Xenogamy Research Articles

Fenologia e Biologia Reprodutiva de Tibouchina papyrus (Pohl) Toledo (melastomataceae) no Parque Estadual da Serra dos Pireneus, Goiás

The phenological and reproductive study of Tibouchina papyrus (Pohl) Toledo (Melastomataceae) was carried out in campo rupestre vegetation, at an altitude of 1,100 m in the Parque Estadual dos Pirineus, located in municipalities of Pirenopolis and Cocalzinho, in the state of Goias. Twenty individuals of the population were selected, marked, and observed for two years regarding phenological processes such as flowering and fruiting. Their reproductive system was evaluated by manual pollination and calculations of reproductive efficacy. The fruits formed were collected and their seeds germinated in Petri dishes with wet filter paper. Treatments of manual pollination indicate this is a facultative xe nogamy species with higher fruit production by cross-pollination (45%) than by self-pollination (12%). Emasculated flowers to induce agamospermy did not produce fruits. The low production of control-fruit (30%) may be explained by low presence of pollinators. The protrusion of the radicle occurred between the 7 th and the 8 th day with 55% of germination. Flowering occurred from December to June, and fruit maturation between April and October, coinciding with seed dispersal and leaf fall during the dry season. This study provides information to understand the reproductive process of T. papyrus , an endemic and still not well studied species.

Ecologia da polinização de Raphiodon echinus (Nees & Mart.) Schauer (Lamiaceae) em Petrolina, PE, Brasil

Raphiodon echinus é uma espécie de hábito rasteiro, que ocorre espontaneamente em áreas de caatinga. No presente trabalho foram observados a biologia reprodutiva desta espécie com o objetivo de contribuir com informações sobre sua ecologia da polinização. As observações foram feitas em áreas de caatinga da Embrapa Semi-Árido, em Petrolina, PE. Para os experimentos de autopolinização espontânea, autopolinização manual, apomixia, geitonogamia, xenogamia, botões foram ensacados, emasculados e polinizados, quando necessário. Flores foram marcadas para estimar a polinização em condições naturais. Os visitantes florais foram observados das 7h30 min às 16h00, totalizando 45 horas de observações. As flores de R. echinus são infundibuliformes, de coloração violeta, exalam odor adocicado e estão reunidas em glomérulos. A antese é diurna, assincrônica, sendo mais freqüente no período da manhã, por volta das 07h00. A duração das flores é de aproximadamente 10 horas e cada inflorescência apresenta número variado de flores/dia. As flores são visitadas por abelhas e borboletas. Centris hyptidis foi responsável por 26% do total das visitas e, de acordo com o comportamento e freqüência de visitas, foi considerada como polinizador efetivo desta espécie. Quanto ao sistema de reprodução, R. echinus é autógama facultativa, produzindo frutos por autopolinização manual (70%), geitonogamia (63%) e xenogamia (40%).

Pollination ecology, breeding system, and conservation of Caldesia grandis (Alismataceae), an endangered marsh plant in China

Caldesia grandis Samuelsson is an endangered wetland herb on the brink of extinction in the vast area of Mainland China, which holds close to one eighth of the world’s vascular plant species. The pollination ecology and breeding system of C. grandis were investigated from three natural populations occurring in two wetlands near the top of Mangshan Mountain in Hunan Province, central China. The species is in flower from early July to late September with a peak in August. The process of flower anthesis in C. grandis begins at about 10.00 am and lasts about four-and-one-quarter h. The flowers lasted ca. 5.5 h. Caldesia grandis is self-compatible; however, autogamy resulted in lower seed set than geitonogamy and xenogamy as well as free pollination. Both pollen viability and the seed set in open-pollinated controls at the same site were typically high (65.44% and 71.78% respectively). Mean pollen: ovule ratios in the three populations ranged from 901.75 to 931.354. No seed germination was observed, either in the field or in laboratory experiments. Propagation is achieved through turions, which commonly occur in the inflorescences. Flies (Insecta; Diptera) were the most frequent visitors to the flowers of C. grandis; however, bees (Insecta; Hymenoptera) composed a larger proportion of effective pollinators. Existence analysis revealed a peak of mortality density in mid-May corresponding to an environmental sieve in the period following the establishment of plantlets. An updated diagnostic of the conservation status of C. grandis in China was formulated. The main threats to this species are catastrophic events, especially human impact activities (agriculture, hobbyists' collections, and infrastructure construction). Establishment of a monitoring program is proposed, and both in-situ and ex-situ strategies are recommended for effective conservation of C. grandis.

The Ratio of Auto- and Xenogamy inSilybum marianum

The Ratio of Auto- and Xenogamy in<i>Silybum marianum</i>