Unit 2 Chapter 36/37 Resource Acquisition/Transport, Soil Nutrition

Growing tall: pros

Stems support and position leaves; height can reduce shading by competitors; branching can increase light capture.

Growing tall: cons

More tissue requires more resources; greater height requires more support and transport.

More leaves =/ maximum photosynthesis

Greater area increases light capture, but may shade one another; may photosynthesize less while still consuming sugars through respiration.

Leaf area index

Leaf area relative to ground area.

Photosynthesis

Makes sugars.

Cellular respiration

Uses sugars.

Respiration > photosynthesis

Shedding.

Stolon

Horizontal stem that grows along the ground; nodes can produce new shoots and new roots; allows for vegetative reproduction.

&&&& Water movement in plants

Apoplast (never inside), Symplast (always inside), Transmembrane route (repeatedly in/out).

&&&& Apoplast

Through cell walls and extracellular spaces; does not cross a plasma membrane (NOT inside the cytosol).

&&&& Symplast

Direct through cytosol; cells connected by plasmodesmata (physical bridgeway from one side to another).

Transmembrane route

Enters and exits successive cells; repeatedly crosses plasma membranes.

Osmosis

Movement of water across a selectively permeable membrane.

&&&& Water movement down its water-potential gradient

More water >>> less water; Less solute >>> more solute.

Water enters plant cell

Cell becomes turgid (firm); hypotonic.

Water leaves plant cell

Cell becomes flaccid; isotonic.

Plasmolysis

Severe water loss; plasma membrane pulls away from cell wall; hypertonic.

Whole plant losing turgor

Can lead to wilting.

Aquaporins

Membrane channels that greatly facilitate water movement.

Transpiration (think xylem)

Process by which moisture is carried through the tree from roots.

Transpiration

Xylem; only upwards; water and minerals travel from roots to the shoots.

Stomatal opening/closing

Open stomata: CO2 enters / O2 leaves; water vapor exits; guard cells' "internal clock" regulate opening; open in day, close at night.

When should stomata open?

Available light; CO2 is depleted; water is available.

Stomata generally close

Photosynthesis is not occurring; water conservation becomes more important.

&&&& Xerophytes

Plants adapted to arid (dry) environments.

Xerophyte adaptations

Shorter life cycles; dormant seeds quickly germinate and bloom when rainy; reduced water loss (spines, prickles); water storage in flesh stems; stomata may remain closed during the day.

Cephalocereus senilis

"Old man cactus"; has long hair-like bristles that help reflect intense sunlight of Mexican Desert.

Bulk flow

Movement of a fluid due to a difference in pressure between 2 locations; independent of solute.

Phloem (Translocation)

Regulates movement of photosynthates (sugars); upwards OR downwards.

Source

Produces and releases sugars.

Sink

Uses or stores sugars; roots, fruits, developing leaves.

Translocation

Phloem; primarily downward (still may go upward); photosynthates travel from shoots to the roots.

Topsoil

Upper, nutrient-rich layer of soil; most root activity.

&&&& Clay and organic matter

Often have negatively charged surfaces.

Leaching

Anions such as nitrate can be more prone to leaching; things washed away after rainfall.

Cations in soil

Bind to negatively charged surfaces strongly and do not easily wash away.

Inorganic fertilizers

Nitrogen, phosphorus, potassium; concentrated mineral nutrients.

&&&& N-P-K ratio

Often labeled with a 3-number code; 15-10-5 means 15% N, 10% P, 5% K.

Crop rotation

Maintains fertility and health; some crops use/remove large amounts of soil nitrogen; some crops with nitrogen-fixing bacteria can produce usable nitrogen.

Soil pH

Affects chemical form and availability of mineral nutrients.

Soil pH too high or too low

Some nutrients become less available; some ions become toxic.

Very acidic soil

Aluminum becomes more soluble; inhibits root growth.

Phytoremediation

Using plants to remove or concentrate pollutants from soil/water.

Thlaspi caerulescens

Can accumulate zinc 300x higher.

Macronutrients

Plants require large amounts; CHNOPS.

Micronutrients

Only needed in small quantities.