Plants Part 2

Photosynthesis and Respiration Taking in Raw Materials 1. food, oxygen produced 2. Movement of Materials a. Take in sunlight, water, carbon dioxide. Give off oxygen. b. Leaves are where gas exchange occurs.

Leaf Structure and Function a. cuticle waxy outer covering b. epidermis top layer of the leaf c. stomata openings in the leaf ;water is lost through stomata d. guard cells cells on either side of the stomata that cause them to open and close e. water enters through roots f. palisade layer just underneath the epidermis. Food is made here. g. spongy layer below the palisade layer

Chloroplasts and Plant Pigments a. chloroplasts take in sunlight b. chlorophyll green pigment inside the chloroplast c. green color of the tree leaves is due to green light energy being reflected from chlorophyll d. In the fall, chlorophyll in the leaves breaks down and leaves change color as the other pigments become visible.

Food-Making Process Photosynthesis Light-Dependent Reactions process in which plant chlorophyll traps light energy and uses the energy from light to make sugars (food). produces nearly all the food for all other forms of life on Earth Light-Dependent Reactions require light chlorophyll traps sunlight during light- dependent and uses it to make food.

Light-Independent Reactions Importance of Photosynthesis does not require light Importance of Photosynthesis produces food/glucose/C 6 H 12 O 6 releases oxygen / O2 As much as 90% of our oxygen comes from photosynthesis.

The Breakdown of Food Respiration – series of chemical reactions that breaks down food molecules and releases energy. changes energy into a food form that all cells can use Aerobic respiration – occurs in the mitochondria of plants and animals with one or more cells and a nucleus (uses oxygen)

Aerobic Respiration Reactants (start with)= Products (results) = Glucose - C 6 H 12 O 6 Oxygen- O2 are taken in. Products (results) = Carbon dioxide(CO2), Water vapor(H2O), and Energy (ATP) are released. Importance of Respiration a. changes food energy into a form the cells can use b. returns carbon dioxide to the atmosphere.

Comparison of Photosynthesis and Respiration Almost reverse equations of each other Photosynthesis occurs only in cells with chloroplasts. (Producers ex. Plants) Any cell with mitochondria can undergo respiration (plants and animals)

Plant Responses What are plant responses? Response Stimuli (stimulus) involves movement either toward or away from the stimulus.  Stimuli (stimulus) external comes from outside the organism internal comes from inside the organism All living things respond to stimuli.

Tropism movement caused by a change in growth; can be positive or negative. Light When plants respond to light, causes a plant to grow toward the source of light. Positive Gravity Downward growth of roots – positive. Upward growth of stem – negative.

Plant Hormones Plant Hormones control the changes in growth of a plant. Examples: (ethylene /auxins / gibberellins / cytokinins ) Ethylene stimulates the ripening process Auxin controls plant growth toward the light Synthetic (man-made) auxins are used as fertilizers; also used as weed killers in high doses Gibberellins mixed with water and sprayed on plants to stimulate plant stems to grow and seeds to germinate (fertilizers) Cytokinins sprayed on stored vegetables to keep them fresh longer

Photoperiodism plant’s response to the number of hours of daylight and darkness. Long-day plants – require less than 10-12 hours of darkness to flower. spinach, lettuce, beets Short-day plants – need 12 or more hours of darkness to flower strawberries, ragweed Day-neutral plants – may have a range of hours of darkness dandelions, roses