Exam 2 M 3 8 in class Q A Fri 3 5 from 4 6pm in WRW 102 Plants grow and reproduce as well as respond to the environment Plants grow and reproduce respond to the environment today transport Types of Plant Cells defined by function and cell wall Plant cell walls are mostly made of cellulose Fig 6 9 Cellulose is made of glucose Fig 5 7 Cellulose is made of glucose Fig 5 8 Only a few prokaryotes and fungi can digest cellulose Fig 5 9 Cell walls contain cellulose pectins proteins Parenchyma cells most common cells primary cell walls Fig 35 10 60 m Parenchyma in a stem Fig 35 17 Collenchyma cells unevenly thickened cell walls flexible support Fig 35 10 80 m Collenchyma in a leaf Sclerenchyma cells Thickened secondary walls inside primary wall with lignin rigid Fig 35 10 5 m 25 m Water conducting cells of Xylem vessels and tracheids types of sclerenchyma Fig 35 10 100 m Sugar conducting cells of Phloem sieve tubes and companion cells Fig 35 10 30 m 15 m Fig 36 2 Plants transport water in xylem sugar in phloem plus minerals and hormones Fig 36 2 Water travels from ground out through stomata via xylem Fig 36 2 The exit of water through stomata is accompanied by gas exchange Fig 36 2 Sunlight powers photosynthesis and these sugars are transported via phloem Fig 36 20 Phloem transport is from source to sink Fig 36 20 Sugar is loaded at sources and unloaded at sinks consuming ATP source leaf sink root flower emerging leaf etc Source and sink locations vary The direction of Phloem transport is versatile Fig 36 10 Much of plant support comes from turgor pressure CB 36 15 Water moves from the ground through roots into the shoot and out stomata in the leaves Fig 35 13 In roots the vascular bundle is in the center Fig 36 11 Plant cell to cell transport can occur by two pathways symplastic and apoplastic plasmodesmata Fig 36 12 The casparian strip of the endodermis keeps water from entering the xylem via a purely apoplastic route What moves the water through the xylem Stomata control entry of CO2 and exit of H2O from plant leaves Fig 36 14 Stomata Stomata on the underside of a leaf Fig 36 17 Guard cell opening is regulated by turgor Fig 36 15 What moves the water through the xylem Transpiration Adhesion Cohesion and Tension water transport limits plant growth More xylem is needed for more water transport secondary growth phloem xylem Xylem is tough and full of lignin inhibits the ability to use plants to produce biofuels phloem xylem Exam 2 M 3 8 in class Q A Fri 3 5 from 4 6pm in WRW 102
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