The chemical identity of intervessel pit membranes in Acer challenges hydrogel control of xylem hydraulic conductivity
| Autor: | Klepsch, MM, Schmitt, M, Knox, JP, Jansen, S |
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| Přispěvatelé: | Oliveira, RS |
| Jazyk: | angličtina |
| Rok vydání: | 2016 |
| Předmět: | |
| Zdroj: | AoB Plants |
| ISSN: | 2041-2851 |
| Popis: | Long-distance water transport in wood is well known to be affected by the ionic concentration of xylem sap. Based on immunocytochemistry, we demonstrate that pectic polysaccharides and glycoproteins are not associated with vessel-vessel pit membranes. Therefore, we challenge the hypothesis that the ion-mediated enhancement of hydraulic conductance is caused by a swelling or shrinking of pectins surrounding pit membrane pores. Our findings reinforce the need for an alternative hypothesis besides the pit membrane chemistry to understand this so-called “ionic effect”. Ion-mediated enhancement of the hydraulic conductivity of xylem tissue (i.e. the ionic effect) has been reported for various angiosperm species. One explanation of the ionic effect is that it is caused by the swelling and shrinking of intervessel pit membranes due to the presence of pectins and/or other cell-wall matrix polymers such as heteroxylans or arabinogalactan–proteins (AGPs) that may contain acidic sugars. Here, we examined the ionic effect for six Acer species and their pit membrane chemistry using immunocytochemistry, including antibodies against glycoproteins. Moreover, anatomical features related to the bordered pit morphology and vessel dimensions were investigated using light and electron microscopy. The ionic effect varied from 18 % (± 9) to 32 % (± 13). Epitopes of homogalacturonan (LM18) and xylan (LM11) were not detected in intervessel pit membranes. Negative results were also obtained for glycoproteins (extensin: LM1, JIM20; AGP glycan: LM2), although AGP (JIM13)-related epitopes were detected in parenchyma cells. The mean vessel length was significantly correlated with the magnitude of the ionic effect, unlike other pit or vessel-related characteristics. Our results suggest that intervessel pit membranes of Acer are unlikely to contain pectic or other acidic polysaccharides. Therefore, alternative explanations should be tested to clarify the ionic effect. |
| Databáze: | OpenAIRE |
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