Plant Physiology 150: 1855-1865 (2009)
In vivo cell wall loosening by hydroxyl radicals during cress (Lepidium sativum L.) seed germination and elongation growth [W][OA]
The Edingburgh Cell Wall Group, Institute of Molecular Plant Sciences, The University of Edinburgh, The King's Buildings, Mayfield Road, Edinburgh EH9 3JH, United Kingdom (R.A.M.V., S.C.F.)
Commissariat à l'Energie Atomique (CEA), iBiTecS, CNRS URA 2096, Service de Bioénergétique, Biologie Structurale et Mécanisme, 91191 Gif-sur-Yvette Cedex, France (A.K.-L.)
Received April 9, 2009; accepted May 29, 2009; published June 3, 2009
www.plantphysiol.org/cgi/doi/10.1104/pp.109.139204
Figure 1. Developmental factors and ROS affect the weakening of the cress endosperm cap. (A) A mature cress seed consists of an embryo surrounded by two covering tissues: the testa and the endosperm. The cap covers the radicle tip. (B) Typical germination: Cress seeds germinate in two steps. After ca. 8 h, the brown testa ruptures, revealing the radicle still covered by the cap, which weakens until at ca. 18 h it is penetrated by the elongating radicle. CON (control) medium without additions. (C) In caps incubated after dissection at 18 h CON (‘isolated caps’), tissue weakening led to the formation of a hole at the place where the radicle would have emerged after 1-2 d. (D) Atypical germination after addition of H2O2 to the medium. (E) Effects of H2O2, ABA, and ABA followed by •OH (Fenton reaction initiated by 100 µM H2O2 and ascorbic acid in caps loaded with Fe2+) on cap weakening quantified by puncture force measurements. In a control treatment with Fe2+ and ascorbic acid, but without H2O2, the puncture force did not decline significantly (34.9 +/- 1.5 mN). Mean values +/- SE of at least three replicates of 25 caps are presented. (A and B) modified from (Müller et al., 2006).
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