Vascular Tissue- Chapter 20

Concept 20.2 Root System

Anchor & Support Absorb minerals and water Monocot root- fibrous-mat -grass Dicot root-tap root-1 vertical root-carrot

Shoot System Stems, leaves, flowers Support Transport-transport tissue

Plant Root and Shoot System Shoot System= stems, leaves, flowers

Undeveloped shoots are buds. Terminal buds- stem tip Axillary- in the axils (angles) between leaf and main

stem. Growth from here produces plant branches. Blade- main part of the leaf. Petiole- stalk connecting the leaf to the stem. Veins- carry water and nutrients-vascular tissue and

support tissue. Examples of modified leaves-

Celery stalks- petioles; spines on cactus, tendrils Grass-no petioles.

Plant tissue system-3 types1. Dermal

Outer covering- “skin”- epidermisProtects

2. Vascular Tissue- 2 types Transport Xylem- water and minerals from roots-

shoots Phloem-food from leaves down. Roots-in center Stems- in vascular bundles. Monocot vs dicot differences

Monocot vs Dicot Root

Monocot vs Dicot stems

3. Ground Tissue- mostly parenchyma cells Fills in between the dermal and vascular tissues. Functions in photosynthesis, storage, and support

in young shoots.

Plant Tissue- Is made up of more than 1 type of plant cell.

Different cell types- Parenchyma- thin c. wall & large vacuoles.

Most abundant in fruit. Makes up phloem.

Collenchyma- thick, uneven; provides support; elongates.

Sclerenchyma- support; forms skeleton; makes up the water-conducting cells of xylem.

Primary Growth- Concept 20.3 Plants grow throughout their lifetime. Meristematic Tissue- differentiates into the

3 main tissues- dermal, vascular, ground. Apical meristems- found tips of roots and

shoots. Primary Growth- growth in length

roots- below ground shoots- above the ground

Primary Growth in Roots and Shoots

Primary Growth- growth in length Figure 20-13 – Root cap-protects delicate cells of apical

meristem. Primary growth -3 cylinders of developing

tissues Outermost cylinder- dermal tissue Middle- cortex Inner cylinder- vascular tissue

Xylem Phloem

Primary Growth of Shoots Apical meristem- tip of terminal bud

Elongation occurs below the meristem,pushing the apical meristem upward.

Axillary buds at bases of newleaves=branching

Shoot cylinders become dermal, ground,vascular tissues.

Concept 20.4- Secondary Growth Woody plants – vines, shrubs, trees Growth in plant thickness- width Cell division in 2 meristematic tissues:

vascular cambium and cork cambium

Vascular cambium- A cylinder of actively dividing cells Between the xylem and phloem Adds cells both sides

Secondary xylem inside Secondary phloem outside

Secondary xylem-wood. Growing season Dormant in winter Stem / root thickens with each new xylem Sapwood- new xylem actively transporting water Heartwood- old xylem not transporting water

Secondary phloem- outside vascular cambium.

Cork cambium- meristem- produces cork

When cork cells die-thick waxy walls-prevent water loss

Barrier of protection Bark- everything to the outside of the

vascular cambium- Includes phloem, cork cambium, and cork

Secondary Growth

Tree rings Age from annual rings = year of growth

Easiest to count dark bands of secondary phloem from outside to inside.

Environmental conditions- differences in ring width.

Each ring- Spring- cool, plenty of water conditions

Produce large, thin walled cells of xylem carry lots of water.

Summer- hot, dry conditions Narrow thick walled cells

Tree Rings- History of the Plant

What nutrients do plants need?Concept 21.1 Plant get nutrients from _____ and _____. Air supplies carbon dioxide and ________. Water supplies hydrogen and serves as a

solvent for dissolved minerals. Plants have simpler needs than animals Plants require 17 chemical elements for

their life cycles

Chemical elements needed/function Nitrogen- proteins and nucleic acids Sulfur- proteins Phosphorous- nucleic acid and ATP Potassium – protein synthesis and osmosis

Na+-K+ pump Calcium-cell wall, enzyme activity Magnesium- chlorophyll synthesis, enzyme

activity

Consequences of poor nutrition Growth –stunted No flowers produced Stems, roots, leaves may die Yellow leaves if no chlorophyll produced

Vascular transport Concept 21.2 Roots –absorb water and minerals

Root hairs & Mycorrhizae

Xylem- moves water and minerals upward 2 forces-

1. Root pressure- Pushes water up the xylem (at night) Root epidermal and ground tissue cells use ATP to

get minerals – into xylem Endodermis around vascular tissue-waxy cells-

prevents leakage of water. Water enters xylem by osmosis

2. Transpiration-pull-

Main force- pulls xylem up Transpiration- loss of water thru leaves due to

evaporation. Cohesion : same kind molecules stick together

water –water Adhesion : attraction between unlike molecules (

water – cellulose (xylem walls)

Regulating water loss Stomata (singular-stoma)

Pores on underside epidermis of leaf gas exchange – CO2 Guard cells-

surround stoma-open and close stoma by changing

shapeOpen- day- to let in CO2

Closed- night- to prevent water loss.

Leaf Diagram- Structure

Water follows potassium ionsfrom surrounding cells into guard cells.

Leaf Structure

Leaf Cross-section

Flow of Phloem Phloem- “food phloem down”

Transports sugar and organic compounds + water.

From source (mature leaves-photosynthesis) to sink (where needed- roots, fruits, developing shoots).

Pressure-flow mechanism-Water follows sugar; high conc. to

low conc.

Sieve tubes carry phloem sapPressure-Flow mechanism- hypothesis for movement of phloem sap.

21.3 Carnivorous Plants Some plants – N from animals Ex: sundews, Venus's flytraps, pitcher

plants Little organic N where they live (wetlands,

cold, acidic water, decay slow) Still photosynthesize

Ch. 22.1 Plant hormones –chemical messengers

Control: Germination Growth Flowering Fruit production

1. Auxins Apical meristems – shoot tips Cell elongation Secondary growth – vascular cambium Seeds – auxin – signal ovary to fruit Auxins - no pollination seedless fruit

Phototropism Auxin builds – shaded side Shaded cells lengthen more, more water Uneven sides = bending

2. Cytokinins Cell division – made in roots Cytokinin with auxin

Fewer / shorter branches near tip

3. Gibberellins Fruit – seedless, larger

4. Abscisic Acid (ABA) Limits cell division Stops growth Dormancy “stress hormone”

5. Ethylene Fruit ripening “leaf drop”

22.2 Plant Responses Rapid plant movements

Touch Rapidly reversible

Tropisms – slowly grow toward or away from a stimulus Slow to reverse

1. Thigmotropism Touch Climbing plants – tendrils Seedling - obstacle

2. Phototropism Light Uneven auxins – light one side

3. Gravitropism Gravity Seedling root / shoot

Disease Viruses, bacteria, fungi Adaptations

Epidermis Chemicals – lignin Resistant genes Thorns, poisons