Rice and Phragmites: effects of organic acids on growth, root permeability, and radial oxygen loss to the rhizosphere

Abstract

Young Phragmites plants were grown in two cocktails of monocarboxylic acids (C(1)-C(5)) at pH 6, where the concentration of each acid was innocuous and the total undissociated (potentially toxic) concentrations were 0.35 mmol/L and 0.42 mmol/L. Rice plants were subjected to 1.5 mmol/L acetic acid at pH 4.5 (undissociated concentration = 1.05 mmol/L). In Phragmites, each cocktail curtailed root growth especially and induced premature shoot senescence. In both species, after 3-5 d of treatment, radial oxygen loss (ROL) from apical regions of adventitious roots, and from Phragmites laterals, was reduced to very low values and associated with cell wall lignification and suberization in the surface cell layers. At later stages of treatment, rice responded to acetic acid in similar ways to Phragmites, with the development of intercellular and callus type occlusions in the gas space system, vascular blockages, and the failure of laterals to emerge. The results are relevant to the supply of oxygen from Phragmites roots to sediments for the phytopurification of waste waters, to the efflux of methane and carbon dioxide from wetlands, and to rice cultivation.

Resposta de plântulas de aveia ao estresse por ácidos acético e butírico

“…The cultivars Brisasul and FAEM 06 showed a linear decrease in RL, especially the cultivar Brisasul, which presented a RL of 9.02 cm in the control and 5.12 cm at the maximum level (12 mM). Root growth of rice seedlings was inhibited by acetic acid (Armstrong and Armstrong, 2001;Sousa and Bortolon, 2002). Another study with rice also showed that with higher levels of acetic acid reduces the RL, but low levels (<6.8 mM) allowed a slight increase (Neves et al, 2010).…”

Methodology adjustments for organic acid tolerance studies in oat under hydroponic systems

“…Thus, an efficient way of evaluating genotypes for tolerance to the presence of organic acids in culture media can be accomplished by using hydroponics under the controlled conditions. Since rice is the primary crop for lowland soils, efficient methodologies for evaluating the toxicity are described in the literature (Rao and Mikkelsen, 1977a,b;Camargo et al, 1993;Armstrong and Armstrong, 2001;Sousa and Bortolon, 2002). Since oat is still a minor crop in lowland areas, there have not been many studies focusing the evaluation of its response to excess organic acids, being a prior necessity the adjustment of a protocol for use in hydroponic systems aiming to identify the tolerant genotypes.…”

Ácidos orgânicos na qualidade fisiológica de sementes de arroz

“…prejudicial na porcentagem de germinação para o processo de comercialização, ou seja, abaixo de 80%. Nas sementes de arroz, os ácidos orgânicos causam a degradação das membranas celulares e perda do conteúdo celular para o meio (KOPP et al, 2007b), mas também cultivares tolerantes devem possuir genes que conferem maior capacidade de formação de membranas celulares que tolerem esses ácidos (ARMSTRONG & ARMSTRONG, 2001). As sementes da cultivar 'IRGA 424' são de elevada capacidade germinativa, podendo ser consideradas insensíveis à toxicidade, devido à maior capacidade de manutenção celular em condição de estresse, causados pelos ácidos acético e butírico, nas concentrações inferiores a 8mM (Figura 1A).…”