Ch. 36 Transportation In Plants

Bryophytes- NO VASCULAR TISSUE Bryophytes- NO VASCULAR TISSUE! Only use osmosis to move water to the top of the plant

Review of Proton Pumps Pump H+ (Protons) and create a membrane potential which can be used to facilitate the movement of ions across a membrane. *pump = ATP required; ACTIVE = against gradient!

Review of Water Potential - Water will move from an area of higher water potential to an area of lower water potential - Both solute concentration and pressure impact the water potential. HOW??   http://www.phschool.com/science/biology_place/labbench/ lab1/factors.html

There are three compartments to a mature plant cell 1. Cell Wall 2. Cytosol/Cytoplasm 3. (Sap/Central) Vacuole. The membrane that surrounds this is called the vacuolar membrane or the tonoplast.

Flow of Goods Symplast- Continuum of flow through the cytoplasm and plasmodesmata. Apoplast- Continuum of flow through extracellular spaces and cell walls (the “back alleys” *around) Bulk Flow- Movement of fluid driven by pressure only, usually in large amounts.

Roots- Absorption of water and minerals Pathway of flow: Epidermis (including the root hairs)  cortex  through endodermis vascular cylinder  up the tracheids - Absorption is greatest closest to the root tips because of the high concentration of root hairs (hydrophilic)

Movement of Water continued.. Mycorrhizae- A fungal symbiont used to increase surface area of root Symplastic Route- Water and minerals will pass through the endoderm freely Apoplastic Route- Leads to a dead end because of the Casparian strip (made of a waxy substance called suberin). Must make it to the symplast in order to get past the endoderm and into the xylem.

Mycorrhizae

Bulk Flow from the Roots to the Shoots (xylem flow) Positive Pressure from root pressure - At night, ions accumulate in the xylem which will LOWER the water potential. Water will continue to be drawn in causing pressure to build in the roots (root pressure). - Can lead to guttation- expulsion of excess water through the leaves.

Negative Pressure from transpiration (Transpiration-Cohesion-Tension Mechanism) - Water exits the stomata and other water will be pulled up the tree because of hydrogen bonding. - Most powerful force that drives xylem up the plant - Both cohesion (water sticking to water) and adhesion (water sticking to the xylem vessels) at work. - Ascent of xylem is primarily driven with solar power, NOT ATP!

Animation

Rate of transpiration- - High humidity SLOWS down transpiration - Wind can increase transpiration - Increase in light intensity will increase transpiration - Closing stomata stops transpiration *THINK ABOUT YOUR LAB HYPOTHESIS!

Role of Stomata in Regulation - Stomata are USUALLY open during the day and closed during the night - Evaporative cooling by transpiration will keep the plants enzymes intact - Desert plants will have fewer stomata, marshy plants will have more - Stomata numbers have decreased in the last 100 years because of increased CO2 levels

Stomata continued… - Surrounded by guard cells What causes the stomata to open? - Lots of water - Depletion of CO2 will open the stomata - Increase in potassium ions - Active transport of H+ ions out of the guard cells

Stomata continued… What causes the stomata to close? - Lack of water - High temperatures- Stimulates cellular respiration in the leaf - Abscisic acid- Chemical that signals the guard cells to close Xerophytic plants- Adapted to live in arid conditions

Phloem and Organic Nutrients - The transportation of the products of photosynthesis is called translocation - Phloem has a large concentration of sucrose - Variable direction of travel, but will ALWAYS flow from a sugar source (a leaf undergoing photosynthesis) to a sugar sink (consumer of the sugar or the storage unit of the sugar like a piece of fruit) - Usually the source is close to the sink - In some angiosperms, pressure flow is used (positive pressure created by high concentrations of sugar in the phloem)

Animation

SIDE NOTE: GREAT REVIEW of MATH STUFF for EXAM! https://slideplayer.com/slide/12521297/75/i mages/6/Chi%20Square%20Practice%20Probl ems%20AP%20Bio%20Equations%20&%20Fo rmulas%20Review%20Sheet%20Solve%20Pro blem%20