Rhizophoraceae Pers.

Collaboration benefits multiple participants: mangrove forests
 

Several species of epiphytes, ants, fungi, and butterflies in mangrove forests provide benefits to each other through mutualism.

 
  "For instance, in [sic] Australian Myrmecodia plants, which may weigh several kilograms, have a bulbous stem honeycombed with tunnels occupied by the ant Iridomyrmex (and, in addition, a butterfly larva). Ants living in such 'ant-house' plants clearly gain protection: is there any advantage to the plant? Another myrmecophyte species, Hydnophytum formicarium, has specialised absorptive chambers. Ants deposit their debris here, and it has been demonstrated experimentally that when the colony is fed radioactively labelled Drosophila larvae radioactive compounds are absorbed into the plant. The relationship is therefore mutual: ants obtain shelter, and the plants a supply of scarce nutrients, particularly nitrogen. Saprophytic fungi growing in the ant galleries probably play a role in releasing soluble nutrients from the ant debris. To make the situation even more complicated, the ants also tend larvae of the butterfly Hypochrysops which feed on the tubers and leaves of the ant plant. An epiphytic plant therefore grows on a mangrove tree, accommodates ants, which tend butterfly larvae and supply nutrients to their host, aided by fungi: two plants, one or more fungi, and two animal species interacting (Huxley 1978; Janzen 1974)." (Hogarth 1999:58)
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Membranes desalinate water: mangrove
 

Mangroves extract salt from water via transpiration and filtering through membranes.

 
  "Nature did not refrain from using energy produced in the power stations of plants for other important functions of life. One example is the desalination of seawater by evaporation energy. At the edge of shallow coastal waters of tropical seas we find the luscious green of mangrove swamps. Mangroves can live on the saline water of the ocean, which destroys other green terrestrial plants. In some species of mangroves the sap is almost salt-free, though the roots are washed by sea water. They extract the salt by using the transpiration energy in the narrow capillaries of their roots to suck up the sea water and then filtering it through thin membranes in which the salt is detained." (Tributsch 1984:184)
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Leaves optimize internal state: mangrove
 

Leaves of mangroves minimize heat gain, enhance cooling, minimize water loss, and maximize photosynthesis by optimizing tilt angles and leaf size.

 
  "Parsimonious use of water leads to other problems. Photosynthesis proceeds most rapidly in Rhizophora at a temperature of 25°C, falling off sharply above 35°C. The optimal temperature is typical of the air temperature within a mangrove forest. However, to maximise photosynthesis a leaf must position itself broadside-on to the sun. Maximising incident light, unfortunately, also maximises heat gain, and the temperature of a leaf in this position rapidly rises to 10--11°C above air temperature. One way of reducing leaf temperature would be to increase the transpiration rate and lose heat by evaporation. Mangroves cannot afford to do this. Instead, they tend to hold their leaves at an angle to the horizontal, so minimising heat gain. The angle varies from about 75° in leaves with greatest exposure to the sun, to 0° (horizontal) in leaves in full shade. Cooling is also enhanced by leaf design. Small leaves lose more heat by convection than large ones: leaves exposed to full sunlight, and heat-stressed, are smaller than those that are shaded. Leaves also tend to be smaller in the more salt-tolerant species, where water economy must be more stringent (Ball 1988a; Ball et al. 1988). Such constraints on leaf morphology may explain the convergent similarity between the leaves of different mangrove species." (Hogarth 1999:17)
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Old leaves help remove excess salt: mangrove
 

The leaves of some mangroves aid in the removal of excess salt because salt is deposited in the old leaves that are about to be shed.

 
  "But the difficulties faced by a human being are as nothing compared with those with which the mangroves themselves must deal. Twice a day the tide rises to drown their roots, and then recedes to expose them to the air. Twice a day the water around them changes from salty as the tide comes in, to almost fresh as it goes out and the flow of the river water pushes back the sea. And every day, there is the danger that the slightest eddy in the current will remove mud that was deposited only yesterday…The trees' problem with sea water is due to the fact that when two solutions with differing concentrations of salt come into contact on either side of a membrane, they tend to equalise. So salt will enter the mangrove's root tissues and water within those tissues will flow out into the sea water. Some mangroves deal with this continuous inward flow of salt by carrying it away from their roots in their sap and depositing it in their older leaves that are soon due to be shed. Others have glands on their leaves which excrete it in solutions that are twenty times more concentrated than their sap, and even greater than it is in sea water." (Attenborough 1995:298)
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