Notes from Lectures
Notes from Lectures HORT 1001
U of M
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This 2 page Class Notes was uploaded by Abbie on Wednesday October 28, 2015. The Class Notes belongs to HORT 1001 at University of Minnesota taught by Thomas Michaels in Fall 2015. Since its upload, it has received 24 views. For similar materials see Plant Propagation in Agriculture and Forestry at University of Minnesota.
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Date Created: 10/28/15
LECTURE 9 INSIDE LEAVES AND TRANSPIRATION OO 0 Leaf Anatomy Upper epidermis w cuticle cutinprotective covering Palisade Mesophyll Densely packed columnarshaped elongated cells full of chloroplasts Highly adapted for capturing light energy region is laced with air channels so it39s highly adapted for gas movement around the cells Vascular Bundle Xylem phloem bundle sheath along with parenchyma Spongy mesophyll Loosely packed cells with large air spaces in between which allow movement and exchange of gases speci cally oxygen carbon dioxide and water vapor Lower epidermis with guard cells that regulate the size of the stomata Chlorophyll absorbs red and blue light wavelengths to power photosynthesis and re ects green light back to our eyes Chromoplasts cellular organelles that contain types and colors of pigments other than the chlorophyll found in chloroplasts In late summer early fall the mesophyll cell chloroplasts produce chlorophyll at a slower rate than earlier in the year Green color fades out of leaves Nongreen pigments remain the same or increase in quantity Cartinoid pigments yellow orange are always present but are hidden by the high concentration of chlorophyll during warmer months Anthocyanin red colors amount differs from autumn to autumn Warm bright days and cool nightsred leaves 0 Higher concentration of sugars from photosynthesis get trapped in the leaves when nights are cooler Transpiration Refers to the movement of water in the plant from root to stem to leaf and out through the stomata to the atmosphere Depends on factors like 0 Increase in lightincrease in rate 0 Increase in temperatureincrease in rate 0 Increase in humidity increase in rate 0 Wind breeze will clear water vapor away from the surface of the leaf leaving the humidity on the leaf surface low and encouraging evaporation Soil water availability water pressure inside the cells turgor pressure is reduced because some water is pulled out of the cells Decrease in turgor pressure relaxes guard cells causing closure of stomata which shuts off a major avenue for gas exchange and main channel for evaporation Plant Type Transpiration also Provides water for photosynthesis Moves minerals up from the roots for use in the leaf Cools the plant through evaporation Mechanisms of Water Movement in Plants Push Explanation Turgor in root cells during nightcloudy days can push water and dissolved materials up into the stem This root pressure is caused by guttation dewlike drops of water that are forced out of leaves Doesn39t explain why water moves up tall plants ie trees Pull Explanation The CohesionAdhesionTension Theory Cohesion hydrogen atoms bond into a strong cord of water molecules Adhesion force between water molecule and xylem walls helps hold the water in the xylem against the downward force of gravity Tension evaporated water creates void in xylem and vacuum is lled by next water molecule as it moves forward it exerts tension on the cord that extends all the way back down to the root