蓝花西番莲种

形态

蓝花西番莲属草质藤本植物，各茎节上均长有卷须以作攀爬。善于攀爬，常可攀爬至树顶，遮盖阳光，但却因此而受人欢迎，常见偶然栽种于公园或庭园而作遮暗用途。随着植株长大，茎节上便会长出花苞，最后开花。

花的结构

不只是蓝花西番莲，大部分西番莲的花都是这个结构。第一层为三块苞片，第二层为五块萼片，萼片的外型极似花瓣，第三层为五块花瓣，第四层为由众多丝状裂片组成的副花冠。花朵正中便是雄蕊和雌蕊，雌蕊具三条柱头，柱头下垂，雄蕊共五枚。

Passiflora caerulea, the blue passionflower, bluecrown passionflower or common passion flower, is a species of flowering plant in the family Passifloraceae. It is native to South America and has been introduced elsewhere.

It forms a vigorous, deciduous or semi-evergreen tendril-bearing vine growing to 10 m (33 ft) or more. Its leaves are palmately lobed, and its fragrant flowers are blue-white with a prominent fringe of coronal filaments in bands of blue, white, yellow, and brown. The ovoid orange fruit grows to 6 cm (2 in) across.

The fruit is edible, but is sometimes described as having an unpalatable or unpleasant flavour. In South America, the plant is known for its medicinal properties, and is used by both the Toba and the Maka peoples.

Description

Passiflora caerulea is a woody vine capable of growing to 25 metres (82 ft) high where supporting trees are available. The leaves are alternate, palmately five-lobed (sometimes three, seven, or nine lobes), and are up to 10 centimetres (4 in) in length while being linear-oblong shaped. The base of each leaf has a flagellate-twining tendril 5–10 cm (2–4 in) long, which twines around supporting vegetation to hold the plant up.

The flower is complex, about 10 cm (4 in) in diameter, with the five sepals and petals similar in appearance, whitish in colour, surmounted by a corona of blue or violet filaments, then five greenish-yellow stamens and three purple stigmas. The fruit is an oval orange-yellow berry, 6 cm (2+1⁄4 in) long by 4 cm (1+1⁄2 in) in diameter, containing an average of 10 to 35 seeds.

While commonly used as an ornamental vine in tropical landscaping, it is an invasive, noxious weed that can take over native wildlife. Plants sometimes send underground shoots up to 15 feet from the mother plant.

Chemical constituents

Compared to P. incarnata, this plant contains higher amounts of the MAO-inhibitor harmine.

Etymology

The specific epithet caerulea means "blue" and refers to the blue coronal filaments.

Cultivation

Passiflora caerulea is widely cultivated as a wall-climber or as groundcover. It is a hardy species, able to survive winter temperatures as low as −10 °C (14 °F), although it requires a sheltered position facing south or west (in the Northern Hemisphere). It can become invasive, the twining shoots constantly appearing unless eradicated. It is the only Passiflora species that volunteers in California. It has gained the Royal Horticultural Society's Award of Garden Merit.

Cultivars

A number of cultivars have been produced from the species:

'Chinensis' (corona filaments paler blue)

'Constance Elliott' was raised by Lucombe, Pince & Co in Exeter, Great Britain in 1884. It has pure white, fragrant flowers; not as free-flowering as many other clones. It has also won the Award of Garden Merit from the Royal Horticultural Society.

'Pierre Pomie', a pale pink flower form

Uses

The fruit is edible to humans when ripe, but its flavour has been described as bland, undesirable or insipid. If allowed to fully ripen in a warm climate and fall naturally from the vine, it has a mild blackberry flavour, though with a lower sugar content than commonly eaten species.

A tea can be made of the flower or leaves; but the leaves contain tetraphyllin B and epi-tetraphyllin B, cyanogenic glycosides that liberate hydrogen cyanide when activated by enzymes. It is possible to boil away most of the cyanide.

In South America, the plant is known for its medicinal uses. It is used in both tisanes (herbal tea) and dietary supplements, as well as in marmalades, ice creams, syrups and beverages. It is also used by the indigenous Argentine Toba and Maka people.

Passiflora caerulea is often used as a rootstock, to which is grafted a scion of the edible P. edulis.

In culture

Passiflora caerulea is the national flower of Paraguay. Its intricate structure has generated Christian symbolism, each part representing a different part of the Passion of Christ.