Plant Adaptations

     I. Adaptation =genetic changes in a group of organisms over time due to natural selection.  Heritable trait for survival in a particular niche.
        A. Environment can be biotic or abiotic
        B. Universal pressure to adapt
        C. Phenotypic variation (non-genetic) or Genotypic variation  (genetic, heritable)

 You will see most of the following examples of plant adaptations in the Adaptations Lab Exercise.  Otherwise, there are great pictures in your textbook:
    Plant adaptations
        Plant root adaptations:
            1. Adventitious roots = roots arising from non-root origins
                a) Prop roots = absorb water and minerals and supports the shoot system. (corn, mangrove tree)
            2. Edible roots: storage of carbohydrates and water. (carrots and sweet potato)
            3. Parasitic roots = relationship between two species in which one benefits while the other is harmed.  (mistletoe, indian pipe)
            4. Contractile roots = pull the shoot tight to the soil surface.  (dandelion and water hyacinth)

        Plant Stem adaptations:
            1. Rhizomes = underground perennial (all year round) stems.  (lily, various ferns)
            2. Tubers = enlarged terminal portions of underground rhizomes. (potato)
            3. Corms = a swollen underground stem base that is modified into a mass of storage tissue. (Gladiolus)
            4. Stolons = above ground horizontal stems, also called runners.  (strawberry plant)
            5. Thorns originate from the axils of leaves.  Function to protect the plant from predators
            6. Succulent, photosynthetic stems store water.
            7.  Parasitic stems strangle other plants.

        Plant leaf adaptations:
            1. Spines = modified leave (various cactuses)
            2. Prickles = modified clusters of epidermal cells (rose stems)
            3. Tendrils = modified leaves that wrap around things and support the shoots
            4. Bulb = an underground mass of fleshy storage  leaves.  (onion)
            5. Some leaves produce plantlets that develop into entire plant  (Kalanchoe plant)
            6. Insectivorous plants (Venus’ fly trap, sundews, pitcher plant)

        Plant adaptations to environmental extremes:
            1. Drought  = dry atmosphere or soil
                a) Xerophytes = plants that grow successfully in very dry climates. Thick cuticle. Leaves conserve/store water.
            2. Flooding  = water table is above the soil surface
                a) Gas exchange (O2 for respiration in the roots) cannot take place since soil air pockets are filled with water
                b) Adventitious roots and aerenchyma cells (cells with wide open spaces) allow O2 to move into the plant for respiration to occur.  (Rice)
            3. Saline (salty) soils.
                a) Halophytes = are salt tolerant plants found near ocean bays etc.
                b) Glycophytes = non-salt tolerant plants.
            4. Heavy metal soils

    II. Coevolution = when two different species interact so closely that evolution in one group causes evolution in another.
        A. Ways in which two organisms from different species can interact
            1. Parasitism: benefits one organism, detrimental to the other organism.  (herbivores, pathogens)
            2. Commensalism: benefits one organism but neutral to the other organism. (epiphytes)
            3. Mutualism or symbiosis: both organisms benefit
        B. Examples of symbiosis
            1. Coral and algae: coral gets sugar from algae photosynthesis; algae gets P, N, and protection from coral
            2. Lichen = fungus + green algae.  Fungus gets sugar from algae photosynthesis; algae gets minerals/water from fungus
            3. Ants and the acacia tree
            4. Microorganisms that interact with plant roots forming symbiotic relationships:
                a) Nitrogen-fixing bacteria on legume roots: bacteria receive sugars from plant; plant receives fixed nitrogen from bacteria. (soybeans, sweet peas)
                b) Mycorrhizae: root + fungal symbiotic relationship in plant roots.  Fungus receives sugars from plant; plant receives phosphate and water from fungus. (Orchids)