Plant Physiology Transpiration The evaporation of water through

Plant Physiology

Transpiration ● The evaporation of water through plant leaves and stems (usually through the stomata) ● It cools the plant and by moving water maintains the flow of nutrients and manufactured food from the root to the top and back

Transpiration ● Plants transpire more when: ○ ○ ○ The soil has adequate moisture, When windy and hot When humidity is low ● Water movement in plants is pulled up by the forces of cohesion and adhesion not pushed up by the roots

Photosynthesis ● Center of leaf are food-making cells that contain chloroplasts ○ ○ The green color comes from chlorophyll These cells manufacture food ● The process by which carbon dioxide and water in the presence of light energy are converted to sugar and oxygen

Photosynthesis ● The beginning of the food chain for ALL living things on earth 6 CO 2 + 6 H 2 O + light energy= C 6 H 12 O 6 + 6 O 2 carbon dioxide+water+light energy= glucose(sugar)+ oxygen

How Does Photosynthesis Work? • Chlorophyll uses the energy to split water molecules, H 2 O, during the first phase of the photosynthetic reaction. • Oxygen atoms from water molecules bond to form O 2. The O 2 escapes through the stomata into the atmosphere. • Hydrogen atoms from the water molecule are incorporated into sugar molecules as the process continues in CO 2 fixation.

How Does Photosynthesis Work? • During the CO 2 fixation phase of the photosynthetic reaction, energy in the form of ATP and NADPH is used to form sugars. • Carbon dioxide enters through the stomata and is available to the chlorophyll in the cells.

How Does Photosynthesis Work? • The CO 2 combines with hydrogen from the water molecule. • Two forms of sugar, glucose and fructose (C 6 H 12 O 6), are assembled. • Although they both have the same formula, the molecular structures differ.

How Does Photosynthesis Work? • Glucose and fructose fuel plant growth. • They are the source of energy for the plant’s life processes. • All live cells in the plant benefit as the sugars are transported through the phloem to the rest of the plant. • The simple sugars can also be combined to form a more complex sugar: sucrose (C 12 H 22 O 11).

How Does Photosynthesis Work? • The sugar molecules may be processed further to form starch and cellulose. • These are huge molecules, resulting from the bonding of thousands of glucose molecules. • Starch serves as the principle way in which food is stored for plants. • When needed, it is easily broken down into glucose or converted into other plant products by plant enzymes.

How Does Photosynthesis Work? • The cellulose is applied to cell walls for strength and rigidity. • Once sugars are converted to cellulose, they are not reclaimed for other purposes.

Respiration ● Plants respire 24 hours a day just as animals do ● In this process they consume oxygen and give off carbon dioxide ● Roots, stems and leaves all use oxygen as they grow

Respiration ● Plants produce more oxygen through photosynthesis than they consume through respiration and growth processes C 6 H 12 O 6 + 6 O 2 + 6 H 20 (ATP) 6 CO 2 + 12 H 20 + Energy

How Does Respiration Work? • Cellular respiration involves sugars produced in the photosynthetic process along with oxygen and water. • In the reaction, chemical energy is released when the molecular bonds of the sugar molecules are broken in combination with oxygen gas.

How Does Respiration Work? • The extracted energy, ATP, drives a variety of chemical reactions in the cell. • By-products of the reaction include carbon dioxide and water. • Water and carbon dioxide are released, as is all of the energy that was contained in the bonds of the glucose molecule.

Photosynthesis VS Respiration ● ● ● Food manufactured Sun’s energy is used Carbon dioxide used by plant Oxygen given off Complex compounds form Produces sugars and starches ● Requires light ● Chlorophyll must be present ● ● ● Food consumed Energy is released Carbon dioxide given off Oxygen is used Simple compounds form Produces carbon dioxide and water ● Goes on day and night ● Carried on in all cells