© 1998 Heron Publishing—Victoria, Canada
Ethylene evolution, radial growth and carbohydrate concentrations in Abies balsamea shoots ringed with Ethrel
Leif Eklund (1) and C. H. Anthony Little (2)
1. Department of Engineering and Natural Science, Växjö University, S-351 95 Växjö, Sweden (Leif.Eklund@itn.hv.se) / 2. Natural Resources Canada, Canadian Forest Service–Atlantic Forestry Centre, P.O. Box 4000, Fredericton, New Brunswick E3B
5P7, Canada / Received April 8, 1997
Summary
The terminal (1-year-old) shoot of quiescent, 2-year-old Abies balsamea (L.) Mill. seedlings was either left untreated or ringed with 0, 1 or 10 mg Ethrel g–1 lanolin. After 5 weeks of culture under environmental conditions favorable for growth, the shoots were harvested to measure
ethylene evolution and carbohydrate concentrations by gas chromatography, and tracheid number and bark radial width by microscopy.
In untreated shoots, the basal rate of ethylene evolution followed the order: cambial region > cortex + periderm = xylem +
pith = needles. Wound-induced ethylene production was not detected until at least 4 h after excision, but was evident in all
fractions 24 h after excision; the increase in wound-induced ethylene evolution followed the order: cambial region > cortex
+ periderm > xylem + pith > needles. Compared with untreated controls, the application of plain lanolin, which involved the
removal of needles and periderm, increased bark radial width and wound-induced ethylene production by the cambial region and
the cortex + periderm, but decreased cambial region concentrations of fructose, glucose and starch at the application point.
At the application point, Ethrel concomitantly increased ethylene evolution from the cambial region and the cortex + periderm,
tracheid number, bark radial width, and the cambial region concentrations of fructose, glucose, sucrose and starch. No effects
of Ethrel treatment were detected above or below the application point, with the exception that the 10 mg g–1 Ethrel treatment stimulated ethylene evolution and decreased starch concentration of the cambial region. The results indicate
that: (1) the cambial region is the major source of endogenous ethylene in the 1-year-old shoot; (2) the magnitude of the
difference in ethylene evolution between particular shoot fractions is different before and after the start of wound-induced
ethylene production; (3) the Ethrel-induced increase in tracheid number and bark radial width at the application point is
positively related to ethylene evolution from the cambial region and the cortex + periderm, respectively; and (4) ethylene
derived from Ethrel applied laterally to a woody stem can mobilize carbohydrates to the application point.
Keywords:
balsam fir, bark, cambium, 2-chloroethylphosphonic acid, cortex, fructose, glucose, starch, sucrose, tracheid, xylem.
