Seeds Survive Various Conditions

a small mangrove plant, a few inches tall, grows in shallow water along a beach landscape with larger mangroves in backround

Biological Strategy

Mangroves

AskNature Team

Image: Asian Development Bank / Flickr / Some rights reserved

Protect From Loss of Liquids

Water is essential to life. Liquids, mostly water, make up 70 to 90% of all living systems, and the loss of even a small percentage can mean the difference between life and death. Living systems must maintain a proper liquid balance, which is especially difficult in dry conditions. To do so, they must control the movement of liquids across their boundaries. Living systems do this using structures or waterproof materials to prevent or slow liquid movement. For example, when humans receive a cut, they must limit blood loss. Scattered throughout the bloodstream are lens-shaped structures that serve to plug the wound.

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Protect From Temperature

Many living systems function best within specific temperature ranges. Temperatures higher or lower than that range can negatively impact a living system’s physiological or chemical processes, and damage its exterior or interior. Living systems must manage high or low temperatures using minimal energy, which often requires controlling responses along incremental temperature changes. To do so, living systems use a variety of strategies, such as avoiding high or low temperatures, removing excess heat, and holding heat in. Insulation is a well-known example of managing low temperatures by retaining heat using thick layers of hair, fur, or feathers to hold warm air next to the skin.

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Disperse Seeds

Plants disperse their seeds using a variety of mechanisms, including wind, rain, and attachment to animals. Seed dispersal can be important if plants growing too close together will compete for resources, such as nutrients and sunlight. Since plants are literally rooted in place, seed dispersal is also an important mechanism for expanding their range or reaching new environments.

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Flowering Plants

Clade Angiosperms (“receptacle seed”): Dandelions, oaks, grasses, cacti, apples

With 416 families containing some 300,000 known species, angiosperms are the most diverse group of plants, and they can be found around the globe in a wide variety of habitats. They are characterized by seeds that grow enclosed in ovaries, which are enclosed in flowers. The floral organs then develop into fruits of myriad kinds and dimensions, from simple seed casings on maples to elaborate fleshy growths like papayas. The oldest flower known from fossils, Montsechia vidalii, appeared during the Jurassic Period 130 million years ago. They are the primary food source for herbivorous animals, which in turn makes them the indirect food source for carnivores as well.

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Some species of mangrove seedlings enhance their chances of survival due to several characteristics: sharp spikes stick in the ground, photosynthesizing stem, and adaptations for both salty and fresh water.

“The aerial prop roots give adult trees considerable stability. But seedlings have more difficulty in getting a hold on the capriciously moving surface of the mud. Some species of mangrove, however, manage to plant their offspring with as much firmness as a gardener armed with a dibble. The seeds germinate while they are still attached to their parent. A long green spike develops that hangs vertically downwards. In some species it may measure as much as two feet. Eventually, it falls. If the tide is out, it may stab straight into the soft mud. Tiny rootlets then grow out from its flanks with great speed and within hours the young seedling may have established itself firmly enough to resist the swill of the returning tide…If the tide happens to be in when the seedling falls, then instead of rooting immediately, it travels. That may be riskier, for it may be swept out to sea and lost altogether. But potentially it is more beneficial for the species as a whole, for the youngster is taken away from its natal swamp where it would be competing with its parent and ferried to territory that may not yet have been colonised by mangroves. At first, it hangs vertically in the brackish water. But if it is carried beyond the estuary then the water becomes saltier and more buoyant so that the seedling begins to float horizontally. That may save its life. If the tender terminal bud, from which leaves will spring in due course, were exposed, unshaded in the tropical sun, it could easily over-heat, even scorch. Floating horizontally, however, it is continually lapped by water and kept cool. The flank of the long root benefits from being exposed along its length for it is green with and is able to photosynthesize. The food it manufactures keeps the whole root alive and growing and it can survive floating at sea for months. If eventually the capricious tides do carry it to another brackish estuary, then the buoyancy of the water is reduced and the young mangrove once again hangs vertically, ready to catch on the bottom of shallows which might be a suitable place to grow.” (Attenborough 1995:298-301)

Last Updated September 14, 2016

References

Book

The Private Life of Plants

21/08/1995 | David Attenborough

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