Reproductive biology of Ludwigia leptocarpa and L. adscendens subsp. diffusa in Ile Ife, Nigeria

Authors: MATTHEW OZIEGBE, JULIUS OLAOYE FALUYI

Abstract: Ludwigia L. (Onagraceae) species are known to be invasive in most parts of the world, serving as a threat to native plant species and blocking navigational channels. In Africa, they block waterways and are serious weeds in wet fields, most especially in rice paddies. The floral morphology, mode of sexual reproduction, and mechanism of fruit dispersal in water of L. leptocarpa (Nutt.) H.Hara and L. adscendens (L.) H.Hara subsp. diffusa (Forssk.) P.H.Raven were assessed in the Department of Botany of Obafemi Awolowo University, Ile Ife, Nigeria, from March 2006 to March 2009. L. leptocarpa produced cylindrical, hairy fruits of 34.80 ± 0.6 mm in length that contained 379.6 ± 8.63 seeds. The fruits of L. leptocarpa remained afloat in water, and seeds were easily dispersed from the fruits and germinated at 3 weeks while floating in water. L. adscendens produced cylindrical, glabrous fruits of 25.30 ± 0.4 mm in length that contained about 67.22 ± 0.84 seeds. All of the fruits of L. adscendens sank in water at 8 weeks, and seeds were not dispersed from the fruit at 22 weeks when germination was observed. The stigma was slightly raised above and separated away from the anthers at anthesis in both species. L. leptocarpa was self-compatible and highly autogamous; L. adscendens was self-compatible, autogamous, and out-crossing.

Keywords: Ludwigia, reproduction, buoyancy, fruits, seeds, dispersal

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