Phenolic compound localisation in Polypodium vulgare L. rhizomes after mannitol-induced dehydration and controlled desiccation

Abstract

Polypodium vulgare L. is a desiccation-tolerant fern that can withstand successive dry periods in its life cycle. To better understand this mechanism, the current study was undertaken to assess the role of phenolic compounds in rhizome dehydration and determine their localisation in the rhizome cells after enforced dehydration in mannitol solution or controlled desiccation with or without abscisic acid (ABA) pretreatment. Phenolic distribution at the subcellular level was studied using gold particle-complexed laccase. Cells from different tissues: cortical parenchyma, endodermis and stelar elements--pericycle, sieve cells and vascular parenchyma were observed under a transmission electron microscope (TEM). The content of phenolic compounds was greater in ABA-untreated rhizomes after enforced dehydration in mannitol solution and subsequent rehydration. After controlled desiccation the phenolic content significantly increased in ABA-untreated rhizomes. A large number of phenolic compound deposits were present in all types of rhizomatous cells. Phenolics were widely distributed in the vacuoles of all cells, and in the secondary cell walls of sieve cells, although scattered labelling was hardly ever observed in the primary cell walls. In dehydrated and plasmolysed cells from the cortex and endodermis, phenolic compounds were present in the apoplastic compartments between the plasma membranes and the cell walls. There is evidence that abscisic acid plays a role as a crucial antioxidant resulting in no damage and a lower level of phenolic increase as compared to ABA-untreated rhizomes. Moreover, the location of phenolics suggests a protective chemical barrier against environmental stresses.

The Synthesis and Storage Sites of Phenolic Compounds in the Root and Rhizome of <i>Echinacea purpurea</i>

“…Few plastids were labeled, only those containing starch grains were marked with some gold granules, and the gold granules gathered around the starch grains or directly on the starch grains. These results were consistent with the immune gold labeling results of polyphenols in rhizome of Polypodium vulgare L. studied by [23]. As to the partial labeling of the starch grains, its reason is not yet clear.…”

“…Some black flocculent substance was found on the cell wall, but only at sites surrounding large intercellular space. Because lipids in the cell are also osmiophilic, it is difficult to differentiate them from the phenolic compounds, but immunocytological localization techniques revealed that cell wall was the distribution sites of phenolic compounds [16,23]. Therefore, laccase-colloidal gold labeling was used to locate the phenolic compounds in the cells.…”

Correlation of the temporal and spatial expression patterns of HQT with the biosynthesis and accumulation of chlorogenic acid in Lonicera japonica flowers

“…These observations led us to speculate that the degradation product of starch grains in the chloroplasts may provide an important precursor for CGA synthesis and that the reduced abundance of laccase-gold particles around the starch grains later might be explained (at least partially) by transfer of CGA into vacuoles for storage at the later stages. Consistent with this notion, previous studies have shown that phenolic acids in Polypodium vulgare L. rhizomes were mainly distributed around the amyloplast starch grains 51 and that starch in the chloroplasts was involved in the synthesis of tannins or phenolic acids 52–54 . In addition, our cellular evidence also suggests that CGA synthesized in the cytoplasm migrated into the large central vacuoles mainly through the aggregation of vesicles and then fusion of the vesicular membranes with the vacuolar membranes.…”

Changes in the nature of phenolic deposits after re-warming as a result of melatonin pre-sowing treatment of Vigna radiata seeds

“…6B) similar to observations in soybean roots (Szafrańska et al, 2005). The predominant vacuolar localization of PhC, as revealed by TEM, was reported by many authors in different plant species (Kuraś et al, 1999;Szafrańska et al, 2005;Bagniewska-Zadworna et al, 2008;Glińska et al, 2009). The chemical character of PhC visualized with OsO 4 remains unknown.…”