Function shapes structure… Structure enables function What functions and structures exist? Those passed on by past generations… Evolution Exam #2 M (3/9) 7:30-9pm in BUR 106

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

Fig 7.6 Plant cell walls are mostly made of cellulose

Fig 8.3 Cell walls contain cellulose, pectins, proteins...

Fig  m Parenchyma cells- most common cells; primary cell walls

Fig Parenchyma in a stem

Fig Collenchyma cells- unevenly thickened cell walls; flexible support 80  m

Collenchyma in a leaf

Sclerenchyma cells- Thickened secondary walls (inside primary wall); with lignin; rigid 5  m 25  m Fig 36.25

Fig Water conducting cells of Xylem: vessels and tracheids (types of sclerenchyma) 100  m

Sugar conducting cells of Phloem: sieve-tubes and companion cells 15  m 30  m Fig 36.27

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 Sunlight powers photosynthesis and these sugars are transported via phloem

Fig Phloem transport is from source to sink.

Fig Sugar is loaded at sources and unloaded at sinks... consuming ATP source: leaf sink: root, flower, emerging leaf etc…

Fig 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 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

Fig 37.8 Plant cell to cell transport can occur by two pathways: symplastic and apoplastic 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 CO 2 and exit of H 2 O from plant leaves Stomata Fig 10.21

Stomata on the underside of a leaf

Fig Guard cell opening is regulated by turgor

Fig What moves the water through the xylem? Transpiration, Adhesion, Cohesion, and Tension

water transport limits plant growth

xylem phloem More xylem is needed for more water transport: secondary growth

xylem phloem Xylem is tough, and full of lignin- inhibits the ability to use plants to produce biofuels

Exam #2 M (3/9) 7:30-9pm in BUR 106 (bring cheat sheet)