Response of Holm oak (Quercus ilex subsp. ballota) and mastic shrub (Pistacia lentiscus L.) seedlings to high concentrations of Cd and Tl in the rhizosphere

Abstract

The impairment of root growth and photosynthetical functioning are the main impacts of trace elements on woody plant seedlings. In this work, we assessed the response of Holm oak (Quercusilex subsp. ballota) and mastic shrub (Pistacia lentiscus) seedlings to high concentrations of Cd and Tl in the rhizosphere. These are non-essential trace elements, with a potential high mobility in the soil-plant system. Seedlings of these species are frequently used in the afforestation of degraded soils in mining areas. Plants were exposed to different levels of Cd (20, 80 and 200 mg L(-1)) and Tl (2, 10 and 20 mg L(-1)) in a sand culture. Biomass allocation, growth rates, chlorophyll fluorescence and gas exchange were studied. Both metals affected root biomass. Cadmium produced an increase in the root mass ratio and a decrease in the specific leaf area of the plants in oak seedlings, while Tl did not provoke such response. Mastic plants were more sensitive to Tl and Cd than oak plants. Between elements, Tl provoked more severe toxic effects in the plants, affecting the antennae complexes and reaction centers of the photosystem II. Both elements decreased net assimilation rates (down to a 20% of the control plants) and stomatal conductance (5-10% of the values for the control plants). Cadmium was highly retained in the roots of both species, while Tl was highly translocated into the leaves. In general, Holm oak showed a higher tolerance for Cd than for Tl, and a higher resistance to both metals than mastic shrub, due to a high capacity for Cd retention at the root level. However, such accumulation in roots may induce water stress in the seedling exposed to Cd.

Enhanced Photosynthesis and Carbon Metabolism Favor Arsenic Tolerance inArtemisia annua, a Medicinal Plant as Revealed by Homology-Based Proteomics

“…The decrease in assimilation rates could be due to low ATP and NADPH contents (Table 2) and consequent impairment of the photosynthesis [47, 62]. Furthermore, the photosynthetic rate is known to weaken in the presence of heavy metals due to alterations in the active site of rubisco subunits [63, 64]. By contrast, PSI complex machinery might be envisioned to support the damaged PSII and maintain NADPH pool in 100  μ M As treated plants as observed in As-tolerant cordgrass Spartina densiflora [65] and Ricinus communis [66].…”

Changes in photosynthesis, antioxidant enzymes and lipid peroxidation in soybean seedlings exposed to UV-B radiation and/or Cd

“…4). The ratio Fv/Fm is often used as a stress indicator and the decreases in Fv/Fm implied that the plants were under stress (Domínguez et al 2011).…”

Studies on Gypsophila fastigiata parameters verifying its suitability to reclamation of post-flotation Zn-Pb wastes

“…In this case, the alterations in chlorophyll production occurred as an effect of decrease in availability of ions such as Fe and Mn or peroxidation of chloroplast membranes resulting from heavy metal induced oxidative stress (Dhir et al 2011). Disturbances in photosynthesis were also noticed in many others plants from different families (Küp-per et al 2002, Liu et al 2004, Mateos-Naranjo et al 2008, Domínguez et al 2011. Thus, in order to better understanding the influence of heavy metals on G. fastigiata photosynthetic apparatus efficiency, more parameters should be examined.…”