effects of humic substances on pinus callus are reversed by 2,4-dichlorophenoxyacetic acid

• Published in: Journal of chemical ecology Vol. 31; no. 3; pp. 577 - 590
• Main Authors: Muscolo, A, Panuccio, M.R, Sidari, M, Nardi, S
• Format: Journal Article
• Language: English
• Published: New York, NY Springer 01.03.2005; Springer Nature B.V
• Subjects: 2,4-D; 2,4-Dichlorophenoxyacetic Acid - pharmacology; Abies alba; Acetic acid; Animal and plant ecology; Animal, plant and microbial ecology; Autoecology; Binding sites; Biological and medical sciences; callus culture; carbohydrate metabolism; Enzymatic activity; Enzymes; Fagus sylvatica; Fundamental and applied biological sciences. Psychology; General aspects; Hormones; Humic Substances; Indoleacetic Acids - physiology; Kinases; Pine trees; Pinus - drug effects; Pinus - physiology; Pinus laricio; sugars; Tissue Culture Techniques; Callus; phosphoglucose isomerase; Enzyme; Transferases; 2,4-dichlorophenoxyacetic acid; Woody plant; Pinus; Pious laricio callus; Humic substances; Organic acids; Acids; invertase; Glucokinase; Gymnospermae; pyruvate kinase; Coniferales; Spermatophyta; Humic substance; aldolase
• ISSN: 0098-0331; 1573-1561
• DOI: 10.1007/s10886-005-2046-1

The reversal of humic matter-induced inhibition of callus growth and metabolism by 2,4-dichlorophenoxyacetic acid (2,4-D) was studied in Pinus laricio. Two forest humic fractions (relative molecular mass (M(r)) > 3500), derived from soil under Fagus sylvatica (Fs) and Abies alba (Aa) plantation, were used. Pinus laricio callus was grown for a subculture period (4 weeks) on Basal Murashige and Skoog (MS) medium plus forest humic matters (Fs or Aa), at a concentration of 1 mg C/l, and then was transferred, for an additional four weeks, to a MS medium culture without humic matter, but with different hormones: indole-3-acetic acid (IAA, 2 mg/1) or 2,4-dichlorophenoxyacetic acid (2,4-D, 0.5 mg/1) and/or 6-benzylaminopurine (BAP, 0.25 mg/1). Growth of calluse, glucose, fructose, and sucrose contents, and activities of soluble and bound invertases, glucokinase, phosphoglucose isomerase, aldolase, and pyruvate kinase were monitored. The results show a negative effect of humic fractions on callus growth, due to decreased utilization of glucose and fructose, and decreased activities of glycolytic enzymes. The effects are reversible. Substitution of humic fractions with 2,4-D+BAP or 2,4-D is followed by an increase of glycolytic enzyme activities and, consequently, by the utilization of glucose and fructose that induces a restart of growth. In contrast, the inhibitory effects of humic fractions persist when they are substituted with BAP alone, indicating that only the auxin 2,4-D is capable of reversing the negative effects. A possible competitive action on the auxin-binding site between 2,4-D and the chemical structures in the forest humic fractions is suggested.