chapter 17: plant structure and nutrient support how plants function and why we need them lecture by...

Chapter 17: Plant Structure and Nutrient Support

How plants function and why we need themLecture by Danielle DuCharme, Waubonsee Community College; Clicker questions by Kris Curran, University of Wisconsin-Whitewater

Learning Objectives

Understand and be able to explain the following:

• the three basic tissue types that give rise to diverse plant characteristics.

• the common structural features shared by most plants.

Learning Objectives

Understand and be able to explain the following:

• how plants obtain sunlight and usable chemical elements to obtain nutrition from their environment.

• how plants transport water, sugar, and minerals through vascular tissue.

17.1 Older, taller, bigger: Plants are extremely diverse.Plants can be “superior” to animals in a variety of ways:

• longevity• height• weight• energy acquisition

Extraordinary Attributes of Plants

Plants Have Three Distinct Parts

The three distinct parts of plants are the:

1) roots2) stems3) leaves

Root System

The roots serve several important functions, including absorbing water and minerals, as well as some oxygen, from the soil and anchoring plants in place.

The Shoot: Stems

Stems provide structural support for the leaves.

Stems have vascular tissue, which conducts food, water, and mineral nutrients throughout the plant.

The Shoot: Leaves

Leaves are the chief sites of photosynthesis in plants, becoming the plant’s primary food factory.

Leaves also are vulnerable to water loss through evaporation.

Which part of a plant evolved to help the plant acquire water and nutrients?

1. Roots2. Stems3. Leaves4. All of the above

Take-home message 17.1

Plants are an extremely diverse and successful group of organisms, generally composed of three distinct parts: roots, stems, and leaves.

17.2 Flowering plants are divided into two major groups.

The flowering plants are classified into two major groups: monocots and dicots.

These names derive from a structure called the cotyledon.

Monocots and Dicots

Plants in which one cotyledon forms are called monocots, and plants in which two cotyledons form are called dicots.

Plants are also divided into these groups by different features in their seeds, leaves stems, flowers, and roots.

Monocots

Monocots generally have:

• parallel veins in their leaves.

• vascular tissue in bundles.

• flower parts in multiples of three.

• many fibrous roots

Dicots

Dicots generally have:

• leaves with branching veins• vascular tissue arranged in an orderly

ring• flower parts in fours in fives• a taproot

Monocots vs. Dicots

Monocot Examples

palm trees orchids lilies most of the grains used in food

products all of the grasses

Dicot Examples

most plants that we consider flowers coffee potatoes most fruits and vegetables most large trees

Roses typically have five petals. Therefore, we would categorize these plants as:

1. Bryophytes2. Mosses3. Monocots4. Dicots


The flowering plants are divided into two major groups—the monocots and the dicots—based on structural features of their seeds, leaves, stems, flowers and roots.

17.3 Plant cells and tissues differ from animal cells and tissues.

There are three main tissue types in plants:

1) dermal tissue2) vascular tissue3) ground tissue

Dermal Tissue Dermal tissue covers and protects the entire plant. Dermal tissue includes a thin epidermis, a waxy

cuticle, and specialized guard and cork cells.

Vascular Tissue Vascular tissue is a system for getting

nutrients to, and removing waste products from, all parts of the plant.

Sap is moved in tissue called xylem and phloem.

Ground Tissue Ground tissue comprises most of the plant body. Three types of cells—parenchyma, collenchyma,

and sclerenchyma—are found in ground tissue.

Plants regulate water loss and gain in the ________________ located in the leaves while most metabolic activities occur in the ___________, part of the ground tissue.

1. xylem; collenchyma2. guard cells; sclerenchyma3. phloem; parenchyma4. guard cells; parenchyma


All vascular plants are organized around the same basic body plan and built from the same three types of tissue.

Dermal tissue covers and protects the surface of the plant.


Vascular tissue transports water, sugars, and minerals throughout the plant body.

And, ground tissue, which makes up the bulk of the plant, is where most of the plant’s metabolic activities are carried out.

17.4 Roots anchor the plant and take up water and minerals. Roots are essential

to plant growth and survival.

They perform three primary functions:

1) absorption2) anchorage3) storage

There Are Two Types of Root Structure: Taproots and Fibrous

Roots

Organization of Tissue within the Root Is Simple

Spaces Exist between Root Cells

Spaces in root cells allow for gas exchange.

In a carrot plant, food is stored in a structure called a ___________ root and in cells called ___________ cells.

1. fibrous; parenchyma2. fibrous; collenchyma3. tap; parenchyma4. tap; collenchyma


Roots have three primary functions in plants:

1) Absorption: the uptake of water and dissolved minerals from soil.

2) Anchorage: securing the plant in place.3) Storage: for water and excess starch

for future use.

17.5 Stems are the backbone of the plant.

Stems provide structural support and house the circulatory system of the plant.

Stem Structure Is More Complex

Growth in stems occurs in meristems (including apical and lateral meristem) and at nodes.

Remember, dicot and monocot stems differ.

There Are Variations in Stem Structure

Which part of the stem contains undifferentiated cells?

1. Cortex2. Apical meristem3. Xylem4. Phloem5. Vascular

bundles

Which example below is NOT a stem?

1. Onion bulb2. White potato3. Tree trunk4. Sweet potato5. Daffodil bulb

Take-home message 17.5 Stems serve three chief functions in

plants:

1) They put leaves in positions where they can intercept sunlight and carry out photosynthesis.

2) They provide structural support for the plant.

3) They contain the xylem and phloem, through which water, minerals, and sugars are distributed throughout the plant body.

17.6 Leaves feed the plant.

The job of the leaves is to produce food for the plant.

Leaves convert the potential energy from the sun into usable chemical energy in sugars.

Plants don’t need to move to get energy—energy comes to them!

The leaf has five layers:1) Waxy cuticle2) Layer of non-

photosynthetic cells3) Photosynthetic cells4) Xylem and phloem5) Non-photosynthetic

cells, with “breathing” holes called stomata.

Leaves Have a Layered Structure

There Are Many Variations in Leaf Structure

The Largest Leaves and the Smallest Leaves

Water lily leaves are amongst the biggest leaves, with individual leaves measuring seven feet across!

Duckweed leaves, on the other hand, are tiny—you need 25 end to end just to measure one inch in length!

Which leaf cells below are photosynthetic?

1. Guard cells2. Xylem3. Palisade cells4. Spongy

mesophyll cells5. 3 and 46. All of the above

Take-home message 17.6 Leaves are thin and have a three-

layer structure that enables them to effectively capture energy and transport water and nutrients.


Leaves intercept sunlight, putting chloroplast-containing photosynthetic cells in the path of that light and converting the potential energy of the sun into the usable chemical energy of sugar.


Leaves also have vascular tissue through which food is transported out of the leaf to the rest of the plant, and water and minerals are transported into the leaf.

17.7 Several structures help plants resist water loss. Water loss by evaporation is

damaging to the plant.

Structures such as the waxy cuticle, surface leaf hairs, and holes called stomata resist against water loss.

These Features Help Reduce Evaporation

Which structure(s) can act as a seal to decrease water loss from the leaf due to evaporation?1. Thick cuticle2. Stomata with guard

cells3. Leaf hairs4. 1 and 25. All of the above


Plants have multiple adaptations that enable them to resist becoming dangerously dehydrated.

These adaptations include the cuticle, leaf hairs, and stomata.

17.8 What are the elements of plant nutrition?Plants require four things for proper nutrition:

1) Sunlight for the energy to build molecules of sugar

2) Water3) Air as a source of

carbon dioxide4) (Usually) soil

Minerals and Essential Nutrients

There are thirteen different minerals that plants require for proper survival and growth.

Six of these essential nutrients are required in large amounts. These are: nitrogen, phosphorus, magnesium, potassium, sulfur, calcium.

Essential Plant Components


Plant growth is dependent on four important factors:

1) Sunlight for energy2) Water3) Air as a source of carbon dioxide4) Minerals, usually obtained from soil

17.9 Nutrients cycle from soil to organisms and back again.

Soil is made of four distinct components:

1) Minerals2) Organic materials3) Air4) Water

Minerals About half of the

total volume of dirt is inorganic material.

These come from the weathering of rocks.

These particles come in three sizes: sand, silt, and clay.

Organic Materials Decomposition of

dead animal and plant material (humus) returns nutrients to the soil.

Decomposition is performed by bacteria, fungus, insects, and earthworms.

CompostingComposting is decomposition of organic matter that can decrease the amount of waste on the planet and speed organic breakdown.

Water and Air

Water and air fill the spaces between the particles of inorganic and organic matter and account for about half of the total volume of soil.

When humans compost their food waste they are creating a type of soil called ________, which is rich in organic materials.1. Humus2. Clay3. Sand4. Silt


Soil is a mixture of minerals, organic materials, air, and water, which serves as an almost perpetual source of nutrients critical to a plant’s health and survival.

17.10 Plants acquire essential nitrogen with the help of bacteria.

Nitrogen is abundant in the atmosphere, but is a factor that can limit plant growth.

Nitrogen is used for protein construction, and that is why it is added to fertilizers.

Nitrogen Fixation

Nitrogen gas in the air must be converted to nitrate or ammonium in soil by bacteria for it to be used by plants.

This is called nitrogen fixation.

How do bacteria and plants form this mutualistic alliance?

Some Plants Have Alternative Ways of Obtaining Nitrogen

These plants ingest animals, such as insects, to obtain nitrogen they do not get in the soil, and are called carnivorous (insectivorous) plants.

One example is the Venus flytrap.

Crop Rotation

To keep the soil rich in nitrogen, farmers should plant those plants that have nitrogen-fixing bacteria (i.e., alfalfa) in a rotation with those that do not (that deplete the nitrogen in the soil).

Which answer is a usable form of nitrogen for plants that is produced by bacteria?

1. Nitrogen gas2. Nitrogen oxide3. Ammonia4. Nitrates5. 3 and 46. All of the above


Among the minerals, nitrogen is the one that most commonly limits plant growth because it is required in nearly all the cells and tissues produced by plants, but does not exist in an easily usable form in nature.


A mutually beneficial relationship has evolved that enables plants to gain access to nitrogen that is “fixed”—that is, chemically modified into a usable form—by bacteria.

17.11 How do plants take up water and minerals?

Water is transported into the root by osmosis.

Mineral Uptake Differs from Water Uptake

Minerals are chemically charged. Therefore, active or facilitated mineral transport

into the plants must be aided by transport proteins.

Plants Again Benefit from a Mutualistic Relationship

Fungi living around and within the roots increase absorptive surface area.

In exchange for providing increased vitamins and minerals to the plant, the fungus receives sugars, amino acids, and vitamins in return.


Plants absorb water from the soil through osmosis occurring in their root hairs.

Absorption of minerals also occurs in the roots, but this requires the help of transport proteins in root cell membranes.


In a mutualistic association called mycorrhizae, fungi growing into and around plant roots increase the water and mineral absorption for the plant, while gaining access to energy and nutrients from the plant.

17.12 Water and minerals are distributed through the xylem. Evaporation is

relentless.

Liquid water is continually converted to water vapor in the dry air.

This evaporation steals necessary moisture from leaves.

How is water moved through a plant?

Cohesion-Tension Mechanism

In the cohesion-tension mechanism, the plant does not need to expend any energy to pump water and minerals up from the roots to the leaves.

Drawback

This system of water transport limits the size to which the tree can effectively grow.

Xylem Stores Sugar to Nourish New Leaf Buds

Human Use of Sap

Humans have concentrated the sugars in sap to enjoy as a food source.

Maple syrup is created in this process.

Cohesion-tension theory explains how the polarity of water molecules helps in their transport from the roots to the top of the plant. Why are minerals also transported in this fashion?

1. The minerals are charged and therefore dissolved in the water.

2. The minerals are light in weight and therefore carried upward by the flow of the water.

3. The minerals are moved through the phloem.4. Minerals are collected from the air and travel

down through the xylem to the roots.

Classroom Catalyst

Celery Water Transport

If we were to repeat this experiment, which growing condition would lead to the fastest migration of colored water to the leaves when compared to our original experiment?1. Fill the glass three quarters full

of water.2. Keep the glass of water + celery

in cooler, dark room.3. Keep the glass of water + celery

in a warmer, well-lit room.4. Fill the glass with warm water.


Xylem directs the flow of water and dissolved minerals from the roots to all the tissues in the plant.


The force driving this flow of fluid (the xylem sap) comes from evaporation of water from the leaves, which pulls water up from the roots.

17.13 Sugar and other nutrients are distributed through the phloem. Phloem is a food delivery system.

Sugar is produced in the leaves (the “source”) and transported to places (“sinks”) where sugars are needed.

Pressure-Flow Mechanism

The phloem “pipeline” moves the sugar produced in the leaves to roots, stems, buds, flowers, and fruits.

This process is the pressure-flow mechanism.

Sugar Movement Through the Plant

Organisms Besides the Plant Benefit from the Sugary

PhloemAphids pierce the plant stem to gain access to the sugary phloem.

Where does the pressure for the pressure-flow mechanism come from?1. Active transport of sugars into the

phloem.2. Diffusion of water into phloem that

is high in sugar.3. Pumps in the leaves that drive the

phloem away from sites of photosynthesis.

4. A combination of 1 and 2.5. All of the above.


The phloem consists of a branching network of vessels made from living cells lined end to end to form sieve tubes, with small openings in their side walls.


Sugar, usually sucrose, is moved in the phloem from sites of production (sources) to sites of use or storage (sinks).


The direction of flow is not always the same: a plant part may be a source at one time, and a sink at another.

chapter 17: plant structure and nutrient support how plants function and why we need them lecture by...

Documents

flowering plants

anchoring plants

distinct parts of plants

plants transport water

plants primary food

diverse plant

plant cells

plant structure