Relaciones existentes entre la acción de las sustancias húmicas sobre el desarrollo vegetal y la síntesis endógena de los principales fitorreguladores

Resumo

RELATIONSHIPS BETWEEN THE ACTION OF HUMIC SUBSTANCES ON PLANT GROWTH AND ENDOGENOUS SYNTHESIS OF MAIN PLANT GROWTH REGULATORS Mora, María Verónica Department of Chemistry and Soil Chemistry, Faculty of Science, University of Navarra, 2010 Numerous studies have reported the ability of humic substances (HS) to increase shoot growth and affect root development and architecure. However, the mechanism responsible for these effects is poorly understood. It is possible that the shoot promoting effect of HS involves an effect on root H+-ATPase activity and nitrate root-shoot distribution that, causes changes in the root-shoot distribution of certain cytokinins, polyamines and abscisic acid. On the other hand, the effect of HS on root development must be related to the presence of plant growth regulators in their structure but the humic acid (HA) employed in this work, are not presence of phytoregulators in their structure. Also, HA application was associated with changes in nitric oxide (NO), indolacetic acid (IAA) concentration and ethylene production, as well as, an increase in root development and changes in their root architecture. Results obtained using inhibitors of auxin transport or action, inhibitors of ethylene biosynthesis or action, and a scavenger of NO indicate that the increase in the root concentration of these three phytoregulators caused by HA, does not play an essential role in the expression of the HA-induced macro-morphological root changes. Other factors, working in conjunction or independently of those HA-affected plant growth regulators, must be involved in HA whole action on root growth and morphology. Likewise, the increases in IAA and ethylene induced by HA are not mediated by the previous increase in NO, and the increase in ethylene root production is controlled by the concomitant increase in IAA root concentration. Finally, the bioactivity of HS on promoting plant growth must be related to the structure and not to the presence of phytoregulators, and HS may act as a regulator of hormonal balance with respect to plant growth.