© 2007 Heron Publishing—Victoria, Canada
Seasonal change in the drought response of wood cell development in poplar
Matthias Arend (1, 2) and Jörg Fromm (1)
1. Fachgebiet Angewandte Holzbiologie, Technische Universität München, Germany / 2. Corresponding author (arend@wzw.tum.de) / Received April 13, 2006; accepted December 5, 2006; published online April 2, 2007
Summary
Field-grown poplar trees (Populus nigra L. × P. maximowiczii Henry, clone Kamabuchi) were exposed to severe drought twice during the growing season to evaluate the impact on wood cell development. The drought
treatment caused a reduction in leaf water potential, leaf wilting and a decreased concentration of osmotically active solutes
in the cambial zone. Drought-induced changes in the anatomy of developing xylem cells were examined in stem sections and macerated
wood samples. In early summer, drought significantly reduced the length and cross-sectional area of newly formed fibers, whereas
no such effects were observed in late summer. In well-watered trees, fiber cross-sectional area declined between early and
late summer. Similarly, drought reduced the cross-sectional area of vessel elements in early summer but not in late summer,
whereas in both control and drought-treated trees, the cross-sectional area of vessel elements decreased between early and
late summer. The vessel area to xylem area ratio was unaffected by drought because the drought-induced decrease in vessel
size was matched by an increase in the number of newly formed vessel cells. In contrast to its effect in early summer, late-summer
drought had no significant effect on fiber and vessel cell development, indicating that sensitivity of wood cell development
to drought varies seasonally.
Keywords:
fibers, vessels, water stress, wood growth.
