Exam 3 (Ch. 5-6: Roots & Stems)

Vascular cambium:

- 2º xylem forms to the interior. - 2º phloem forms to the exterior.

A root system may function in...

- Absorption & conduction - Anchorage & storage - Growth - Production of new roots

Propagative Roots:

- Adventitious buds on roots that develop into suckers (aerial stems) - Fruit trees - Strawberries - Cherries - Pando tree

Defensive Roots

- Adventitious roots form spikes

Purpose of roots?

- Anchors plants into soil. - Absorption of water & minerals. - Storage of food & water. (Sugar as starch) - Conduction of water & nutrients upward. - Interact w/ soil microbes. - Detection of gravity.

Life span of plants:

- Annuals - Biennial - Perennial

Phyllotaxy:

- Arrangement of leaves on a stem.

Mutualistic Roots:

- Both fungus & root benefit & are dependent upon association for normal development. - Fungi facilitate absorption & concentration of nutrients, especially phosphorous for roots. - Plant w/ mycorrhizae develop few root hairs compared w/ those growing w/o an associated fungus. - Mycorrhizae

The stem functions in asexual reproduction to form...

- Bulbils - Stolons - Rhizomes - Runners

Zone of Maturation:

- Cell differentiation - Protoderm - Ground meristem - Provascular

Zone of Elongation:

- Cell expansion

What are stems?

- Component of the shoot system. - The central axis to which all other parts of the shoot system are attached. - Have leaves & flowers. - Epicotyl

Root Nodules:

- Contain large number of nitrogen-fixing bacteria. - Plants cannot convert free nitrogen to usable form. - A few species of bacteria produce enzymes that convert nitrogen nitrates & other nitrogenous substances readily absorbed by roots.

Apical Dominance:

- Control exerted by shoot apex over the lateral buds.

Vascular Cylinder (Stele):

- Core of tissue - Pericycle - Vascular tissue - Contains pith; only in monocots

Primary growth:

- Creation of vascular tissues, epidermis, & ground tissue. - Increase in length of stem. - Apical meristem creates pro cambium, ground meristem, protoderm.

Bud:

- Embryonic shoot. - Contains apical meristem. - Terminal/Axillary bud

Bulbils:

- Enlarged axillary buds. - Fleshy & round EX: Garlic

Root Structure:

- Epidermis - Cortex - Endodermis

Root development:

- First organ of the plant. - Upon germination, the embryo's radicle grows out & develops into the root.

Epicotyl:

- First stem to emerge from seed.

Cladophylls:

- Flattened, leaf-like stems. - Photosynthesis - Store water - Prickly pear cactus

Cork cambium:

- Forms in 2º phloem. - Produces cork. - Replaces the epidermis in roots & stems. - Forms part of the Secondary plant body. EX: Xylem makes up the wood of trees & shrubs. EX: Live phloem cells form the green bark. EX: Dead cork cells make up the bark.

Terminal bud:

- Forms new stem.

Mycorrhizae:

- Fungi that forms a mutualistic association w/ plant roots.

Rhizomes:

- Horizontal stems just below-ground. - Irises, some grasses, ferns.

Runners:

- Horizontal stems. - Makes new plants at end. - Strawberries

Auxins:

- Hormone produced by Apical Meristem. - Causes lateral buds to go dormant for a time.

Leaf scar:

- Imprint or scar left on stem tissue after a leaf breaks off at the petiole.

Pneumatophores:

- In plants w/ roots growing in water. - Roots extend above water for aeration.

Bulbs:

- Large buds w/ fleshy leaves & small stem. - Store food - Make new plants - Onions, lilies, hyacinths, tulips.

Axillary bud:

- Lateral bud. - Forms in axil of leaf. - Branch, flower.

Secondary growth:

- Lateral meristems (Lateral cambium) - Produces: • Cork cambium • Vascular cambium

Bud scales:

- Leaf-like scales covering a bud. - Protects bud between growing seasons.

Xylem:

- Makes up Vascular Cylinder. - Transport water & nutrients to leaves. - Upward

Phloem:

- Makes up Vascular Cylinder. - Transports food to roots. - Downward

Bud scale scar:

- Mark on the plant where bud scale falls from the emerging bud. - Indicates yearly growth.

Parasitic Roots:

- Most have no chlorophyll & dependent on chlorophyll-bearing plants for nutrition.

Corms:

- Mostly stem tissue, w/ papery leaves. - Store food. - Makes new plants. - Corcus & gladiolus

Mucigel:

- Mucigel & the root cap protect the root apical meristem as it pushes through the soil. - Mucigel is like a lube, which protects the root apical meristem & makes it easier to push through the soil.

Organ made of:

- Nodes - Internodes - Budes (Terminal/Axillary) - Stipules - Bud scars - Leaf scars

Pericycle:

- Outer boundary of the vascular cylinder. - Single-celled layer toward the inside of the endodermis. - Forms later roots.

Epidermis of roots:

- Outermost, single layer of cells. - Function: Protection & absorption

Cortex of roots:

- Parenchyma cells between epidermis & vascular cylinder. - Consists of parenchyma tissue & endodermis. - Storage - Support

Root Cap:

- Penetration, padding. - Thimble-shaped mass of parenchyma cells covering each root tip. - Protects tissues from damage as root grows. - Functions in gravitropism. - Protects the root apical meristem as it pushes through the soil.

Monocot roots:

- Pericycle produces only lateral roots. - Numerous Xylem & Phloem (8+) - Xylem are oval or round. - Pith large & well developed. - No secondary growth.

Perennial:

- Plant lives for more than 2 years.

Annuals:

- Plants that die after going from seed to maturity within one growing season.

Biennial:

- Plants that take 2 years to complete their lifecycle. 1st year: plant grows leaves, stems, roots. 2nd year: plant produces flowers, fruits, seeds, then dies.

Stolons:

- Produces beneath the surface & give rise to tubers.

Secondary plant body:

- Products of Lateral Meristems. - Not in monocots - Vascular cambium - Cork cambium - 2º xylem, 2º phloem, bark

Primary plant body:

- Products of the Apical Meristem. - 1º xylem, pith - Stem elongation

Apical Meristem:

- Protoderm --> Epidermis (dermal tissue system) - Ground meristem --> Ground tissues (parenchyma, collenchyma, & sclerenchyma) (ground tissue system) - Procambium --> 1º xylem & phloem (vascular tissue system)

Prop roots:

- Provide mechanical support - Lift tree out of water (stilt root) - "Prop up" the plant to stay up.

Contractile roots:

- Pull plant deeper into the soil. - Lilly bulbs - Dandelions

Water Storage roots:

- Pumpkin family - Especially in arid regions.

Food Storage roots (Enlarged taproot):

- Radishes - Beets - Carrots

Epidermis in Primary & Secondary growth:

- Reduces evaporation - Gas exchange

Aerial roots:

- Roots not covered by soil. - Exposed to air. - Facilitate climbing - Support branches - Photosynthetic

Stipules:

- Small leaf-like appendages at base of leaf. - Protects leaf in the bud.

Dicot roots:

- Solid core of xylem, w/ "arms" in cross section (like a star) - Pericycle gives rise to lateral roots, cork cambium. - Xylem & Phloem limited (2-6 or 8 max) - Xylem angular or polygonal. - Pith absent or very small - Secondary growth occurs.

Human relevance of roots:

- Sources of food - Spices - Dyes - Drugs - Insecticide

Buttressed Roots:

- Stability in shallow soil. - Tropical trees.

Statocytes:

- Starch granules found in Columella cells.

Internode:

- Stem region "space" between nodes. - Indicates yearly growth. - Space between years of growth.

Modified stems:

- Stolon - Runner - Tuber - Tendrils & thorns

Node:

- Structure at which 2 or more leaves are attached. - Contains buds - Phyllotaxy (alternate, spiral, opposite, whorled)

Stem functions:

- Support: leaves, flowers, fruits (leaves for food, flowers for fertilization, & fruit for dispersal. - Conduction: of water, minerals & sugar. - Photosynthesis - Storage: water & starch - Defense - Reproduction: Asexual

Endodermis of roots:

- Surrounds the Vascular cylinder. - Inner boundary of cortex, consisting of a single-layered cylinder of compact cells. - Cell walls impregnated w/ suberin & lignin on radial & transverse walls in bands called Casparian strips.

Food Storage roots (Swollen adventitious roots):

- Sweet potatoes - Cassava - Ginger

Tubers:

- Swollen, fleshy, underground stem. - Store food. - Potatoes - Eyes: nodes for making new plants.

What are the 2 pathways that roots absorb water & nutrients?

- Symplastic - Apoplastic

What are the 2 root systems?

- Taproot - Fibrous

Root development in Dicots:

- The radicle develops into a single taproot. - Persists - Grows deep into the ground. - Some lateral roots.

Root development in Monocots:

- The radicle initially develops into a taproot. - Smaller lateral branches arise. - Taproot dies - Adventitious roots arise from the shoot. - Shallow root system.

The stem stores starch to form...

- Tubers - Corms - Bulbs

Symplastic:

- Water & ions enter a plant through root hair. - Goes through cell membrane into cytoplasm. - Goes cell-to-cell through plasmodesmata. - Selective transport. - Affected by root metabolism. - Slower

Apoplastic:

- Water & ions enter a plant through root hair. - Goes through intercellular spaces. -Goes cell wall-to-cell wall (does NOT enter cytoplasm) - Can only go to endodermis (blocked by Casparian strip)

Casparian Strips:

- Water-impermeable strip of waxy material (lignin & suberin) found embedded in middle of cell walls of endodermal cells. - Controls water flow.

4 regions of Root Structure:

1. Root cap 2. Region of cell division 3. Region of cell elongation 4. Region of maturation

In addition to anchoring a plant, roots usually function directly in which process?

Absorption of minerals in solution.

Roots that develop from an organ OTHER than an existing root are called...

Adventitious roots

Cells of the apical meristem...

Are generally cuboidal in shape

The tissue just inside the root epidermis is called ______.

Cortex

Cells in the region of __________ are responsible for the growth in length of roots.

Elongation

Radicle:

Emerges from seed

Which tissue is common in roots but not in stems?

Endodermis

Tubular extensions of epidermal cells in the root are called root __________.

Hairs

How does the cuticle of root hairs compare to that of stems and leaves?

It's thinner

In the region of cell division of roots, cell division occurs in the apical __________.

Meristem

In mycorrhizal associations, what does the plant provide to the fungus, and what does the fungus provide to the plant?

Plant provides organic food; fungus provides mineral nutrients

Epidermal cells come from the meristem known as the __________.

Protoderm

What is the part of the embryo of a seed?

Radicle

In roots, tissue differentiation occurs in which region?

Region of maturation

______ root systems develop from the radicle.

Taproot

The perception of gravity by a root takes place in...

The root cap

Stems use ________ as defense.

Thorns

The most abundant cell type in periderm is...

cork

Typical root systems form up to ______ of the total dry biomass of a plant.

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