Unit 7--Plants Chapter 25 Plant Responses & Adaptations.
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Transcript of Unit 7--Plants Chapter 25 Plant Responses & Adaptations.
Unit 7--Plants
Chapter 25
Plant Responses & Adaptations
Plant Hormones
• Auxin = first discovered
• located in growing tips of roots/stems
• for stem elongation
• inhibits bud growth
• leaf & fruit drop
Plant Hormones
• Ethylene = for fruit ripening & drop or leaf & flower drop
Place fruits in a brown bag to trap ethylene gas release to speed up ripening
Plant Hormones
• Gibberellins = for seed germination, fruit development & stem elongation
Tropisms
• Growth response toward a stimulus
• Phototropism = toward light
• Ex: sunflower
Tropisms• Gravitropism (or geotropism)
• toward earth’s center
• Ex: roots (positive) & stems (negative)
Tropisms
• Thigmotropism =
• toward a support or something “touched”
• Ex: tendrils on a climbing vine
Modified Leaves
• Cactus spines
• Tendrils
• Carnivorous plants
Specialized Plants
• Parasitic plants
– Ex: mistletoe
• Epiphytes
– Ex: orchids, ball moss
Classification by life span
• Annuals =– entire life cycle
in one growing season
• Ex: tomato plant
Classification by life span
• Biennials – lives through two
growing seasons, separated by dormancy
• Ex: cabbage & carrot
Classification by life span
• Perennials =– live many years
and through many periods of dormancy
– Ex: trees, shrubs– Also, bluebonnets