Cd, Fe, and Light Sensitivity: Interrelationships in Cd-Treated Populus

Abstract

Cadmium is a toxic heavy metal causing iron deficiency in the shoot and light sensitivity of photosynthetic tissues that leads to decreased photosynthetic performance and biomass production. Light intensity had strong impact on both photosynthetic activity and metal accumulation of cadmium-treated plants. At elevated irradiation, cadmium accumulation increased due to the higher dry mass of plants, but its allocation hardly changed. A considerable amount of iron accumulated in the roots, and iron concentration was higher in leaves developed at moderate rather than low irradiation. At the same time, the higher the irradiation the lower the maximal photochemical quantum efficiency. The decreased photochemical efficiency, however, started to recover after a week of Cd treatment at moderate light without substantial change in metal concentrations but following the accumulation of green fluorescent compounds. Both cadmium treatment and higher light caused the accumulation of flavonoids in leaf mesophyll vacuoles/chloroplasts, but accumulation of flavonols, fluorescing at 510 nm, was characteristic to cadmium stress. Therefore, flavonoids, which may act by scavenging reactive radicals, chelating Cd, and shielding against excess irradiation, play an important part in Cd stress tolerance of Populus, and may have special impact on its phytoremediation capacity.

Properties and applications of flavonoid metal complexes

“…(poplar) was observed as a response to Cd stress. 240 Elevated accumulation of the avonoid taxifolin and other phenolic compounds is also observed in the Al-tolerant maize variety Cateto when compared with Al-sensitive maize. This may be, besides increased Al exclusion, the mechanism of resistance of Cateto maize to high Al content in soil.…”

Stress hardening under long-term cadmium treatment is correlated with the activation of antioxidative defence and iron acquisition of chloroplasts in Populus

“…The elevated concentration of zeaxanthin under light conditions contributed to the increase of Φ NPQ . Nevertheless, it has to be noticed that the ΔpH-dependent quenching was low during the entire experimental time, even in Ctrl samples, because of the applied low light intensity (Cd treated plants are light sensitive, see: [42]). …”

“…In fact, they may also have a role in increasing leaf dry weight, since they contribute to secondary cell wall biosynthesis. An increase in the monomeric constituents of the secondary cell wall has previously been become obvious from the elevated level of blue-emitting cell wall phenolics, like ferulic acid [42,46] During long-term Cd treatment, poplar plants were able to overcome oxidative damage. Thus, following the acute phase of Cd stress, lipid peroxidation decreased.…”

S-methylmethionine contributes to enhanced defense against Maize dwarf mosaic virus infection in maize

“…The soluble phenolics, located in the cell vacuoles, only slightly contribute to the overall blue-green fluorescence emission (Lichtenthaler and Schweiger 1998). Vacuole accumulating flavonoids emitting green-yellow fluorescence also contribute to the increase of F520 emission under high light and heavy metal stresses (Solti et al 2011).…”