Adaptations

Limitations to survival

• Dynamic environment including flood events and tidal flow

• High salinity due to ocean water entering river at high tide

• Lack of atmospheric oxygen due to the plant growing underwater

Adaptations

• Rhizomes - seagrasses send out 'runners' to hold the plants down in the soft substrate

• Salt tolerance gene - sea grasses have gene which allows them to have more sodium than the saltwater by storing it inside their cell vacuoles

• Air canals - some of the oxygen produced in the leaves during photosynthesis is transported down to the rhizomes and roots via air canals in the leaves

Limitations to survival

• Low oxygen due to water logging of soil when roots are inundated at high tide

• High salinity due to ocean water entering river at high tide

• Seeds removed by tides before anchoring into substrate

Adaptations

• Lenticels - pores on trunk are used to obtain oxygen, as roots are unable to absorb oxygen in waterlogged soil

• Excretion - leaves excrete excess salt which can be seen in the form of crystals on the upper surface

• Elimination - salts are directed to dying leaves which then drop off the plant

• Exclusion - salt is excluded from entering the mangrove by having significantly impermeable (not allowing fluid to pass through) roots which act as a filtration system

• Propagules - see Grey Mangrove adaptations

Limitations to survival

• High salinity due to ocean water entering river at high tide

• Low oxygen due to water logging of soil when roots are inundated at high tide

• Seeds removed by tides before anchoring into substrate

Adaptations

• 'Excretion', 'Elimination', 'Exclusion' - (see River Mangrove adaptations above).

• Pneumatophores - specialised root-like structures which stick up out of the soil. Lenticels (pores) on the surface of the pneumatophore allow oxygen to be absorbed when the pneumatophores are exposed at low tide and stored for use when inundated at high tide

• Propagules - to provide a better chance of survival, mangrove seeds begin sprouting roots while still attached to the parent plant. They then drop to the water below and float upright until their roots to take hold in the mud

Limitations to survival

• High salinity due to ocean water entering river at high tide

• Low oxygen due to waterlogging of soil

Adaptations

• Accumulation - salt entering the plant is directed to the extremities of the succulent (seen as red beads) which shrivel up and drop off when full of salt

• Remnant leaves - the leaves are reduced to tiny leaf sheaths, so that less water is lost through transpiration, thus reducing the need for the tree to absorb the salty water

• Succulence - the stems are succulent (spongy) to hold water and therefore reduce uptake of salty water

• Ion loading - samphire plants load their tissues with ions to maintain cell pressure, while excluding salt from their sap flow

• Low stomate density - the low amount of (stomates) pores from which plants lose water reduces water loss by transpiration

• Oxygen storage - cavities in the stem of the plant hold oxygen for use when the plant is inundated by water for short periods of time

Limitations to survival

• High salinity due to ocean water entering river at high tide

• Low oxygen due to water logging of soil

Adaptations

• Salt excretion glands - special balloon glands on the surface of the leaf accumulate salt. When a gland fills with salt it falls off and another gland takes its place.

• Avoidance - saltbush is not well adapted to grow in areas low in oxygen so it is unable to grow in the lower areas of the saltmarsh where waterlogging is frequent. This plant would not be able to survive the low levels of soil oxygen in the low tide zone where mangroves can grow

Limitations to survival

• High salinity due to ocean water entering river at high tide

• Low oxygen due to waterlogging of soil

• Competition for space and resources

Adaptations

• Remnant leaves - the leaves are reduced to tiny leaf sheaths, so that less water is lost through transpiration, thus reducing the need for the tree to absorb the salty water

• Avoidance - Sheoaks are not well adapted to grow in areas low in oxygen so it is unable to grow in the lower areas of the saltmarsh where waterlogging is frequent. This plant would not be able to survive the low levels of soil oxygen in the low tide zone where mangroves can grow

• Allelopathy - the release of chemicals that inhibit the growth and development of competing plants