title: Indolacetic and humic acids induce lateral root development through a concerted plasmalemma and tonoplast H+ pumps activation.
abstract: Increasing evidences have indicated that humic substances can induce plant growth and productivity by functioning as an environmental source of auxinic activity. Here we comparatively evaluate the effects of indole-3-acetic acid (IAA) and humic acids (HA) isolated from two different soils (Inseptsol and Ultisol) and two different organic residues (vermicompost and sewage sludge) on root development and on activities of plasmalemma and tonoplast H(+ )pumps from maize roots. The data show that HA isolated from these different sources as well as low IAA concentrations (10(-10) and 10(-15) M) improve root growth through a markedly proliferation of lateral roots along with a differential activation not only of the plasmalemma but also of vacuolar H(+)-ATPases and H(+)-pyrophosphatase. Further, the vacuolar H(+)-ATPase had a peak of stimulation in a range from 10(-8) to 10(-10) M IAA, whereas the H(+)-pyrophosphatase was sensitive to a much broader range of IAA concentrations from 10(-3) to 10(-15) M. It is proposed a complementary view of the acid growth mechanism in which a concerted activation of the plasmalemma and tonoplast H(+ )pumps plays a key role in the root cell expansion process driven by environment-derived molecules endowed with auxinic activity, such as that of humic substances.
authors.affiliation: Laboratório de Biologia Celular e Tecidual (LBCT), Centro de Biociências e Biotecnologia (CBB), Universidade Estadual do Norte Fluminense (UENF), Campos dos Goytacazes, Rio de Janeiro, CEP 28013-600, Brazil.
authors.forename: Daniel Basílio
authors.initials: DB
authors.lastname: Zandonadi
authors.forename: Luciano Pasqualoto
authors.initials: LP
authors.lastname: Canellas
authors.forename: Arnoldo Rocha
authors.initials: AR
authors.lastname: Façanha
mesh_terms: D025222:Chloroplast Proton-Translocating ATPases / Q000378:metabolism*; D006812:Humic Substances; D007210:Indoleacetic Acids / Q000494:pharmacology*; D018517:Plant Roots / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development*; D011522:Protons; D003313:Zea mays / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism*
chemical_list: D006812:Humic Substances; D007210:Indoleacetic Acids; D011522:Protons; C030737:indoleacetic acid; D025222:Chloroplast Proton-Translocating ATPases