Flowering phenology and wind-pollination efficacy of heterodichogamous Juglans mandshurica (Juglandaceae).
OBJECTIVE
Heterodichogamy differs from normal dichogamy, in that it involves two mating types (protogyny and protandry) that occur at a 1 : 1 ratio in a population. Flowering phases of the two mating types are synchronized and reciprocal, which was considered to ensure between-type outcrossing. This study aims to quantify the flowering pattern and pollination efficacy in Juglans mandshurica, a wind-pollinated heterodichogamous tree.


METHODS
The pattern of flowering phenology was monitored within individual trees and pollen traps were used to measure air-borne pollen loads during the spring in 2003 and 2004. Pollen longevity was determined by staining technique. Also a pollen supplementation experiment was performed in 2004 to assess pollen limitation of fruit production.


RESULTS
There was no overlap between sexual functions within individual trees. Flowering periods of the two mating types were reciprocal and synchronous in both 2003 and 2004. Air-borne pollen loads were large, and protogynous and protandrous individuals each produced a high pollination peak, consistent with the two blooming periods. Maximum pollen longevity was about 4 h for protandrous individuals, and 3 h for protogynous individuals. Pollen supplementation did not increase fruit production in either protogynous or protandrous individuals.


CONCLUSIONS
Heterodichogamous flowering in Juglans mandshurica effectively avoids selfing, promotes between-type outcrossing, and leads to efficient pollination in a natural population.
Bai
Wei-Ning
WN
Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering and Institute of Ecology, Beijing Normal University, Beijing 100875, China.
Zeng
Yan-Fei
YF
Liao
Wan-Jin
WJ
Zhang
Da-Yong
DY
D001947:Breeding; D035264:Flowers / Q000033:anatomy & histology / Q000254:growth & development / Q000502:physiology*; D031324:Juglans / Q000033:anatomy & histology / Q000254:growth & development / Q000502:physiology*; D010507:Periodicity; D011058:Pollen / Q000502:physiology; D012098:Reproduction / Q000502:physiology