Obviously green, why is it called mangroves?

Whenever the tide is up, Xiamen Binhai Wetland Park will perform a romantic scene -the woods on the three islands are submerged by the sea, and only some higher tree species of forest crown expose the water, like a "sea forest". It will be found that this is a painting composed of love and five -star.

On the side of the torch bridge of Xiamen Xiatanwei, the mangrove landscape of Binhai Wetland Park (Picture Source: Xiamen University Institute of Environment and Ecology)

But seeing this, some inland friends may be curious: there are trees that can live in the sea, and even grow and reproduce normally. Is this too amazing?

That's right, this magical tree is mangroves.

Ye Zi is obviously green. Why is Manga?

Specifically, mangroves refer to a class of wooden plants that grow in the tide of tropical and subtropical coasts, not a certain species. As for why it is called a mangrove, as the name suggests, it does not mean that its leaves are red, but because such plants will show a red appearance in some cases.

Many members of mangrove plants belong to the Rhizophoraceae. The bark of these mangrove species contains a substance called tannins, which will be oxidized after contacting the air. Is the "red tree"?

Manga plant bark is oxidized into red picture source after the air in the air in the bark of Mangrove Plants: Environment.bm

Mangrove plants can be divided into real mangrove plants and semi -mangrove plants according to their characteristics. True mangrove plants generally refer to species that are only distributed in coastal tide bands, while semi -mangroves are species that can grow in the tide belt and can survive on the land. But whether it is a real mangrove plant or a semi -mangrove plant, they have a common feature that can survive in the periodic flooding environment of seawater.

The tide rises, the source of the mangrove picture source: the author shoots

This is unimaginable for many plants. Everyone knows that if you pour salt water at the family, our love flowers may be "fragrant and jade" within a few days. The high -salt and hypoxia environment brought by the cyclical flooding of the tide is very harsh for plants. Not only that, the high temperature and scorching sun by the sea of ​​tropical and subtropical areas is also a great challenge for them.

The magic of mangrove plants is that it has evolved many interesting traits, such as the root system structure and special reproduction method to adapt to such a harsh environment.

Not only are you rooting, but you also "vomit" salt?

Let's take a look at the peculiar root structure of mangrove plants. The root types of common mangrove plants include: pillar roots, bamboo shoots, surface roots, plate -shaped roots, finger -shaped roots, and knee -shaped roots. Based on these names, everyone should easily imagine the general appearance of these special roots. These special root systems are rich in ventilation tissue, which can help mangrove plants better exchange gas.

Source of the pillar roots of mangrove plants: asknature.org

In addition, in order to cope with the high salt environment, mangrove plants also derived a series of measures to avoid salt and salt. On the one hand, by controlling the internal salinity of the cells to protect the effect of high salt under the threshold, on the other hand Deduate salt into the body through organs such as salt glands.

Salt of mangrove plants Source: Ocean.si.ed

Is the viviparous plant really existed?

Compared with these tricks above, mangrove plants also have a wonderful birthday to respond to extreme environments in the tide belt! Speaking of "viviparous", everyone may not think there is anything special, after all, this is too common for mammals. But it is not difficult to believe that there is also a so -called "viviparous" phenomenon in mangrove plants.

Of course, this viviparity is not the other, but the common point is that the descendants start to develop on the mother's body, and the development of the maternal body will not be separated from the mother. This kind of "viviparous" also exists in rice, but it is called Suomeng. The rice seeds on the ears will germinate immediately. This will have a negative impact on agriculture. ah?

Back to the topic, for many mangrove plants, the phenomenon of "birth" refers to their seeds that they have germinated when they leave their mother's body, and then grew into stick -shaped embryo axes. Finally, the mother's body dropped to the tide room. In the mud.

Manga plant embryo axis source: mangRoveactionproject.org

As a special reproduction mechanism derived from the environment of mangrove plants, the importance of the survival, reproduction and expansion of mangrove plants is self -evident. Compared with adult individuals, the survival of seeds in harsh environments is undoubtedly more challenging. At this time, if you can germinate on the mother and rely on the nutrient development of the mother to a certain stage, the survival rate of these "seeds" can be increased.

Embryoscopic axis picture of rooting in the tide: reference

Moreover, the development of seeds on the mother's body can not only increase the survival rate of these "mangrove babies" in the tide, but also allow them to put a strong layer of "armor" when crossing the ocean.

The embryo axis will accumulate a certain amount of tannins during the development, which is the material that makes the mangrove "red" that mentioned earlier. Tannin is a natural preservative. When the embryo axis fluttering along the ocean, Tannin can give it to given The embryo axis must be protected, so that it is not easy to be corroded by seawater. I have to say that mangrove plants are really a magical group. In the long evolutionary time, they are tough and successfully cope with the adjustment of the difficult environment. Can the coastal guards continue to adhere to?

Due to reclamation and improper development, since the 21st century, the global mangrove area has been declining year by year, and the Food and Agriculture Organization of the United National (2015) shows that: 2015 global Mangrove area is 14,752 kHa, a decrease of 3.98%compared with 2010.

1990-2015 World Mangrove area changes in the picture source: Author self-made

In China, due to factors such as aquaculture, real estate development, port and pier facilities, the growth territory of mangroves has been occupied. Caused a certain degree of destruction.

Fortunately, as the value of mangrove ecosystem services has been paid more and more attention, the state has strengthened the protection of mangroves and ecological restoration of mangroves, and the area of ​​artificial forests has increased year by year.

After tens of millions of years, the seawater is flooded during the tide, like a green island in the water; when the tide is decrealed, the roots are wrong, like the coastal guards standing in the tide belt. Who wants the "forest in the sea" to disappear?

Produced: Popular Science China

Author: EVEE Peking University School of Life Sciences

Producer: China Science Popularization Expo

references:

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.

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