The effect of cadmium on morpho-anatomical characteristics of the great duckweed Spirodela polyrhiza (L.) Schleid

Promjene u morfološkim i anatomskim obilježjima dio su strategije prilagodbe biljaka na nepovoljne uvjete okoliša, poput onečišćenja teškim metalima. U radu je istraživan učinak kadmija (0, 7, 28 i 111 µM) na morfoanatomske značajke velike barske leće, Spirodela polyrhiza (L.) Schleid u različitim razvojnim fazama. U svim ispitivanim tretmanima kadmij je uzrokovao pojavu kloroze, odbacivanje korijena i epinastiju frondova. Najveća koncentracija kadmija (111 µM) uzrokovala je smanjenje debljine najstarijih frondova, smanjenje intercelularnih prostora te deformaciju stanica spužvastog parenhima. Nisu utvrđene promjene u debljini najmlađih frondova, ali su, ovisno o koncentraciji kadmija, opažene razlike u veličini, obliku i broju intercelulara, obliku i veličini stanica spužvastog parenhima, te u debljini asimilacijskog parenhima. Povećanje koncentracije kadmija utjecalo je na progresivno nakupljanje škrobnih zrnaca u najmlađim frondovima, dok je u najstarijim frondovima najveća količina škrobnih zrnaca detektirana u najmanjoj koncentraciji kadmija. Istraživanja morfo-anatomskih promjena biljaka u različitim razvojnim fazama poboljšat će razumijevanje staničnog odgovora biljaka (mehanizama tolerancije i homeostaze) na toksičnost teških metala poput kadmija.Changes in morphological and anatomical characteristics are a part of plant adaptation strategies to adverse environmental conditions, like heavy metal contamination. The paper investigates the effect of cadmium (0, 7, 28, and 111 µM) on the morpho-anatomical features of giant duckweed, Spirodela polyrhiza (L.) Schleid in different developmental stages. In all examined treatments, cadmium caused chlorosis, root rejection, and epinasty of the fronds. The highest cadmium concentration (111 µM) caused a decrease in the thickness of the oldest fronds, decrease in the intercellular spaces, and deformations of spongy parenchyma cells. No changes in the thickness of the youngest fronds were found, but, depending on the cadmium concentration, differences in the size, shape, and number of intercellular spaces, the shape and size of the spongy parenchyma cells, and the thickness of the assimilation parenchyma were observed. An increase in cadmium concentration caused a progressive accumulation of starch grains in the youngest fronds. In contrast, in the oldest fronds, the largest amount of starch grains was detected in the lowest cadmium concentration. Research of the plants morpho-anatomical changes in the different developmental stages can improve the understanding of plants cellular response (mechanisms of tolerance and homeostasis) to the toxicity of heavy metals such as cadmium