O. Dünisch, M. Schulte, K. Kruse
Cambial Growth of Swietenia macrophylla King Studied under Controlled Conditions by High Resolution Laser Measurements
Summary
The kinetics of phloem and xylem formation of two-year-old plants of Swietenia macrophylla King (true mahogany) was studied in a model system along the shoot circumference (experiment 1) and along the shoot axis (experiment 2). The radius increment of the shoot was registered by high resolution laser measurements (accuracy: ±2 ?m) in a spatial resolution of 7.8 to 41.3 ?m along the stem circumference and 1.5 mm along the stem axis. The temporal resolution of the measurements was 2 s in experiment 1 and 20 s in experiment 2. The radius increment of the shoot detected by the laser measurements was predominately due to the radial enlargement of the phloem and xylem derivatives. On the phloem side the reinitiation of radial cell enlargement after a cambial dormancy occurred first in sieve tubes with contact to ray parenchyma cells, while on the xylem side the radial cell enlargement of vessels and paratracheal parenchyma was induced almost simultaneously along the shoot circumference. In the phloem and xylem derivatives, which were formed first after the cambial reactivation, radial cell enlargement was induced almost simultaneously along the shoot axis. In more advanced phases of phloem and xylem formation, radial cell enlargement of phloem and xylem derivatives was induced shoot downwards with a rate of approximately 13 mm per min. The mean rate of radial cell enlargement of the phloem and xylem derivatives was 2.26 and 4.37 ?m per min, respectively. These findings suggest that the kinetics of cambial growth of tropical tree species differ significantly from kinetics observed in trees from temperate regions. The laser measurements might provide a useful experimental approach for studies of cambial activity in situ.
Holzforschung, Walter de Gruyter
Print ISSN: 0018-3830
Volume: 57, 02/2003
Pages: 196 - 206
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