Chapter - 25 - Plant Nutrition and Transport

What are essential plant nutrients?

Chemical elements plants need to grow, develop, and complete their life cycles.

What are macronutrients?

Essential nutrients required by plants in relatively large amounts.

What are micronutrients?

Essential nutrients required by plants in relatively small amounts.

What are examples of plant macronutrients?

Carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, sulfur, calcium, and magnesium.

What are examples of plant micronutrients?

Iron, manganese, boron, copper, zinc, molybdenum, nickel, and chlorine.

What is the difference between macronutrients and micronutrients?

Plants need macronutrients in larger amounts and micronutrients in smaller amounts; both are essential.

What do the letters N-P-K on fertilizer labels represent?

Nitrogen, phosphorus, and potassium.

Why is nitrogen important to plants?

It is needed to make proteins and nucleic acids and supports growth.

Why is phosphorus important to plants?

It is part of ATP, nucleic acids, and phospholipids.

Why is potassium important to plants?

It helps regulate processes such as enzyme activity and water balance.

What is a nutrient deficiency?

A condition in which a plant lacks enough of an essential nutrient for normal growth.

How can nutrient deficiencies affect plants?

They can cause poor growth, discoloration, or other abnormal symptoms.

What is soil made of?

Mineral particles, organic matter, living organisms, water, and air.

What is humus?

Decomposed organic matter in soil that helps improve soil structure and nutrient availability.

What are the three major mineral particle sizes in soil?

Sand, silt, and clay.

Which soil particle is largest: sand, silt, or clay?

Sand.

Which soil particle is smallest: sand, silt, or clay?

Clay.

What is loam?

Soil containing a relatively balanced mixture of sand, silt, and clay, often suitable for plant growth.

What is a soil horizon?

A distinct layer of soil with characteristic properties.

What is the A horizon?

The topsoil layer, usually containing mineral particles and relatively abundant organic matter.

What is the B horizon?

The subsoil layer where materials leached from upper layers may accumulate.

What is leaching?

The movement of dissolved substances downward through soil as water passes through it.

What is soil erosion?

The removal and movement of soil by agents such as water and wind.

How can agriculture contribute to soil erosion?

Practices that leave soil exposed or disturb it heavily can increase erosion.

How can farmers reduce soil erosion?

Practices such as reduced tillage, crop rotation, and maintaining plant cover can help.

Where do plants obtain carbon for photosynthesis?

From carbon dioxide in the air.

Where do plants obtain most of their water and mineral nutrients?

From the soil through their roots.

How do mycorrhizal fungi help plants obtain nutrients?

Their fungal hyphae increase access to soil resources, especially water and minerals such as phosphorus.

What are rhizobia?

Bacteria that live in root nodules of certain plants and help convert atmospheric nitrogen into usable forms.

What is nitrogen fixation?

The conversion of atmospheric nitrogen gas into nitrogen-containing compounds organisms can use.

Where is the Casparian strip located?

In the endodermis of roots.

What does the Casparian strip do?

It blocks uncontrolled movement through cell walls, forcing water and dissolved substances to cross membranes before entering the vascular cylinder.

Why is the Casparian strip important?

It helps regulate which substances enter the root's vascular tissue.

What is water potential?

A measure of the potential energy of water that helps predict the direction water will move.

In which direction does water move along a water-potential gradient?

From higher water potential to lower water potential.

How does solute concentration affect water potential?

More dissolved solute lowers water potential.

What is pressure potential?

The contribution of physical pressure to water potential.

What is solute potential?

The contribution of dissolved substances to water potential; it becomes more negative as solute concentration increases.

What is root pressure?

Positive pressure generated in roots when water enters, which can push water upward through xylem.

Is root pressure the main explanation for water reaching the tops of tall plants?

No. The cohesion-tension mechanism is the major explanation for upward xylem transport.

What is transpiration?

The loss of water vapor from plant surfaces, especially through stomata.

What is the cohesion-tension mechanism?

Transpiration creates tension that pulls a continuous column of water upward through xylem.

What is cohesion in water transport?

The attraction between water molecules that helps keep the water column connected.

What is adhesion in water transport?

The attraction between water molecules and the walls of xylem vessels or tracheids.

How does transpiration help move water upward?

Water evaporating from leaves creates tension that pulls more water up from the roots.

What is the role of xylem in plant transport?

It carries water and dissolved minerals mainly from roots toward the shoots.

What is the role of phloem in plant transport?

It moves sugars and other organic substances from sources to sinks.

What is a source in the phloem pressure-flow model?

A plant region that supplies sugars to the phloem, such as a photosynthesizing leaf.

What is a sink in the phloem pressure-flow model?

A plant region that uses or stores sugars, such as a growing root, fruit, or developing seed.

What happens when sugar is loaded into phloem at a source?

Sugar concentration rises, water enters from nearby xylem, and pressure increases.

What happens when sugar is unloaded at a sink?

Sugar concentration decreases, water may leave the phloem, and pressure decreases.

How does the pressure-flow model move sugars?

A pressure difference drives phloem sap from a source toward a sink.

What are guard cells?

Specialized cells surrounding a stoma that control its opening and closing.

What happens when guard cells take up potassium ions?

Water enters by osmosis, the cells become more turgid, and the stoma generally opens.

What happens when guard cells lose potassium ions?

Water leaves by osmosis, the cells become less turgid, and the stoma generally closes.

Why do plants open and close their stomata?

To balance carbon dioxide uptake for photosynthesis with water conservation.

How do xylem and phloem differ?

Xylem transports water and minerals, mainly upward; phloem transports sugars from sources to sinks.

What is the difference between transpiration and translocation?

Transpiration is water loss from plant surfaces; translocation is the movement of sugars and other organic materials through phloem.