Increase in pollen contribution in colonies of Apis mellifera bees by induction of flowering of black Jurema ( Mimosa tenuiflora ) during the dry season in the savanna low jaguaribe Ceará

This study aimed to investigate the possibility of inducing blooming by Mimosa tenuiflora, a plant species of common occurrence and abundance in Caatinga (shrub vegetation of NE Brazil), in order to provide pollen for honey bees (Apis mellifera) in the dry season, as well as to evaluate the use or not of this resource by bees, besides studying the floral biology of this plant species and its flower visitors. The experiment was carried out at Apiário Altamira Apícola in the county of Limoeiro do Norte, state of Ceará, Brazil, from August to December 2012. Fifteen plants were chosen and split into five groups of treatments to receive different levels of water (T1 = 0 L, T2 = 250 L, T3 = 500 L, T4 = 750L and T5 = 1,000 L) to investigate the beginning, peak and decline of the blooming stages. In order to collect pollen samples, ten apiaries were selected, each one with twelve colonies of Africanized honey bees. The apiaries were split in two treatments in a way that the five apiaries of Treatment 1 were at distances greater than 3 km to the sites where M. tenuiflora plants were induced to bloom, while apiaries of Treatment 2 were only 20 m away of the blooming plants. Three colonies out of the twelve present in each apiary were randomly chosen to receive pollen collectors, totalizing fifteen colonies with collector per treatment. Pollen samples were collected at 7:30h and 17:30h, three days before the blooming of M. tenuiflora and then three days during the flowering period. The results showed that on the first day of blooming – which is equivalent to the eighth day after flowering induction –, only plants submitted to treatments 3, 4 and 5 presented blooming, and the largest number of inflorescences was obtained in T5 – 1.000 L, which differed significantly (p<0.05) to the other treatments. Apis mellifera began to collect resources at 5:00h and stopped at 7:00h, collecting only pollen. The other flower visitors were Trigona spinipes, Melipona subnitida and some wasps, but in a lower frequency of visitation. Pollen analysis showed that M. tenuiflora contributed 59.16% in the pollen diet of bees from colonies of Treatment 2 and only 9.81% in the colonies of Treatment 1. Thus, we concluded that M. tenuiflora is a species that, once in bloom, increases the offer and collection of pollen by bees during the dearth period of the year, exempting the use of alternative protein feeds. Therefore, it is of paramount importance to conserve and increase the number of M. tenuiflora plants in places where beekeeping is practiced.O presente trabalho teve por objetivo investigar a possibilidade de induzir o florescimento de uma espécie vegetal, jurema preta (Mimosa tenuiflora), de ocorrência comum e abundante na caatinga visando disponibilizar pólen para a abelha melífera (Apis mellifera) no período de estiagem, bem como avaliar o uso ou não deste recurso pelas abelhas, além de estudar a biologia floral desta espécie vegetal e os visitantes florais. O experimento foi realizado no Apiário Altamira Apícola, no município de Limoeiro do Norte – Ceará, no período de agosto a dezembro de 2012. Quinze plantas foram escolhidas e divididas em cinco tratamentos para receberem diferentes níveis de água (T1 = 0 L, T2 = 250 L, T3 = 500 L, T4 = 750 L e T5 = 1.000 L) para o conhecimento do início, pico e declínio do florescimento. As coletas das amostras de pólen foram realizadas em dez núcleos selecionados, cada um com doze colônias de abelhas africanizadas. Os núcleos foram divididos em dois tratamentos de forma que os cinco núcleos do Tratamento 1 encontravam-se em distância superior a 3 km dos locais onde houve a indução das plantas de jurema preta, enquanto que os núcleos do Tratamento 2 estavam a apenas 20 m de distância. Das doze colmeias que havia em cada núcleo, três foram sorteadas ao acaso para receberem coletores de pólen, totalizando quinze colônias com coletor por tratamento. As amostras de pólen foram coletadas as 7:30h e as 17:30h, durante três dias antes do início do florescimento da jurema preta e três dias durante o período de florescimento. Os resultados mostraram que no primeiro dia de florescimento, que equivale ao oitavo dia após a indução, apenas as plantas submetidas aos tratamentos 3, 4 e 5 apresentaram florescimento, sendo que a maior quantidade de inflorescências foi contabilizada no T5 – 1.000 L, que diferiu significativamente (p