How plants respond to the environment

Explain why plants need to respond to their environment in terms of the need to avoid predation and abiotic stress

  • To cope with changing conditions and avoid abiotic stress

  • To maximise photosynthesis by obtaining more light, more water, and more minerals

  • To avoid herbivory and grazing

  • To ensure the germination of its seeds in suitable conditions

Responding to herbivory

Physical

Thorns

Barbs

Spikes

Inedible tissues

Hairy leaves

Stings

Chemical

Tannins

  • Types of phenols

  • Bitter taste dettering herbivory

  • Toxic to insects

Alkaloids

  • Very bitter N compound

  • Acts as drugs affecting animals metabolism. e.g. caffeine, nicotine

  • Can be toxic to insects and fungi

Terpenoid

  • Produced by plants as essential oils

  • Toxic to insects and fungi

  • Can be used as insect repellent e.g. lemongrass (citronella)

Pheromones

  • Chemical made by an organism which affects social behaviour of other members of the same species

Pheromone

Effect of pheromone

Maple tree

Pheromone causes CALLOSE (polysaccharide/physical barrier) to form when the tree is under attack from insects.

Causes response in adjacent branches and on adjacent trees.

Apple tree

When under attack from spider mites, pheromone released and attracts predatory mites to destroy apple tree pest.

Cabbages

Attacked by the caterpillars of the cabbage white butterfly. Pheromone released that attracts parasitic wasp. Wasp lays eggs in caterpillar which then gets eaten alive.

Different pheromones can be released by cabbage if under attack by a different pest e.g. green fly and different parasitic wasp is attracted