Pollination ecology and pollination system of Impatiens reptans (Balsaminaceae) endemic to China.
OBJECTIVE
China is one of the centres of geographical distribution of Impatiens L. Studies of the pollination ecology of this genus in China have, until now, been unreported. Impatiens reptans, a species endemic to China, was studied. The aims were to examine the pollination ecology and pollination system of this species, to compare its pollination ecology with other Impatiens species growing in Sumatra and Japan, and to discuss possible reasons for its limited distribution.


METHODS
The pollination ecology of I. reptans was studied by carrying out continuous observations within three naturally growing populations. Its pollination system was studied using different pollination methods, marking and counting pollen grains, assessing pollen viability and observing pollinator behaviour.


RESULTS
The flowering phase of the protandrous I. reptans lasted for 89 d. The life span of an individual flower was 3.6 d. Primary pollinators were honey-bees and bumble-bees. Secondary pollinators were diurnal hawk moths and butterflies. Bombus briviceps and Bombus sp. were nectar gatherers. The mean nectar sugar concentration was 29.5 %, and the mean value of sucrose/glucose + fructose was 0.82. The proportion of seed set ranged from 0.857 to 0.873. Distances that seeds were ejected ranged from 0.58 to 1.17 m. Percentage seed germination under controlled conditions was 23.1. Pollen viability was highest on the day of anthesis and thereafter decreased. Ratios of pollen : ovules ranged from 958.8 to 970.6.


CONCLUSIONS
Impatiens reptans reproduces by means of cross-pollination. Its dependence on a specialized habitat, a narrow environmental niche, a low percentage of seed germination, and habitat loss could be reasons for its limited distribution and endemism.
Tian
Jianping
J
College of Life Sciences, Hunan Normal University, Changsha 410081, China.
Liu
Keming
K
Hu
Guangwan
G
D000818:Animals; D001516:Bees; D002080:Butterflies; D002470:Cell Survival; D002681:China; D017753:Ecosystem; D035264:Flowers / Q000502:physiology; D005843:Geography; D029069:Impatiens / Q000502:physiology*; D011058:Pollen / Q000166:cytology / Q000502:physiology*; D012098:Reproduction; D012621:Seasons