Chapter 9: Water

How are odors able to be detected?

Without being in mediate physical proximity to the source

Molecules are constantly in:

Motion

What are molecules movement similar to?

Moving tennis balls in a room

How does molecular movement work in terms of tennis balls?

Tennis balls in one room entering another through a hole in the wall, which would becomes equal over time

How can Brownian movement be viewed?

Using a light microscope

What is an example of a brownian movement showed using a light microscope?

A diluted drop of ink on a slide with high power, which shows the particles in constant motion

How is the concentration of molecules affected if concentration gradient is present?

A high concentration of molecules in one region and a lower concentration of molecules in an adjacent region

How is the movement of molecules affected if concentration gradient is present?

Molecules move alone a concentration gradient from high to low concentration

What type of molecule movement is against concentration gradient?

Moving from lower to higher concentration

Diffusion

Movement of molecules from a region of higher concentration to a region of lower concentration

State of equilibrium

Molecules distributed throughout available space

What does the rate of diffusion depend on?

Pressure, temperature, and density of medium

Solvent

Liquid in which substances dissolve

Semi-permeable membranes

Membranes in which different substances diffuse at different rates

Which type of cells have semipermeable membranes?

All plant cell membranes

Osmosis

Diffusion of a solvent (usually water) through a semipermeable membrane

What are the regions included in the diffusion process? (Osmosis)

A region where water is more concentrated to a region where it is less concentrated

How can osmosis be measured?

Using an osmometer

Osmotic pressure

Pressure required to prevent osmosis

How is the Osmotic potential balanced?

By resistance of cell wall

Pressure potential (Turgor Pressure)

Pressure that develops against walls as result of water entering cell

Turgid cell

Firm cell due to water gained by osmosis

What does the water potential of a cell include?

Osmotic pressure + pressure potential

What is Osmosis the primary means of?

By which water enters plant cells

Where does water move in cell walls?

Intercellular spaces of the epidermis and root hairs until it reaches the endodermis

What does the water move across to reach the xylem?

The endodermal cells

Where does the water move throughout the plant?

The xylem and diffuses out through stomata

Plasmolysis

Loss of water through osmosis

What is plasmolysis usually accompanied by?

Shrinkage of protoplasm away from the cell wall

What do large molecules (such as cellulose, starch) develop when wet?

Electrical charges, which attract water molecules

What do water molecules adhere to?

Large molecules

What is the result of water molecules adhering to large molecules?

Swelling of tissues

What is the first step in germination of seed?

Imbibition

Active Transport

A process used to absorb and retain solutes against a diffusion, or electrical, gradient by expenditure of energy

Active transport involves:

Proton pump

Proton pump

Enzyme complex in plasma membrane energized by ATP molecules

What does the transfer of protein allow for/facilitate?

Transfer of solutes to outside and to inside of cell

How are some plants able to survive in salty environments?

By accumulating large amounts of organic solutes, which drive osmosis

Transpiration

Water vapor loss form internal leaf atmosphere

How much percent of the water entering a plant is transpired?

More than 90%

How can water vapor be demonstrated?

By covering the soil of a potted plant, then covering the plant with a bell jar

What did Nehemiah Grew suggest about movement of water in plants?

Cells surrounding xylem produce a pumping action

Why was Nehemiah Grew’s suggestion not supported?

Water moves in dead stems

What did Marcelo Malpghigi suggest about movement of water in plants?

Capillary action moves water in plants

Why did Malpighi’s suggestion not work?

Air must be present above the water column

What did Stephen Hale suggest about movement of water in plants?

Plants need root pressure to move water

Why is Stephen Hale’s suggestion not true?

In summer root, pressure is minimal

Cohesion-Tension Theory

Transpiration generated tension to pull water columns through plants from roots to leaves

What does the Cohesion-Tension Theory say about when water columns are created?

When water molecules adhere to tracheids and vessels of xylem and cohere to each other

What occurs when water evaporates from mesophyll cells?

They develop a lower water potential than adjacent cells

What does water move into mesophyll and adjacent cells with?

A higher water potential

How long is the water movement process continued?

Until veins are reached

What does the movement of water create on water columns?

Tension, drawing water all the way through entire span of xylem cells

How does water continue to enter root?

By osmosis

What is water forced by to enter?

By Casparian strips to enter endodermal cells, which leads to the xylem

What does the stomatal apparatus regulate?

Transpiration and gas exchange

What is included in a stomal apparatus?

2 guard cells + stoma (opening)

What are transpiration rates influenced by?

Humidity, light, temperature, and carbon dioxide concentration

What occurs when the stomata opens?

Photosynthesis

What do guard cells acquire through the expansion of energy?

Potassium ions from adjacent epidermal cells

What occurs to water potential in guard cells after the stomata opens?

Lower water potential

How does water enter the guard cells?

Through osmosis

What happens to the guard cells after stomata opens?

They become turgid

When does photosynthesis not occur?

When stomata closes

What leaves the guard cells once the stomata closes?

Potassium ions, causing water to leave and for cells to become less turgid

What time of day is stomata open in most plants?

During the day

What time of day is the stomata closed in most plants?

At night

Which plants contain an open stomata at night?

Desert plants

Why does the stomata only open at night in desert plants?

To conserve water

What is carbon dioxide converted into during CAM photosynthesis at night?

To organic acids and stored in vacuoles

What is carbon dioxide converted into in CAM photosynthesis during the day?

Carbon dioxide

Which type of plants is the stomata recessed below the surface of leaf or in chambers?

Desert plants, pines

Guttation

Loss of liquid water

If cool night follows a warm, humid day, what is produced?

Water droplets through hydathodes at tips of veins

How is the water forced out of the hydathodes?

Through the absence of transportation at night, pressure in xylem

What is an important function of water?

Translocation of food substances in solution by phloem

What occurs during flow hypothesis?

Organic solutes flow from source, where water enters by osmosis, to sinks and exits

Where is the food utilized by water during flow hypothesis?

In sinks

Where do organic solutes move along concentration gradients?

Between sources and sinks

Phloem Loading

Sugar enters by active transport into sieve tubes

What occurs to the water potential of sieve tubes?

Water potential decreases, but allows for water to enter by osmosis

What does the development of turgor pressure do?

Drives fluid through sieve tubes toward sinks

Where does mass flows occur?

From higher pressure at source to lower pressure at sink

What does the water diffuse into at the end of the Flow-Hypothesis?

Xylem

Essential elements

Essential as building blocks for compounds synthesized by plants

Macronutrients

Used in plants in greater amounts

What are examples of macronutrients?

Nitrogen, potassium, calcium, phosphorus, magnesium and sulfur

Micronutrients

Needed by the plants in very small amounts

What are examples of micronutrients?

Iron, sodium, chlorine, copper, maganese, cobalt, zinc, molybdenum and boron

What are the symptoms of Potassium deficiency in plants?

Yellowing of leaves at margins and center, lower leaves mottled and often brown at tip

What are the symptoms of Phosphorus deficiency in plants?

Plant is stunned with darker green colored leaves, lower leaves often purplish between veins

What are the symptoms of Calcium deficiency in plants?

Terminal bud often dead, young leaves often appear hooked at ripe, tips and margins withered, roots dead or dying

What are the symptoms of Nitrogen deficiency in plants?

Relatively uniform loss of color in leaves, occurring first in the older leaves

What are the symptoms of Sulfur deficiency in plants?

Leaves pale green with dead spots, veins lighter in color

What are the symptoms of Magnesium deficiency in plants?

Veins of leaves green but yellow between them, dead spots suddenly appearing, leaf margins curling

What are the symptoms of Iron deficiency in plants?

Large veins remain green while rest of leaf yellows, mainly found in young leaves