Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Number of cells a in the cambial zone, b in radial enlargement, c in secondary wall thickening and lignification and d mature xylem cells during 2009. Bars represent confidence intervals at P < 0.05. Horizontal thin line in a indicates the number of dormant cambial cells (bs = bud swelling and onset shoot elongation).
