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 .

 picture

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 .

01

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? ?

 picture

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

picture source :environment.bm

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 .

 picture

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 .

02

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 .

 picture

The supporting roots of mangrove plants picture source :asknature.org

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 .

 picture

Salt secretion of mangrove plants picture source :ocean.si.edu

03

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 .

 picture

The hypocotyl of mangrove plants picture source :mangroveactionproject.org

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 .

 picture

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 .

04

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%.

 picture

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.

copyright notice
author[Popular science in China],Please bring the original link to reprint, thank you.
https://en.fheadline.com/2022/175/202206240051420901.html

Random recommended