Present address: Department of Biology and Nature Conservation, Plant Developmental Physiology, Agricultural University of Norway, PO Box 5014, N-1432 Ås, Norway.
The shoot apical meristem restores its symplasmic organization during chilling-induced release from dormancy
Article first published online: 23 DEC 2001
The Plant Journal
Volume 26, Issue 3, pages 249–264, May 2001
How to Cite
Rinne, P. L. H., Kaikuranta, P. M. and Van Der Schoot, C. (2001), The shoot apical meristem restores its symplasmic organization during chilling-induced release from dormancy. The Plant Journal, 26: 249–264. doi: 10.1046/j.1365-313X.2001.01022.x
- Issue published online: 23 DEC 2001
- Article first published online: 23 DEC 2001
- Received 27 November 2000; revised 13 February 2001; accepted 16 February 2001.
- shoot apical meristem;
- cell–cell communication
The shoot apex of overwintering perennials ceases its morphogenetic activity at the end of the growing season and transforms into a bud which is dormant and freezing-tolerant. In birch (Betula pubescens) these events are triggered by short photoperiod, and involve the production of 1,3-β-d-glucan containing sphincters on the plasmodesmata. As a result, all symplasmic pathways shut down. Here we show that breakage of bud dormancy by chilling involves restoration of the symplasmic organization of the meristem. This restoration is likely to be mediated by 1,3-β-d-glucanase, which was present in small spherosome-like vacuoles that arose de novo during dormancy induction. During chilling these vacuoles were displaced from the bulk cytoplasm to the cortical cytoplasm where they became aligned with the plasma membrane, often associated with plasmodesmata. At this stage the enzyme also appeared outside the vacuoles. During chilling, 1,3-β-d-glucan disappeared from the plasmodesmal channels and wall sleeves, and the plasmodesmata regained the capacity for cell–cell transport, as demonstrated by microinjection of Lucifer Yellow CH and Fluorescein-tagged gibberellic acid. Collectively, the present experiments demonstrate that restoration of the symplasmic organization of the meristem is indispensable for the release of buds from dormancy and the assumption of a proliferation-competent state, and implicate 1,3-β-d-glucanase action at the plasmodesmata. Based on these findings we propose a model for ‘dormancy cycling’ which depicts the meristem as passing through three sequential states of cellular communication with characteristic sensitivities to distinct environmental cues.