Proline content and protein patterns in Eucalyptus grandis shoots submitted to high and low temperature shocks

Proline content and protein patterns changes in response to temperature shocks of both acclimated and non acclimated E. grandis shoots cultivated in vitro were investigated. Analysis of soluble proteins through SDS-PAGE and proline were carried out after 12h at 12ºC (cold acclimation) or 33ºC (heat acclimation), and immediately after temperature shocks at 41ºC and 0ºC. Analyses were also performed 24h after the temperature shocks (recovery period). Temperature treatment at 0ºC did not change soluble protein patterns both in acclimatized and non acclimatized plants, whereas cold temperature induced high proline levels, which kept relatively high after recovery period. Three novel, probably HSPs, proteins (90.5, 75 and 39 kDa) were observed in both acclimated and non acclimated plants submitted to high temperatures. Plants exposed at 41ºC were able to recover from heat shocks after 24h, whereas they did not recover completely from cold shocks. The effect of the acclimation period on the recovering (homeostasis) varied depending on the parameter evaluated, and type and duration of the temperature shock.<br>As respostas às mudanças de temperatura de plantas aclimatadas e não aclimatadas de E. grandis cultivadas in vitro foram avaliadas considerando alterações dos níveis de prolina e proteínas solúveis totais. Análises de proteínas solúveis através de SDS-PAGE e prolina foram realizadas após 12h a 12ºC (aclimatação ao frio) ou a 33ºC (aclimatação ao calor), e imediatamente depois dos choques térmicos a 41ºC e 0ºC. Análises também foram realizadas após um período de 24h depois dos choques térmicos (período de recuperação). O tratamento de temperatura a 0ºC não alterou o padrão de proteínas nas plantas aclimatadas e não aclimatadas, entretanto a temperatura baixa induziu altos níveis de prolina, que se mantiveram relativamente altos após o período de recuperação. Três novas proteínas (90,5, 75 e 39 kDa), provavelmente HSPs, foram observadas nas plantas aclimatadas e não aclimatadas submetidas às temperaturas altas. As plantas expostas a 41ºC foram capazes de recuperar-se dos choques após o período de recuperação, entretanto não houve recuperação completa das plantas expostas às baixas temperaturas. O efeito da aclimatação sobre a recuperação (homeostasis) pode variar dependendo do parâmetro avaliado, tipo e duração do choque térmico

Macrophyte-induced thermal stratification in a shallow urban lake promotes conditions suitable for nitrogen-fixing cyanobacteria

© 2017, Springer International Publishing AG. Densely vegetated shallow lakes often experience low water column nutrient levels and reduced phytoplankton growth, but in some cases a high phytoplankton biomass can co-exist with subme rged macrophytes. The conditions that favour phytoplankton blooms within areas colonized by submerged macrophytes remain largely unexplored. We investigated changes in water quality variables and phytoplankton community composition data in relation to macrophyte-induced thermal stratification in a shallow urban lake. The results indicate that submerged macrophytes may favour internal loadings of phosphorus and low DIN:TP ratios, in periods when macrophyte-induced thermal stratification of the water column is common. Blooms of nitrogen-fixing cyanobacteria occurred under the strongly stratified conditions triggered by the high macrophyte biomass and elevated canopy, even though nitrogen limitation was apparent during the whole growing season. These findings suggest that submerged macrophytes can promote blooms of nitrogen-fixing cyanobacteria once they are sufficiently tall and dense to induce stable water column conditions