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De Souza T.C.,Federal University of Lavras | Souza E.D.S.,Federal University of Vicosa | Dousseau S.,Federal University of Lavras | de Castro E.M.,Federal University of Lavras | Magalhaes P.C.,National Maize and Sorghum Research Center
Aquatic Botany | Year: 2013

Garcinia brasiliensis (Mart.) is a native Amazonian tree cultivated throughout Brazil. This plant can tolerate flooding or submergence for several days, during certain periods of the year. The morphophysiological changes of G. brasiliensis (Mart.) seedlings were assessed that may favor their survival in flooded environments. Seedlings with six fully expanded leaves were placed in tanks so that their roots were submerged for 90 days. Antioxidant enzymatic activity and the contents of H2O2, soluble sugar, starch, and amino acid of the roots were evaluated on six harvesting occasions. At the end of the experiment, the dry mass and root morphology of the seedlings were determined. Flooding lead to a decrease in dry mass of roots and aboveground parts, as well as root length (58%), surface area (51%) and volume (43%), especially of roots with smaller diameter. The roots of the flooded seedlings presented thicker exodermis and greater xylem number, thicker phloem and fewer xylem fibers. There was a small amount of aerenchyma in the roots and hypertrophied lenticels were detected at the base of the stem. Superoxide dismutase activity was significantly higher in flooded roots at all harvesting times, and ascorbate peroxidase and catalase activities were highest during the last two harvestings. H2O2 content increased after 40 and 55 days of flooding, followed by a drastic decrease. After 70 and 90 days of flooding there was an expressive increase in soluble sugars, and at 90 days, a reduction in starch content. No differences were observed in amino acid content. © 2013 Elsevier B.V.

Magalhaes P.C.,National Maize and Sorghum Research Center | de Souza T.C.,Federal University of Lavras | Cantao F.R.O.,University of Illinois at Urbana - Champaign
Plant, Soil and Environment | Year: 2011

In Brazil savanna type of soils presents problems with phosphorus content. Te selection and identifcation of maize genotypes to such environments is a high priority of Brazilian research. Te purpose of this paper was to evaluate, in soils with diferent P concentrations, the dry mass attributes and characteristics of root morphology in eight maize lines with diferent genetic background and origins of the Breeding Program of the National Research Center for Maize and Sorghum. Te experiment was carried out in plots prepared with two levels of phosphorus: high phosphorus (HP) and low phosphorus (LP). Te experimental design was randomized blocks with three replications. Te evaluation of the characteristics of the shoots and the root system morphology was performed 21 days after sowing. Te WinRhizo program of images analysis was used for the root morphology. Tere were no diferenc-es between the phosphorus levels for the dry mass attributes. However, when we compared P levels, root morphology of L13.1.2 strain performed the highest surface area (SA) and total root length (RL), length of thin (TRL) and very thin (VTRL) roots in low P concentration. Te root systems digital images analysis techniques allowed efcient discrimination of maize genotypes in environments with low P levels.

De Souza T.C.,Federal University of Lavras | De Castro E.M.,Federal University of Lavras | Magalhaes P.C.,National Maize and Sorghum Research Center | Alves E.T.,Federal University of Lavras | Pereira F.J.,National Maize and Sorghum Research Center
Plant Breeding | Year: 2012

To insert maize crop in the lowlands, the National Maize and Sorghum Research Center has developed, through the recurrent phenotypical selection, a maize variety called Saracura-BRS-4154, which has the capability to survive in periods of flooding. This study was carried out with the purpose of characterizing young plants of successive selection cycles of the variety 'Saracura', under flooding, concerning the morpho-physiology. The assay was carried out in greenhouse by sowing 10 alternate selection cycles and a BR 107 variety known for its susceptibility to flooding. It was found that the last selection cycles resulted in a greater development of thin roots, greater volume and root length. The selection cycles decreased the exodermis and increased aerenchyma formation in the roots over time. There was also leaf plasticity throughout the cycles, and it was noted an increase in the gas exchange parameters and also in the stomata number and size. Our results showed that there was a genetic gain in the morpho-physiological changes related to flooding throughout the selection cycles of 'Saracura' maize young plants. © 2012 Blackwell Verlag GmbH.

de Souza T.C.,Federal University of Lavras | Magalhaes P.C.,National Maize and Sorghum Research Center | de Castro E.M.,Federal University of Lavras | Carneiro N.P.,National Maize and Sorghum Research Center | And 2 more authors.
Plant Growth Regulation | Year: 2014

The objective of this study was to evaluate the effects of abscisic acid (ABA) related to the increase of water-stress tolerance in two drought contrasting maize hybrids: DKB 390 (tolerant) and BRS 1030 (sensitive). The characterization of water status (pre-dawn leaf water potential, Ψpd; midday leaf water potential, Ψmd and stem water potential, Ψst) and antioxidant enzyme activity was conducted on greenhouse grown plants. The ABA, hydrogen peroxide (H2O2), and malondialdehyde (MDA) contents were also analyzed. Water deficit was imposed for 10 days at the flowering stage and a dosage of 100 μM ABA was applied to plant canopy. Measurements were taken during 10 days after the water recovery. With 5 days of stress, the tolerant hybrid showed lower MDA content, decrease in the water status, and higher activity of the enzymes superoxide dismutase, catalase, ascorbate peroxidase, as well as guaiacol, glutathione reductase, dehydroascorbate reductase, polyphenol oxidase, and l-phenylalanine ammonia-lyase, as compared to the sensitive hybrid. With 10 days of stress, DKB 390 had a decrease in the activity of enzymes whereas BRS 1030 showed a higher activity. In addition, the latter showed greater amounts of H2O2 and MDA. ABA application led to a higher tolerance only in DKB 390, due to the increase of water status and the enzymatic activity, mainly the catalase. © 2013 Springer Science+Business Media Dordrecht.

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