Photosynthetic pigments content, δ-aminolevulinic acid dehydratase and acid phosphatase activities and mineral nutrients concentration in cadmium-exposed Cucumis sativus L.

Abstract

In this study, the effects of cadmium chloride (CdCl2) on plant growth, histology of roots, photosynthetic pigments content, δ-aminolevulinic acid dehydratase (ALA-D; E.C. 4.2.1.24) and acid phosphatase activities (AP; E.C. 3.1.3.2), soluble phosphorus (Pi) measurement and mineral nutrients content in cucumber seedlings (Cucumis sativus L.) were investigated. Cucumber seedlings were grown in vitro in an agar-solidified substrate containing four CdCl2 treatments (0, 100, 400, and 1000 µM) for ten days. Cd was readily absorbed by seedlings and its content was greater in the roots than in the shoot. Cd reduced shoot and root length, and fresh and dry biomass of seedlings. Inhibition of root cell elongation in Cd-treated seedlings was observed by the increase of the mean radial size of cells belonging to three zones of the root tip. The highest level of Cd reduced in a similar manner chlorophyll a, chlorophyll b and total chlorophyll contents. Increasing concentrations of Cd resulted in a linear decrease in carotenoids levels of cotyledons. Interestingly, the ALA-D activity in cotyledons was inhibited only at the highest level of Cd. Root and shoot AP activities were, respectively, activated and inhibited at all CdCl2 concentrations. Root Pi concentration was increased in all Cd treatments and it was not altered in the shoot tissues. Moreover, in general, the nutrient contents were increased in the root and decreased in the shoot. Therefore, we suggest that Cd affects negatively growth, photosynthetic pigments, ALA-D and AP activities and partition of mineral nutrients in cucumber seedlings.

Concentration of some metals in soil and plant organs and their biochemical profiles in Tulipa luanica, T. kosovarica and T. albanica native plant species

“…The negative correlation between Cu concentration and ALA-D activity in the leaves of T. kosovarica and T. albanica can be as a consequence of synergetic effect of Cu and Ni, since the Ni concentration in T. luanica leaves was under the limit of detection. Our results are consistent with results of Ghasemi et al (2009), showing toxic effects in Alyssum inflatum plant experimentally exposed in medium with Cu and Ni supplementation in contrast to medium only with Cu.…”

Detection of Cadmium Risk to the Photosynthetic Performance of Hybrid Pennisetum

“…The chloroplast reduction could be explained by Cd replacing the magnesium atom within chlorophyll to form a chlorophyll-Cd complex. This replacement results in damage to the photosynthetic apparatus (Siedlecka et al, 1998) and inhibits the production of chlorophyll by obstructing the formation of the protochlorophyllide reductase ternary complex and the synthesis of 5-aminolaevulinic acid (Huang et al, 1997) and by reducing chlorophyll synthesis (Gonçalves et al, 2009) or enhancing enzymatic degradation (Somashekaraiah et al, 1992).…”

Structural and functional alterations in photosynthetic apparatus of plants under cadmium stress

“…Cd inhibits ALA synthesis at the site of availability of glutamate for ALA synthesis and interferes by interacting with SH group of enzymes, δ-aminolevulinic acid dehydratase (Mysliwa-Kurdziel and Strzalka 2002 ) and porphobilinogen deaminase, (Skrebsky et al 2008 ) leading to the accumulation of chlorophyll biosynthesis intermediates like ALA and porphyrins. In fact ALA accumulation is considered to be a reason for generation of reactive oxygen species which alters redox status of plants and thus disturbing plant homeostasis as reported in Soybean (0-100 μM, 10 DAT) and Cucumis (0-1000 μM, 10 DAT) (Noriega et al 2007 ; Goncalves et al 2009 ). Additionally Cd reacts with protochlorophillide reductase, which causes photoreduction of protochlorophillide into chlorophyllide thus diminishing the raw material for chlorophyll synthesis (Stobart et al 1985 ).…”