Pop-Quiz Define a negative feedback system Which organ produces the hormones that are used in regulation of blood glucose? Define Homeostasis?

answer A negative feedback system involves an original stimulus and the body reacting to return that stimulus back to a normal level Regulation of blood glucose involves two hormones produced by the pancreas

Plant Responses and Adaptations

Hormone- producing cells Target cells Movement of hormone Hormone Action on Plants A. Plant cells can produce hormones: which are chemical messengers that travel throughout the plant causing other cells called target cells to respond. B. In plants, hormones control: 1.Plant growth & development 2.Plant responses to environment Cells in one blooming flower signals other blooms using hormones to open.

Plant Hormones Hormones in plants are responsible for: Phototropism Geotropism Apical dominance Ripening of fruit abscission Plants are also in an environment that is constantly changing. They need to have a way to do this. Even though they do not have a nervous system plants do have hormones.

Plant cells will send signals to one another to tell them: 1.When trees to drop their leaves. 2.When to start new growth. 3.When to cause fruit to ripen. 4.When to cause flowers to bloom. 5.When to cause seeds to sprout. Leaf Drop Fruit Ripening Sprouting Corn Seeds Cactus Blooming Tree Budding

Plant hormones The main groups of plant hormones are: Auxins Gibberellins Cytokinins Abscisic acid ethylene

Auxins Auxins promote growth of new shoots, trigger positive phototropism and negative geotropism of shoots and are responsible for apical dominance (inhibition of growth of lower branches) Eg Indoleacetic Acid (IAA), it is responsible for Geotrophism

Gibberellins Gibberellins (GAs) are plant hormones that regulate growth and influence various developmental processes, including stem elongation, Initiates seed germination, dormancy, flowering, sex expression, and leaf and fruit senescence. plant hormones developmental processesdormancy flowering expressionsenescence

Cytokinins Cytokinins work in conjunction with Auxins to stimulate cell division and differentiation (cell reproduction). Cytokinins are synthesised in stems, leaves and roots

Abscisic acid Growth inhibiting hormone with actions opposite to those of auxins. Its roles include abscission of flowers fruits and leaves and control of stomatal movement. Inhibits growth Abscisic acid suppresses cell growth. It also promotes leaf senescence (towards death) which results in the colour changes of leaves in autumn before they are dropped from deciduous plants.

Ethylene causes Fruit to Ripen 1.Fruit tissues release a small amount of ethylene 2.Causes fruits to ripen. 3.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.

Plants responding to external environments Plants do not monitor internal environment but are sensitive to environmental stimuli such as: Light, gravity, temperature, touch, water, carbon dioxide. We have seen how they respond to these stimulus using hormones.

summary Hormones in plants are responsible for phototropism, geotropism, apical dominance, ripening of fruit, abscission. The main groups of hormones are Auxins, gibberellins, cytokinins, abscisic acid and Ethylene