Claudia Travaglia

Exogenous Abscisic Acid Increases Carbohydrate Accumulation and Redistribution to the Grains in Wheat Grown Under Field Conditions of Soil Water Restriction

This work investigates the effects of abscisic acid (ABA) on physiologic parameters related to yield in wheat (Triticum aestivum) grown under field conditions with water restriction ranging between 45.7% and 49.5% of field capacity during anthesis and postanthesis. ABA (300 mg L−1) was sprayed onto the plants at the beginning of shoot lengthening which significantly promoted leaf area and higher concentrations of chlorophylls and carotenoids in flag leaf at anthesis. ABA also increased soluble carbohydrates in shoots at anthesis, which were then re-exported to the grains at maturity. This correlated with a yield increase that was achieved by a higher number and weight of grains per spike, but protein content was not significantly affected.

Azospirillum brasilense ameliorates the response of Arabidopsis thaliana to drought mainly via enhancement of ABA levels

Production of phytohormones is one of the main mechanisms to explain the beneficial effects of plant growth-promoting rhizobacteria (PGPR) such as Azospirillum sp. The PGPRs induce plant growth and development, and reduce stress susceptibility. However, little is known regarding the stress-related phytohormone abscisic acid (ABA) produced by bacteria. We investigated the effects of Azospirillum brasilense Sp 245 strain on Arabidopsis thaliana Col-0 and aba2-1 mutant plants, evaluating the morphophysiological and biochemical responses when watered and in drought. We used an in vitro-grown system to study changes in the root volume and architecture after inoculation with Azospirillum in Arabidopsis wild-type Col-0 and on the mutant aba2-1, during early growth. To examine Arabidopsis development and reproductive success as affected by the bacteria, ABA and drought, a pot experiment using Arabidopsis Col-0 plants was also carried out. Azospirillum brasilense augmented plant biomass, altered root architecture by increasing lateral roots number, stimulated photosynthetic and photoprotective pigments and retarded water loss in correlation with incremented ABA levels. As well, inoculation improved plants seed yield, plants survival, proline levels and relative leaf water content; it also decreased stomatal conductance, malondialdehyde and relative soil water content in plants submitted to drought. Arabidopsis inoculation with A. brasilense improved plants performance, especially in drought.

An endophytic bacterium isolated from roots of the halophyte Prosopis strombulifera produces ABA, IAA, gibberellins A1 and A3 and jasmonic acid in chemically-defined culture medium

This paper informs the characterization by 16SrDNA partial sequence analysis of an endophytic diazotrophic bacterium isolated from roots of the halophyte shrub Prosopis strombulifera. The bacterium produced ABA, IAA, GA1, GA3 and jasmonic acid in chemically-defined culture medium as assessed by GC-EIMS. The results emphasize the role of phytohormones produced by endophytic bacteria in the association host-beneficial microorganisms, especially under conditions of adverse environments.

Application of abscisic acid promotes yield in field-cultured soybean by enhancing production of carbohydrates and their allocation in seed

This study investigates the effect of abscisic acid (ABA) and gibberellin (GA3) applications on physiological and productive parameters in complementary experiments performed with soybean cultured in the field for 3 crop seasons and in the greenhouse for 1 crop season. ABA 300 mg/L was sprayed at the V7 and R2 phenological stages, while GA3 300 mg/L was sprayed at R2 and repeated 7 days later. GA3-treated plants had longer shoots and ABA-treated plants had greater dry weight of aerial parts. Nodule formation was not affected, but both shoot diameter and root density were greater in ABA-treated plants. ABA increased leaf area and chlorophyll content, while GA3 diminished them. In ABA-treated plants, there was a significant reduction in leaf conductance 24 h after the hormone had been applied, but then the conductance values started to rise and equalled those of the controls 11 days later. Although there were no differences in number of pods, in GA3-treated plants the number of seeds per pod was lower, and in ABA-treated plants, young pods were bigger. ABA application increased soybean yield by enhancing carbon allocation and partitioning to the seed. Exogenous ABA also improved the seed quality since it did not affect protein levels but enhanced oil concentration, while GA3 spraying increased oil concentration but diminished seed proteins.

ABA action on the production and redistribution of field-grown maize carbohydrates in semiarid regions

The aim of this study is to analyze the response of exogenous abscisic acid (ABA) application in plants grown under field conditions in semiarid zones in order to increase maize production. For this, it is necessary to understand the factors, such as the size and capacity of transport system involved in the mobilization and distribution of assimilates. The vascular transport capacity of ABA-treated and control plants was compared in terms of number of vascular bundles, phloem area per bundle, and the proportion of phloem in the ear peduncle of female inflorescences. This study showed that the application of exogenous ABA in field-grown maize under moderate drought allows a greater amount of maize production, an increase in the level of photosynthetic pigments, the carbohydrates remobilization to grain, and the capacity of this transport by an increase in the number of vascular bundles and the phloem area in peduncle. Evidence obtained in this study suggests that ABA could help improve agricultural production in rain-fed crops in which irrigation is not possible. This will allow us to follow a new technological strategy to increase the effective filling of organs during crops in unfavorable water conditions.

Arsenic stress induces changes in lipid signalling and evokes the stomata closure in soybean

Soybean (Glycine max) is often exposed to high arsenic (As) level in soils or through irrigation with groundwater. In previous studies on As-treated soybean seedlings we showed deleterious effect on growth, structural alterations mainly in root vascular system and induction of antioxidant enzymes. However, there are not reports concerning signal transduction pathways triggered by the metalloid in order to develop adaptive mechanisms. Phosphatidic acid (PA), a key messenger in plants, can be generated via phospholipase D (PLD) or via phospholipase C (PLC) coupled to diacylglycerol kinase (DGK). Thus, changes in PA and in an enzyme involved in its metabolism (PLD) were analysed in soybean seedlings treated with 25 μM AsV or AsIII. The present study demonstrated that As triggers the PA signal by PLD and also via PLC/DGK mainly after 48 h of As treatment. DGPP, other lipid messenger produced by phosphorylation of PA by PAK increased in As treated roots. Arsenic also induced rapid and significant stomatal closure after 1.5 h of treatment, mainly with AsIII, probably as an adaptive response to the metalloid to reduce water loss by transpiration. This report constitute the first evidence that shows the effects of As on lipid signalling events in soybean seedlings which would be crucial in adaptation and survival of soybean seedlings under As stress.

Anatomical, Morphological, and Phytochemical Effects of Inoculation with Plant Growth- Promoting Rhizobacteria on Peppermint (Mentha piperita)

Plant growth-promoting rhizobacteria (PGPR) generally exert their effects through enhancement of plant nutrient status and/or phytohormone production. The effects of PGPR on aromatic plant species are poorly known. We measured plant growth parameters, chlorophyll content, trichome density, stomatal density, and levels of secondary metabolites in peppermint (Mentha piperita) seedlings inoculated with PGPR strains Bacillus subtilis GB03, Pseudomonas fluorescens WCS417r, P. putida SJ04, or a combination of WCS417r + SJ04. The treated plants, in comparison with controls, showed increases in shoot biomass, root biomass, leaf area, node number, trichome density, and stomatal density, and marked qualitative and quantitative changes in monoterpene content. Improved knowledge of the factors that control or affect biosynthesis of secondary metabolites and monoterpene accumulation will lead to strategies for improved cultivation and productivity of aromatic plants and other agricultural crops without the use of chemical fertilizers or pesticides.

ABA Increased Soybean Yield by Enhancing Production of Carbohydrates and Their Allocation in Seed

Herminda Reinoso1,3, Claudia Travaglia1 and Ruben Bottini2 1Morfologia Vegetal, Facultad de Ciencias Exactas, Fisico Quimicas y Naturales, Universidad Nacional de Rio Cuarto, Campus Universitario, 5800 Rio Cuarto 2Instituto de Biologia Agricola de Mendoza, Facultad de Ciencias Agrarias, Universidad Nacional de Cuyo-Consejo Nacional de Investigaciones Cientificas y Tecnicas, Almirante Brown 500, 5505 Chacras de Coria, Argentina