Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / O objetivo deste trabalho foi estudar aspectos fisiolÃgicos, bioquÃmicos e morfolÃgicos da germinaÃÃo de sementes de mandacaru. Inicialmente, foi analisado o efeito da luz e temperatura, na germinaÃÃo das sementes de mandacaru, submetidas aos tratamentos de luz (branca, ausÃncia, vermelha e vermelho-distante) associados aos de temperaturas [15, 20, 20-30 (alternada), 25, 30 e 35ÂC]. O Ãndice de velocidade de germinaÃÃo e a percentagem de germinaÃÃo foram maiores a 25 e 30 ÂC associadas à luz branca, sendo o tempo mÃdio de germinaÃÃo menor sob essas condiÃÃes e mais acentuado na condiÃÃo de escuro a 20ÂC. A morfologia das sementes e as anÃlises citoquÃmicas revelaram que as sementes de mandacaru apresentam paredes celulares finas quando coradas com o azul de toluidina (AT) e que se mantiveram inalteradas ao longo do processo germinativo. As cÃlulas dos cotilÃdones e eixo hipocÃtilo-radÃcula apresentaram o mesmo tipo de parede celular, entretanto, houve diferenÃas no formato das cÃlulas entre esses tecidos. A composiÃÃo e a mobilizaÃÃo das reservas das sementes de mandacaru durante a germinaÃÃo tambÃm foram avaliadas, atravÃs de anÃlises citoquÃmicas e bioquÃmicas, nos diferentes perÃodos de germinaÃÃo. Os lipÃdios foram detectados como a principal substÃncia de reserva dessas sementes, correspondendo a 54,50% e 61,70%, da massa seca dos cotilÃdones e do eixo hipocÃtilo-radÃcula, respectivamente. A mobilizaÃÃo dessas reservas teve inÃcio logo depois da embebiÃÃo, progredindo atà o Ãltimo perÃodo analisado (12 DAE). Os carboidratos representaram apenas 2,13% da massa seca da semente, correspondendo aos aÃÃcares solÃveis (redutores e nÃo-redutores) e amido, devido a isso tiveram pequena participaÃÃo na mobilizaÃÃo das sementes de mandacaru. Por outro lado, as proteÃnas que corresponderam a cerca de 30% da massa seca das sementes de mandacaru, foram evidentemente mobilizadas, ao longo do perÃodo de germinaÃÃo avaliado. Em relaÃÃo Ãs fraÃÃes protÃicas, as albuminas e as glutelinas foram as principais proteÃnas de reserva detectadas, correspondendo aos grupos que mais foram mobilizadas durante a germinaÃÃo destas sementes. As anÃlises mostraram diferentes padrÃes de degradaÃÃo de proteÃnas, que foram confirmadas por eletroforese sob condiÃÃes desnaturantes (SDS-PAGE). Apesar das globulinas e prolaminas terem sido detectadas, estas representaram uma pequena percentagem da proteÃna total dessas sementes. Em conclusÃo, as sementes de mandacaru sÃo consideradas insensÃveis à luz, embora sua germinaÃÃo seja aumentada sob condiÃÃes de luz e altas temperaturas, como 25 e 30ÂC. Os lipÃdios e as proteÃnas foram as principais substÃncias de reserva detectadas nessas sementes, sendo, portanto os principais recursos fornecidos para o desenvolvimento das plÃntulas de mandacaru. / The aim of this work was to study the physiology, biochemistry and morphology of mandacaru (Cereus jamacaru D.C) germination. Firstly, we analyzed the effects of light and temperature on mandacaru germination under four light treatments (white, dark, red and far-red) associated to six different temperatures [15, 20, 20-30 (alternated), 25, 30 and 35ÂC]. The germination speed index and germination percentage ratio were bigger at 25 and 30ÂC, associated to white light. On the other hand, the medium time germination was fewer in these conditions, and more pronounced in the dark at 20ÂC. Secondly, we studied seed morphology and cytochemical analyses revealed thin cell wall stained by Toluidin Blue (TB), which maintained unchanged during seed germination. Cotyledons and embryo-axes showed the same cell wall pattern, although had been observed differences in the cell form between them. Thirdly, we studied the main reserves composition and their mobilization during and following germination of C. jamacaru D.C seeds. We analyzed seeds in seven different periods after imbibitions, through biochemical and cytochemical analyses. Lipids were detectable as the major reserve, with 54,50% and 61,70% of seed dry mass of cotyledons and embryo-axes, respectively. This compound was one of the most involved on seed mobilization, which started after imbibition, carrying until the last stage analyzed (12 DAE). Carbohydrates represented only 2,13% of seed dry mass, comprising soluble sugars and starch, in this way, these compounds had little participation on mandacaru seed mobilization. On the other hand, proteins comprise about thirty percent of seed dry mass, playing an important role in C.jamacaru germination. In concern about their fractions, albumins and glutelins were the major reserve proteins detectable in these seeds, which were mobilized during seed germination. These results showed different protein degradation, which were confirmed by polyacrylamide gel electrophoresis under denaturing conditions (SDS-PAGE). In spite of globulins and prolamins had been observed on C. jamacaru seeds, they represent a little percentage of this seeds, did not play essential role in these seeds. In conclusion, seeds of C. jamacaru are insensitive to light, although their germination increases under light and high temperature conditions, as 25 and 30ÂC. Lipids and proteins are the major reserves of Cereus jamacaru seeds, therefore corresponding to the main sources involved in the initial seedling development.