plant diseases

• What can infect plants?

  Pathogens
• How do pathogens spread between plants?

  Through soil, water, vectors, and sap
• What is one way pathogens spread through water?

  In the soil or water they grow in
• What are vectors in the context of plant pathogens?

  Insects that carry pathogens
• How can sap contribute to the spread of pathogens?

  By landing on a wound of another plant
• How do fungal spores spread?

  Through the wind
• What is one way pathogens can enter plants?

  Through the stomata
• What virus infects tobacco plants?

  Tobacco mosaic virus (TMV)
• Which plants are affected by TMV?

  Tobacco, tomatoes, and peppers
• How is TMV transmitted between plants?

  By contact between plants or contaminated items
• What part of the plant does TMV infect?

  The chloroplasts of plant leaves
• What effect does TMV have on photosynthesis?

  It reduces the plant's ability to photosynthesize
• What visible changes occur in leaves infected by TMV?

  Leaves change color and develop a mosaic pattern
• What happens to the glucose production in plants infected by TMV?

  It decreases, affecting growth and yields
• What measures should farmers take to control TMV spread?

  • Dig up and destroy infected plants
  • Wash hands after handling infected plants
  • Wash tools with detergent or bleach
  • Rotate crops in contaminated fields for two years
• How have plant scientists addressed TMV resistance?

  • Selective breeding
  • Genetic engineering
  • Producing resistant crop varieties
• What is the external layer of dead cells on plants called?

  Thick bark
• How does thick bark protect plants?

  It forms a physical barrier against infection
• What is the function of the cellulose cell wall in plant cells?

  Acts as a barrier against infection
• What additional substance can plants add to their cell walls for strength?

  Pectin
• What is the purpose of callose in plants?

  To repair breaks in the cell wall
• What do leaves have that prevents infection by bacteria and fungi?

  A thick waxy cuticle
• What type of chemicals do some plants produce to repel insects?

  Repellent chemicals
• What is the function of insecticides produced by some plants?

  To kill insects that transmit pathogens
• What type of compounds do some plants produce to kill bacteria?

  Antibacterial compounds
• What do some plants produce to kill fungi?

  Antifungal compounds
• What type of chemicals can some plants produce that are toxic?

  Toxic chemicals
• What are the physical and chemical defenses of plants against pathogens?

  Physical defenses:

  • Thick bark
  • Cellulose cell wall
  • Pectin in cell wall
  • Callose for repairs
  • Waxy cuticles on leaves

  
  

  Chemical defenses:

  • Repellent chemicals for insects
  • Insecticides to kill insects
  • Antibacterial compounds
  • Antifungal compounds
  • Toxic chemicals
• What bacterium causes crown gall disease in plants?


  Agrobacterium tumefaciens
• How does crown gall disease affect plants?

  It causes tumor development like cancer
• Where do tumors often appear in infected plants?

  In the stems or roots
• What does crown gall disease restrict in plants?

  Movement of sucrose and amino acids
• Can many plant species be infected by Agrobacterium tumefaciens?

  Yes, many plant species can be infected
• What does Agrobacterium tumefaciens transfer to the infected plant cell?

  Some of its own DNA
• How can scientists confirm crown gall disease in plants?

  By testing the DNA of infected plants
• What must farmers do to control crown gall disease?

  • Dig up and destroy infected plants
  • Wash hands after handling infected plants
  • Wash tools with detergent or bleach
  • Rotate crops in contaminated fields for two years
• What fungus causes barley powdery mildew?


  Erysiphe Graminis
• What does barley powdery mildew cause on infected leaves?

  A fluffy white growth
• In what type of climate is powdery mildew common?

  Cooler, damper climates
• What happens to the plant's ability to photosynthesize due to powdery mildew?

  It stops making chlorophyll