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

Fig 35.17 Parenchyma in a stem

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

100 m Water conducting cells of Xylem: vessels and tracheids (types of sclerenchyma) Fig 35.10

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…

Water travels from ground out through stomata via xylem Fig 36.2 Water travels from ground out through stomata via xylem

The exit of water through stomata is accompanied by gas exchange 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

Phloem transport is from source to sink. Fig 36.20 Phloem transport is from source to sink.

Sugar is loaded at sources and unloaded at sinks... Fig 36.20 source: leaf Sugar is loaded at sources and unloaded at sinks... consuming ATP sink: root, flower, emerging leaf etc…

Source and sink locations vary...

The direction of Phloem transport is versatile.

Much of plant support comes from turgor pressure. 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.

In roots the vascular bundle is in the center 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

Guard cell opening is regulated by turgor 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