Genetic Differences in Leaf Abscission and the Activity of Naturally Occurring Growth Regulators in Peach

Abstract

Leaf abscission in peach is correlated with the release of tryptophan into the cytoplasm following a sudden drop in air temperature below the physiological minimum. The tryptophan accumulates in the variety Elberta and results in increased activity levels of 5-hydroxytryptamine, 5-hydroxyindoleacetic acid, and an unidentified neutral growth promoter. The rapid defoliation of the canker resistant variety Elberta was, however, associated more closely with the endogenous levels of tryptophan and 5-hydroxytryptamine. Susceptible Dixired variety, which defoliates slowly, contains lower activity levels of these compounds at the time of leaf abscission, and shows enhanced activity of kynurenic and xanthurenic acids throughout this same period. This suggests that tryptophan does not accumulate in Dixired to cause rapid abscission because of a greater genetic capacity for degradation by way of the kynurenine, hydroxyanthranilic, nicotinic acid pathway common in the metabolism of animals.

Identification and Quantitative Analysis of Indole-3-Acetyl-l-Aspartate from Seeds of Glycine max L.

“…Thus, although the comparative activities of D-and L-IAAsp have yet to be studied, the enantiomeric form is probably an important biologic determinant. Although no studies of the enantiomeric form of the amino acid component of IAA conjugates formed by plants have been made previously, the bioassay data obtained using purified extracts did suggest the L configuration (28,30).…”

“…In addition, amino acid conjugates are produced by cells grown in tissue culture on an auxin-containing medium (12,(14)(15)(16). Several reports of the occurrence of IAAsp as an endogenous, naturally-occurring compound have appeared (22,(25)(26)(27)(28)30) (Aldrich) coupling in acetonitrile followed by 2 N NaOH hydrolysis, as previously described (5). DEAE-Sephacel and Sephadex LH-20 were products of Pharmacia and Dowex 5OX 2-400 was from Sigma.…”

“…In addition, amino acid conjugates are produced by cells grown in tissue culture on an auxin-containing medium (12,(14)(15)(16). Several reports of the occurrence of IAAsp as an endogenous, naturally-occurring compound have appeared (22,(25)(26)(27)(28)30), but the identifications were tentative being based on chromatographic properties of crude preparations. The methyl ester of 4-chloro-IAAsp was identified as a naturally occurring auxin conjugate in immature pea seeds (19), and the occurrence of amide-linked IAA conjugates has been suggested by selective hydrolysis (3).…”

Mechanism of Naphthaleneacetic Acid Conjugation

“…He also proposed that only auxin found in the cytoplasm was biologically active, and that it is in equilibrium with both the auxin present in solution and that bound within the cell. However, on several occasions IAAsp has been found in plants in the absence of exogenous application of IAA (19,26,27,30,35,37). conjugates of IAA and NAA, respectively (40).…”

Occurrence of Endogenous Indol‐3yI‐Aspartic Acid in Light and Dark‐Grown Bean Seedlings (Phaseolus vulgaris)

“…Presence of IAAsp without application of IAA has earlier been demonstrated in dry seeds, green tissue and fruits of some ten other plant species (e.g. by Klambt I960, Row et al 1961, v. Raussen-dorflF-Bargen 1962, Weawer and Jackson 1963, Olney 1968.…”