Azospirillum brasilense modifies root architecture of Arabidopsis thalina

ANA COHEN; DANIELA MORENO; HERNÁN BOCCALANDRO; RUBÉN BOTTINI; PATRICIA PICCOLI

Tucumán

Congreso; VII Congreso Argentino de Microbiología General. SAMIGE DEL BICENTENARIO; 2011

Sociedad Argentina de Microbiología General

Azospirillum sp is a plant growth promoting rhizobacteria (PGPR) that improves growth and yield of many important crops. The main effect of root colonization by Azospirillum sp is the increase of the radical system, which enhances mineral and water absorption. The mechanism proposed to explain the root growth promotion is the production phytohormones of the bacteria. These hormones include indole-3-acetic acid, gibberellins and abscisic acid (ABA) in which may alter metabolism and morphology of plants that leads to better absorption of minerals and water uptake. Drought is among the main adverse environmental conditions that reduce crop yield worldwide. In plants experiencing drought, ABA is produced by roots and acts as the signal that prepares the plant to resist the water restriction stimulating stomatal closure and thus helping water conservation by plants during the drought period. The purpose of this work was to evaluate the morphological and physiological changes produced in Arabidopsis thaliana plants inoculated with A. brasilense, using two different experimental models. 1) Petri dishes with MS agar, and 2) plastic pots with peat:perlite (3:1). In experiment 1, 7 days-old A. thaliana plants inoculated with A. brasilense in PBS or PBS (control) were cultivated under a photoperiod of 12 h. After 30 days, leaf area (LA), root length (RL), root and shoot fresh and dry weight (RFW, SFW, RDW, SDW) of inoculated and control plants were measured. Inoculated plants retarded water loss after cutting aerial part, anticipating water deficit detection as compared to control plants. In experiment 2, 15 days-old A. thaliana plants inoculated or not with A. brasilense C with 12 h light.°were grown at 24  The rosette growth and rod length were measured weekly and the seed production at the end of the experiment. In addition, ABA was measured by GC-MS in both experiments. A. brasilense significantly increased the aerial part and root surface of the plants assessed as LA, RL, RFW, SFW, RDW and SDW. Root-growth promotion by A. brasilense posses developmental (increasing lateral-root number) and growth bases (enhancing lateral-root length). Also, the plants inoculated anticipated the phenological stages respect non inoculated ones, with a significant increase in rosette growth, rod length and number of seeds per plant. The inoculation with A. brasilense in Arabidopsis caused an increase in the plants ABA content. Taken together our results show that Arabidopsis inoculation with A. brasilense enhances plant biomass and yield. Increments in LA could enhance water transpiration per plant. Nevertheless the parallel enhancement in root surface and ABA levels, that could explain the higher sensitivity of inoculated plants to induce stomata closure when experienced water deficit, suggest that A. brasilense inoculation could enhance drought tolerance.