The contents of free amino acids and elements in As-hyperaccumulator Pteris cretica and non-hyperaccumulator Pteris straminea during reversible senescence

Abstract

Several species of the genus Pteris including P. vittata and P. cretica (PC) have been identified as arsenic hyperaccumulators (Luongo and Ma 2005). On the other hand, Meharg (2003) first reported P. straminea (PS) as a non-hyperaccumulator plant. The phytochelatins play a key role in As (arsenic) detoxification in non-hyperaccumulators (Raab et al. 2004). In contrast to non-hyperaccumulators, hyperaccumulators complex only 1-3% As with phytochelatins (Zhao et al. 2003, Vetterlein et al. 2009), because As detoxification is associated with the conversion of As V to As III and As methylation (Gonzaga et al. 2006). The low As content in Pteris hyperaccumulators promotes plant growth; a high content inhibits growth (Cao et al. 2004). This finding confirms that As induces a hormetic response in these plants. A high level of detoxified As leads to its re-oxidation and to demethylation and As becomes toxic after degradation of complexes that substituted As III/V species with CH 3 in cells (Tu et al. 2003 The objectives of this study were to analyse the relationship between the contents of elements and free amino acids (AAs) in fronds of As-hyperaccumulator Pteris cretica cv. Albo-lineata (PC) and non-hyperaccumulator Pteris straminea (PS) during reversible senescence. The time-course effect on senescence was also investigated. The two ferns were grown in a pot experiment with soil containing 16 mg As total /kg soil for 160 days. The contents of elements and AAs in both ferns and in individual sampling periods differed. The highest accumulation of elements and AAs was measured in PS fronds after 83 days; however, the accumulation of As, Ca, Cu, Fe, Mg, P and asparagin in PC fronds was highest after 160 days. The results of principal component analysis showed more rapid senescence of PS compared to PC. This was caused by changes in the relationship between the contents of elements (cofactors of metalloenzymes, stress metabolites) and AAs (transport of NH 2 group and stress metabolites). The hyperaccumulator plant (PC) was more resistant than the bioindicator plant (PS) to the conversion from reversible to irreversible senescence.

Response of cytokinins and nitrogen metabolism in the fronds of Pteris sp. under arsenic stress

“…in the drop of photosynthetic performance under As(V) toxicity is attributed to a decrease in maximal rate of RuBisCO carboxylation, which is reversed by nitrogen availability. Arsenic toxicity was found to be compensated primarily by upregulation of photosynthetic parameters and key nitrogen metabolizing enzymes [36]. In this experiment with Solanum lycopersicum L., major photosynthetic criteria like net photosynthetic rate and maximum quantum efficiency of photosystem II were significantly reduced under As(V) stress.…”

“…Our previous results show that N flow via amino acids can change dramatically in response to stress caused by toxic elements [35][36][37]. Pityrogramma calomelanos tolerates high concentrations of As due to its ability to upregulate the biosynthesis of amino acids and antioxidants, without greatly disturbing central carbon metabolism [33].…”

Response of Carrot (Daucus carota L.) to Multi-Contaminated Soil from Historic Mining and Smelting Activities

“…SAR was detected only in the leaves of the Multi variant. Pavlíková et al [90] observed that SAR and HYP were not detected in the As hyperaccumulator Pteris cretica or the non-hyperaccumulator P. straminea. However, SAR content was confirmed in hyperaccumulators of Noccaea species [83], and the authors assumed that SAR could form complexes with Cd and other metals and protect nucleic acids from oxidative stress [91].…”