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Plant Adaptations.

posted Jun 16, 2015, 3:31 PM by Upali Salpadoru   [ updated Jul 16, 2016, 2:55 PM ]










Fig. 1. The leaves of this creeper are modified as pitchers to catch insects.

Pitcher plant-Nepenthus.



Although Plant adaptations could mean the changes that have taken place in forming various parts such as the root, stem and leaves etc. one may rightly consider the flattened structure of the leaf is an adaptation to receive the maximum amount of sunlight and the fact that roots grow into the soil is an adaptation to fix the plant as well as to search for  water.
In our study adaptations are limited to changes that have taken  place in plants due to the adverse conditions in the environment. For example plants growing in water are adapted to currents and the buoyancy of water. Land plants have strong stems to lift the foliage to light and air and a deeply penetrating root system to keep the plant erect.

Let us look at this phenomenon from an ecological point of view.

 

 

Adaptations

 

Normal functions

Land plants

Aquatic plants.

 

 

A typical specimen

Fig, Parts of a plant

A typical specimen

Fig, Parts of a sea weed.

Root

·        Keeps the plant fixed to soil.

·       Grow towards water and absorb water and nutrients. Hydrophorbic.

·       Store food.eg. yams.

·       Buttress roots and stilt roots as extra support in loose soil and to resist strong wind.

·         Reduced in size, as absorption is not a function.

·         Gives a strong attachment to rocks.

·         Usually they have air cavities or tubes.

Stem

·         To expose foliage to sun and air.

·         To conduct water and nutrients through Xylem.

·         To bring the synthesized food to roots for storage through phloem.

·         Breathing through lenticels.

·         Woody stem for strength. Trees.

·         Bark to protect even against bush fires.

·         Store food. Eg sugar cane, potato.

·         Store water. Eg. Succulents.

·         Flexible to resist the force due to water movement..

·         Usually they have air cavities or tubes.

·         Adjustable to changing water level.

Leaf

·         Synthesize food. Photosynthesis.

·         Breathing through stomata.

·         Un avoidable loss of water. Transpiration.

 

·         Surface area depend mainly on availability of water.

·         Many steps are taken to control transpiration.

·         Shape size and thickness can vary widely.

·         Some have to perform unexpected tasks such as catching insects. eg Pitcher plant, sundew.

 

·         Long and flexible.

·         Air bubbles present to lift them up to get sun light.

  • Tendrils coil round a support in climbing plants like gourds.

Flowers.

·         Sexual reproduction.

·         All floral parts vary in colour, shape and design.

·         Even blooming times vary to attract the exact pollinator.

·         Wind pollinated flowers produce a vast amount of male flowers.

·         Always above the water level.

Fruits

·         Dry fruits

·         Fleshy fruits.

Dry fruits

Small, not very attractive sometimes contain toxic substances.

Some have wings to be carried away by the wind.

Some dispersed by water. Gyrocarpus.

Fleshy fruits

Pleasant smell, attractive to get the animals to pick them.

 

 

Seeds

·         Carry the plant embryo

·         There is stored food.

·         Generally dispersed by wind and animals.

·         Some have a parachute mechanism for dispersal. Calotropis.

·         Some resort to an explosive mechanism. Balsam.

 



1. More about Aquatic Plants
    As the water can lift the plant up strong stems are absent. Even the leaves are flexible to survive water currents. Some have cavities or bubbles for air. Some plants can even be floating.
                  
                
    

 Vallisnaria                    Hydrilla                       Kelp - a sea weed.



Lotus Nelumbium under ground stem (rhizome) has tubes for air exchange.

A floating fresh water plant Pistia stratiotes. Water lettuce.
Mangrove swarms
  


Breathing roots , Pneumataphores in Avicinnia.







Xerophytes

These are plants growing in dry regions. They adapted to tolerate blazing sun and drought conditions. Some of the adaptations include shiny leaves to reflect light reduced surfaces to reduce evaporation. They store water either in fleshy stems or leaves. Some leaves are modified to thorns as a protective measure against herbivores.    










Opuntia

Euphorbia tirucalli.

Tropical Rain forest

These have almost the ideal conditions for the plants to grow. Bright sun shine for over 8.hous a day throughout the year, over 80% humidity to reduce evaporation and a thick mulch formed by the fallen leaves that keeps water like a sponge and supply all the essential nutrients as they decay due to bacteria, fungi etc. 

When the conditions become favourable every specie that happens to land there try to establish a colony. What happens then? Cut throat competition starts. One tree will try to grow taller to catch more sunlight another rapidly growing a thin stem will wrap round the giant climb up and spread over the canopy. Another seed will come either by the wind, or with the help of a bird and perch on a branch produce dangling roots to absorb water from humid air will mature and display a cluster of flowers to the flying insects for pollination.     





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