Pollination biology of an invasive weed Ipomoea cairica (Convolvulaceae) in Guangdong Province, China

Abstract

During May to July, 2006 and April to May, 2007, we studied pollination biology in Ipomoea cairica, an invasive weed in Guangdong Province, China. Ipomoea cairica is a perennial creeping or climbing herbaceous vine, blooming all year round in Guangdong. The flowers gathered in cymes, with a purple or bluish purple bell-formed corolla. The petals unfolded at about 4:30-5:20 and closed at 17:40, lasting for about 12 hours. The proximity of the stigma and anthers during flowering period facilitated the transfer of self-pollen. The mean volume of nectar per flower was 5.82±2.47 μL (n=10), with a sugar concentration of 41.03±6.52% and an amino acid concentration of ca. 0.042mg/mL. During anthesis, both pollen viability and stigma receptivity remained at a high level (＞90%). The mean P/O ratio was 4,778.18±264.58 (n=10). Carpenter Bees (Xylocopa sp.) were considered as effective pollinators, while flies and butterflies were occasional visitors. Ipomoea cairica is self-incompatible as determined by an absence of fruit set in the flowers following controlled hand self-pollination, producing fruits and viable seeds only after cross-pollination.