Floral biology, floral visitors and reproductive system of Lotus tenuis

AMELA GARCÍA, M. T; PASSALIA, M. G.; VEGA, A. S.; TORRETTA, J. P.; VALSECCHI, I.; HOC, P. S.; MOLLARD, F.; GENNA, M.

Chascomús

Workshop; VI Workshop of Lotus spp.; 2016

Instituto de Investigaciones Biológicas e Instituto Tecnológico de Chascomús, UNSAM-CONICET

The knowledge of the sexual reproduction of a plant is necessary for its cultivation or management. The great value of Lotus tenuis Waldst. et Kit ex Willd. as forage, its wide naturalization in Argentina and the controversy about its self-compatibility deserve the study of its breeding system, the floral biology and pollinators in the different sites where it grows.Data were recorded in a population that occupied 50 m2, disposed in several patches, in the experimental field of the Facultad de Ciencias Exactas y Naturales of the Universidad de Buenos Aires, from March 13-25, 1999.Pre-anthesis buds have nectar, the stigma receptive, the anthers dehiscent and pollen accumulated in the keel in contact with the stigma. Three floral stages proceed, differing mainly in the position and coloration of the floral pieces, which change successively from yellow, orange and red, when they are pollinated. The pollination mechanism of each flower can be activated repeatedly. The color change intensifies while the visits increase. In the visible spectrum, nectar guide lines converge to the flag base. The UV absorption is stronger in the corolla. The fresh and light aroma is emitted by the wings and flag. Nectar, produced by an annular nectary, accumulates inside the staminal tube. Induced self-pollination produced no fruits, suggesting self-incompatibility. The two pollen sizes encountered in 3 anther types differed in viability. Several species of Megachilidae and Apis mellifera pollinated the flowers while heteropterans and lepidopterans robbed and stole nectar, respectively. L. tenuis constituted more than 90 % of the hymenopterans? pollen load.Due to the self-incompatibility, the pollen contact with the stigma in the bud and the homogamy would not provoke self-fecundation; on the other hand, the pollinator activity becomes essential for fructification and seed set. The floral features correspond to mellitophily, corroborated by the medium-sized bees registered.