Like most animals, plants also sleep at night. At least, many do, but not, unfortunately, Arabidopsis, and our scientific over-reliance on this one species has hampered understanding of nyctinasty, sleeping movements of leaves. A new commentrary in PNAS discusses the genetic basis for sleepy plants, and is well worth a read:
Genetic basis of the “sleeping leaves” revealed. PNAS USA 6 July 2012, doi: 10.1073/pnas.1209532109
Conserved genetic determinant of motor organ identity in Medicago truncatula and related legumes. PNAS USA, 11 June 2012, doi: 10.1073/pnas.1204566109
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 structures and proportions during evolution.