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Botany

Grains of fertility

Botanist makes the first detailed description of the pollen of the pernambuco wood

IRWANDRO PIRES / IB / USPPollen in detail: a full view (1,500 times) IRWANDRO PIRES / IB / USP

With supreme delicacy, botanist Angela Maria Corrêa has been studying pernambuco wood pollen – light, yellowish particles, 0.05 millimeters in diameter – over almost six months. She compared samples collected in Ceará, the Federal District, Rio de Janeiro and Rio Grande do Norte, kept in the herbarium of the São Paulo Botany Institute, where she is a researcher, and did the first detailed description of the pollen of Caesalpinia echinata, a tree native to the Atlantic Rain Forest that, under another name, the brazilwood tree, helped to give the country its name. Besides assisting in the identification of this species, the information gathered should serve as a standard for the comparative study of the trees distributed along the Brazilian coast or cultivated in urban environments.

Seen under the optical microscope, pernambuco pollen is revealed as a slightly flattened sphere, with three openings, through which the so-called pollen tube germinates, carrying the male cells to the flower’s female reproductive cells. “The openings in pernambuco pollen are complex structures, very different from those found in other species”, says Angela, the author of the study published in the Revista Brasileira de Botânica [Brazilian Botany Magazine]. The outer layer of the pollen shows itself to be in the form of a net, whose structure becomes clearer under the scanning electron microscope. Around the openings, there is an even finer weaving.

The pollen, which contains the male reproductive cells, is to be found in the anthers, one of the reproductive structures of a flower. When carried by insects, it can find another flower and join up with its female cells – which is when fertilization occurs. Her study is part of a wider project coordinated by Rita de Cássia Figueiredo Ribeiro, from the Botany Institute, with funding from FAPESP, aimed at the conservation of this tree, which has been intensively exploited for five centuries.

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