黄独种

形态

多年生缠绕藤本。地下有球形或圆锥形块茎。叶腋内常生球形或卵圆形珠芽，大小不一，外皮黄褐色。

心状卵形的叶子互生，先端尖锐，具有方格状小横脉，全缘，叶脉明显，7-9条，基出；叶柄基部扭曲而稍宽，与叶片等长或稍短。夏秋开花，单性，雌雄异株，穗状花序丛生。果期9-10月，有小毒的生物碱，对于肝细胞有毒作用，会导致肝损伤，可溶于水，须适当加工去除后再煮熟后才可食用。

分布

分布于大洋洲、朝鲜、非洲、印度、日本、缅甸、台湾以及江苏、广东、广西、安徽、江西、四川、甘肃、云南、湖南、西藏、河南、福建、浙江、贵州、湖北、陕西等地，生长于海拔300米至2,000米的地区，多生于河谷边、山谷阴沟或杂木林边缘，目前尚未由人工引种栽培。

在美洲也可发现其踪迹，对美洲而言是外来种，有机会在农田大量繁殖，攀上高树争取日照。英文别名为air potato。

别名

黄药（本草原始），山慈姑（植物名实图考），零余子薯蓣（俄、拉、汉种子植物名称），零余薯（广州植物志、海南植物志），黄药子（江苏、安徽、浙江、云南等省药材名），山慈姑（云南楚雄）

文化

唐朝诗人杜甫在同谷（今甘肃成县）时，饥寒交迫，挖黄独充饥，诗中提到“黄独无苗山雪盛”，后世不解其义，改黄独为“黄精”。

Dioscorea bulbifera (commonly known as the air potato, air yam, bitter yam, cheeky yam, potato yam, aerial yam, and parsnip yam) is a species of true yam in the yam family, Dioscoreaceae. It is native to Africa, Asia and northern Australia. It is widely cultivated and has become naturalized in many regions.

Description

Dioscorea bulbifera is a perennial vine with broad, alternate leaves, and two types of storage organs. The plant forms bulbils in the leaf axils of the twining stems, and tubers beneath the ground. These tubers are like small, oblong potatoes.

Air potato can grow extremely quickly, roughly 20 centimetres (8 in) per day, and eventually reach over 18 metres (60 ft) long. It typically climbs to the tops of trees and has a tendency to take over native plants. New plants develop from bulbils that form on the plant, and these bulbils serve as a means of dispersal. The aerial stems of air potato die back in winter, but resprouting occurs from bulbils and underground tubers.

When it twists around another plant or some sort of support, it always twists counterclockwise, unlike the winged yam Dioscorea alata.

The primary means of spread and reproduction are by the bulbils. The smallest bulbils make control of air potato difficult due to their ability to sprout at a very small stage. The vine produces small white flowers; however, these are rarely seen when it grows in places such as Florida. The fruits are capsules.

Distribution and habitat

It is native to Africa, Asia and northern Australia. It is widely cultivated and has become naturalized in many regions (Latin America, the West Indies, the southeastern United States, and various oceanic islands).

It has been observed growing in habitats such as along forest edges, roadsides, as well as other environments with mesic, loamy sand.

As an invasive species

In some places, such as Florida, it is considered a noxious weed because of its quick-growing, large-leafed vine that spreads tenaciously and shades out any plants growing beneath it. The bulbils on the vines sprout and become new vines, twisting around each other to form a thick mat. If the plant is cut to the ground, the tubers can survive for extended periods and send up new shoots later.

The leaf beetle Lilioceris cheni has been studied and employed as an agent of biological pest control for the plant, with releases in 2012.

Toxicity

Uncultivated forms, such as those found growing wild in Florida, can be poisonous. These varieties contain the steroid diosgenin, which is a principal material used in the manufacture of a number of synthetic steroidal hormones, such as those used in hormonal contraception. There have been claims that even the wild forms are rendered edible after drying and boiling, leading to confusion over actual toxicity.

Uses

Some varieties produce edible tubers and are cultivated as a food crop, especially in West Africa. The tubers of edible varieties often have a bitter taste, which can be removed by boiling. They can then be prepared in the same way as other yams, potatoes, and sweet potatoes.

Air potato has been used as a folk remedy to treat conjunctivitis, diarrhoea, and dysentery, among other ailments.

D. bulbifera is highly important to the Tiwi people of Australia, who use it in an important ceremony called kulama. During the ceremony, the tubers are ritually cooked, and eaten on the third day.

It is known as the up-yam in Nigerian Pidgin English, since the plant is cultivated more for its bulbils than for its tubers.