Fig. 4. Stem cross sections of supported (a, c, and e) and
unsupported plants (b, d, and f) at different distances from the shoot
apex: one meter (a and b), two meters (c and d), and three meters (e and
f). Lianescent xylem is produced only in supported plants (white
arrows), from 1.5 meters from the apex along the proximal portion of the
stem (c and e). In contrast, only self-supporting xylem is produced by
unsupported plants (d and f). Note the smaller xylem production in
supported plants, measured by the distance between the pith (P, not
shown in d and f) and the cambium (C). Scale: 30 µm. Unstained sections.
All plants produced
self-supporting xylem near the stem apex (Fig. 5a and b), while the
production of lianescent xylem was observed only in plants grown with
physical supports. Lianescent xylem formation started from 1.5 – 2 m
from the apex and extended through the proximal portion of the stem in
supported plants (Fig. 5c and 5e). In contrast, unsupported plants only
produced self-supporting xylem along the entire stem (Fig. 5d and 5f).
The production of lianescent
xylem was associated with a smaller xylem production, measured as the
linear distance between the cambium and the beginning of the secondary
xylem (Fig. 5). In contrast, unsupported plants, which only formed the
self-supporting xylem, produced more secondary xylem at the same
distance from the apex compared to supported plants
These findings indicate that lianescent xylem formation occurs in
response to stem attachment to physical supports, leading to reduced
cambial activity, increased vessel size, and enhanced xylem
conductivity.