Distribution of Endogenous Indole-3-Acetic Acid and Compression Wood Formation in Reoriented Branches of Douglas-Fir

Abstract

Five-year-old segments of intact 7-year-old branches of Douglas-fir (Pseudotsuga meziesii [Mirb.] Franco) were reoriented to determine the relation between indole-3-acetic acid (IAA) and the formation of compression wood. Eight branches per treatment were either left at their original angle (mean of 690, the control), or bent proximal to the segment to reorient it up or down 300.Differentiating xylem tissue from the upper and lower sides of each segment was collected and extracted separately for IAA analysis by in-line fluorescence detection of free IAA and IAA methyl ester after sequential C1i reversed-phase high performance liquid chromatography. The IAA methyl ester was confirmed by gas chromatography-mass spectroscopy. Compression wood formed on the upper side of branches reoriented up and on the lower side of controls or branches reoriented down. IAA was present in all samples. The difference in IAA concentration between upper and lower sides was either not correlated, or negatively correlated in segments reoriented down, with both the occurrence of compression wood and the rate of new tracheid production. Mean concentrations for whole branch segments were not affected by the treatments, regardless of whether IAA concentrations were expressed on a surface area, weight, or cell basis.

Patterns of Auxin Distribution during Gravitational Induction of Reaction Wood in Poplar and Pine

“…This lack of growth response provided an opportunity to specifically evaluate the role of auxin in the differentiation of compression wood tracheids. Other studies have found lower IAA levels associated to compression wood formation (Wilson et al, 1989;Sundberg et al, 1994), although the study by Wilson only measured IAA in tissues of differentiating tracheids (xylem scrapings), thus excluded most of the auxin, which is present in the cambial meristem and its recent derivatives (Uggla et al, 1996). Funada and coworkers (1990), on the other hand, found higher IAA contents in cambial region tissues forming compression wood compared to tissues forming normal wood after 1 week, but not after 4 weeks, of gravistimulation in Cryptomeria trees, but limited their studies to a single tree.…”

“…Moreover, to advance hypotheses developed from application experiments we need to know the balance of endogenous hormones under natural conditions in the processes they are supposed to control. In reaction wood formation, reliable measurements of endogenous IAA are scarce, contradictory, and limited because small numbers of samples were evaluated (Wilson et al, 1989;Funada et al, 1990;Moyle et al, 2002). Interpretation of endogenous IAA levels in cambial region tissues is further complicated by its large variation in concentrations across the developing wood tissues (Uggla et al, 1996(Uggla et al, , 1998.…”

Effects of the Indole-3-Acetic Acid (IAA) Transport Inhibitors N-1-Naphthylphthalamic Acid and Morphactin on Endogenous IAA Dynamics in Relation to Compression Wood Formation in 1-Year-Old Pinus sylvestris (L.) Shoots

“…3 and 4) that compression wood formation above the application site in NPA-or CF-treated shoots was associated with IAA levels in the cambial region that were lower than those in control shoots, where normal tracheids were formed. Thus, it is necessary to re-evaluate the oft-stated supposition that compression wood formation in conifers that is induced by strangling or by IAA transport inhibitors is the result of endogenous IAA accumulation above the treatment point (Blum, 1970;Smolinski et al, 1972Smolinski et al, , 1973Phelps et al, 1974Phelps et al, , 1977Yamaguchi et al, 1980Yamaguchi et al, , 1983 (Funada et al, 1990 I, it was not in Pseua'otsuga menziesii (Wilson et al, 1989) or P. sylvestris (B. Sundberg and C.H.A. Little, unpublished restdts).…”

“…This would explain the anomaly that high levels of exogenous IAA induce compression wood formation (Timell, 1986), whereas decreased levels of endogenous IAA have bem found in shoots forming compression wood (Figs. 3 and 4; Wilson et al, 1989;B. Sundberg and C.H.A.…”

An Overview of the Biology of Reaction Wood Formation

“…Measurement with the Triticum coleoptile test also showed a positive correlation of IAA to compression wood formation in pine branches (Necesaný 1958). In contrast, based on an analysis by high-performance liquid chromatography (HPLC) fluorescence detection, Wilson et al (1989) rejected a positive correlation between compression wood formation and a higher cambial IAA concentration. Quantification using the most accurate method gas chromatography-mass spectrometry (GC-MS) also yielded contrasting results.…”