19.4–19.7
19.4–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.

Q

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

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

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

Which of the following is not a plant hormone?

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

High concentrations of __________ stimulate root production.

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