TROPISM NEXT TROPISM Plant growth in response to

TROPISM NEXT

TROPISM Plant growth in response to a stimulus (“tropo” – ”turn”) There are many types of tropisms : • Phototropism • Geotropism 3 main types • Thigmotropism • Hydrotropism • Chemotropism • Thermotropism NEXT

TROPISM Plant growth in response to a stimulus (“tropo” – ”turn”) There are many types of tropisms : • Phototropism – growth in response to light • Geotropism – growth in response to gravity • Thigmotropism – growth in response to touch • Hydrotropism – growth in response to water *Can be positive • Chemotropism – growth in response to chemical (towards stimulus) or negative (away stimuli from stimulus) • Thermotropism – growth in response to heat NEXT

PHOTOTROPISM (“Photo” – light) The growth response of a plant in response to light direction is called phototropism. Ex. Stems growing toward the window to get to the light NEXT

Why is phototropism important to a plant?

IMPORTANCE OF PHOTOTROPISM Enables leaves to be in the best position possible to receive adequate light for photosynthesis http: //www. darienps. org/teachers/otterspoor/botany/tropisms/Gra vitropismwlight. jpg NEXT

GEOTROPISM (“Geo” – Earth) Geotropism is the growth of a plant in response to gravity. NEXT

What is positive and negative geotropism?

Positive Geotropism It is the growth of a plant towards the center of the earth-down with gravity. Ex. roots growing down Negative Geotropism It is the growth of a plant away from the center of the earth-opposite from the pull of gravity Ex. stems grow up Positive Geotropism

Why is geotropism important to a plant?

IMPORTANCE OF GEOTROPISM • Pulls roots down to anchor a plant • Roots can get needed water and minerals if they stay in the soil NEXT

THIGMOTROPISM (“Thigmo” – “touch”) Thigmotropism is the growth of a plant in response to touch/contact. Photo by Christopher Meloche Tendrils on a sweet pea Vines growing on a wall or fence NEXT

SOME OTHER TYPES OF TROPISM NEXT

THERMOTROPIS Thermotropism is M the tendency of plants or other (“Therm” – “heat”) organisms to bend toward or away from heat. HYDROTROPISM (“hydro” – “water”) Ex. curling of Rhododendron leaves in Hydrotropism is the growth in response to water. Ex. roots growing toward response to cold temperatures. moisture Chemotropism (“Chemo” – chemical”) Chemotropism is movement caused by chemical stimuli. Ex. Growth of a pollen tube is always towards the ovules so that reproduction can occur NEXT

Photo/Geotropism: http: //plantsinmotion. bio. indiana. ed u/plantmotion/movements/tropism/t ropisms. html Thigmotropism http: //www. youtube. com/watch? v= y. MHm. U 3 e. Zs. Yk Corn plant growing: http: //www. youtube. com/watch? v=i. FCd. Ag e. MGOA&feature=related

Plant Responses & Hormones

Plant Hormones Hormone = Gr. “to excite” 1) active in small amounts 2) produced in one part of plant & transported to another for action 3) action is specific for that site

Each has a Multiplicity of Effects (hormones can cause different things to happen) Depending on site of action Developmental stage of plant Concentration of hormone

Auxins ◦ stimulate growth but too much inhibits growth ◦ functions: ◦ 1) root initiation, stem elongation ◦ 2) retard abscission (loss) of leaves & fruits. ◦ 3) stimulates cell differentiation ◦ 4) apical dominance

Gibberellins discovered due to a fungus Giberella which causes Japanese “foolish” rice seedling disease induces flowering stimulates growth by increasing cell size & numbers.

Effect of Gibberellin Seedless grapes are usually smaller than seeded grapes because the developing seeds produce another hormone, gibberellin, that promotes the fruits increase in size and sugar content. By spraying seedless grapes with gibberellins artificially, the farmer can produce large, marketable grapes.

Cytokinins 1) induces cell division (cytokinesis) 2) affects root growth & differentiation 3) stimulates germination 4) delays senescence (aging); the progression of irreversible change that eventually leads to death

Abscisic Acid 1) stimulates abscission 2) converts vegetative buds (active) to dormant buds 3) inhibits growth

Ethylene 1) promotes fruit ripening 2) stimulates production of cellulase

1. Tropism is a growth or turning movement of a plant in response to – a) A response b) A stimulus c) A reaction d) An effect

2. Which of the following tropisms is the same as geotropism? a. thigmotropism b. hydrotropism c. phototropism d. gravitropism

3. What benefit does positive geotropism provide for a growing plant?

4) Removal of the tip of a plant stimulates lateral growth AND the plant gets bushier, because the tip of a stem produces: A) auxins B) cytokinins C) gibberellins D) ethylene

5) Ripening of fruits, such as bananas, is hastened (sped up) by A) B) C) D) abiscisic acid cytokinin indoleacetic acid ethylene

Today’s Lab Today we will be studying the effects of tropism on germinated cucumber seeds. Materials needed ◦ ◦ ◦ Petri Dish Marker 3 seedlings Cotton Water

� Make sure the cotton is fluffy. � Take a photo of the prepared dish, then seal the petri dish around the perimeter. � Shoot � Root

Hypothesis – Will tropism have an effect on the growth of the seedlings? If so which types of tropism will be displayed? Will they be positive or negative?

Lab Report ◦ ◦ ◦ ◦ 1 -2 Pages Introduction Materials Procedure Results (Data) Conclusion http: //www. biologycorner. com/worksheets/labrepo rt. html