current position:Home>It is green. Why is it called mangrove?

It is green. Why is it called mangrove?

2022-06-24 04:13:41Popular science in China

At high tide , Xiamen Coastal Wetland Park will stage a romantic scene —— The trees on the three islands were submerged by the sea , Only the canopy of some higher tree species is exposed to the water , Like a piece “ Sea forest ”, If you look down from a high altitude , It turns out that this is a painting composed of love and five stars .


Xiamen xiatanwei torch bridge , Mangrove landscape of coastal wetland park

( picture source : School of environment and ecology, Xiamen University )

But seeing this , Some inland friends may be curious : There are trees that can still live in the sea , Even grow and reproduce normally , It's amazing ?

you 're right , This magical tree is mangrove .


The leaves are clearly green , Why is mangrove ?

To be specific , Mangrove generally refers to a kind of woody plants growing in the intertidal zone of tropical and subtropical coasts , Not a species . As for why it is called mangrove , seeing the name of a thing one thinks of its function , Not that its leaves are red , It's because in some cases these plants have a red appearance .

Many members of mangrove plants belong to the mangrove family (Rhizophoraceae), The bark of these mangrove species contains a substance called tannin , It will be oxidized to red after contact with air , thus , It's not “ mangrove ” Did you? ?


Tannins in mangrove bark are oxidized to red when exposed to air

picture source

Mangrove plants can be divided into true mangrove plants and semi mangrove plants according to their characteristics . True mangroves generally refer to species that are only distributed in the coastal intertidal zone , Semi mangroves are those that can grow in the intertidal zone , Species that can also live on land . But whether it is true mangrove or semi mangrove , They have one thing in common , Can survive the periodic flooding of seawater .


The tide rose , Over the mangroves picture source : The author shot

This is unimaginable for many plants . Everybody knows , If you pour salt water on the plants at home , In a few days our love flowers may “ die ”. The high salinity and anoxic environment caused by periodic flooding of intertidal seawater is very harsh for plants , More Than This , tropic 、 The high temperature and scorching sun at the seaside in subtropical areas is also a great challenge for them .

The magic of mangroves is that they have evolved many interesting characters , Such as specific root structure 、 Special breeding methods to adapt to such harsh environment .


Not only does it take root , Will “ spit ” salt ?

Let's take a look at the peculiar root structure of mangrove plants , Common root types of mangrove plants include : Pillar root 、 Shoot like root 、 Surface root 、 Buttress root 、 Finger root, knee root, etc . According to these names , It should be easy to imagine the general appearance of these special roots , These special roots contain abundant aerenchyma , It can help mangrove plants to exchange gas better .


The supporting roots of mangrove plants picture source

Besides , In order to cope with the high salt environment , Mangrove plants have also developed a series of measures to avoid salt and secrete salt , On the one hand, it can protect cells from high salt by controlling the intracellular salinity below the threshold , On the other hand, salt is excreted from the body through salt glands and other organs .


Salt secretion of mangrove plants picture source


Viviparous plants , Does it really exist ?

Compared with the above tips , Mangroves also have a wonderful way to cope with the extreme environment in the intertidal zone ! Speaking of “ Viviparity ”, You probably won't find anything special , After all, this is too common for mammals . But it's not hard to believe , In mangroves , There are also so-called “ Viviparity ” The phenomenon .

Of course , This viviparity is not another viviparity , But the common ground is that the offspring begin to develop on the mother , It will not leave the mother until it is mature . This kind of “ Viviparity ” It also exists in rice , But it's called suimeng , The rice seeds on the panicle will germinate immediately under suitable environmental conditions , This will have a negative impact on Agriculture , The seeds all germinated , What else shall we eat ?

Back to business , For many mangrove plants ,“ Viviparity ” Phenomenon refers to the germination of their seeds before they leave their mother , Then it grows into a rod-shaped hypocotyl , Finally, it falls from the parent body to the silt in the intertidal zone .


The hypocotyl of mangrove plants picture source

Viviparity is a special reproductive mechanism derived from mangrove plants in response to intertidal environment , For mangrove plant survival 、 The importance of reproduction and expansion is self-evident . Compared to adult individuals , The survival of seeds in harsh environments is undoubtedly more challenging , Now , If it can germinate on the mother body , Depending on the nutrients of the mother body, it develops to a certain stage , You can add these “ seeds ” Our survival rate .


Hypocotyl rooted in intertidal zone picture source : reference

and , The development of seeds into hypocotyls on the mother body can not only increase these “ Baby mangrove ” Our survival rate in the intertidal zone , They can also be covered with a solid layer when crossing the ocean “ Armor ”.

The hypocotyl will accumulate a certain amount of tannins during development , It is the mangrove tree mentioned above “ Turn red ” The material , Tannins are natural preservatives , When the hypocotyl is floating along the ocean current , Tannins can protect the hypocotyl , Make it not easy to be corroded by seawater . Have to say , Mangroves are really a magical group , In the long time of evolution , They have successfully and tenaciously coped with the adjustment brought about by the difficult environment .


Can the coast guard still hold on ?

Because of reclamation 、 Improper development and other reasons , since 21 Since the 20th century , The global mangrove area is declining year by year , The world food and agriculture organization (Food and agriculture organization of the united nations, FAO) Global forest resources assessment report (2015) Show :2015 In, the global mangrove area was 14,752 kha, a 2010 Decreased in 3.98%.


1990-2015 Changes in mangrove area in the world in picture source : Self made by the author

At home , Due to aquaculture 、 Real estate development 、 Port and wharf facilities construction and other factors , The growth territory of mangroves has been invaded , More Than This , The aquatic 、 Sewage discharge and water eutrophication caused by livestock and poultry breeding have also caused damage to mangroves to a certain extent .

Fortunately , As the ecosystem service value of mangroves has been paid more and more attention , The state has strengthened the protection of mangroves , And ecological restoration of mangroves , The area of plantation is also increasing year by year .

Mangroves have gone through thousands of years , Seawater flooding at high tide , Like a green island in the water ; When the tide is low , with twisted roots and gnarled branches , Standing like a coast guard in the intertidal zone , Who would wish “ Forest in the sea ” Just disappear ?

Produce : The popular science of China

author :EVEE School of life sciences, Peking University

Supervise the manufacture of : China Science Fair

reference :

Alongi, D. M. (2012). Carbon sequestration in mangrove forests. Carbon management, 3(3), 313–322.

Amos, W., & Harwood, J. (1998). Factors affecting levels of genetic diversity in natural populations. Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences, 353(1366), 177–186.

Hoque, R. R., & Balachandran, S. (2019). Handbook of environmental materials management. C. M. Hussain (Ed.). Cham, Switzerland: Springer.

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