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

Abstract

Given the close relationship between cytokinins (CKs), photosynthesis and nitrogen metabolism, this study assessed the effect of arsenic (As) contamination on these metabolic components in the As-hyperaccumulators Pteris cretica L. var. Albo-lineata (Pc-A) and var. Parkerii (Pc-P) as well as the As-non-hyperaccumulator Pteris straminea Mett. ex Baker (Ps). The ferns were cultivated in a pot experiment for 23 weeks in soil spiked with As at the levels 20 and 100 mg�kg-1. For the purpose of this study, the CKs were placed into five functionally different groups according to their structure and physiological roles: bioactive forms (bCKs; CK free bases); inactive or weakly active forms (dCKs; CK N-glucosides); transport forms (tCKs; CK ribosides); storage forms (sCKs; O-glucosides); and primary products of CK biosynthesis (ppbCKs; CK nucleotides). An important finding was higher CKs total content, accumulation of sCKs and reduction of dCKs in As-hyperaccumulators in contrast to non-hyperaccumulator ferns. A significant depletion of C resources was confirmed in ferns, especially Ps, which was determined by measuring the photosynthetic rate and chlorophyll fluorescence. A fluorescence decrease signified a reduction in the C/N ratio, inducing an increase of bioactive CKs forms in Pc-P and Ps. The impact of As on N utilization was significant in As-hyperaccumulators. The glutamic acid/glutamine ratio, an indicator of primary N assimilation, diminished in all ferns with increased As level in the soil. In conclusion, the results indicate a large phenotypic diversity of Pteris species to As and suggest that the CKs composition and the glutamic acid/glutamine ratio can be used as a tool to diagnose As stress in plants.

Free amino acid regulation in fronds and roots of two Pteris cretica L. ferns under arsenic stress

“…In the present study, As content in Pc-Al was > 1 000 mg/kg, whereas As content in Pc-Pa was under the limit of hyperaccumulation (Table 1). Similar results for Pc-Pa were shown in our previous study (Pavlíková et al 2020), as well as for Pc-Al (Zemanová et al 2020). In contrast to our results, Luongo and Ma (2005) determined As content in Pc-Pa > 1 000 mg/kg and identified this fern as an As-hyperaccumulator.…”

“…Furthermore, our results showed a decrease in the GLU/GLN ratio by As treatment in fronds of Pc-Al and Pc-Pa (Figure 2). Similarly, in our previous study, GLU/GLN ratio decreased with As levels in fronds of Pc-Al and Pc-Pa, which indicated a negative As effect by depletion of the C pool as a source for the biosynthesis of other free AAs (Pavlíková et al 2020).…”

“…The changes in tAA contents and family ratios were caused by As as a result of affected N metabolism in ferns. Arsenic impacted N metabolism in non-As-hyperaccumulators (Finnegan andChen 2012, Pathare et al 2013), as well as in As-hyperaccumulators (Pavlíková et al 2020). Disturbances to AA metabolism can be lethal for plants because AAs are major N carriers in the plants' long-distance transport system and N storage molecules (Okumoto et al 2016).…”

“…Ferns were grown in these pots for 90 days. Details of harvesting and analysis of As and free AAs were described previously by Pavlíková et al (2020).…”

Arsenic Toxicity-Induced Physiological and Metabolic Changes in the Shoots of Pteris cretica and Spinacia oleracea

“…The results of As bioaccumulation and translocation confirmed P. cretica ‘Albo-lineata’ as an As-hyperaccumulating fern. Similar results were previously observed [ 21 , 23 , 28 , 37 , 38 ].…”