Bio 102 Chapter 32 Transport in Plants

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1 Bio 102 Chapter 32 Transport in Plants

Passive Water & Mineral Absorption Water absorption

membrane WATER POTENTIAL determines direction of

AQUAPORIN transport proteins CHANGE RATE NOT DIRECTION

water enters TURGID cells become Plants in HYPERTONIC

3 Passive Water & Mineral Absorption Water absorption from soil OSMOSIS = transport of WATER across cell membrane WATER POTENTIAL determines direction of movement water moves from HIGH LOW water potential AQUAPORIN transport proteins CHANGE RATE NOT DIRECTION of water movement Plants in HYPOTONIC environment water enters TURGID cells become Plants in HYPERTONIC environment water leaves; FLACCID cells become aquaporin root hair H 2 O

4 Active Mineral Absorption Active transport PROTON PUMPS uses energy from ATP to pump H + ions out of cell proton pumps

5 Proton Pumps CHEMIOSMOSIS Produces H + gradient creates membrane potential difference in charge drives COTRANSPORT CATIONS INTO CELL moves ANIONS (NO 3- ) & SUGARS INTO cell when H + returns

6 HOW WATER & SOLUTES MOVE IN PLANTS TRANSMEMBRANE cell walls + cytosol pathway SYMPLAST continuum of CYTOSOL neighboring cells connected by PLASMODESMATA APOPLAST continuum of CELL WALLS + extracellular spaces ACROSS THE MEMBRANE SIMPLE NO WALLS POP THE WALL

7 Overview Bulk Flow Sugars transport in phloem bulk flow Calvin cycle in leaves loads sucrose into phloem positive pressure H 2 O & minerals transport in xylem transpiration evaporation, adhesion & cohesion negative pressure Gas exchange photosynthesis CO 2 in; O 2 out stomates respiration O 2 in; CO 2 out roots exchange gases within air spaces in soil Why does over-watering kill a plant?

8 Water flow through root Water taken up by EPIDERMIS & ROOT HAIRS & MYCORRHIZAE increase surface area Porous cell wall Casparian strip

surface area for absorption of water & minerals increases

9 Mycorrhizae increase absorption Symbiotic relationship between fungi & plant symbiotic fungi greatly increases surface area for absorption of water & minerals increases volume of soil reached by plant increases transport to host plant

10 Mycorrhizae

11 Controlling the route of water in root CASPARIAN STRIP - belt of waxy SUBARIN, surrounds vascular cylinder of root Blocks APOPLAST path Forces water via INTO XYLEM path SYMPLAST Aaaah Structure Function yet again!

12 Root anatomy Dicot (Taproot) Monocot (Fibrous Roots)

13 TRANSPIRATION-COHESION-TENSION XYLEM MOVES ONE WAY ---- UP! Evaporation of water from leaves = TRANSPIRATION Creates pressure NEGATIVE to pull water up from roots to shoots Water forms column and moves by (water CAPILLARY ACTION moving in tube) COHESION (water molecules stick to each other due to HYDROGEN BONDING) ADHESION (water molecules stick to surface of xylem cells)

14 Ascent of xylem fluid Transpiration pull generated by leaf

15 GUTTATION At night transpiration is low roots still pump ions into xylem Movement of water creates root pressure = upward push of xylem sap Excess water drops are exuded from tips of plant; (NOT SAME AS DEW)

water follows; TURGID cell = stomata OPEN Loss of K

16 TURGOR PRESSURE in GUARD CELLS controls water loss through STOMATA K + transported into guard cells; water follows; TURGID cell = stomata OPEN Loss of K + and water makes guard cells FLACCID = stomata CLOSE

Control of Stomates Uptake of K + ions by guard cells proton pumps water enters by osmosis guard cells become turgid Loss of K + ions by guard cells water leaves by osmosis guard cells become flaccid

17 Control of Stomates Uptake of K + ions by guard cells proton pumps water enters by osmosis guard cells become turgid Loss of K + ions by guard cells water leaves by osmosis guard cells become flaccid Guard cell H 2 O K + Chloroplasts H 2 O Thickened inner cell wall (rigid) Epidermal cell Nucleus K + K + H 2 O H 2 O H 2 O H 2 O K + K + K + H 2 O H 2 O H 2 O H 2 O K + K + K + K + Stoma open Stoma closed water moves into guard cells K + K + H 2 O H 2 O water moves out of guard cells

18 Pressure Flow Mechanism Mass flow hypothesis PHLOEM SAP source to sink flow Driven by POSITIVE PRESSURE COMPANION CELLS help load sugars into SIEVE TUBE ELEMENTS HIGH sugar concentration REDUCES ; WATER POTENTIAL water moves into tubes; pressure moves sap downward can flow 1m/hr On a plant What s a source What s a sink?

19 Sugar Source - Leaf

20 Sink Cell - Root

21 Removal of sugar at sink in sieve tubes INCREASES WATER POTENTIAL water moves out of tubes into xylem

22 Transport of sugars in phloem Loading of sucrose into phloem flow through cells via plasmodesmata proton pumps cotransport of sucrose into cells down proton gradient

23 Experimentation Testing pressure flow hypothesis using aphids to measure sap flow & sugar concentration along plant stem

24 Maple sugaring

transpire more than its weight in water in a day this loss

25 Control of transpiration Balancing stomate function always a compromise between photosynthesis & transpiration leaf may transpire more than its weight in water in a day this loss must be balanced with plant s need for CO 2 for photosynthesis

The essential nutrient of plants A. Hydroponics i. Can be used to determine essential nutrients ii. Grow plants in a solution (NO soil) of minerals with known concentration iii.

27 The essential nutrient of plants A. Hydroponics i. Can be used to determine essential nutrients ii. Grow plants in a solution (NO soil) of minerals with known concentration iii. Air bubbled into solution so roots get enough oxygen for cellular respiration iv. Remove minerals(s) or change concentration of mineral(s) and compare to control plant Fig. 32.6

Ca, K, Mg - (Ca ++ ) - cell walls, combines with proteins to form glue of middle lamina, regulate selective

28 Essential nutrients of plants A. Macronutrients i. 9 out of 17 ii. Need in large (macro) amounts iii. C, N, O, H, S, P (The big six, 98% weight) iv. Ca, K, Mg - (Ca ++ ) - cell walls, combines with proteins to form glue of middle lamina, regulate selective permeability - (K + ) cofactor of many enzymes, opening and closing stomata (main solute for osmotic regulation) - (Mg ++ ) -component of chlorophyll, cofactor of many enzymes

29 Essential nutrients of plants B. Micronutrients i. The other 8 ii. Need in small (micro) amounts iii. Fe, Cl, Cu, Mn, Zn, Mo, B, Ni - cofactors of enzymes a. ex. Fe (iron) is a cofactor of many ETC proteins as it accepts and donates electrons - Recycled over and over again (need very little) a. ex. There is one molybdenum (Mo) for every 16,000,000 hydrogens

30 Quality of nutrients in soil determines quality of your own nutrition Corn growth in nitrogen rich (left) vs. nitrogen poor (right) soil Fig. 32.6

Roots secrete H + (acid) in exchange for another cation - acid rain strips away the cation nutrients E.

31 Root hairs use cation exchange A. Cation i. Positively charged ion (K +, Mg ++, Ca ++ ) B. Clay negatively charged C. Cations stick to clay - keeps them from draining away D. Roots secrete H + (acid) in exchange for another cation - acid rain strips away the cation nutrients E. Anions are easier for roots to absorb (NO 3 - (nitrate) vs. NH 4 + (ammonium) - anions drain out of soil easily - unfertile soil, eutrophication Fig. 32.8

32 Connection: Soil Conservation Essential to Life Human agriculture degrades soil Irrigation makes soil salty Plowed land subject to wind, rain Chemical fertilizers can contaminate H2O Good soil Management Water-conserving irrigation Erosion control Prudent used of herbicides and fertilizers

35 Parasitic plants A. Dodder i. yellow-orange threads ii. No photosynthesis iii. Gets organic nutrients from host iv. Uses specialized root to tap into vascular tissue B. Mistletoe i. CAN do photosynthesis ii. Supplements diet by siphoning sap from vascular tissue of host Dodder Mistletoe Both dodder and mistletoe may kill host by blocking too much light or taking too much food Fig

36 Carnivorous plants A. Sundew and venus flytrap i. Get nitrogen by digesting flies ii. Sundew- sticky sugar stuff to attract & trap insects iii. Venus flytrap - touch sensory hairs that close when touched twice in a row iv. Both secrete digestive enzymes onto their prey Sundew video Fig

37 Plants depend on bacteria for N 2 A. Recall the nitrogen cycle i. Plants can t use N 2 (N N) ii. Nitrogen cycle: iii. Ammonium is a cation (gets stuck to clay and therefore hard to absorb) iv. Plants prefer Nitrates (anion)

38 Plants depend on bacteria for N 2 A. Recall the nitrogen cycle v. Plants will convert nitrates back to ammonium for amino acid biosynthesis

Rhizobium - convert N 2 directly to ammonium, which can be used by plant directly (it s already inside) - excess leaks

39 Legumes house nitrogen-fixing bacteria A. Legumes (plants produce pods) i. Have nodules on roots filled with Rhizobium - genus of most nitrogen-fixing bacteria in roots of legumes ii. Rhizobium - convert N 2 directly to ammonium, which can be used by plant directly (it s already inside) - excess leaks into soil makes fertile a. This is why farmers tend to rotate their crops: one year legume, one year non-legume iii. Plants give organic molecules to Rhizobium (mutualistic) Fig

40 Genetic engineering plants A. Gene gun i. Used to shoot foreign genes into plant (or animal cell) ii. DNA integrates into genome iii. Cells now make new protein Fig

Genetic engineering plants Many new organisms made this way: - virus resistant cotton plants - potato plants that produce their own insecticide - slow spoil tomatoes -Can

41 Genetic engineering plants Many new organisms made this way: - virus resistant cotton plants - potato plants that produce their own insecticide - slow spoil tomatoes -Can we get plants to synthesize medicine? -Make grain with all eight essential amino acids? -Put genes for nitrogen fixation into non-leguminous plants? Insect resistant corn

42 Don t get mad Get answers!! Ask Questions! 2006-

Transport in Plants AP Biology

Transport in Plants AP Biology Transport in Plants 2006-2007 Water & mineral absorption Water absorption from soil osmosis aquaporins Mineral absorption active transport proton pumps active transport of H + aquaporin root hair proton