A study was conducted in a greenhouse, to investigate the effects of arbuscular mycorrhizal fungi (Glomus intraradices), soil salinity and P availability on growth (leaf area and dry weight), nutrient absorption and ion leakage, chlorophyll, soluble sugar and proline content and alkaline phosphatase activity of pepper plants (Capsicum annuum L.). Plants were grown at four levels of salinity (0, 50, 100 and 200 mM NaCl) and two P levels (10 and 40 mg kg -1). Colonisation was 80% to 51% in non-stressed and high salt-stressed plants, respectively. The mycorrhizal dependency was high and only reduced at the higher salinity level. Mycorrhizal plants maintained greater root and shoot biomass at all salinity levels compared to non-mycorrhizal plants, regardless the P level. Interactions between salinity, phosphorous and mycorrhizae were significant for leaf area, root and shoot dry mass. Non-mycorrhizal plants accumulated higher Na and lower K and P compared to mycorrhizal plants. The cell membrane integrity was greater in mycorrhizal plants than in non-mycorrhizal ones. The proline content increases with increasing salt stress and was significantly higher in leaves than in roots The results indicate that the mycorrhizal inoculation is capable of alleviating the damage caused by salt stress conditions on pepper plants, to maintaining the membranes stability and plant growth, and this could be related to P nutrition.

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In this work we present evidence that the drought stress syndrome in the flag leaves and ears of wheat plants, provoked by the production of ethylene (shortening the grain filling period and lowering the grain weight) is reversed by the application of a free radical scavenger, sodium benzoate or the ethylene synthesis inhibitor, aminoethoxyvinylglycine. Rehydration by watering also attenuated the detrimental effect of the water deficit. Consequently, the grain filling period was longer, the grain weight increased, and the total protein content was higher than that in plants watered regularly.

This work was aimed at testing the involvement of ethylene in the maturation of grain and senescence of the foliar structures of the wheat inflorescence . Whole wheat ears emitted ethylene to the atmosphere . From pre-anthesis, ethylene emission progressively increased from 0.76 nl g -1 FW h -1 to a peak 1 .53 nl g -1 FW h -1 at the hard dough stage of the grains, to fall to a minimum of 0 .10 nl g -1 FW h -1 at the dormant seed stage . Ethephon increased the ethylene release, hastened the process of grain maturation and senescence of the ears . Aminoethoxyvinylglycine and silver thiosulfate produced the opposite effects . It is concluded that ethylene plays a role in grain maturation and in the senescence of the green bracts of the inflorescence .Abbreviations : Ag+ = silver ion ; AVG = aminoethoxyvinylglycine ; SAM = S-adenosylmethionine ; STS = silver thiosulfate ; TGW = thousand grain weight 107

The aim of this paper was to investigate the contribution of the arbuscular mycorrhizal fungus Glomus claroideum to drought stress tolerance in wheat plants grown under controlled conditions in a growth chamber, and subjected to moderate or severe water stress and rewatering. Water stress tolerance was determined through total dry weight, leaf relative water content, leakage of solutes and leaf chlorophyll and protein concentrations in mycorrhizal and nonmycorrhizal wheat plants. Total dry weight and leaf chlorophyll concentrations were significantly higher in mycorrhizal plants after moderate or severe water stress treatments compared with non-mycorrhizal ones. Electrolyte leakage was significantly lower in water-stressed inoculated plants. Compared to non-inoculated plants, leaf relative water content and total protein concentration of inoculated individuals increased only under severe water stress. When irrigation was re-established, mycorrhizal plants increased their total dry weight and leaf chlorophyll concentration, and recovered cell membrane permeability in leaves compared with non-mycorrhizal plants. In conclusion, root colonization by G. claroideum could be an adequate strategy to alleviate the deleterious effects of drought stress and retard the senescence syndrome in wheat. Key words: mycorrhizae, relative water content, rewatering, solute leakage, water deficit A melhoria da tolerância do trigo (Triticum aestivum L.) ao estresse hídrico e à reidratação pelo fungo micorrízico arbuscular (Glomus claroideum): Efeito sobre o crescimento e estabilidade das membranas celulares: O objetivo do trabalho foi pesquisar a contribuição do fungo micorrízico arbuscular Glomus claroideum à tolerância ao déficit hídrico em plantas de trigo cultivadas sob condições controladas em uma câmara de crescimento, submetidas ao estresse hídrico moderado ou severo e reidratação. A tolerância das plantas ao estresse hídrico foi determinada mediante o peso seco total, conteúdo relativo de água foliar, extravasamento de solutos e concentrações foliares de clorofilas e proteínas totais nas plantas de trigo micorrizadas e não-micorrizadas. O peso seco total e a concentração de clorofila foram significativamente maiores nas plantas micorrizadas sob estresse hídrico moderado ou severo, quando comparadas com as não-micorrizadas. O extravasamento de solutos foi significativamente menor nas plantas inoculadas estressadas. O conteúdo relativo de água foliar e a concentração de proteínas totais nas plantas inoculadas aumentaram apenas em condições de estresse hídrico severo. Após a re-irrigação, nas plantas micorrizadas, houve aumento do peso seco total e da concentração de clorofilas, além da recuperação da integridade das membranas celulares, quando comparadas com as plantas não-micorrizadas. Em suma, a colonização das raízes por G. claroideum poderia ser uma estratégia adequada para reduzir os efeitos deletérios do estresse hídrico e retardar a síndrome da senescência em trigo. Palavras-chave: conteúdo relativo de água, déficit hídri...

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In general, heavy metals interfere with several physiological processes and reduce plant growth. Plants naturally establish symbiotic associations with soil microorganisms, such as mycorrhizal fungi. The aim of this research was to determine if inoculation with mycorrhizal fungi increases tolerance to Cr, evidenced by growth and biochemical parameters and the effect on roots membranes in Capsicum annum. Plants were either non-inoculated or inoculated with Glomus mosseae or Glomus intraradices, and grown in the presence of different concentration of Cr (K 2 Cr 2 O 4 ) in soil. Pepper plants grown without Cr behaved as mycotrophic species. At the highest concentration (200 mM K 2 Cr 2 O 4 ), Cr reduced root colonization by G. mosseae or G. intraradices (to 23 and 20% respectively). Moderate and high concentrations of Cr reduced all growth parameters. The interaction of inoculation and Cr increased leaf chlorophyll and proline content while reduced the leaf protein and root proline content. Carotenoid content was not affected by treatments. High Cr concentrations increased significantly electrolytes leakage in roots, either non-inoculated or inoculated plants. At the highest Cr concentration, inoculated plants had double the biomass of non-inoculated plants. Cr content in roots of inoculated plants was significantly higher than in non-inoculated plants. Chromium accumulation was low in leaves and showed no differences between treatments. Mycorrhization increased pepper plant tolerance to Cr in the soil, modifying proline metabolism to assure a more efficient response.

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