Portulaca pilosa is a herbaceous plant occasionally found near seashores in Hong Kong. According to
Flora of Hong Kong, the species are found in sandy places near by the sea.
P. pilosa is featured by its terete leaves and clusters of long hairs in axils of leaves. These characteristics are very likely adaptations to survive in a dry environment. The clusters of long hairs may reduce the transpiration of young leaves emerging from a shoot. The terete leaves, which are commonly found in xerophytes in deserts, can reduce the surface area to volume ratio. The plant also has a visible, beautiful network of veins in the thick leaves supporting the survival of the cells.
P. pilosa, among with species such as
Sesuvium portulacastrum,
Scaevola hainanensis, Tetragonia tetragonioides,
Suaeda australis, and other plants living in the seashore all have thick leaves, waxy cuticle, and relatively small flowers. As the discussion in (
HKWildlife.net) suggests, this may be an example of convergent evolution in which various species adopt similar physiological features under similar survival pressures.
The photos below are taken on a hill in the New Territories. Interestingly, the population lives far from the seashore and besides a cement road. Given there are man made objects and construction going on near the site, my hypothesis is that the seeds of plant may be brought up in the delivery of construction materials.
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| Whole plant |
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| Shoot, showing leave veins and white hairs |
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| Pinkish flower, an ant seems to help pollinating it |
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Another flower
The structure at the right of the flower is a fruit with seeds gone |
