The germination of three cerrado herbaceous species: Bidens gardneri, Vernonia herbacea (Asteraceae) and Psychotria barbiflora (Rubiaceae) was studied using seeds stored in cerrado soil and in refrigerator at 4°C. The field experiment was carried out at a preserved area of cerrado, the Reserva Biológica e Estação Experimental de Mogi-Guaçu, State of São Paulo, Brazil. The soil was collected in the same cerrado where the experiment was carried out. The achenes of Bidens gardneri are light sensitive, but this sensitivity disappeared when the achenes were stored in soil. With 3 months storage in cerrado soil no differences in germination in light or darkness were detected. The number of intact achenes retrieved from storage in soil decreased with increasing time of storage. A large number of seeds had already germinated during the 3 months storage in soil. The longevity of seeds of this species stored for nearly 10 years at 4°C was checked: the achenes were viable for a long period of time but less than 10 years. Intact achenes of Vernonia herbacea could be retrieved from the soil only with 1 month storage. Germination was always very low and only 15% of the achenes possessed embryos. The number of intact seeds of Psychotria barbiflora decreased the longer the period of storage in soil. Germination of seeds stored at 4°C or in the soil was always very low. From the germination studies of stored seeds in cerrado it can be concluded that Vernonia herbacea does not form a seed bank and Bidens gardneri and Psychotria barbiflora may form a temporary seed bank in cerrado.

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-(Response of Dalbergia miscolobium Benth. seedlings, a cerrado tree species, to a mineral nutrient supply). The soil under the Brazilian cerrado vegetation is very poor in nutrients. The aim of this study was to investigate the effect of the addition of a nutrient solution in the early growth of D. miscolobium, a typical cerrado tree species, cultivated in cerrado soil. Seeds were germinated in Petri dishes and seven-day old seedlings were transfered to pots containing cerrado soil. These were supplied once a week with a normal, 1/2 or 1/10 strength nutrient solution. Four growth analysis were done over a period of 145 days from seed imbibition, in terms of dry mass, leaf area and carbohydrate and nitrogen contents. Other derived parameters were also analysed. The addition of a nutrient solution promoted early growth with a preferential separation of dry matter towards the tops; in the control seedlings (no nutrient addition) more dry matter accumulated in the root system. This suggests a preferential investment in root growth in poor soils such as the cerrado ones. Reliable evidence of this is given by the level of carbohydrate and protein which was higher in the roots than in the tops of plants growing in cerrado soil without the addition of nutrients.RESUMO -(Resposta das plântulas de Dalbergia miscolobium Benth., uma espécie arbórea de cerrado, à adição de nutrientes minerais). O solo sob vegetação do cerrado brasileiro é muito pobre em nutrientes. O objetivo deste trabalho foi o estudo do efeito da adição de solução nutritiva sobre o crescimento inicial de D. miscolobium, uma espécie arbórea nativa do cerrado, cultivada em solo de cerrado. As sementes foram germinadas em placas de Petri e plântulas com sete dias foram transferidas para recipientes contendo solo de cerrado. Estas foram supridas, uma vez por semana, com solução nutritiva normal, diluída duas vezes ou diluída 10 vezes. Quatro análises de crescimento foram feitas por um período de 145 dias desde o início da embebição das sementes, em termos de massa de matéria seca, área foliar e conteúdo de carboidratos e de nitrogênio. Outros parâmetros derivados também foram avaliados. A adição da solução nutritiva promoveu o crescimento inicial com partição preferencial de matéria seca para a parte aérea; nas plântulas controle (sem adição de nutrientes) mais matéria seca foi acumulada no sistema radicular. Isto sugere um investimento preferencial no crescimento da raiz em solos mais pobres como os de cerrado.Uma boa evidência sobre isso é dada pelo nível de carboidratos e proteínas, o qual foi maior nas raízes do que nas partes aéreas em plantas crescendo em solo de cerrado sem solução nutritiva.

-(Effects of moisture content and temperature during storage on germination of the achenes of Bidens gardneri Baker). Bidens gardneri is a herbaceous species of the cerrados, whose seeds are light sensitive at 25°C, but they become indifferent to light when stored in soil. In this work the effects of moisture content, temperature and light (during storage) upon light sensitivity during germination were studied. Ripe achenes were collected in the cerrados of Itirapina and Moji Guaçu, State of São Paulo, Brazil. The storage conditions of the achenes varied in each experiment. Achenes were stored in darkness or light, in closed bottles, at 4°C, 20/30°C or 25°C. Achenes were imbibed for 24 h at 4°C, 25°C or 20/30°C (in darkness) and then stored for 1, 10, 20, 30 and 40 days (40 days only for 4°C and 25°C). Germination tests were conducted at 25°C and 20/30°C. The achenes not previously imbibed showed sensitivity to light during germination. High moisture content did not affect light sensitivity of the achenes during germination but high moisture content together with storage temperatures of 25°C and 20/30°C had a deleterious effect upon the longevity of the achenes. Alternate temperatures during germination did not change the light sensitivity of newly collected achenes from Itirapina but changed the light sensitivity of the achenes stored imbibed at 4°C in darkness. Alternate temperatures during storage of achenes with low moisture content did not change their photoblastism when germination was carried out at 25°C. Alternate temperatures during storage of achenes with high moisture content followed by alternate temperatures during germination changed the light sensitivity of the achenes.RESUMO -(Efeito do conteúdo de água e temperatura durante o armazenamento na germinação dos aquênios de Bidens gardneri Baker). Bidens gardneri é uma espécie herbácea dos cerrados, cujas sementes são fotoblásticas positivas a 25°C, mas tornam-se indiferentes à luz quando armazenadas em solo. Neste trabalho, foram estudados os efeitos do conteúdo de água dos aquênios, da temperatura e da luz (durante o armazenamento) na sensibilidade à luz durante a germinação. Os aquênios foram coletados nos cerrados de Itirapina e de Moji Guaçu, estado de São Paulo, Brasil. As condições de armazenamento variaram em cada experimento. Os aquênios foram armazenados no escuro ou em luz, em vidros fechados a 4°C, 25°C e 20/30°C. Os aquênios foram embebidos por 24 horas a 4°C, 25°C e 20/30°C (no escuro) e então armazenados por 1, 10, 20, 30 e 40 dias (40 dias somente para 4°C e 25°C). Os testes de germinação foram conduzidos a 25°C e 20/30°C. Os aquênios que não foram embebidos apresentaram sensibilidade à luz durante a germinação. O conteúdo alto de água durante o armazenamento não afetou a resposta à luz dos aquênios durante a germinação, mas o conteúdo alto de água em temperaturas de armazenamento de 25°C e 20/30°C tiveram efeito deletério na longevidade dos mesmos. As temperaturas alternadas durante a germinação não alteraram a resposta à lu...