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