Inhibition of the Water Oxidizing Complex of Photosystem II and the Reoxidation of the Quinone Acceptor QA− by Pb2+

Makowski

et al. 2020

IJMS

Ceylon leadwort (Plumbago zeylanica) is ornamental plant known for its pharmacological properties arising from the abundant production of various secondary metabolites. It often grows in lead polluted areas. The aim of presented study was to evaluate the survival strategy of P. zeylanica to lead toxicity via photosynthetic apparatus acclimatization. Shoots of P. zeylanica were cultivated on media with different Pb concentrations (0.0, 0.05, and 0.1 g Pb∙l−1). After a four-week culture, the efficiency of the photosynthetic apparatus of plants was evaluated by Chl a fluorescence measurement, photosynthetic pigment, and Lhcb1, PsbA, PsbO, and RuBisCo protein accumulation, antioxidant enzymes activity, and chloroplast ultrastructure observation. Plants from lower Pb concentration revealed no changes in photosynthetic pigments content and light-harvesting complex (LHCII) size, as well as no limitation on the donor side of Photosystem II Reaction Centre (PSII RC). However, the activity and content of antioxidant enzymes indicated a high risk of limitation on the acceptor side of Photosystem I. In turn, plants from 0.1 g Pb∙l−1 showed a significant decrease in pigments content, LHCII size, the amount of active PSII RC, oxygen-evolving complex activity, and significant remodeling of chloroplast ultrastructure indicated limitation of PSII RC donor side. Obtained results indicate that P. zeylanica plants acclimate to lead toxicity by Pb accumulation in roots and, depending on Pb concentration, by adjusting their photosynthetic apparatus via the activation of alternative (cyclic and pseudocyclic) electron transport pathways.

Section: Discussionsupporting

confidence: 50%

Can Ceylon Leadwort (Plumbago zeylanica L.) Acclimate to Lead Toxicity?—Studies of Photosynthetic Apparatus Efficiency

Makowski

et al. 2020

IJMS

“…(2) On the PSII RC—substitution of Mg 2+ by Pb 2+ in the chlorophyll porphyrin ring, what is very dangerous especially in PSII RCs and antenna systems (Harpaz-Saad et al 2007 ). (3) On the acceptor side—substitution Fe 2+ by Pb 2+ in protonation complex which is responsible for the protonation of the semichinol radical Q B − (Belatik et al 2013 ). Since chl a fluorescence measurement is a useful, non-invasive, and reliable method for estimation of heavy metal impact on photosynthetic apparatus (Papageorgiou et al 2007 ; Kodru et al 2015 ; Stirbet et al 2014 ; Kalaji et al 2016 ), the fast fluorescence chl a kinetics test was used to assess the condition of Anthyllis vulneraria photosynthetic apparatus.…”

Section: Discussionmentioning

confidence: 99%

The acclimatization strategies of kidney vetch (Anthyllis vulneraria L.) to Pb toxicity

Piwowarczyk

Muszyńska

et al. 2018

Environ Sci Pollut Res

Kidney vetch (Anthyllis vulneraria L.) is a well-known Zn hyperaccumulator. Zn often occurs with Pb in one ore; thus, plants inhabiting waste dumps are exposed not only to Zn but also to Pb toxicity. While the response of kidney vetch to Zn toxicity is relatively well known, the Pb survival strategy of Anthyllis vulneraria has not been the subject of investigations. The aim of presented research was to determine the survival strategy of kidney vetch exposed to high lead concentrations. Shoot explants of a calamine kidney vetch ecotype were placed on agar media containing 0.0, 0.5, 1.0, and 1.5 mM Pb. Morphological, physiological, and biochemical responses, in particular photosynthetic apparatus of plantlets, were examined. The most pronounced changes were observed in plants grown on media supplemented with 1.5 mM Pb after 8 weeks of culture. Increased dry weight and high lead accumulation were observed in roots. Similarly, in shoots, increased dry weight and a decreased number of newly formed shoots were recorded. The accumulation of lead was many times lower in shoots than in roots. In leaf cells’ ultra-structure, looser arrangement of chloroplast thylakoid grana was observed. Despite the decrease in chlorophyll a and carotenoid content, the photosynthetic apparatus remained efficient due to the lack of photoinhibition and increased electron transport rate beyond photosystem II (PSII). For the first time, an acclimatization mechanism based on maintaining the high efficiency of photosynthetic apparatus resulting from increasing of electron transport rate was described.

International Journal of Phytoremediation

“…Previous studies have already pointed out that PSI is particularly sensitive to heavy metal stress (Wodala et al 2012), as well as to other oxidative stress factors (Bussotti et al 2011;Mereu et al 2011;Salvatori et al 2014). Moreover, it has been recently shown that Pb 2+ is able to interact with PSI at the plastocyanin (PC) level, thus specifically inhibiting the electron transfer process at the PSI donor side (Belatik, Hotchandani and Carpentier 2013). Although in our experiment the Pb concentration in leaves was relatively low (88.8 ± 11.3 mg kg -1 ), it was 50.7% more than the control, therefore the persistence of the I-P phase alteration after the recovery of gas exchanges suggests that such phytotoxic effects at the leaf level cannot be excluded.…”

Section: Discussionmentioning

confidence: 99%

Effects of high Zn and Pb concentrations onPhragmites australis(Cav.) Trin. Ex. Steudel: Photosynthetic performance and metal accumulation capacity under controlled conditions

Bernardini

Salvatori

Guerrini

et al. 2015

The response of Phragmites australis (Cav.) Trin. Ex. Steudel to zinc (Zn) and lead (Pb) was studied separately in two hydroponic tests, during a three weeks experiment. The effects on ecophysiology and biomass partitioning were evaluated during the metal treatments and at the recovery, and total metal content and accumulation capacity in different plant organs were assessed. Zn and Pb had different effects on the overall measured parameters, highlighting different mechanism of action. In particular, Zn concentration was higher in roots and, being a micronutrient, it was translocated into leaves, producing a reduction of assimilation rate, stomatal conductance (-71.9 and -81.3% respect to the control plant respectively), and a strong down regulation of photosystems functionality both at PSII and PSI level. Otherwise, Pb was accumulated mainly in the more lignified tissue such as rhizomes, with slightly effect on gas exchange. Chlorophyll a fluorescence highlighted that Pb inhibits the electron transfer process at the PSI donor side, without recovery after the removal of the metal stress. Despite these physiological limitations, P. australis showed a high capacity to accumulate both metals, and only slight reduction of biomass, being therefore a suitable species for phytoremediation interventions.