19.4–19.7: Hormones regulate growth and development.

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Plant hormones are chemical signals produced by plant cells that enable the plant to respond to environmental variables and that influence its growth and development.

Question 19.14

Some acacia plants in Africa and Central America have developed a mutualistic association with:

  • a) butterflies.
  • b) bats.
  • c) aphids.
  • d) caterpillars.
  • e) ants.

Question 19.15

Which plant hormone or group of hormones do grape-growers spray on their crop in order to get seedless grape plants to grow fruits that are as large as grapes with seeds?

  • a) gibberellins
  • b) ethylene
  • c) cytokinins
  • d) auxins
  • e) abscisic acid

Question 19.16

Which of the following is not a plant hormone?

  • a) auxin
  • b) abscisic acid
  • c) prolactin
  • d) gibberellin
  • e) cytokinin

Question 19.17

High concentrations of __________ stimulate root production.

  • a) gibberellins
  • b) cytokinins
  • c) auxins
  • d) ethylene
  • e) abscisic acid