Plant Parts and their Functions

Plant Parts and their Functions1Leaves-Internal

2Upper Epidermis: single layer of cells used to protect the leaf from loss of too much moisture.Guard Cells: open and close the stoma to allow the leaf to breathe and transpire (will open when the plant becomes turgid)Stoma: space or pore on the underside of the leaf that is used to exchange gases as oxygen and carbon dioxide (transpiration)Chloroplasts: green particles that contain chlorophyll and are contained in food making cellsChlorophyll: the green substance that gives many plants their green color and is necessary for photosynthesisPhotosynthesis: process by which carbon dioxide and water in the presence of light are converted to sugar and oxygen. (begins the food chain process for all living things) 6CO2 + 6H20 + 672kcal(kilocalorie) = 6C6H12O6 + 6O2 or carbon dioxide + water + light energy = glucose (sugar) + oxygenFood is moved through the leaves down to the roots to be stored in the form of sugar, starch or protein.Molecular ExpressionsLeaves-InternalChloroplasts-small green particles that contain chlorophyllgives leaves their green colornecessary for photosynthesis

5Leaves-InternalAir Space: CO2 & O2

Vein: Movement of Fluid

Xylem: transport water up

Phloem: transport glucose

4Leaves-Internal

6Functions of LeavesPhotosynthesis-manufactures food in green plants which is the beginning of the food chain for all living thingsPhotosynthesis is the process by which carbon dioxide and water in the presence of light are converted to sugar and oxygen7photosynthesis

8Functions of Whole PlantRespiration the process through which plant leaves, stems and roots consume oxygen and give off carbon dioxide.Plants produce much more oxygen through photosynthesis than they use through respiration.9Respiration At night photosynthesis cannot occur.

The guard cells lose water. This causes the guard cells to become limp, closing the stomata.

With the stoma closed, CO2 does not enter the leaf, and H2O does not leave.

Since photosynthesis does not occur at night, there is no need for CO2.

11Functions of LeavesTranspiration loss of water through the leaves or stems of plantsTranspiration exchange gases as oxygen and carbon dioxide 12Transpiration occurs as the sun warms the water inside the blade.

The warming changes much of the water into vapor.

This gas can then escape through the stomata.

Transpiration Transpiration helps cool the inside of the leaf because the escaping vapor has absorbed heat.

Simply, transpiration is the plant giving off moisture and an exchange of gas.Transpiration Transpiration also helps keep water flowing up the stem from the roots.

Water forms a continuous column as it flows up the roots, through the stem, and into the leaves.Increases turgid pressure in the plant.

As water molecules are lost through transpiration, the entire column of water is pulled upward. Transpiration

StemsMovement of Materials

Support of the leaves and reproductive structures

Food storages

Reproduction with stem cuttings or grafting17Stems-Internal (dicot)

18Stems-InternalPith-dead center of stem for supportHeartwood-old inactive xylemSapwood-new active xylemCambium-thin, green, actively growing tissue located between bark and wood and produces all new stem cellsPhloem-activeBark-old inactive phloem

19The outer bark is the trees protection from the outside world. Continually renewed from within, it helps keep out moisture in the rain, and prevents the tree from losing moisture when the air is dry. It insulates against cold and heat and wards off insect enemies.The inner bark, or phloem, is pipeline through which food is passed to the rest of the tree. It lives for only a short time, then dies and turns to cork to become part of the protective outer bark.The cambium cell layer is the growing part of the trunk. It annually produces new bark and new wood in response to hormones that pass down through the phloem with food from the leaves. These hormones, called auxins, stimulate growth in cells. Auxins are produced by leaf buds at the ends of branches as soon as they start growing in spring.Sapwood is the trees pipeline for water moving up to the leaves. Sapwood is new wood. As newer rings of sapwood are laid down, inner cells lose their vitality and turn to heartwood. xylemHeartwood is the central, supporting pillar of the tree. Although dead, it will not decay or lose strength while the outer layers are intact. A composite of hollow, needlelike cellulose fibers bound together by a chemical glue called lignin, it is in many ways as strong as steel. A piece 12" long and 1" by 2" in cross section set vertically can support a weight of twenty tons!

Stems-Internal (Translocation)Xylem-tissue that transports water and nutrients up from the roots to stems and leavesPhloem-tissue that transports food down from leaves to rootsPhloemPhloemXylem21Stems-InternalMonocot : examples: corn, grasses

Dicot: example: trees

22Functions of StemsTranslocation move water and minerals from roots up to leaves & move food from leaves down to the rootsXylem and phloem cells help with this process.23Roots-InternalMuch like stems in that they have a phloem, cambium, and xylem layerPhloem-the outer layer that carries food down the rootXylem-the inner layer that carries water and minerals up to the stem24Layers of RootsFibrous-many branched shallow rootsare easier to transplantTap-long root with few branched onesmore difficult to transplant25Functions of RootsAbsorption-take water and nutrients from the soil and conduct them to the stemAnchor the plant and hold it uprightStore food for plant useAsexual reproduction in some plants26