bio213 chapter 35/36/37

What is primary growth?

Found in apical meristem

• when apical meristem cell divide (undifferentiated), some daughter cells remain the apical meristem, ensuring a continuing population of stem cells

What is secondary growth?

Two lateral meristems extending along the length of a shoot where primary growth has ceased

• vascular cambium, cork cambium

What are lateral meristems?

Cylinders of dividing cells that are one cell thick

What are cambium cell divisions?

Cell division in the plane perpendicular to the surface of the shoot

• enable cambium to inc circumference as the stem widens

What is the process of secondary growth?

1. When vascular cambium and cork cambium become active in stem/root, primary growth has ceased in that area

2. A stem/root thickening as secondary xylem, secondary phloem, and cork cells are added

3. Most of the shells are secondary xylem

4. The cells in the cortex stretch and are eventually crushed

What are the properties of vascular cambium cell?

Divides in a plane parallel to surface of the shoot

• thin band of dividing cells between xylem and phloem

• Makes new xylem (inside) and phloem (outside)

Where are apical meristems found?

Found at tips of roots and shoots

• cause growth in height (primary growth)

What are the properties of cork cambium?

Makes new outer protection, makes cork (part of bark)

• helps prevent water loss

• Protects stem from damage

What are the 3 primary meristems?

1. Protoderm

2. Procambium

3. Ground meristem

What are the 3 primary meristems?

1. Protoderm

2. Procambium

3. Ground meristem

What is the protoderm?

Outermost primary meristem that gives rise to epidermis of stem or root

What is the procambium?

Xylem and phloem (transport tissues)

What is the ground meristem?

Inside tissue (storage and support)

What is a cambium?

Type of lateral meristems extending along

• thin layer of dividing cells

What is heartwood?

Innermost layer of xylem (dead) for structural support

What is sapwood?

Alive xylem outside of heartwood that is used to transport water

What is the layering structure of a tree from superficial to deep?

1. Cork

2. Cork cambium

3. Phloem

4. Xylem

• sapwood, heartwood

what are intercalary meristems?

Found at bases of leaves or stems (common in grasses)

• allow regrowth after cutting, grazing

What is the root cap?

Protects growing tip of root

What is the area of elongation?

A cells grow longer, pushing root downwards

What is the area of maturation?

Region where cells differentiate

• where root hairs form

What is an herbaceous stem?

Soft and green stem

What is a woody stem?

Thick, woody, bark

What are the properties of herbaceous stems?

Mostly primary growth

• usually no wood

• Often die back at end of season

What are the properties of woody stems?

have secondary growth (grow thicker over time)

• wood→ xylem

• Secondary xylem→ new xylem made during thickening

• Builds up every year

what are tree rings?

Yearly growth in wood

• each year, new xylem is made

• Spring→ bigger cells

• Summer→ smaller cells

• One year of xylem growth→ one ring

What are vascular rays?

Thin bands of cells that run sideways (from the center of the stem outward)

What are xylem rays?

Move water/minerals sideways through the wood

What are phloem rays?

Move sugars sideways through the phloem

What is bark?

Tissues outside the vascular cambium

• helps protect the stem

• Can include layers of cork and crushed phloem

What is developmental plasticity?

Plants respond to environment by changing how they grow

• diff leaf shapes

• Branching patterns

• Root growth direction

• Flowering timing

What is an annual plant?

Completes life cycle in one growing season

What is perennial growth?

Live many years and flower repeatedly

1. Germination

2. Growth

3. Flowering

4. Dormancy (back to growth)

What is biennial growth?

Completed life cycle in 2 growing seasons

1. Germination

2. Growth

3. Dormancy

4. Growth

5. Flowering

6. Death

What are the adaptations for resource acquisition for plants?

1. Shoot maximize light capture

2. Roots maximize water and mineral uptake

3. Leaves balance photosynthesis vs water oss

4. Mycorrhizae promotes nutrient absorption

What is phyllotaxy?

Arrangement of leaves on a stem

• important feature in light capture

• Determined by shoot apical meristem

What is self-pruning?

Nonproductive leaves/branches undergo apoptosis and eventually shed

What is alternate leave arrangement?

One leaf per node

What is opposite arrangement?

2 leaves per node (opposite from each other)

what is a whorled leaf arrangement?

3+ leaves per node

What is leaf area index?

Total leaf area/ ground area

What is the role of the stomata?

1. CO2 enters stomata

2. O2 and water vapor exit→ transpiration

What is the apoplast?

Consists of everything external to plasma membrane of living cels and includes cell walls, extracellular spaces, and interior of dead cells

What is the symplast?

Consists of the entire mass of cytosol of all the living cells in a plant (including plasmodesmata)

What is the apoplastic route?

Water and solutes (dissolved chemicals) move along the continuum of cell walls and extracellular spaces

How does water enter a plant?

1. Water enters through roots via osmosis

2. Moves to xylem

what is the symplastic route?

Water and solutes move along continuum of cytosol

• requires substances to cross a plasma membrane once

• After entering one cell, substances can move from cell to cell via plasmodesmata

What is the transmembrane route?

Water and solutes move out of one cell, across the cell walls, and into the neighboring cell

• requires repeated crossing of plasma membranes

What is the role of H+ regarding membrane potential?

The plasma membranes of plant cell use ATP-dependent proton pumps to pump H+ out of cell

• pumps contribute to the membrane potential and the establishment of a pH gradient across the membrane

• two energy forms of potential energy can drive transport of solutes

What is the role of H+ and cotransport of neutral solutes?

Sugars can be loaded into plants via cotransport w/ H+ ions

• helps get sugar into the phloem for transport

What is the role of H+ and the cotransport of ions?

H+ regulates ion fluxes in and out of cells

• helps with NO3- uptake by plant roots

What is an endodermis?

Single layer of cells that makes a ring around vascular tissue

• final checkpoint

What is the casparian strip?

Thin layer of wax that wraps around the cells of the endodermis

• blocks apoplastic route→ water must cross membrane into cytoplasm of endodermal cell to cross strip

What is water potential?

The physical property that predicts that direction in which water will flow

• Free water moves from regions of higher water potential to regions of lower water potential if there is no barrier to its flow

• Potential→ water’s capacity to move from higher to lower water potential

What is a proton pump?

Uses ATP to pump H+ out of the cell

• creates electrochemical gradient

What is a megapascal (MPa)?

Unit of pressure of pure water in a container open to atmosphere under standard conditions

What is the water potential equation?

MPa= MPa(s) + MPa(p)

What is the solute potential (MPa(s))?

Proportional to its molarity

• solutes affect the direction of osmosis

• As solute concentration increases, MPa(s) will become more negative

What are the properties of guard cells?

When guard cells gain water→ become turgid, stomata open

When guard cells lose water→ become flaccid, stomata close

What is transpiration?

Loss of water vapor from leaves

• controlled evaporation from leaves

• 90% of water lost this way

What is pressure potential (MPa(p))?

Physical pressure on a solution

• can be positive or negative relative to atmospheric pressure

What is a solution being withdrawn by a syringe an example of?

Negative pressure (MPa(p))

What is the tension cohesion theory?

Water molecules stick to each other→ cohesion

Water molecules stick to xylem walls→ adhesion

• as water evaporates from leaves, more water is pulled upward

• Forms continuous column of water

What is the protoplast?

Living part of cell that includes plasma membrane

What is turgor pressure?

Protoplast presses against cell wall

• helps maintain stiffness of plant tissues

• Driving force of cell elongation

What is wilting?

leaves and stems droop as a result of cells losing water→ turgid pressure lost

what are aquaporins?

Transport proteins that facilitate the transport of water molecules across plant cell plasma membranes

• affect the rate at which water moves osmotically across membrane

What is a plasmolyzed cell?

Membrane pulls away from cell wall

• shriveled

What is bulk flow?

Movement of liquid in response to a pressure gradient

• independent of solute concentration

• Occurs from higher t o lower pressure

What is the pressure flow hypothesis?

1. Leaves make sugars

2. Sugars build up in leaves

3. Water enters where sugar concentration is high

4. Creates pressure

5. Pressure pushes sugars to other plant parts (sinks)

What factors affect transpiration?

1. Light→ transpiration inc

2. Temperature→ faster evaporation

3. Humidity→ dry air inc. water loss

4. Drought→ stomata close

What is in the soil?

1. Mineral particles

2. Water

3. Air spaces

4. Organic matter

5. Living organisms

6. Topsoil

What are the properties of roots?

Bind soil→ reduce erosion

• release acids→ lower pH

• Alter soil texture and chemistry

What is sustainable agriculture?

Repeated farming depletes soil (plant-soil feedback)

• nutrient loss

• Erosion risk

• Conservation-minded practices

• Long-term productivity

What was the dust bowl?

Only monocultures were planted

• drought

• Wind erosion

• Loss of topsoil

• Reduced productivity

What are the most common fertilizers?

Nitrogen, Phosphate, Potassium

What are the properties of soil pH?

Affects nutrient availability

• slightly acidic often ideal

• Influences nutrient solubility

What are strategies to prevent erosion?

Windbreaks, terracing, contour farming

What is phytoremediation?

Plants remove pollutants

• biological cleanup

• Restores contaminated habitats

• Used commonly for heavy metals (Pb, Zn)

What are macronutrients?

Large amounts needed of N, P,K, Ca Mg, S

What are micronutrients?

Small amounts of B, Cl, Cu, Fe, Mn, Mo, Ni, Zn

Where r does plant mass come from?

Fresh mass: mostly water

Dry mass: mostly CO2-deprived

What is chlorosis?

Yellowing in leaves

• stunted growth

• Mobile nutrients pulled to new growth

• Older leaves affected first

• N, P, K nutrient deficient

What is the rhizosphere?

The zone of soil that surrounds and is influenced by plant roots

• roots release substances that affect this area

• Many microbes live and interact w/ roots here

What is an epiphyte?

A plant that grows on top of another plant

What is a fruit?

Mature ovary that contains seeds

• all fruits develop from flowers

• Fruits occur only in flowering plants

What are the structures of a fruit?

1. Exocarp: outer skin

2. Mesocarp: fleshy middle layer

3. Endocarp: inner fruit layer surrounding seeds

4. Pericarp: all layers (fruit wall)

How do fruits differentiate?

1. Size and shape

2. Texture (fleshy or dry)

3. Number of seeds

4. Fruits may develop from one flower or many flowers

What are fleshy fruits?

Have a soft or juicy pericarp at maturity

• often eaten by animals

• Usually contain one or more seeds

What are simple fleshy fruits?

One ovary per flower

• have soft or juicy pericarp at maturity

• Often dispersed by animals

What are berries?

Simple fleshy fruit w/ soft pericarp

• seeds embedded in flesh

• True botanical berries: tomatoes, grapes, blueberries, bananas, peppers

What are drupes?

Simple flesh fruit w/ fleshy outer part, hard inner layer (pit)

• one seed inside pit

Ex. Peaches, cherries, plums, olives

What are pomes?

Simple fleshy fruit where ovary is in center

• Edible part is accessory tissue, not ovary

What are aggregate fleshy fruits?

Fruits cluster together→ many ovaries

ex. Raspberries, blackberries, strawberries

What are multiple fruits?

Many flowers, each w/ one ovary

• fruits fuse together into one structure

Ex. Pineapple, fig, mulberry

What are dry fruits?

Develop from flower’s ovary

• pericarp becomes dry at maturity

• Contain seeds w/ a dry pericarp

What are the two types of dry fruits?

Dehiscent fruits, indehiscent fruits

What are dehiscent fruits?

Split open at maturity

• releases seeds into environment

Ex. Legumes, capsules, siliques

What are indehiscent fruits?

Remain closed at maturity

• fruits and seed disperse together

Ex. Acorns, sunflower seeds, grains

What is botanical nut?

Hard outer shell (fruit wall)

• one seed inside