(32b) Plant responses

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(32b) Plant responses by Mind Map: (32b) Plant responses

1. If anything causes a Reaction in an organism or in any of its parts (stimulus), the activity of a cell or organism as a result is called a response

1.1. Examples in plants

1.1.1. light > growth

1.2. Examples in animals

1.2.1. noise > movement hunger > feeding

1.3. Structures needed

1.3.1. A nerve and sense organ system (only found in Animals) Plants only have a chemical co-ordination system, which is a lot slower than our nervous system

1.3.2. Chemical or hormonal system (present in plants and animals)

1.3.3. A method of movement, which includes growth (present in plants and animals) In animals along with muscular and skeletal systems

2. Growth regulators (often called plant hormones)

2.1. Properties

2.1.1. Mainly produced in meristems

2.1.2. Active in very small amounts

2.1.3. Effects depend on concentration location in the plant

2.1.4. Interact with each other

2.2. Growth promoters

2.2.1. Auxin (i.e. IAA) Produced in the meristems (just behind the tip of the root and just behind the tip of the shoot root) Transported through the vascular system (xylem and phloem) causes Apical dominance (inhibits side branching) If apical bud is removed then side buds grow (bushier plant Causes cell elongation in stem (phototropism) and root (geotropism, at low c) Fruit formation (and inhibits fruit drop) May cause parthenocarpic fruit (if IAA is artificially applied to flowers before pollination occurs, the ovary enlarges and forms seedless fruit)

2.2.2. Uses of commercially prepared plant regulators Rooting powders Tissue culturing (growing cells outside the body on a sterile medium)

2.3. Growth inhibitors

2.3.1. Ethene Gas produced by ripe fruits Makes it possible to harvest fruit green, ripen it and sell it ripe (often only the surface is ripe)

3. Growth in plants

3.1. External factors

3.1.1. day length (>fruit, seed, flower formation)

3.1.2. temperature (>rate of enzyme reactions)

3.1.3. Light (provides Energy for photosynthesis to make food;

3.2. Tropism (trop>to turn): Growth response of a plant to an external stimulus

3.2.1. Either towards the stimulus (positive tropism) or away from it (negative tropism)

3.2.2. Different tropisms

3.2.3. The benefit of tropisms is that they help the plant to achieve the best growing conditions

3.3. Internal factors

3.3.1. growth regulators

4. Plant adaptions for protection

4.1. Anatomical protective features

4.1.1. Epidermis covered with a cuticle (prevent entry of pathogens and reduce water loss)

4.1.2. Needles formed by epidermis (protect against predators)

4.2. Chemical protective features

4.2.1. heat shock proteins (protect agains high temperatures)

4.2.2. Poisonous chemicals (protect agains predators (pic: poison ivy)