Slide 1 Structure of Plants

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

B. Root Types Slide 3 Tap Root 1. Fibrous Roots: branching roots hold soil in place to prevent soil erosion Ex. Grasses 2. Tap Roots –larger central root reaches deep water sources underground Ex. Trees, Carrots, & Dandelions

C. The Structure of a Root Slide 4 Root Hairs Root Hairs: increase surface area for water & mineral absorption Meristem: region where new cells are produced Root Cap: protects tip of growing root Phloem Xylem Meristem Root Cap

A. Functions of Stems Support system for plant body Slide 5 Support system for plant body Transport system carries water & nutrients Holds leaves & branches upright Looking at the picture to the left: What years had the most rain? What years experienced the worst drought? 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.

Need for transport systems Plants need sugars and water to stay alive Water needs to travel from the roots to the leaves Sugars need to travel from the leaves to the rest of the plant

Xylem Hollow dead tubes Water and minerals transported in an upwards direction Made of lignin Very strong so help support the plant

Phloem Transports sugar around plant Made of living cells Companion cells provide the energy for the tube cells. The end walls of the tube cells have pores through which food is transported from cell to cell in the form of dissolved sugars

A. Functions of Leaves Main photosynthetic organ Slide # 6 Main photosynthetic organ Broad, flat surface increases surface area for light absorption Have systems to prevent water loss Stomata open in day but close at night or when hot to conserve water waxy cuticle on surface System of gas exchange Allow CO2 in and O2 out of leaf Elephant Ear Plant

Helps to catch more light energy Structure Wide Helps to catch more light energy Thin Help get carbon dioxide from bottom to top of leaf for photosynthesis

B. Leaf Structures Leaf Cross-Section Slide # 7 Leaf Cross-Section Cuticle: waxy layer; covers upper surface Protects leaf against water loss Veins: transports water, nutrients and food Made of xylem and phloem Mesophyll: contains cells that perform photosynthesis b/c they contain Chloroplasts. Cuticle Veins Mesophyll Stoma (Opening) 2 Guard Cells Surround each Stoma Stoma- singular Stomata-plural

cells that open and close the stoma More Plant Parts… Slide # 8 Guard cells: cells that open and close the stoma Stomata: openings in leaf’s surface; when open: GAS EXCHANGE: Allows CO2 in & O2 out of leaf TRANSPIRATION: Allows excess H2O out of leaf Guard Cells Stoma

Leaf structure Greener on top CO2 gets in here

Leaf diagram – palisade layer Most chlorophyll CO2

Leaf cell - palisade Position? Upper surface of leaf Features? Box shape Chloroplasts Function? Photosynthesis

Gas exchange Leaves are designed to allow carbon dioxide to get to the main chlorophyll layer at the top of the leaf They have small holes called stomata on the under surface Each hole is open & closed by 2 guard cells

Leaf diagram – stoma and guard cells

Stoma position

Stoma is a small hole Its size is controlled by 2 guard cells closed open

Stoma function is for gas exchange in the leaf oxygen Guard cell Provided plant is photosynthesising Carbon dioxide

Stomata open and close at different times of the day When it is light the plant needs CO2 for photosynthesis so the stoma open At night (darkness) they close

Gas exchange

Function of Stomata Slide # 9 What process involves using CO2 and H2O releasing O2 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? Guard Cells Guard Cells What goes out? O2 H2O CO2 What goes in? Stoma Open Stoma Closed Stoma

Function of Guard Cells Slide # 10 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 Guard Cells Guard Cells Stoma Open Stoma Closed Guard cells open by inflating with extra water. They do this by pumping K+ ions into the cell, which causes water to rush in via osmosis to diffuse the high ion concentration.

C. Plants find a use for Transpiration Slide # 11 Transpiration: loss of excess water from plant leaves 2. Significance: Transpiration causes enough pressure to help pull water (& required nutrients) up stem from roots. As part of the water cycle, trees transpire water back into the atmosphere. Transpiration provides much of the daily rain in rainforest. A B 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.