Roles of glycine betaine and proline in improving plant abiotic stress resistance

Salt tolerance and salinity effects on plants: a review.

Developments in nanotechnology are leading to a rapid proliferation of new materials that are likely to become a source of engineered nanoparticles (ENPs) to the environment, where their possible ecotoxicological impacts remain unknown. The surface properties of ENPs are of essential importance for their aggregation behavior, and thus for their mobility in aquatic and terrestrial systems and for their interactions with algae, plants and, fungi. Interactions of ENPs with natural organic matter have to be considered as well, as those will alter the ENPs aggregation behavior in surface waters or in soils. Cells of plants, algae, and fungi possess cell walls that constitute a primary site for interaction and a barrier for the entrance of ENPs. Mechanisms allowing ENPs to pass through cell walls and membranes are as yet poorly understood. Inside cells, ENPs might directly provoke alterations of membranes and other cell structures and molecules, as well as protective mechanisms. Indirect effects of ENPs depend on their chemical and physical properties and may include physical restraints (clogging effects), solubilization of toxic ENP compounds, or production of reactive oxygen species. Many questions regarding the bioavailability of ENPs, their uptake by algae, plants, and fungi and the toxicity mechanisms remain to be elucidated.

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Environmental behavior and ecotoxicity of engineered nanoparticles to algae, plants, and fungi

Nanoparticulate material delivery to plants

Photosynthesis and activity of superoxide dismutase, peroxidase and glutathione reductase in cotton under salt stress

Iron plays a pivotal role in the redox reactions of photosynthesis and metabolic pro- cesses such as chlorophyll synthesis. Iron availability in waterlogged soils can reach toxic levels and promote oxidative stress. Fe toxicity is the most concerning of stresses for rice in many lowland environments around the world and may cause severe impairments in rice photosynthe- sis. This study aimed to investigate the extension of oxidative stress after excess Fe exposure and its effects on the photosynthesis of rice cultivars with differential sensitivity. Three Brazilian rice cultivars (EPAGRI 107, BRSMG SELETA and BR IRGA 409) were grown in Hoagland nutrient solution (pH 4.0) with two Fe-EDTA doses corresponding to excess Fe (7 mM) and control (0.009 mM) treatments. After just three days of excess Fe exposure, there was a significant increase in iron concentration in the shoots. The BR IRGA 409 cultivar exhibited higher Fe accumulation in its shoots, and the EPAGRI 107 cultivar recorded the lowest values, which were below the criti- cal toxicity level, as a resistance strategy. Impairment in light energy partitioning and oxidative damage became evident before changes in stomatal resistance, chlorophyll content, maximal PSII quantum yield or visual symptoms for the most sensitive cultivar (BR IRGA 409). The photo- synthesis limitations, in addition to the impairment of excess energy dissipation in rice from iron toxicity, are the results of oxidative damage.

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Oxidative damage and photosynthetic impairment in tropical rice cultivars upon

Green and brown seeds of the leguminous Cratylia floribunda , with and without scarification, were used to study the effect of decreasing water potential on their respiration, imbibition and germination. The water potential was determined in a solution of mannitol. It was also studied the effect of different levels of dehydration (induced in a dessicator with silica gel) and of rehydration on the respiration of scarified and imbibed green seeds of C. floribunda . In the non scarified green seeds, imbibition, respiratory activity and germination were not observed for any of the osmotic conditions used. Lower water potential affected the imbibition rate of the scarified green seeds. However it did not affect the final amount of water absorbed, respiration or the percent of germination. Concerning the respiration and the germination, it was concluded that the imbibition effect of mannitol is superior than the water potentials themselves. Germination was not detected with brown seeds. A problem of dormancy or internal damage is concluded for this case. The respiratory pattern of the scarified brown seeds was different from the scarified green seeds in spite of a similar imbibition. However, an accumulation of water for the highest potential and a depression effect of the lower potentials for the brown seed without scarification were observed, probably due to an inhibitory effect of mannitol. During the dehydration, the respiratory intensity variation was related to the remaining water content of the seed: high respiratory rates with low loss of water, and low respiratory rates with severe loss of water were observed. Related to the control, the variations of respiratory intensities were not markedly different from the rehydration. The high percentage of germination obtained after the rehydration suggests that dehydration had only a slight effect.

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Efeito do potencial hídrico sobre a embebição, a respiração e a germinação da leguminosa Cratylia floribunda

O crescimento e a eficiencia na conversao da energia solar foram estudados em feijao ( Phaseolus vulgaris L. cv. 'Negrito 897'), cultivado em condicoes de campo, sob tres niveis de luz (30%, 70% e 100% da radiacao solar incidente) e tres doses de nitrogenio (0, 30 e 60 kg/ha de N). As taxas de producao de materia seca, de crescimento relativo e assimilatoria liquida aumentaram com o incremento da densidade do fluxo radiante e doses de nitrogenio. As variacoes na taxa de crescimento relativo envolveram mudancas na taxa assimilatoria liquida e na razao de area foliar; ambas apresentaram uma forte tendencia de decrescimo com a ontogenia das plantas. A razao de area foliar aumentou com a reducao da densidade do fluxo radiante, em virtude da maior area foliar e concomitante reducao do peso da materia seca das plantas sombreadas. Entretanto, a razao de peso foliar nao foi influenciada pelo sombreamento nem pelas doses de nitrogenio, pois ambos reduziram, de maneira similar, a materia seca das folhas e da planta toda. Ja a area foliar especifica aumentou com a reducao da densidade do fluxo luminoso, em virtude do aumento na area foliar e reducao do peso da materia seca das folhas do feijoeiro sombreado, sem mostrar, contudo, diferencas a doses de nitrogenio. Houve aumento na eficiencia da conversao da energia solar, com a reducao da radiacao solar e incremento da adubacao nitrogenada.

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Doses de nitrogênio e densidades de luz no crescimento do feijoeiro e na conservação da energia solar

Estudou-se a influencia do aluminio sobre o desenvolvimento e o teor de alguns nutrientes em soja ( Glycine max (L.) Merril), procurando-se determinar alguma possivel diferenca na tolerância a este cation entre as cultivares IAC-5 e Santa Rosa. Plântulas com dez dias de idade foram submetidas a 0, 4, 8, 10 e 12 ppm de Al em solucao nutritiva. Apos 35 dias de cultivo, coletou-se o sistema radicular, o caule e as folhas, para a determinacao do peso da materia seca e dos teores de N, P, K, Ca, Mg, Fe e Al. A parte aerea de ambas as cultivares mostrou-se mais sensivel ao Al que o sistema radicular. A cultivar IAC-5 acumulou mais materia seca que a Santa Rosa no sistema radicular em relacao a parte aerea; no entanto, as duas cultivares apresentaram respostas semelhantes, ao Al. Este cation alterou significativamente a composicao mineral das plantas, reduzindo, de maneira acentuada, o teor de Ca na parte aerea, e o de P e Mg, tanto na parte aerea como no sistema radicular. Observou-se um acumulo de Al no sistema radicular; apenas uma pequena quantidade deste elemento foi translocada para a parte aerea. Os efeitos do Al foram pouco acentuados sobre o teor de K, mas evidenciaram-se sobre a distribuicao de N, que se acumulou no caule, e sobre o teor de Fe. Em presenca do Al, as duas cultivares estudadas nao apresentaram diferencas marcantes, quanto a eficiencia nutricional, e portanto nao se justifica enquadra-las em faixas distintas de tolerância.

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Efeito do alumínio sobre a produtividade e composição da soja

The effect of light flux density (30%, 50%, 70% and 100% of sunlight) on soybean ( Glycine max (L.) Merrill cv. UFV-2) nodulation was studied under field conditions. Shade reduced the number, dry weight, growth rate of nodules, and also accelerated their senescence. Nodule number, dry weight and growth rate decayed quickly during pod filling, evidencing a competition for assimilate between seeds and nodules. Nitrogen content was shown to be related to light flux density.

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Marco Antonio Oliva

Papers

Oxidative damage and photosynthetic impairment in tropical rice cultivars upon

Efeito do potencial hídrico sobre a embebição, a respiração e a germinação da leguminosa Cratylia floribunda

Doses de nitrogênio e densidades de luz no crescimento do feijoeiro e na conservação da energia solar

Efeito do alumínio sobre a produtividade e composição da soja

Efeito da densidade do fluxo radiante sobre a nodulação da soja