Structure of Plants

A. Functions of Roots 1.Anchor & support plant in the ground 2.Absorb water & minerals 3.Hold soil in place Fibrous Roots Root Hairs

B. Root Types 2. Tap Roots – larger central root reaches deep water sources underground Ex. Trees, Carrots, & Dandelions 1. Fibrous Roots: branching roots hold soil in place to prevent soil erosion Ex. Grasses Tap Root

1.Root Hairs: increase surface area for water & mineral absorption 2.Meristem: region where new cells are produced 3.Root Cap: protects tip of growing root C. The Structure of a Root Root Hairs Meristem Root Cap Xylem Phloem

A. Functions of Stems 1.Support system for plant body 2.Transport system carries water & nutrients 3.Holds leaves & branches upright Each light and dark tree ring equals one year of annual growth. Light rings for fast spring growth, dark for slow summer growth. Smaller rings tell of past droughts that have occurred. Looking at the picture to the left: What years had the most rain? What years experienced the worst drought?

A. Functions of Leaves 1.Main photosynthetic organ 2.Broad, flat surface increases surface area for light absorption 3.Have systems to prevent water loss Stomata open in day but close at night or when hot to conserve water waxy cuticle on surface 4.System of gas exchange Allow CO 2 in and O 2 out of leaf Elephant Ear Plant

B. Leaf Structures 1.Cuticle: waxy layer; covers upper surface Protects leaf against water loss 2.Veins: transports water, nutrients and food Made of xylem and phloem 3.Mesophyll: contains cells that perform photosynthesis b/c they contain Chloroplasts. 2 Guard Cells Surround each Stoma M e s o p h y l l (Opening) Leaf Cross-Section Veins Cuticle Stoma Stoma- singular Stomata-plural

More Plant Parts… Guard Cells 4.Guard cells: cells that open and close the stoma 5.Stomata: openings in leaf’s surface; when open: GAS EXCHANGE: Allows CO 2 in & O 2 out of leaf TRANSPIRATION: Allows excess H 2 O out of leaf Stoma

Stoma Open Stoma Closed Guard Cells Stoma Function of Stomata Guard Cells CO 2 O2O2 H2OH2O What goes in? What goes out? What process involves using CO 2 and H 2 O releasing O 2 as a waste product? Photosynthesis What is the plant using this process to make? Carbohydrates-glucose If the plant needs water for photosynthesis, why is water coming out of the stoma?

Stoma Open Stoma Closed Guard Cells Function of Guard Cells Guard Cells These stomata (leaf openings) naturally allow water to evaporate out. Why would the plant close stomata with guard cells? Prevent excess water loss through transpiration. (conserve water) So what is the point of having stomata? Allow gas exchange for photosynthesis

A average size maple tree can transpire 200 liters of water per hour during the summer. Transpiration is the #1 driving force for pulling water up stems from roots. C. Plants find a use for Transpiration 1.Transpiration: loss of excess water from plant leaves 2. Significance: B A a.Transpiration causes enough pressure to help pull water (& required nutrients) up stem from roots. b.As part of the water cycle, trees transpire water back into the atmosphere. c.Transpiration provides much of the daily rain in rainforest.

Chapter 25 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.

C. 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

D. Ethylene causes Fruit to Ripen 1.Fruit tissues release a small amount of ethlyene 2.Causes fruits to ripen. 3.As fruit become ripe, they produce more and more ethlyene, accelerating the ripening process. Ethylene released by apples and tomatoes causes fruit to age quickly.

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

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