TROPISM NEXT

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

NEXT 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 Chemotropism – growth in response to chemical stimuli Thermotropism – growth in response to heat TROPISM Plant growth in response to a stimulus (“tropo” – ”turn”) *Can be positive (towards stimulus) or negative (away from stimulus)

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

Why is phototropism important to a plant?

IMPORTANCE OF PHOTOTROPISM NEXT Enables leaves to be in the best position possible to receive adequate light for photosynthesis vitropismwlight.jpg

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

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 Negative Geotropism Positive Geotropism

Why is geotropism important to a plant?

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

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

SOME OTHER TYPES OF TROPISM NEXT

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

Photo/Geotropism: u/plantmotion/movements/tropism/t ropisms.html Corn plant growing: eMGOA&feature=related Thigmotropism - yMHmU3eZsYk

 Hormone  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

 Depending on site of action  Developmental stage of plant  Concentration of hormone

◦ 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

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

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.

 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

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

 1) promotes fruit ripening cellulase  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)abiscisic acid B) cytokinin C)indoleacetic acid D)ethylene

 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 ◦ rt.html