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Exam #2 M (3/9) 7:30-9pm in BUR 106 Function shapes structure… Structure enables function What functions and structures exist? Those passed on by past generations… Evolution 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 7.6 Cell walls contain cellulose, pectins, proteins... Fig 8.3 Parenchyma cells- most common cells; primary cell walls Fig 36.22 60 m Parenchyma in a stem Fig 36.18 Collenchyma cells- unevenly thickened cell walls; flexible support Fig 36.24 80 m Collenchyma in a leaf Sclerenchyma cells- Thickened secondary walls (inside primary wall); with lignin; rigid 5 m Fig 36.25 25 m Water conducting cells of Xylem: vessels and tracheids (types of sclerenchyma) Fig 36.26 100 m Sugar conducting cells of Phloem: sieve-tubes and companion cells Fig 36.27 30 m 15 m Fig 36.2 Plants transport water, sugar, minerals, hormones, etc through the vascular system comprised of xylem and phloem Fig 37.4 Water travels from ground out through stomata via xylem Fig 37.4 The exit of water through stomata is accompanied by gas exchange Fig 37.17 Sunlight powers photosynthesis and these sugars are transported via phloem Fig 37.18 Phloem transport is from source to sink. Fig 37.20 Sugar is loaded at sources and unloaded at sinks... source: consuming ATP sink: leaf root, flower, emerging leaf etc… Fig 37.18 Source and sink locations vary... The direction of Phloem transport is versatile. Plants transport water, sugar, minerals, hormones… Fig 37.5 Much of plant support comes from turgor pressure. CB 36.13 Water moves from the ground through roots into the shoot and out stomata in the leaves. Fig 37.7 In roots the vascular bundle is in the center Plant cell to cell transport can occur by two pathways: symplastic and apoplastic Fig 37.8 plasmodesmata Fig 37.8 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 10.21 Stomata Stomata on the underside of a leaf Fig 36.20 Guard cell opening is regulated by turgor Fig 37.4+.11 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 (3/9) 7:30-9pm in BUR 106 (bring cheat sheet)