Indole-3-acetic Acid in Douglas Fir

Abstract

We sought evidence for the occurrence and seasonal variaton of indole-3acetic acid (1AA) in shoots of Dous fir (Pseudotsuga menziesii [Mirb.J Franco).Collections obtained in December and June were exacted with methanol and diethyl ether. Extracts were purified by solvent partitioning and with Sephadex LH-20. Qualitative and qntitative information was acquired by gas-liquid chromatography of methyl, trimethylsilyl, or both derivadives of plant extract components. Analysis was performed with polar (XE-60) and moderately polar (HI-Eff-8-BP) stationary phases. Results from three collections demonstrated that IAA does occur in Douls fir and that amounts vary seasonally. Mass analysis of the proposed endogenous IAA peak from two representative extracts supported gas-liquid chromatography data and established the presence of IAA in Douglas fir.Analyses of IAA in tissues of plants have been made for more than half a century. Yet, during the 40 years before 1970, conclusive evidence of the occurrence of IAA in coniferous forest trees was not forthcoming. During that time, the most common method for isolation and identification was paper chromatographic separation of a partitioned extract followed by analysis with semispecific chromogenic reagents and a pertinent bioassay sensitive to IAA (8,28).New analytical techniques for the study of plant hormones were initiated in the early 1960s. Spectrophotometric methods, such as colorimetry (12), UV spectrophotometry (26), fluorimetry (26), and phosphorometry (7), have been utilized by various workers for auxin determination. These methods are inadequate, however, because spectra of related indoles and different component classes can be misinterpreted easily, especially in plant extracts (14). IR spectrophotometry has the potential of providing definitive analysis of IAA (22), if complete separation of interfering components has been achieved (19).In the last 10 years, GLC has been added for final separation and analysis of plant extracts because of its ability to fractionate volatilized components in a specific and reproducible fashion (1,3, 21,27). If several stationary phases of differing physical character are included, the data produced are even more reliable. Subsequent analysis by mass spectrometry or mass fragmentography gives precise information on the nature of the compound under investigation (2, 10). Extraction. The shoots were trimmed to 7 cm, stripped of their needles, and placed in 95% methanol or anhydrous diethyl ether. Five hundred leafless shoots, equivalent to 300 g fresh weight, were used in each of the two extractions. The extracts were kept below -20 C during the 3-week extraction period, and the respective solvents were replaced with fresh solvent semiweekly. Accumulated extracts were combined, dried by flash evaporation at 30 and 20 C, respectively, and stored at -20 C in 10 to 30 ml of methanol. These storage conditions reduce enzymic activity capable of oxidizing IAA and inhibit epiphytic bacteria from producing IAA (18). An additional collec...

Changes in the content of indole-3-acetic acid in the needles of dwarf pine in the course of year

“…The low level during the phase of dormancy is suggested to be the result of a low activity of the apex. The intensive growth of annual shoots is correlated with high auxin levels in the plant (Allen 1960) which is also confirmed by the results obtained in the present paper.…”

“…They secure realization of the genetic information and simultaneously the plant response to the external enviroment (for review see Saunders 1978). Auxin is transported basipetally from apical part and from the assimilatory apparatus and inhibits the growth of lateral and axillary buds (for review see Goldsmith 1977). Later the correlative inhibition of these buds pass into dormancy.…”

“…On the contrary, IAA was not detected during dormancy in the winter season (Alden 1971). Likewise, a low IAA level in needles was estimated during dormancy ofPseudotsuga menziesii (DeYoe and Zaerr 1976) or Picea abies (Ivonis et al I983, Psota et al 1992).…”

The Use of Auxin Quantification for Understanding Clonal Tree Propagation

“…The use of GC-MS for auxin analysis in forest species commenced with research on Pseudotsuga menziesii (Mirb.) Franco [122][123][124]. GC-MS was later applied to assess seasonal variation in IAA concentrations in Pinus sylvestris Thunb.…”