Plant Responses and Adaptations Slide # 16 Plant Responses and Adaptations

Hormone Action on Plants Hormone-producing cells Target Movement of hormone Plant cells can produce hormones which are chemical messengers that travel throughout the plant causing other cells called target cells to respond. In plants, hormones control: Plant growth & development Plant responses to environment Cells in one blooming flower signals other blooms to open using hormones.

Plant cells will send signals to one another to tell them: When to drop their leaves. When to start new growth. When to cause fruit to ripen. When to cause flowers to bloom. When to cause seeds to sprout. Leaf Drop Tree Budding Fruit Ripening Cactus Blooming Sprouting Corn Seeds

There are 5 major classes of hormones Gibberellins Cytokinins Oligosaccharins Abscisic Acid (ABA) Ethylene

Gibberellins Are produced in the apical meristem. They promote stem growth. Gibberellins also increase the starch uptake of the embryo, stimulating the development of vascular tissue.

Cytokinins Cytokinins promote cell division and cell differentiation. They also delay the aging of fruit and leaves.

Oligosaccharins Stimulate plants to produce antibiotics in response to attack by fungi or bacteria.

Abscisic Acid (ABA) Is a growth inhibitor and is mainly manufactured in mature leaves. ABA inhibits the growth of germinating seeds Growth of buds Plant stems and blocks the uptake of CO2 by controlling leaf stomata

Ethylene causes Fruit to Ripen Fruit tissues release a small amount of ethylene Causes fruits to ripen. As fruit become ripe, they produce more and more ethylene, accelerating the ripening process. Ethylene released by apples and tomatoes causes fruit to age quickly.

Adaptations: Plant Tropisms 1. Tropism: the way a plant grows in response to stimuli in the environment. Phototropism: growth response to light -Plants bend towards light b. Geotrophism: growth response to gravity -plant roots grow down with gravity, shoots (stems) grow up against gravity and out of the soil. c. Thigmotropism: growth response to touch -vines grow up around trees, Venus flytrap closes when leaves are touched

Geotropism Thigmotrophism Geotropism Phototropism What type of tropism is shown in these pictures? Geotropism Phototropism Thigmotrophism Geotropism Phototropism