Biology Week 14- Plant Tissues

Day 1 | Day 2 | Day 3 | Lab | Weekly Quiz | Quizstar

Ground tissue Parenchyma Collenchyma Sclerenchyma Dermal tissue Epidermis Stomata Guard cell Cork Vascular tissue Xylem Phloem Meristem Apical meristem Lateral meristem Vascular cambium	Cork cambium Taproot Fibrous root Primary root Adventitious root Root cap Root hairs Herbaceous stem Woody stem Tree ring Springwood Summerwood Heartwood Sapwood Petiole	Simple leaf Compound leaf Hormone Auxin Gibberellin Ethylene Cytokinin Abscisic acid Tropism Phototropism Thigmotropism Gravitropism Hydrotropism Photoperiodism Critical length

Plant Tissues:
groups of cells that perform a common function.

What are the tallest trees in the world?

1. Ground tissue system: ground tissue provides storage, metabolism, and support.

   Parenchyma

   • Large, loosely packed, rectangular cells with thin cell walls.
   • Responsible for photosynthesis and food storage.
   • Over 80 % of the cells in non-woody plants.

   Collenchyma

   • Elongated cells with uneven, flexible cell walls.
   • This tissue supports the growth regions of a plant.

   Sclerenchyma

   • Cells are short-lived with thick cell walls.
   • Serves to support the plant.
   • The cells that give a plant its "woody" characteristics.

2. Dermal tissue system: dermal tissue forms the outside covering of plants and provides protection.

   

   Epidermis

   • The outer layer of cells.
   • Protects the plant and reduces water loss.
   Stomata
   • Regulate gases passing into and out of the plant
   • Usually located on the under side of leaves.
   • Guard cells regulate the opening by changing water pressure within the cell to swell or shrink.
   Cork: closely packed cells protecting a woody stem.

3. Vascular tissue system: vascular tissue provides transport and support.

   

   Xylem: straw-like tubes conducting water and minerals upward in a plant.

   Water is moved to the tops of very tall trees by capillary action, the adhesion/cohesion of water, transpirational pull, and root pressure. The largest force (transpirational pull) results from the evaporation of water from the leaves at the top of the tree. A tree behaves like a big straw, as water moves out of the leaves at the top and water moves in at the roots to replace it. Capillary action (what holds the water together) is a consequence of the high surface tension of water due to hydrogen bonding. Theoretically this process could continue at a very great height, but in practical terms trees are restricted to a maximum of about 400 feet (California redwoods) because of the requirements of stability. Water has been measured traveling up the stems of some oak trees at a rate of 60 meters per hour.

   Phloem: straw-like tubes conducting food downward in a plant.

4. Meristems: growing regions where cells divide.

   Apical meristem - located at the tips of stems and roots.

   Apical meristems produce growth in length, primary growth.

   Lateral meristem - located around the outer edge of stems and roots.

   Lateral meristems produce growth in circumference, secondary growth.

   Two types of lateral meristems:
   1. Vascular cambium - located between the xylem and phloem, it produces additional vascular tissues.
   2. Cork cambium - located outside the phloem, it produces the cork.

Day 1 Assignment - Plant Tissues
This assignment must be turned in by the beginning of class tomorrow to receive credit.
Scoring criteria

1. Name the 3 different types of plant tissue systems.
2. Draw a diagram of a plant and label the location of each plant tissue.
3. From the drawing above make an enlargement diagram of a cross section of a leaf and lable the parts (What is inside?)
4. Write no less than a paragraph discussing meristematic growth of a plant or draw a diagram showing the process.
5. Which of the ground tissues give plants its "woody" characteristics.
6. What type of dermal tissue is responsible for regulating gases that pass in and out of a plant.
7. California redwoods can be as much as 100 meters high. Explain how water gets to the top of these tall trees?
8. How are vascular tissues related to a successful plant graft?

Day 2

What causes tree rings to form?

The 3 major plant parts:

Roots anchor plant in ground, absorb water and minerals, and store food.

• Taproot system - the primary root grows much larger than the other roots of the plant.
• Fibrous root system - the primary root does not grow large so that many roots of the plant are similar in size.
• Primary root - the first root to grow out of a seed.
• Adventitious roots - specialized roots that grow from plant stems or leaves.
• Root cap - a shield of parenchyma cells covering the apical meristem at the root tip.
• Root hairs - small extensions of a root, these greatly increase the surface area of the root for absorption.

Stems support the plant, transport materials in the plant, and serve as a storage area.

• Herbaceous plants have stems with very little sclerenchyma tissue which makes their stems "soft". These "non-woody" plants have vascular tissues arranged in bundles. These vascular bundles are either scattered throughout the stem or found in a ring toward the edge of the stem.
• Woody plants are mostly sclerenchyma, with the phloem located in a ring near the outside of the stem while the xylem is located more to the inside.
• Tree rings:
  • Springwood - when water is plentiful, wide xylem cells with thin walls are produced.
  • Summerwood - during dry weather, new xylem cells are smaller with thicker walls.
  • This produces a visible difference in the appearence of the woody stem. Since one sequence of this occurs each year, the age of a tree can be closely estimated by counting the "rings".
• Heartwood - when the xylem becomes clogged, it can no longer transport water and will take on a dark color. This can be seen in the center of most trees.
• Sapwood - the lighter-colored wood in a tree. Even if the cells are no longer living, they can still function to transport water.

Leaves are specialized for capturing sunlight for photosynthesis.

• The blade of a leaf is attached to the stem by a stalklike petiole.
• A simple leaf has one blade and one petiole.
• In compound leaves, the blade is divided into leaflets on the same petiole.

Day 2 Assignment - Plant Tissues
Scoring criteria

1. Summarize how roots absorb water.
2. The "heartwood" in a woody stem is darker than the surrounding wood. Why?
3. How are tree rings formed? What is Dendrochronology?
4. There are two types of root systems pictured above, fibrous and taproot. Which type is more common in monocots and which in dicots?
5. Roots absorb minerals from the soil. There are ten minerals needed for normal plant growth. All of these are considered to be "essential" nutrients but some are called macronutrients and others micronutrients. Explain the difference between macronutrients and micronutrients.
6. Find two pictures of different types of leaves cut and past or draw them and then label the parts using the leaf characteristics discussed on our web page.

Day 3

What environmental stimulus causes plants and tree leaves to begin to grow in the spring?

Farm Manager

Plant hormones: Chemical messengers that affect a plant's ability to respond to its environment.

Auxins - hormones that promote plant-cell elongation, apical dominance, and rooting.
Gibberellins - a group of hormones that primarily stimulate elongation growth.
Ethylene - the hormone responsible for the ripening of fruit.
Cytokinins - a group of hormones that promote cell division.
Abscisic acid - a hormone that generally inhibits other hormones.

There is a group of synthetic chemicals that does not fit into any of the five classes of hormones. Growth retardants are chemicals that prevent plant growth. Most of the developed chemicals slow the growth of woody plants.

  (bio lab 294)
Tropisms: plant movement toward or away from an environmental stimulus.

Phototropism - a growth response to light. Solar tracking is the phototropism of leaves or flowers as they follow the sun's movement across the sky. Thigmotropism - a growth response to contact with a solid object. Thigmotropism allows vines to climb. It is thought that an auxin or ethylene are involved in this response. Gravitropism - a growth response to gravity. Roots are positively gravitropic, usually growing downward and stems are negatively gravitropic, usually growing upward. Auxins are probably responsible for this growth. Chemotropism - a response to chemicals. The growth of a pollen tube is in response to chemicals produced produced by the plant ovary. Hydrotropism - a response to water. Most plants have a positive response to water.

Photoperiodism: plant response to changes in the length of days and nights.

Critical length is the length of daylight above or below which a species of plant will flower. Long-day plants flower only when exposed to day lengths longer than their critical length. These are usually late spring and early summer flowers. Short-day plants flower only when exposed to day lengths shorter than their critical length. These are usually early spring and fall flowers. Day-neutral plants are not affected by the length of days and nights.

Day 3 Assignment - Plant Tissues (Test Your Concept Understanding) What is the phototropic response of plant leaves to light? What type of tropism controls the growth of plant roots? Both auxins and cytokinins make plants grow bigger, but they do it in different ways. How do each of these plant hormones "regulate growth"? Which part of a plant to both auxins and gibberellins cause to grow? Why don't all species of plants produce flowers at the same time? Why do tree leaves change color in the fall?

Research Links:

• Plants national data base - United States Department of Agriculture
• Plants-in-motion - Indiana University, Dept. of Biology
• Botony - Encyclopedia of plants
• Plant and Animal Cells - DVHS Biology Class
• Plant Taxonomy - DVHS Botany Class
• Botany 201 - Texas A&M University
• Plant Tissues - Georgia Perimeter College
• The Families of Flowering Plants - Delta Database
• A Glossary of Terms for Vascular Plants - Australian National Botanic Gardens
• Grafting - Central Florida Heritage Rose Society
• Propagation Resources - Texas A&M Horticulture
• Selected Botanical WWW Sites - University of Florida

California redwoods are the tallest trees in the world, growing nearly 400 feet tall.

Xylem cells grow large in the spring when water is plentiful, but much smaller in the summer when there is less water. The visible difference in these spring and summer cells causes what we know as tree rings.

Plants and tree leaves begin to grow in the spring as a response to the increasing length of daylight hours.