Table II.

Stem anatomy in the wild type and in the transgenic lines C and G

Anatomical CharacteristicsUnitWild TypeTransgenic CTransgenic G
Radial width of stem tissues
 Cortexμm336 ± 29316 ± 21335 ± 16
 Phloemμm351 ± 41369 ± 16433 ± 27
 Xylemmm4.14 ± 0.314.16 ± 0.173.90 ± 0.14
 Phloem/xylem ratio0.085 ± 0.0100.089 ± 0.0040.111 ± 0.009
Cell morphology
 Cambial zone cells, no.12.2 ± 1.112.3 ± 0.419.6 ± 0.40
 Sieve tubes, radial diameterμm18.8 ± 1.116.9 ± 0.6718.1 ± 0.45
 Companion cells, lengthμm44.2 ± 2.141.5 ± 0.6543.5 ± 1.43
 Xylem fibers, lengthμm519 ± 10516 ± 8.8521 ± 17
 Xylem fibers, lumen areaμm2 116 ± 2.0112 ± 6.5120 ± 7.3
 Xylem vessel elements, lengthμm326 ± 7.3318 ± 6.3320 ± 7.4
 Xylem vessel elements, lumen areaμm2 1,274 ± 621,216 ± 321,219 ± 41

All measurements, except for fiber and vessel element length, were done on microscopic sections taken from the base of the stem in one section per tree. Cortex, phloem, sieve tubes, and companion cells were measured in radial sections, while the other measurements were done in transverse sections. The lengths of the fibers and the vessel elements were measured in macerate samples from the outermost xylem of the basal stem sample. Radial widths of different stem tissues and the number of cambial zone cells were measured in 10 cell files. Sieve tubes and companion cells and the lumen area of xylem fibers and vessels were measured in images from the mature phloem and mature xylem with a computer-assisted image analysis system. All parameters were measured in five trees per line, except the lengths of the xylem fibers and vessel elements, which were measured in four trees per line. Values are means ± se.