Plant Leaves & Photosynthesis

Plant Leaves & Photosynthesis

3/2/21

Leaves

The energy that is captured and stored in the leaves of plants allows for the synthesis (making of) sugars, starches, and oils that feed almost all animals including, humans

What is a leaf?

Anatomy of Leaves

The structure of a leaf is optimized to absorb light & carry out photosynthesis

To carry out photosynthesis, they must be able to obtain carbon dioxide & water

Anatomy of Leaves (cont'd)

From the stem, a thin stalk called a petiole attaches a blade

A blade = thin flattened part of a leaf

The blade's shape and size is designed to maximize the collection of sunlight

Anatomy of Leaves (cont'd)

On each blade, veins are visible that run from the stem all throughout the leaf = vascular tissues that are directly connected to vascular tissues in stem

Multiple Choice

the stalk that joins a leaf to a stem; leafstalk.

• annual

• perennial

• petiole

• simple leaf

Multiple Choice

What is the name of the area where the leaves connect to the stem?

• Internode
• Compound
• Petiole
• Node

Anatomy of Leaves (cont'd)

The outer layer of leaf = epidermis protected by waxy cuticle to limit the loss of water through evaporation

The innermost layer = mesophyll, the area between leaf veins where photosynthesis occurs. Sugars produced during photosynthesis enter the veins

Mesophyll

• Palisade Mesophyll- closely packed cells that absorb light that enters the leaf

• Spongy Mesophyll- loose tissue w/ air spaces between cells that connect to stomata

• Stomata = small opening in the epidermis; allow exchange of CO2, O2, H2O in & out of leaf

Multiple Choice

The mesophyll is responsible for

• Photosynthesis 
• Gas exchange
• Storage
• All of the Above

Multiple Choice

The flat broad surface part of the leaf is called the _,

• Petiole
• Node
• Blade
• Mesophyll

Multiple Choice

Where do most plants produce their food?

• Stem

• Leaves

• Roots

• Seeds

Multiple Choice

The waxy, waterproof layer that covers most leaves is called the what?

• spore
• cuticle
• seed coat
• xylem

Multiple Choice

The is the "middle" of the leaf...

• Palisade Mesophyll

• Spongy Mesophyll

• Epidermis

• Cuticle

Multiple Choice

This layer is found just below the waxy layer if present, and is the "skin" of the leaf

• Cuticle

• Epidermis

• Mesophyll

• Stomata

Photosynthesis

The process in which autotrophs are able to capture & convert the energy from the sun to synthesize carbohydrates such as sugars & starches, that can be used as food

Reactant = Carbon Dioxide, water, sunlight energy

Products = sugar, oxygen, heat*

Light energy converted to chemical energy

Photosynthesis

Only a small fraction of water that plants bring to the leaves is used for photosynthesis. The rest is lost through transpiration

Transpiration = loss of water through leaves into the atmosphere (water cycle); happens so that gas exchange can take place in mesophyll layer of leaves

Helps to cool leaves on hot days, BUT can threaten leaf's survival if H2O is scarce (a.ka. "wilting")

Photosynthesis in Action

• Guard cells & Stomata

• Mesophyll

• chloroplast

• thylakoids

• chlorophyll

Factors that affect Photosynthesis

• Temperature (ideal range 0-35 Degrees Celsius)

• Light intensity (High light increases rate of photosynthesis)

• Availability to water (shortage of water can slow/stop photosynthesis)

Multiple Choice

When light intensity goes up, the rate of photosynthesis goes _______.

• up

• down

• at the same rate. It does not change.

Multiple Choice

What are the end products of photosynthesis?

• Carbon Dioxide and Water

• Glucose and Carbon Dioxide

• Oxygen and Glucose

• Water and Glucose

Multiple Choice

Photosynthesis produces Glucose for plants. This is a form of __________________________ for plants.

• Chemical energy

• Thermal energy

• Light energy

• Radiant energy