Abstract
The study was focused on assessing the presence of arabinogalactan proteins (AGPs) and pectins within the cell walls as well as prenyl lipids, sodium and chlorine content in leaves of Tilia x euchlora trees. The leaves that were analyzed were collected from trees with and without signs of damage that were all growing in the same salt stress conditions. The reason for undertaking these investigations was the observations over many years that indicated that there are trees that present a healthy appearance and trees that have visible symptoms of decay in the same habitat. Leaf samples were collected from trees growing in the median strip between roadways that have been intensively salted during the winter season for many years. The sodium content was determined using atomic spectrophotometry, chloride using potentiometric titration and poly-isoprenoids using HPLC/UV. AGPs and pectins were determined using immunohistochemistry methods. The immunohistochemical analysis showed that rhamnogalacturonans I (RG-I) and homogalacturonans were differentially distributed in leaves from healthy trees in contrast to leaves from injured trees. In the case of AGPs, the most visible difference was the presence of the JIM16 epitope. Chemical analyses of sodium and chloride showed that in the leaves from injured trees, the level of these ions was higher than in the leaves from healthy trees. Based on chromatographic analysis, four poly-isoprenoid alcohols were identified in the leaves of T. x euchlora. The levels of these lipids were higher in the leaves from healthy trees. The results suggest that the differences that were detected in the apoplast and symplasm may be part of the defensive strategy of T. x euchlora trees to salt stress, which rely on changes in the chemical composition of the cell wall with respect to the pectic and AGP epitopes and an increased synthesis of prenyl lipids.
Highlights
Salt stress is a complex process that includes changes in plants on the physiological, histological, cellular and molecular levels by limiting nutrient uptake and disrupting the ionic balance [1,2,3,4,5].The cell wall is an integral part of a plant cell, it is metabolically active and dynamically changes in response to internal and external factors
The aim of the present study was to attempt to answer the question of whether healthy trees can develop a defense strategy based on changes in 1) the cellular distribution of selected pectic and arabinogalactan proteins (AGPs) epitopes in their leaves, and 2) the content of sodium, chloride and prenyl lipids in order to overcome the harmful effects of salt stress
The detailed spatial distribution of AGP (JIM8, JIM16, JIM13, and LM2) and pectic (LM5, LM6, LM19, and LM20) epitopes in different tissues of T. x euchlora leaves was determined both in the leaf lamina and the petiole from trees grown under the same level of salt stress but exhibiting differences in their health status
Summary
The cell wall is an integral part of a plant cell, it is metabolically active and dynamically changes in response to internal and external factors. The diversity of the cell wall chemical components is an expression of the changes in cells that are under the influence of various factors. Pectins are components that are subjected to changes in relation to the operating biotic and abiotic factors [6,7,8]. Arabinogalactan proteins (AGPs) play an important role in the control of plant development [18,19,20,21,22], and changes in the AGPs indicate that they respond to both biotic and abiotic factors including salinity [23,24,25,26,27,28]
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