Changing Colorful Leaves and Photosynthesis

What do autumn leaves and ripening bananas have in common?

Photosynthesis Review Photosynthesis with the students: What’s needed? Light, CO2, and water What’s produced? Glucose, Sugars or carbohydrates, Oxygen

The Electromagnetic Spectrum Light we can see!

Chlorophyll A and B Absorbs energy from the sunlight to transform carbon dioxide and water into carbohydrates Chlorophyll is what gives plants their green color Two types of chlorophyll are found in the chloroplast of plants and green algae are chlorophyll a and b. Both chlorophylls absorb light most strongly in the red and violet parts of the spectrum. Green light is absorbed poorly. Thus when white light shines on chlorophyll-containing structures like leaves, green light is transmitted and reflected and the structures appear green. Chlorophyll A- has a more green-blue color Chlorophyll B-has a deep green color The only difference between these two is a slight variation in the chemical composition and structure

Carotene and Xanthophyll Yellow and orange accessory pigments found in plants Carotenoids which also participate in photosynthesis Present all year long Chloroplasts also contain carotenoids. These are also pigments with colors ranging from red to yellow. Carotenoids absorb light most strongly in the blue portion of the spectrum. They thus enable the chloroplast to trap are larger fraction of the radiant energy falling on it. Carotenoids are often the major pigments in flowers and fruits. The red of a ripe tomato and the orange of a carrot are produced by their carotenoids. In leaves, the carotenoids are usually masked by the chlorophylls. In the autumn, as the quantity of chlorophyll in the leaf declines, the carotenoids become visible and produce the yellows and reds of autumn foliage.

Seasons SUMMER Long hours of sunlight Good supply of liquid water Plants are busy making carbohydrates Plants storing food Plants growing WINTER Days are shorter Water is harder to come across Annuals, Perennials, Evergreens

Perennials Live for more than two years trees and shrubs, and herbaceous plants with soft, fleshy stems. Woody parts of trees and shrubs can survive the cold. The above ground parts of herbaceous plants (leaves, stalks) will die off Underground parts (roots, bulbs) will remain alive. In the winter, plants rest and live off stored food until spring. Annuals complete their life cycle in one growing season. Garden flowers, bulbs Die when winter comes, but their seeds remain, ready to sprout again in the spring Evergreens keep most of their leaves during the winter have special leaves, resistant to cold and moisture loss Pine, fir trees, holly may continue to photosynthesize during the winter as long as they get enough water

Summer to Fall As the bright green fades away, we begin to see yellow and orange colors. JUST LIKE AS THE CHLOROPHYLL DISSOLVES IN A GREEN BANANA TO REVEAL A YELLOW BANANA! Small amounts of these colors have been in the leaves all along. We just can't see them in the summer, because they are covered up by the green chlorophyll

Colors of Fall Reds and Purples Brown Maples, glucose is trapped in the leaves after photosynthesis stops. Anthocyanins pigments Sunlight and the cool nights of autumn cause the leaves turn this glucose into a red color. Brown - Oaks, due to wastes left in the leaves.