Non-uniform distribution and seasonal variation of endogenous indol-3yl-acetic acid in the cambial region ofPinus contortaDougl.
✍ Scribed by R. A. Savidge; J. K. Heald; P. F. Wareing
- Publisher
- Springer-Verlag
- Year
- 1982
- Tongue
- English
- Weight
- 727 KB
- Volume
- 155
- Category
- Article
- ISSN
- 0032-0935
No coin nor oath required. For personal study only.
✦ Synopsis
Endogenous, free indol-3yl-acetic acid (IAA) levels were measured in the m a i n stem in the 10-year-old cambial zone, in the adjoining differentiating xylem, and in the adjoining m a t u r e xylem of 15 20-year-old P i n u s c o n t o r t a Dougl. by single-ioncurrent monitoring, c o m b i n e d gas c h r o m a t o g r a p h y -mass spectrometry, on several dates from early spring to early winter. M i c r o s c o p y was used to determine the state of cambial activity on each harvest date. The I A A levels were found to be nearly constant at 1 gg g -1 D W in the cambial zone from M a r c h to July, then to increase to near 2 ~tg g -1 D W during the r e m a i n d e r of the growth season. N o clear correlation was evident between n u m b e r of fusiform cells per radial file and I A A content in the cambial zone. By contrast, the I A A content in differentiating xylem was higher than that in the adjoining meristematic zone on all harvest dates and also exhibited m a r k e d seasonal variation, peaking near 16 g g g -1 D W in mid summer, and declining to 1 gg g -1 D W in autumn. In m a t u r e xylem, I A A levels were very low and showed negligible variation. The fresh weight to dry weight ratio of differentiating xylem was greater than that of the cambial zone, and greater in the cambial zone than in m a t u r e xylem. Key W o r d s : Indol-3yl-acetic acid -P h y t o h o r m o n e s -P i n u s Xylem differentiation -Vascular c a m b i u m .