雅思听力背景资料：Passion Fruit
雅思听力此前也考查到过关于某种植物或水果，比如香蕉的种植和栽培，这样的部分，大部分都是大家比较熟悉的事物，但这次考查的passion fruit究竟为何物，很多同学一点概念都没有，英汉词典的解释为西番莲果，西番莲的一种可食果实。好像还不是能够比较全面的了解这究竟是个什么东东。笔者查阅了大量的原版外文资料，总结了一下passion fruit的方方面面。
Common Names： Passion Fruit， Granadilla， Purple Granadilla， Yellow Passion Fruit
The passionfruit is a vigorous， shallow rooted， perennial vine that climbs by means of tendrils. There are two types of passionfruit. They are the yellow passionfruit （Passiflora edulis forma flavicarpa） which is suited to tropical conditions， and the purple passionfruit （Passiflora edulis forma edulis） which grows best under sub-tropical conditions. The yellow passionfruit is tolerant to most of the soil borne pests and diseases that affectthe purple type， and is more prolific， bearing larger， heavier fruit with more juice， which has a higher acid content than the purpletype. The flavour of the purple type is preferred over that of the yellow type.
Origin： The purple passion fruit is native from southern Brazil through Paraguay to northern Argentina. It has been stated that the yellow form is of unknown origin， or perhaps native to the Amazon region of Brazil， or is a hybridbetween P. edulis and P. ligularis . Cytological studies have not borne out the hybrid theory. In Australia the purple passion fruit was flourishing and partially naturalized in coastal areas of Queensland before 1900. In Hawaii， seeds of the purple passion fruit， brought from Australia， were first planted in 1880 and the vine came to be popular in home gardens.
Adaptation： The purple passion fruit is subtropical and prefers a frost-free climate. However， there are cultivars that can take temperatures into the upper 20's （°F） without serious damage. The plant is widely grown in California as far north as San Jose， the Monterey Bay Area and the San Franciso Bay Area. The vines may lose some of their leaves in cool winters. The roots often resprout even if the top is killed. The plant does not grow well in intense summer heat. The yellow passion fruit is tropicalor near-tropical and is much more intolerant of frost. Both forms need protection from the wind. Generally， annual rainfall should be at least 35 inches. Passion fruit vines make good container specimens but require maintenance. They perform well indoors.
Growth Habit： The passion fruit is a vigorous， climbing vine that clings by tendrils to almost any support. It can grow 15 to 20 ft. per year once establishedand must have strong support. It is generally short-lived （5 to 7 years）。
Flowers： A single， fragrant flower， 2 to 3 inches wide， is born at each node on the new growth. The bloom， clasped by 3 large， green， lifelike bracts， consists of 5 greenish-white sepals， 5 white petals and a fringelike corona of straight， white-tipped rays， rich purple at the base. It also has 5 stamens with large anthers， the ovary and triple-branched style forming a prominent central structure. Purple passion fruit is self-fruitful， but pollination is best under humid conditions. The flowers of the yellow form are perfect but self-sterile. Carpenter bees are the most efficientpollinator， much more so than honey bees. Wind is ineffective because of the heaviness and stickiness of the pollen. The flowers can also be hand pollinated.
Fruit： The nearly round or ovoid fruit， 1-1/2 to 3 inches wide， has a tough rind that is smooth and waxy and ranging in hue from dark purple with faint， fine white specks， to light yellow or pumpkin-color. Within is a cavity more or less filled with an aromaticmass of double walled， membranous sacs containing orange-colored， pulpy juice and as many as 250 small， hard， dark brown or black， pitted seeds. The unique flavor is appealing， musky， guava-like and sweet/tart to tart. The yellow form has generally larger fruit than the purple， but the pulp of the purple is less acid， richer in aroma and flavor， and has a higher proportion of juice （35-38%）。 Numeroushybrids have been made between purple and the yellow passion fruit， often yielding colors and other characteristic intermediate between the two forms. The vine， especially the yellow form， is fast-growing and will begin to bear in 1 to 3 years. Ripening occurs 70 to 80 days after pollination
Pest and Disease Control
Pests and diseases may attack plants as early as the nursery stage. Caterpillars and slugs may attack the plants， while fungi may cause damping-off and loss of plants. Slugbait should be spread around seedling or a liquid slug control could be incorporated into the fungicide drenches （benomyl） for the control of damping-off. An insecticide is sprayed at the recommended rate every two to four weeks for caterpillarcontrol. Both insect and fungal problems in passionfruit could be controlled through proper cultural practices and chemical sprays.
Harvesting
A passionfruit orchard may have a life span of 3-5 years. There are two major seasons of production， June to August and November to January. Fruits are harvested when they have dropped to the ground. Green or immature fruits should not be picked off the vine as they will not ripen， they will also be off flavored and have a higher concentration of cyanogenic glycosides （a toxin produced by the vine）。 Fruits should be collected 2 to 3 times per week.
Processing
Passion fruits are processed into juices， which are sold either in single strength or as frozen concentrates. The passion fruit juice is also used in the production of cordials， alcoholic beverages， ice creams， and confectionery and mixed fruit blends.
考题中考查到passion fruit的生长地点，产量，生长气候，价格等问题，以选择题和填空题为主，难度颇大，比如涉及到addictive-free， socio-economic effects 等概念，对于词汇量比较少，知识面又窄的同学来说确实难度不小。平时切实需要多阅读，扩大自己的知识面，才能在考试中不心慌，不着急。