Tagged: xyloglucan

Guard cells around stomata

A fresh look at guard cell walls

Arguably, one of the best known ‘structure-function’ relationships in plant biology is the role played by cellulose microfibrils within the walls of the guard cells in stomatal opening. Stomata* are the controllable orifices found primarily within the epidermis of the above-ground organs of higher plants. When open they permit ready exchange of gases (e.g. CO2, O2) between the interior of the plant and the environment thereby facilitating photosynthesis, and aerobic respiration. However, when open, H2O – in the gaseous form of water vapour – can also leave the plant in the process known as transpiration. Where water in the soil...

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Hemicellulose evolution in monilophytes (Research in Context)

Hemicellulose evolution in monilophytes (Research in Context)

The Equisetopsida emerged in the Upper Devonian (>370 mya), and Equisetum (horsetails) may be the oldest surviving vascular plant genus. Horsetails and the Poales are the only plants possessing the hemicellulose (1->3, 1->4)-b-d-glucan (MLG). Xue and Fry show that variation has occurred in MLG structure during horsetail diversification, and that E. bogotense (the earliest-diverging species) has MLG composed almost solely of an ancestral tetrasaccharide repeat-unit, G4G4G3G, whereas other species in both subgenera (Equisetum and Hippochaete) have additional di- and trisaccharide repeats. Quantitatively, xyloglucan is down-played in monilophyte species rich in MLG or mannans. They conclude that plants have ‘experimented’ extensively with hemicellulose...

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