Mangroves are evergreen deciduous plants that have settled on tropical and subtropical coasts and have adapted to life in the conditions of constant ebbs and flows. They grow up to 15 meters and have bizarre root types: stilted (lifting a tree above water) and respiratory (pneumophores) sticking out of the soil, like straws, and absorbing oxygen.
Few plants would survive in salt water, but this does not apply to mangroves. They have developed filtration mechanisms. Water absorbed by their roots contains less than 0.1% salt. The remaining salt is secreted by the leaves through special leaf glands, forming white crystals on the surface.
The soil on which mangrove trees grow is always saturated with water, there is not enough oxygen in it. Under such conditions, anaerobic bacteria secrete nitrogen, phosphates, iron, methane, sulfides, etc., creating a specific smell of trees. Roots lacking oxygen, as has been said, absorb from the air, and nutrients from the soil.
The leaves of these plants are hard, leathery, juicy, bright green in color. Given the salinity of the soil and the lack of fresh water, they adapted to the limited loss of moisture. The leaves can regulate the degree of openness of stomata, which undergo gas exchange during photosynthesis, and rotate, avoiding hot sunlight.
Mangrove trees grow in belts, each of which is dominated by certain species. This is due to the frequency and duration of flooding, the nature of the substrate (sandy or silty), and the ratios of sea and fresh water (in
river mouths). The front line is occupied by rhizophores with blood-red wood, the color of which is determined by the high content of tannin. This species is under water about 40% of the time. They are followed by aviation, lagularia, etc.
As the mangrove tree itself is atypical, its fruits (seeds) are unusual. They are covered with airborne fabric, due to which they are able to swim for a certain time, changing their density if necessary. Many mangroves are viviparous. Their seeds, not separated from the tree, germinate. The seedling moves either inside the fruit, or through the fruit outward. By the time of separation, he is ready to eat independently due to photosynthesis.
Having disconnected from the tree (usually at low tide), the seedling falls and quickly fixes in the soil. Or carried away by water, possibly at a decent distance. It is so tenacious that it can wait up to a year for a favorable moment to take root.
Mangroves are a refuge and habitat for many organisms. Algae, oysters, barnacles, sponges, bryozoans need to attach to something when filtering food. Numerous roots are great for this. Tropical fish, arthropods, snakes live in water near the root systems. Hummingbirds, frigates, parrots, gulls and other birds settled in the branches of trees.
Mangrove trees, quickly forming thickets, protect the coast from erosion by sea waves. They, stepping on the sea, conquer new sites from him. Thickly interwoven roots retain the applied sludge, helping to drain the soil. The local population uses the conquered lands, creating plantations of coconut palms, citrus fruits and other crops.