Cadmium-induced changes in pigments, total phenolics, and phenylalanine ammonia-lyase activity in fronds ofAzolla imbricata

Abstract

This study was designed to examine the effects of cadmium on several color-related parameters (including chlorophyll, carotenoid, and anthocyanin), total phenolics, and phenylalanine ammonia-lyase (PAL) activity in an aquatic fern species Azolla imbricate (A. imbricata). Cd accumulation and effects in the fronds were closely related with Cd concentration in the growth medium. The fronds under 0.5 mg/L Cd treatment turned red on the 3rd day, and this color change also appeared under 0.05 and 0.1 mg/L Cd treatment on the 5th day. Correlated with the color change, the contents of chlorophyll and carotenoid in the fronds significantly decreased in the presence of high Cd concentrations, while the anthocyanin content increased during the experiment. Significant increase in total phenolics content and PAL activity were also detected during Cd treatment. The results suggested that the Cd-induced change in color of fronds might be due to the decrease in chlorophyll and carotenoid and the increase in anthocyanin. Anthocyanin, total phenolics and their biosynthesis-related PAL might play a role in detoxification of Cd in A. imbricata.

Physiological responses of Matricaria chamomilla to cadmium and copper excess

“…In line with our results, Ali et al (2006) observed higher PAL activity and total phenols in root suspension cultures of Panax ginseng, comparing 40th and 20th days of exposure to Cu doses up to 50 lM. In fronds of the fern Azolla imbricata, Dai et al (2006) observed that Cd at a dose of 4.45 lM increased PAL activity up to the 5th day of exposure, but then it decreased up to the 9th day of exposure. This finding could support our hypothesis on the different time dynamics of PAL activity under Cd and Cu excess.…”

“…Its enhanced activity could therefore be assumed in stressed plant tissue. Recently, Ali et al (2006) recorded a stimulatory effect of Cu on PAL in Panax ginseng and the influence of Cd on PAL activity has been studied in fronds of Azolla imbricata (Dai et al, 2006). Notwithstanding, data related to cadmium effect on PAL activity under Cd stress and the comparison of metals with different redox properties is scarce.…”

Phytoremediation Potential of Aquatic Macrophyte, Azolla

“…The Pb content was 0.37, 2.3, and 1.8% of the dry weight after 2, 4, and 6 days of growth, respectively, in the whole plant, while the isolated Azolla apoplast contained 0.125, 1.22, and 1.4% Pb, respectively. Sela et al (1989) reported that A. filiculoides also accumulate heavy metals such as Cd, Cr, Cu, and Zn and their content was 10,000, 1990, 9000, A. imbricata Cd 0.5 lg l -1 9 183 lg Cd g -1 Dai et al (2006) and 6500 ppm, respectively (Table 4). Arora et al (2004Arora et al ( , 2006 (Bennicelli et al 2004).…”

“…The bioaccumulation of heavy metals by Azolla spp. is known to exhibit a concentration-dependent relationship (Stepniewska et al 2005;Arora et al 2006;Dai et al 2006;Rai and Tripathi 2009). Duncan (1997, 1998a, b) investigated the removal of sexivalent Cr, Ni, and Zn by A. filiculoides from aqueous solution and from electroplating rinse effluent.…”

“…Toxicity of heavy metals in relation to biochemical parameters-pigments, photosynthesis, and activities of oxidative enzymes have been worked out by only few researchers (Sarkar and Jana 1986;Shi et al 2003;Dai et al 2006). Sarkar and Jana (1986) observed that the treatment of A. pinnata with As, Pb, Cu, Cd, and Cr (2 and 5 mg l -1 each), decreased Hill activity, chlorophyll content, protein and dry weight, and increased tissue permeability with respect to control.…”