Changes in root development of Arabidopsis promoted by organic matter from oxisols

Abstract

The presence of ramified and abundant lateral roots is fundamental to plant growth on highly weathered soils. In this work, the effects of humic acid (HA), fulvic acid and hexanic-methanolic (HM) extract, after alkaline extraction from topsoil of seven different oxisols, on the development of roots of Arabidopsis thaliana was evaluated. Furthermore, we used another emergent plant model, that is, micro-tom (MT) tomatoes with size similar to that of Arabidopsis to test the effects of HA. It was observed that both humic fractions and the HM extract were able to change the root development, improving the number of lateral roots and their development in comparison to control plants. The promotion of root growth by the three organic matter fractions was higher than that observed by 10 26 mol L 21 indole acetic acid. The treatment of MT tomato mutant, less sensitive to auxin, with HA did not promote the emergence of lateral roots, being an additional indication of auxin-like activities of HA. However, some organic matter fractions exhibited, besides promotion of lateral roots number, increase in the length of principal root, which is not a typical auxin effect, indicating that these substances could contain other physiologically active substances.

Humic substances isolated from residues of sugar cane industry as root growth promoter

“…ure 2). One similar curve was showed for lateral root density of Arabidopsis treated with HA isolated from Oxisols (Dobbss et al, 2007). The authors also found that inhibition concentration varies from 250 to 400 mg L -1 .…”

Root growth of Arabidopsis thaliana (L.) Heynh. treated with humic acids isolated from typical soils of Rio de Janeiro state, Brazil

“…The hormone-like effect, especially similar to that of auxins, as discussed by Canellas et al (2002), Nardi et al (2005), Zandonadi et al (2007) and Dobbss et al (2007), is based on the increase in formation and length of lateral roots in relation to the growth of the main root in plants treated with humic acids. For the Acrisol and Latosol, particularly in subsurface layers, the fertility is limited to the point that humic acids did not provide an effect different from the control.…”

“…Five days after germination, the seedlings were thinned to four plants per plate, and Hoogland solution modified to a final concentration of 1 mmol L -1 N was applied (Dobbss et al, 2007). Four mL of solution containing 0, 20, 40 and 80 mg L -1 of humic acids were added to each plate and 4 mL of deionized water only to the control treatment.…”

“…Evaluation of humic acids bioactivity followed was according to the protocol by Dobbss et al (2007). Seeds of Arabidopsis thaliana, ecotype Columbia 4 (co4), were sterilized in 95% ethanol (v/v) for 5 min, in 20% NaClO for 7 min, and washed five times with distilled water.…”

“…These substances favor growth (Canellas et al, , 2004Rodda et al 2006;Zandonadi et al 2007;Dobbss et al 2007;Canellas et al, 2008a) and nutrient accumulation in several plants of agronomic interest (Vaughan & Malcolm, 1985;Chen & Avaide, 1990;Chen et al, 2004). These effects reflect in the increase of root growth rate, increases in plant biomass and root architectural changes (root hairs and thin lateral roots), resulting in increased surface area and/or in root length .…”