Abstract
Two species of Pb-adapted shrubs, Alyssum montanum and Daphne jasminea, were evaluated in vitro for their tolerance to elevated concentrations of cadmium. Shoot cultures were treated with 0.5, 2.5, and 5.0 μM CdCl2 for 16 weeks and analyzed for their organogenic response, biomass accretion, pigment content, and macronutrient status. Cadmium accumulation and its root-to-shoot translocation were also determined. In both species, rooted microplantlets, suitable for acclimatization, were obtained in the presence of Cd applied as selection agent. In A. montanum, low and moderate dose of Cd stimulated multiplication, rooting, and biomass production. Growth tolerance index (GTI) in Cd-treated shoots ranged from 120 to 215%, while in the roots 51–202%. In turn, in Cd-treated D. jasminea proliferation and rooting were inhibited, and GTI for shoots decreased with increasing doses of Cd. However, roots exposed to Cd had higher biomass accretion. Both species accumulated Cd in developed organs, and its content increased with increasing CdCl2 dose. Interestingly, D. jasminea accumulated higher amounts of Cd in the roots than A. montanum and immobilized this metal in the root system. On the contrary, A. montanum translocated some part of accumulated Cd to the shoots, but with low efficiency. In the presence of Cd, A. montanum maintained macronutrient homeostasis and synthesized higher amounts of phytosynthetic pigments in the shoots. D. jasminea accumulated root biomass, immobilized Cd, and restricted its translocation at the expense of nutrient balance. Considering remediation potential, A. montanum could be exploited in phytoextraction, while D. jasminea in phytostabilization of polluted substrate.
Highlights
Heavy metals naturally occur in the soils as rare element, but their excessive amounts in the environment are mainly consequence of anthropogenic activities such as mining, smelting, burning of fossil fuels and intensive use of fertilizers (Wiłkomirski et al 2011; Candeias et al 2015; Reimann et al 2017)
Cadmium impact on photosynthesis may be shown in the decline of chlorophyll content and/or chlorophyll a/b ratio due to the inhibition of chlorophyll biosynthesis enzymes and disorganization of granum ultrastructure (Gill et al 2012; Mohamed et al 2012; Perveen et al 2012)
We focused on developing efficient culture system with intent to obtain propagative lines of shrubs tolerant to cadmium, suitable for acclimatization, to be applied to plant-based technologies of soil remediation
Summary
Heavy metals naturally occur in the soils as rare element, but their excessive amounts in the environment are mainly consequence of anthropogenic activities such as mining, smelting, burning of fossil fuels and intensive use of fertilizers (Wiłkomirski et al 2011; Candeias et al 2015; Reimann et al 2017). Since the photosynthetic apparatus is susceptible to Cd, a reduction of photosynthesis is a common response in plants exposed to Cd ions (Monteiro et al 2009; Gill et al 2012). Disturbances in this basic life process, revealed as a limitation of net CO2 assimilation rate, have been noted in such species as Lactuca sativa (Dias et al 2013) or Lepidium sativum (Gill et al 2012). Mineral deficiencies are reflected in leaf chlorosis and necrosis, stunting of a plant and its death (Astolfi et al 2012, Mohamed et al 2012; Shi et al 2015)
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