VOA科学技术2024--Study Reveals History, Travels of Baobab Tree

The baobab tree is a special thing to see. During the dry season, its leafless branches look like roots coming from a thick trunk. It appears as if someone took a tree from the ground, flipped¹ it on its head and put it back into the earth.

That is why the tree is sometimes called the "upside down tree."

Baobab trees grow in Madagascar, mainland Africa and Australia. The origins and history of the baobab have been something of a mystery. But a new study that looked at all eight recognized species helps tell the baobab's story.

The baobab originated in Madagascar about 21 million years ago. It reached the African continent and Australia sometime in the past 12 million years, researchers found. Madagascar, an island off Africa's southeastern coast, has a large ecosystem². It is home to many kinds of plants.

Two baobab lineages went extinct in Madagascar. But the lineages established themselves elsewhere, one in mainland Africa and one in Australia, the study showed.

It appears that baobab seed pods floated from Madagascar to mainland Africa, located about 400 kilometers to the west. The seeds also traveled to Australia, nearly 7,000 kilometers to the east.

"The plants almost certainly got to Africa and Australia floating on or with vegetation rafts," said plant expert Tao Wan³ of the Wuhan Botanical Garden in China. He is one of the writers of the study, which appeared recently in the publication Nature.

Wan added that the seeds were able to travel to Australia because of the Indian Ocean gyre, an oceanic current.

Baobab trees provide food, shelter and nesting places for wildlife, including bees, birds and various mammals. Their fruits also provide important nutrients⁵ and medicines for people. Baobab leaves can be eaten, too.

The trees produce large, sweet-smelling flowers. Their sugary nectar appeals to nighttime pollinators like fruit bats and hawk⁶ moths⁷. Their flowers also attract two kinds of primates⁸ -- lemurs in Madagascar and bush babies in Africa.

Ilia Leitch is a plant geneticist at the Royal Botanic Gardens Kew in London. He is also a study co-writer. He said baobabs can grow to be very large and live for thousands of years.

Their very large root systems "play an important ecological⁹ role, helping¹⁰ to slow down soil erosion and enabling nutrient⁴ recycling," he said.

Baobabs are a water source for local people during the dry season. But Africa's baobabs are at risk from elephant damage. The animals sometimes cut the tree trunks with their tusks¹² to get water.

Words in This Story

trunk - n. the thick main stem of a tree

origin - n. the point or place where something begins or is created

lineage - n. the people who were in someone's family in past times

pod - n. a long, thin part of some plants that has seeds inside

raft - n. a flat structure that is used for floating or sailing on water

pollinator - n. to give pollen¹³ from another plant of the same kind so that seeds will be produced

erosion - n. the gradual destruction of something by natural forces

enable - v. to make able to do or to be something

tusk¹¹ - n. a very long, large tooth that sticks out of the mouth of an animal

1 flipped   

轻弹( flip的过去式和过去分词 )； 按（开关）； 快速翻转； 急挥

参考例句：

• The plane flipped and crashed. 飞机猛地翻转，撞毁了。
• The carter flipped at the horse with his whip. 赶大车的人扬鞭朝着马轻轻地抽打。

2 ecosystem   

n.生态系统

参考例句：

• This destroyed the ecosystem of the island.这样破坏了岛上的生态系统。
• We all have an interest in maintaining the integrity of the ecosystem.维持生态系统的完整是我们共同的利益。

3 wan   

(wide area network)广域网

参考例句：

• The shared connection can be an Ethernet,wireless LAN,or wireless WAN connection.提供共享的网络连接可以是以太网、无线局域网或无线广域网。

4 nutrient   

adj.营养的，滋养的；n.营养物，营养品

参考例句：

• Magnesium is the nutrient element in plant growth.镁是植物生长的营养要素。
• The roots transmit moisture and nutrient to the trunk and branches.根将水分和养料输送到干和枝。

5 nutrients   

n.（食品或化学品）营养物，营养品( nutrient的名词复数 )

参考例句：

• a lack of essential nutrients 基本营养的缺乏
• Nutrients are absorbed into the bloodstream. 营养素被吸收进血液。 来自《简明英汉词典》

6 hawk   

n.鹰，骗子；鹰派成员

参考例句：

• The hawk swooped down on the rabbit and killed it.鹰猛地朝兔子扑下来,并把它杀死。
• The hawk snatched the chicken and flew away.老鹰叼了小鸡就飞走了。

7 moths   

n.蛾( moth的名词复数 )

参考例句：

• The moths have eaten holes in my wool coat. 蛀虫将我的羊毛衫蛀蚀了几个小洞。 来自《简明英汉词典》
• The moths tapped and blurred at the window screen. 飞蛾在窗帘上跳来跳去，弄上了许多污点。 来自《现代英汉综合大词典》

8 primates   

primate的复数

参考例句：

• Primates are alert, inquisitive animals. 灵长目动物是机灵、好奇的动物。
• Consciousness or cerebration has been said to have emerged in the evolution of higher primates. 据说意识或思考在较高级灵长类的进化中已出现。

9 ecological   

adj.生态的，生态学的

参考例句：

• The region has been declared an ecological disaster zone.这个地区已经宣布为生态灾难区。
• Each animal has its ecological niche.每种动物都有自己的生态位.

10 helping   

n.食物的一份&adj.帮助人的，辅助的

参考例句：

• The poor children regularly pony up for a second helping of my hamburger. 那些可怜的孩子们总是要求我把我的汉堡包再给他们一份。
• By doing this, they may at times be helping to restore competition. 这样一来, 他在某些时候,有助于竞争的加强。

11 tusk   

n.獠牙，长牙，象牙

参考例句：

• The wild boar had its tusk sunk deeply into a tree and howled desperately.野猪的獠牙陷在了树里，绝望地嗥叫着。
• A huge tusk decorated the wall of his study.他书房的墙上装饰着一支巨大的象牙。

12 tusks   

n.（象等动物的）长牙( tusk的名词复数 )；獠牙；尖形物；尖头

参考例句：

• The elephants are poached for their tusks. 为获取象牙而偷猎大象。
• Elephant tusks, monkey tails and salt were used in some parts of Africa. 非洲的一些地区则使用象牙、猴尾和盐。 来自英语晨读30分（高一）

13 pollen   

n.[植]花粉

参考例句：

• Hummingbirds have discovered that nectar and pollen are very nutritious.蜂鸟发现花蜜和花粉是很有营养的。
• He developed an allergy to pollen.他对花粉过敏。