponically using Hoagland&rsquo;s nutrient<br />solution containing different concentrations of Ni and Cd (10-4 and 10-5 M). Genetic<br />specificity of studied traits was evident, as well as the interclonal variability in<br />treated plants. Phytotoxic effects of the heavy metals (stunted growth, chlorosis)<br />were noticed in all poplar clones, and their intensity depended on the metal and<br />concentration applied. Effect on plant height and biomass, photosynthetic<br />characteristics, uptake and distribution of macro- and micronutrients, and structure<br />of leaves and roots varied between poplar clones and the treatments. Chemical<br />analysis of plant organs (leaves, stem, roots) revealed the highest accumulation of<br />Cd and Ni in roots in all poplar clones. On the basis of biomass production as the<br />tolerance indicator of studied clones, it could be concluded that the most tolerant<br />clones to Cd and Ni were B-81 and M-1, respectively, in the range of applied<br />concentrations.</p>