Gas Exchange, Root Morphology and Nutrients in Maize Plants Inoculated with Azospirillum brasilense Cultivated Under Two Water Conditions

HIGHLIGHTS Azospirillum brasilense stimulates root growth in maize under water deficit. Maize inoculated with A. brasilense shows greater photosynthesis under drought conditions. Under water deficit, maize plants inoculated with A. brasilense showed greater water use efficiency (WUE).

Abstract The objective of this study was to evaluate the gas exchange, root morphology and nutrient concentration in maize plants inoculated with A. brasilense under two water conditions. The experiments were carried out in a greenhouse, one under irrigation and the other under water deficit. The treatments consisted of four A. brasilense inoculants (control (without inoculation), Az1 (CMS 7 + 26), Az2 (CMS 11 + 26) and Az3 (CMS 26 +42). At the V6 plant stage, water stress was imposed on maize plants for 15 days. The phytotechnical characteristics, gas exchange, root morphology, root dry matter and macronutrient analysis were evaluated after 15 days of water deficit imposition. The water deficit caused a reduction in the development of maize plants. The presence of A. brasilense Az1 under the same condition yielded higher photosynthesis, carboxylation efficiency, water use efficiency, and greater soil exploration with increased length, surface area and root volume of plants. Inoculation by A. brasilense increased root system volume by an average of 40 and 47% under irrigation and water deficit, respectively, when compared to non-inoculated plants. The inoculant Az1 attenuated the deleterious effects caused by drought and yielded the best growth of the root system, resulting in the tolerance of maize plants to water deficit.

Differences in intracellular localization of corn stunt spiroplasmas in magnesium treated maize

Maize plants infected with Spiroplasma kunkelii show symptoms similar to that of plants in a magnesium-deficient soil, and it has been shown that the spiroplasma alters the plants' magnesium absorption. In the current study we compared changes associated to either spiroplasma infection, two soil magnesium levels and their combinations. Plant symptoms were recorded and correlated with transmission electron microscopy observations. Plants grown on a high magnesium treatment showed no macroscopical alterations nor organelle ultrastructural alterations, while plants on a low magnesium treatment showed macroscopical vein yellowing and, ultrastructurally, they had most chloroplasts and mitochondrial membranes altered. Infected plants on a low magnesium treatment had an ageing aspect, ultrastructurally showed chloroplast s and mitochondrial alterations similar to those non-infected and grown on a low magnesium treatment, and spiroplasma cells were found in phloem cells, but outside their cytoplasm. Infected plants on a high magnesium treatment showed similar symptoms and ultrastructural alterations as either non-infected plants on the low magnesium treatment or in infected plants on the low magnesium treatment, but differ from them in that the spiroplasma cells were located inside the cytoplasm. Results suggest that magnesium is involved in the plant-pathogen interaction.

Padrões eletroforéticos das proteínas de reserva em grãos de sorgo com presença e ausência de tanino / Electrophoretic patterns of grain storage proteins of sorghum with presence and absence of tannin

Muitos métodos para determinar a presença de taninos são descritos na literatura, mas nenhum deles é universalmente aceito como ideal ou utilizado de forma unânime. Alguns métodos colorimétricos não diferenciam taninos de outros compostos fenólicos, outros utilizam substâncias que não são adequadas como padrão. Métodos que utilizam a capacidade dos taninos de precipitar as proteínas podem causar resultados divergentes devido às diferenças na conformação dessas moléculas. Assim, objetivou-se, neste estudo, identificar a presença de taninos em 10 híbridos de sorgo através da análise de padrões proteicos obtidos por eletroforese. O método colorimétrico Azul da Prússia foi utilizado para quantificar os taninos nas amostras. A precipitação das proteínas pelos taninos permitiu identificar os genótipos de sorgo com tanino através dos padrões proteicos das frações albuminas, globulinas e prolaminas. A análise eletroforética das prolaminas mostrou que as bandas produzidas pelo polipeptídeo kafirina, podem ser utilizadas na identificação de sorgo sem tanino no grão.

Several methods are described on the literature to determine the presence of tannin, however none of them is universally accepted as the ideal or even are used in a unanimous way. Some colorimetric methods do not differentiate tannins from others phenolic compounds, others use substances which are not appropriate to use as standard. Methods that use the capacity of tannins to precipitate proteins may end up with divergent results due to differences on the molecule conformation. Thus, the objective of this study was to identify the presence of tannin in 10 hybrids of sorghum throughout analysis of pattern proteins obtained by electrophoresis. The colored method Prussian Blue was used to quantify tannins on the samples. The protein precipitation by tannins permitted to identify the sorghum genotypes with grain tannin through protein standards of fractions of albumin, globulin and prolamins. The electrophoresis analysis of the prolamins showed that the bands produced by the kafirin polypeptide may be used in sorghum identification without the presence of tannin in grain.

Avaliação de três características fisiológicas em 4 ciclos de seleção no cultivar de milho BRS-4154 sob o solo encharcado / Evaluation of three physiologic characteristics in four cycles of selection in maize cultivar BRS-4154 under tolerance to waterlogging of the soil

Conduziu-se este trabalho, com o objetivo de avaliar plantas de milho (Zea mays L.) dos diferentes ciclos de seleção recorrentes da variedade de milho BRS 4154 - 'Saracura' quanto aos ganhos genéticos obtidos ao longo dos ciclos de seleção sob encharcamento do solo. Quatro ciclos de seleção da variedade de milho BRS 4154 foram plantados sob delineamento em blocos casualizados nos quais foram avaliados os ciclos 1, 5, 9 e 15, incluindo a variedade BR 107 e o híbrido simples BRS 1010 como testemunhas, por serem sensíveis ao encharcamento. Foram avaliados: fluorescência e teor de clorofila, área foliar e porosidade de raiz. O estresse causado pelo excesso de água no solo não influenciou a característica fluorescência da clorofila, demonstrando que essa não é uma boa característica para avaliação de tolerância ao encharcamento do solo. Houve uma significativa redução de área foliar do milho nas áreas de solo encharcado. Adicionalmente, a porosidade da raiz foi uma característica que apresentou significativa discrepância entre os dois ambientes de cultivo, tendo um aumento significativo em função do encharcamento.

This work aimed to evaluate plants of different cycles of recurrent selection of the maize (Zea mays L.) variety BRS 4154 - 'Saracura' for the genetic faced to the gains obtained along the selection cycles under waterlogging of the soil. Four cycles of selection of the maize variety BRS 4154 were planted in randomized block outline for evaluation of cycles 1, 5, 9 and 15, including the variety BR 107 and the simple hybrid BRS 1010 used as control, once they are sensitive to the waterlogging. One evaluated: chlorophylls fluorescence and content, leaf surface area and root porosity. The stress caused by the excess of water in the soil didn't influence the characteristic of chlorophyll fluorescence, demonstrating this is not a good characteristic to evaluate flooding tolerance. There was significant leaf surface area decrease of the corn in the areas of soaked soil. Additionally, the porosity of the root was a characteristic that presented significant discrepancy between the two cultivation environments, having a significant increase in function of waterlogging.