Comparative Studies on Reproductive Mechanisms of Three Species in Globba (Zingiberaceae)

The characteristics of sexual and asexual reproduction of three species of Globba (G. barthei, G. schomburgkii, and G. lancangensis) those are native perennial herbs in Xishuangbanna, Yunnan Province of Southeast China were studied. Both G. barthei and G. schomburgkii mostly depended on bulbils for their reproduction, and the one year aged plants produced 16.46±3.56(mean±SD,N=60) and 14.25±3.63 (mean±SD,N=153) bulbils per ramet. No seed set were observed for the two species while by artificial selfing and crossing. The abnormal pollens (>98% of total pollens observed) in G. barthei and low pollen viability in G. schomburgkii (<12%) may be ascribable to no seed-set. For G. lancangensis, however, it mainly engaged in sexual reproduction with a seed-set ratios (seed/ovule ratios) of 64.5%±12.1% in the field (N=36) and produced relatively few bulbils (2.2±1.4 per ramet, N=184). G. lancangensis bears both male and hermaphrodite on same ramet, which is termed as andromonocy. There were no (signifi)-(cant) differences for the fruit-set ratios between hand-selfing and hand-crossing,but significant differences of seed-set ratios (seed/ovule ratios), which suggested that this plant might maintain the mechanism of self-incompatibility. Additionally, three species of Globba have the (ability) of clonal reproduction with underground stems. The corolla tuber length of three species differed significantly by the order: G. barthei>G. schomburgkii>G. lancangensis. All pollinators of three Globba we observed were definitely honeybees other than butterflies, and the latter was previously suggested by other authors. Megapis dorstata was the only pollinator for G. barthei, while M. dorstata, Nomia strigata and Xylocopa collaris visited G. G. schomburgki, M. dorstata and N. strigata were the main visitors for G. lancangensis. Three species have much longer corolla tuber comparing with the tongue length of three visitors. Nectar in G. barthei (during) a day can only reach the height of 3/4 corolla tuber length, which may prevent bee with short tongue (e.g., Nomia strigata) visiting the flowers. The flowers of G. schomburgkii produce large amount of nectar and nectar overflows the corolla tuber after 9:00 A.M., which make bees with different tongue length, can easily suck the nectar. Thus, the visitation of different bees appeared to be influenced by both corolla tuber length and the amount of nectar produced.