Please sit next to a partner you are an A or a B
Plants Transport in Vascular Plants
Transport Overview Vascular tissue transports nutrients throughout a plant Such transport may occur over long distances Sequoia sempervirens: 112m/367ft Figure 36.1
Transport Overview Key vocabulary: apoplast symplast tonoplast cytoplasmic continuum plasmodesmata Main points to know today: cellular geography of transport structures involved in maximizing uptake mechanism of forcing water into xylem mech. of xylem transport overview of phloem transport
Transport
Transport
Transport
Transport
How do plants regulate transport? Transport in plants is regulated by membrane proteins compartmental structure of plant cells Three compartments cell wall cytosol vacuole
Vacuole Large organelle that can occupy as much as 90% of more of the protoplast s volume The vacuolar membrane = Transport proteins in the plasma membrane regulate traffic of molecules between the cytosol and the cell wall. Cell wall Cytosol Vacuole Transport proteins in the vacuolar membrane regulate traffic of molecules between the cytosol and the vacuole. (a) Plasmodesma Plasma membrane Vacuolar membrane (tonoplast) Cell compartments. The cell wall, cytosol, and vacuole are the three main compartments of most mature plant cells.
Transport between compartments Cell walls and cytosol are continuous from cell to cell The cytoplasmic continuum = Continuum of cell walls plus extracellular spaces =
Transport between compartments Water and minerals can travel through a plant by one of three routes Out of one cell, across a cell wall, and into another cell Via the symplast Along the apoplast
Bulk Flow in Long- Distance Transport Movement driven by pressure differences at opposite ends of both xylem vessels and sieve tubes
Transport in Roots How does water get to the Xylem? 1: ID the numbers below 2: ID brackets below
Concept Check If you are a B, explain to your partner the type of transport(s) necessary for water to gain access to xylem cells.
How do plants maximize uptake? 2.5 mm Root hairs surface area? Mycorrhizae symbiosis mutualism two types...
Endomycorrhizae
Ectomycorrhizae
surrounds vasc cylinder Includes Casparian strip Endodermis 3D view of root endodermis cells (LS). Cas.Strip in olive En= endo. cells S= towards tip Z=stele R=bark (acc. to Luttge & Higinbotham, 1979)
Xylem Transport Minerals that need to be taken up from the soil include: K+, Na+, Ca2+, NH4+, PO43- and NO3- Root cells: proton pumps, actively pump H+ ions to soil, displacing the + charged minerals. (the - charged minerals bind to H+ ions and are reabsorbed) How do water and minerals get up the plant? Root pressure guttation Cohesion-tension Figure
Cohesion-Tension Mechanism 1.Water vapor leaves stomata 2.Water pulled from xylem into leaf 3.Water pulled up xylem cohesion (H2O <-> H2O) adhesion (H2O <-> call walls)
Transpiration Leaves have large surface areas Inc. PS, water loss (90%...) How do leaves control water loss? 20 µm Figure 36.14
Transpiration Each stoma is flanked by guard cells open when turgid closed when flaccid
Xerophyte Adaptations That Reduce Transpiration Xerophytes Adapted to arid climates Leaf mods limit water loss:
Adaptations of Hydrophytes Cuticle Stomata Flat leaves, with air sacs Roots
Sugar Sources to Sugar Sinks Phloem sap mostly sucrose travels from source to sink Sugar source organ producing sugar (eg mature leaves) Sugar sink organ consuming or storing sugar (eg tuber or bulb)
Sugar Sources to Sugar Sinks Where are sugars made? Sugar must be loaded into sieve-tube members Loading sucrose into phloem requires proton pumping and cotransport of sucrose, K + and H + sugar may move by symplastic and apoplastic pathways Mesophyll cell Cell walls (apoplast) Plasma membrane Plasmodesmata Companion (transfer) cell Sieve-tube member Mesophyll cell Bundlesheath cell Phloem parenchyma cell
Pressure Flow Mechanism Sap moves through a sieve tube by bulk flow driven by positive pressure Requires active loading and unloading (green arrows)