Root growth of tomato seedlings intensified by humic substances from peat bogs

• Main Authors: Alexandre Christofaro Silva, Luciano Pasqualoto Canellas, Fábio Lopes Olivares, Leonardo Barros Dobbss, Natalia Oliveira Aguiar, Daniele Ângela Rossinol Frade, Carlos Eduardo Rezende, Lázaro Eustáquio Pereira Peres
• Format: Article
• Language: English
• Published: Sociedade Brasileira de Ciência do Solo 2011-10-01
• Series: Revista Brasileira de Ciência do Solo
• Subjects: efeitos fisiológicos; bioatividade
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832011000500015&lng=en&tlng=en

Peats are an important reserve of humified carbon in terrestrial ecosystems. The interest in the use of humic substances as plant growth promoters is continuously increasing. The objective of this study was to evaluate the bioactivity of alkaline soluble humic substances (HS), humic (HA) and fulvic acids (FA) isolated from peats with different decomposition stages of organic matter (sapric, fibric and hemic) in the Serra do Espinhaço Meridional, state of Minas Gerais. Dose-response curves were established for the number of lateral roots growing from the main plant axis of tomato seedlings. The bioactivity of HA was greatest (highest response in lateral roots at lowest concentration) while FA did not intensify root growth. Both HS and HA stimulated root hair formation. At low concentrations, HS and HA induced root hair formation near the root cap, a typical hormonal imbalance effect in plants. Transgenic tomato with reporter gene DR5::GUS allowed the observation that the auxin-related signalling pathway was involved in root growth promotion by HA.