Original Article

Planta

, Volume 225, Issue 6, pp 1583-1595

Indolacetic and humic acids induce lateral root development through a concerted plasmalemma and tonoplast H+ pumps activation

  • Daniel Basílio ZandonadiAffiliated withLaboratório de Biologia Celular e Tecidual (LBCT), Centro de Biociências e Biotecnologia (CBB), Universidade Estadual do Norte Fluminense (UENF)
  • , Luciano Pasqualoto CanellasAffiliated withLaboratório de Solos, Centro de Ciências e Tecnologias Agropecuárias, Universidade Estadual do Norte Fluminense
  • , Arnoldo Rocha FaçanhaAffiliated withLaboratório de Biologia Celular e Tecidual (LBCT), Centro de Biociências e Biotecnologia (CBB), Universidade Estadual do Norte Fluminense (UENF) Email author 

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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.

Keywords

Cell expansion H+-PPase Humic substances Lateral root initiation Plant growth regulators V-ATPase