Long-term social recognition memory in adult male rats: factor analysis of the social and non-social behaviors

A modified version of the intruder-resident paradigm was used to investigate if social recognition memory lasts at least 24 h. One hundred and forty-six adult male Wistar rats were used. Independent groups of rats were exposed to an intruder for 0.083, 0.5, 2, 24, or 168 h and tested 24 h after the first encounter with the familiar or a different conspecific. Factor analysis was employed to identify associations between behaviors and treatments. Resident rats exhibited a 24-h social recognition memory, as indicated by a 3- to 5-fold decrease in social behaviors in the second encounter with the same conspecific compared to those observed for a different conspecific, when the duration of the first encounter was 2 h or longer. It was possible to distinguish between two different categories of social behaviors and their expression depended on the duration of the first encounter. Sniffing the anogenital area (49.9% of the social behaviors), sniffing the body (17.9%), sniffing the head (3%), and following the conspecific (3.1%), exhibited mostly by resident rats, characterized social investigation and revealed long-term social recognition memory. However, dominance (23.8%) and mild aggression (2.3%), exhibited by both resident and intruders, characterized social agonistic behaviors and were not affected by memory. Differently, sniffing the environment (76.8% of the non-social behaviors) and rearing (14.3%), both exhibited mostly by adult intruder rats, characterized non-social behaviors. Together, these results show that social recognition memory in rats may last at least 24 h after a 2-h or longer exposure to the conspecific

Photosynthetic response of poikilochlorophyllous desiccation-tolerant Pleurostima purpurea (Velloziaceae) to dehydration and rehydration

The poikilochorophyllous, desiccation-tolerant (PDT) angiosperm, Pleurostima purpurea, normally occurs in less exposed \ud rock faces and slightly shady sites. Our aim was to evaluate the light susceptibility of the photosynthetic apparatus during \ud dehydration-rehydration cycle in P. purpurea. In a controlled environment, the potted plants were subjected to water \ud deficit under two different photosynthetic photon flux densities [PPFD, 100 and 400 µmol(photon) m–2 s–1]. In the higher \ud PPFD, net photosynthetic rate (PN) become undetectable after stomata closure but photochemical efficiency of \ud photosystem II, electron transport rate, and photochemical quenching coefficient were maintained relatively high, despite \ud a partial decrease. The photochemical activity was inhibited only after the complete loss of chlorophylls, when leaf relative \ud water content dropped below 72% and total carotenoids reached maximal accumulation. Nonphotochemical energy \ud dissipation increased earlier in response to dehydration under higher PPFD. PN and photochemical activity were fully \ud recovered after rehydration under both light treatments. Our results suggested that the natural occurrence of P. purpurea \ud should not be restricted by the light intensity during the complete desiccation-rehydration cycles.Fundação de Amparo à Pesquisa do Estado de São PauloCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Herança da resistência em feijoeiro à murcha causada por Curtobacterium flaccumfaciens pv. flaccumfaciens

O objetivo deste trabalho foi determinar a herança da resistência à murcha de Curtobacterium em feijoeiro. Foram realizados dois experimentos: no primeiro, cinco genótipos de feijoeiro, com diferentes reações de resistência à murcha de Curtobacterium, foram cruzados em arranjo dialélico; e no segundo, dois cruzamentos entre genótipos resistentes e suscetíveis - IAC Carioca Aruã x SCS Guará e IAC Carioca Pyatã x Pérola - foram realizados para dar origem às gerações P1, P2, F1, F2, RC1 e RC2. Em ambos os experimentos, a resistência do feijoeiro à murcha bacteriana foi avaliada por meio da inoculação do isolado Cff 2634. A análise dialélica mostrou que, embora efeitos aditivos e não aditivos estejam envolvidos, houve maior participação de genes com efeito aditivo no controle genético da resistência à murcha bacteriana, o que mostra a possibilidade de se obter sucesso com a seleção. A herança da resistência à murcha de Curtobacterium é complexa, com mais de três genes envolvidos, e herdabilidade no sentido restrito de 29%, para o cruzamento 'IAC Carioca Aruã' x 'SCS Guará', e de 44%, para o cruzamento 'IAC Carioca Pyatã' x 'Pérola'

Photosynthetic response of poikilochlorophyllous desiccation-tolerant Pleurostima purpurea (Velloziaceae) to dehydration and rehydration.

The poikilochorophyllous, desiccation-tolerant (PDT) angiosperm, Pleurostima purpurea, normally occurs in less exposed rock faces and slightly shady sites. Our aim was to evaluate the light susceptibility of the photosynthetic apparatus during dehydration-rehydration cycle in P. purpurea. In a controlled environment, the potted plants were subjected to water deficit under two different photosynthetic photon flux densities [PPFD, 100 and 400 μmol(photon) m?2 s?1]. In the higher PPFD, net photosynthetic rate (PN) become undetectable after stomata closure but photochemical efficiency of photosystem II, electron transport rate, and photochemical quenching coefficient were maintained relatively high, despite a partial decrease. The photochemical activity was inhibited only after the complete loss of chlorophylls, when leaf relative water content dropped below 72% and total carotenoids reached maximal accumulation. Nonphotochemical energy dissipation increased earlier in response to dehydration under higher PPFD. PN and photochemical activity were fully recovered after rehydration under both light treatments. Our results suggested that the natural occurrence of P. purpurea should not be restricted by the light intensity during the complete desiccation-rehydration cycles. Additional key words: chlorophyll fluorescence; gas exchange; photoprotective mechanisms; vegetative desiccation toleranc