Lesson

Objective

- Understand how plant
structures facilitate the
transport of water,
minerals, and sugars.

- Learn the roles of
xylem and phloem in
plant transport.

Root System

•Key Features:

•- Functions:

•

- Anchors the plant.

•

- Absorbs water and minerals.

•

- Stores sugars.

•- Types of Roots:

•

- Taproot: Dominant central
root.

•

- Fibrous roots: Thin, branching
roots.

•

- Root hairs: Increase surface
area for absorption.

Xylem

•Xylem: type of vascular tissue in plants that is responsible for
transporting water and dissolved minerals from the roots to the
rest of the plant.

•Key Features of Xylem:

•Composition: Made up of specialized cells like tracheid and vessel
elements, which are dead at maturity and form hollow tubes.

•Direction of Flow: Transports water and minerals upward from
roots to leaves.

•Additional Role: Provides structural support due to the presence
of lignin, a rigid compound in its cell walls.

This Photo by Unknown Author is licensed under CC BY-SA-NC

Phloem

•Key Features of Phloem:

•Function: Transports sugars (mainly
sucrose) and other organic molecules
from the leaves (source) to other parts
of the plant (sink).

•Direction of Flow: Bidirectional,
depending on the plant's needs:

•From leaves to roots, flowers,
fruits, or storage organs.

•From storage organs to growing
parts during periods of low
photosynthesis.

Phloem: vascular tissue in plants responsible for transporting sugars, nutrients, and other organic compounds throughout the plant

Shoot
System

•Key Components:

•- Stems: Transport
water and sugars
through xylem and
phloem.

•- Leaves:

•

- Photosynthesis site.

•

- Gas exchange
through stomata.

Transport
in Plants

•Water Movement:

•- Pathway: Root → Stem
→ Leaf → Exit through
stomata.

•- Processes Involved:

•

- Osmosis: Water
enters roots.

•

- Transpiration: Water
vapor exits via stomata.

Turgor Pressure

•Definition: Pressure exerted by
water on cell walls.

•How Turgor Pressure Works:

1.Water Uptake:

1. Water enters plant cells by

osmosis due to higher solute
concentration inside the cell
compared to its surroundings.

2.Vacuole Role:

1. The central vacuole fills with

water, increasing its volume.

3.Pressure Against the Cell Wall:

1. As the vacuole expands, it

pushes the plasma membrane
outward against the rigid cell
wall, creating turgor pressure.

Explanation Slide...

Pressure exerted by water on cell walls

Importance of Turgor Pressure:

•Structural Support:
•High turgor pressure keeps plants upright and leaves firm.
•Low turgor pressure causes wilting.
•Cell Expansion:
•Drives cell elongation during growth.
•Stomatal Function:
•Turgor pressure in guard cells regulates the opening and
closing of stomata for gas exchange and transpiration.

•High pressure – plant erect
•Low pressure – plant wilts

This Photo by Unknown Author is
licensed under CC BY

Transpiration

•Definition: Water vapor diffuses
through stomata in leaves.

•Steps in Transpiration:

1.Water Absorption:

1. Water is absorbed by the

roots from the soil.

2.Water Movement:

1. Water travels upward through

the xylem to the leaves,
driven by transpiration pull,
cohesion, and adhesion.

3.Evaporation:

1. Water evaporates from the

surface of mesophyll cells
inside the leaf into the air
spaces.

4.Diffusion:

1. Water vapor diffuses out of

the leaf through the stomata
into the atmosphere.

Importance of Transpiration:

Creates a transpiration pull that draws water and nutrients from roots to
shoots.

Water

Transport:

Cools the plant by evaporative cooling, especially in hot environments.
Cooling

Mechanism:

Facilitates the exchange of gases needed for photosynthesis and respiration.

Gas Exchange:

Helps maintain cell structure and function.

Maintains

Turgor

Pressure:

Summary
of Day 1

•Key Takeaways:

•- Root system absorbs water and minerals.

•- Shoot system transports materials and
supports photosynthesis.

•- Xylem moves water; phloem moves
sugars.

•- Transpiration and turgor pressure
maintain plant health.

Exit Ticket

Plant Systems and Interactions

Overview of Plant Reproduction

Key Points:

• Plants reproduce both sexually and asexually.

• Sexual reproduction involves flowers and the fusion of gametes.

• Asexual reproduction produces genetically identical offspring.

​

• Plants reproduce sexually through flowers, which contain male and female reproductive organs.

• Stamen (Anther + Filament).

• Carpel (Stigma + Style + Ovary).

• Seeds: Result of fertilized ovules.

• Fruit: Ripened ovary aiding seed dispersal.

​Sexual Reproduction

​

• Produces and releases pollen grains, which contain male gametes (sperm).

• Pollen grains have a tough coat to protect the sperm during transfer to the female structures.

​​Anther

​A stalk that supports the anther, positioning it for effective pollen transfer by wind, insects, or animals.

​​Filament

​Male Reproductive Parts

​

• The sticky surface at the top of the carpel where pollen grains land during pollination.

• Specialized to capture and germinate compatible pollen grains.

​​Stigma

​

• A tube-like structure that connects the stigma to the ovary.

• Guides the pollen tube to the ovule for fertilization.

​​Style

​

• Contains ovules, which house the female gametes (eggs).

• After fertilization, the ovary develops into a fruit.

​​Ovary

​Female Reproductive Parts

​Embryo: The young plant that will develop into the mature plant after germination.

Cotyledons: Store nutrients that support the embryo during germination.

Seed Coat: Protects the seed from physical damage and prevents water loss.

Seeds

​

• Protects the developing seeds.

• Facilitates seed dispersal through mechanisms like being eaten by animals, floating in water, or carried by the wind.

​​Fruits

Explanation Slide...

Protects the seed from physical damage and water damage

​Seed Dispersal Methods:

• Wind (e.g., dandelions).

• Water (e.g., coconuts).

• Animals (e.g., berries).

• Explosions (e.g., peas).

• Gravity (e.g., apples).

​Seed Dispersal

• Self-Pollination: Occurs when pollen from the same plant fertilizes its ovules.

• Cross-Pollination: Involves pollen transfer between different plants, increasing genetic diversity.

​

​Pollination

• A pollen tube grows from the pollen grain down the style to the ovary.

• Sperm cells travel through the tube to fertilize the ovule, forming a zygote.

​Fertilization

​Key Points:
Asexual Reproduction: produces plants that are genetically identical to the parent plant

• Methods:

  • Roots: Tuberous roots (e.g., sweet potatoes).

  • Stems: Stolons, runners, bulbs (e.g., strawberries, onions).

  • Leaves: Vegetative propagation (e.g., Bryophyllum).

• Advantages: Faster reproduction; stable environments.

• Disadvantages: No genetic variation.
  

​Asexual Reproduction

Exit Ticket

​What are the main differences between sexual and asexual reproduction in plants? Provide one example of each.

Tropisms and Plant Responses

What are Tropisms?
Tropisms: Directional growth responses of plants toward or away from environmental stimuli.

Significance: These responses enable plants to adapt to their surroundings, ensuring survival, reproduction, and resource acquisition.

​Tropisms

​

• Example: Roots grow downward into the soil.

• Function: Helps anchor the plant and absorb water and nutrients from the soil.

​​Positive Geotropism

• Example: Stems grow upward, away from gravity.

• Function: Maximizes access to sunlight for photosynthesis.

Negative Geotropism

​

• Plant cells detect gravity through organelles called statoliths.

• Hormones like auxin redistribute in response to gravity, promoting growth in specific directions.

​​Mechanism

​Geotropism (Gravitropism)

​Geotropism: Growth response to gravity

​Example: Stems and leaves bend toward light.

Function: Maximizes photosynthesis by exposing leaves to optimal light.

​​Positive Phototropism

​

• Auxins accumulate on the shaded side of the plant.

• Cells on the shaded side elongate, causing the plant to bend toward the light source.

​​Mechanism

​Phototropism: Growth response to light

Explanation Slide...

Growth response to gravity

​

• Helps climbing plants secure themselves for better access to light.

• Protects certain plants by allowing them to retract or curl when touched (e.g., tendrils).

Function

​Contact with an object triggers rapid growth on the opposite side, causing the plant to bend or wrap around the object.

​​Mechanism

• Vines wrapping around a trellis or support structure.

• Sensitive plants reacting to physical touch.

​​Examples

​Thigmotropism

​Growth response to touch or physical contact.

​

• Example: Roots grow toward areas of higher moisture.

• Function: Ensures plants access water, crucial for photosynthesis and nutrient transport.

​​Positive Hydrotropism

​

• Root tips detect water gradients in the soil.

• Cells on the side of the root facing less water elongate, bending the root toward the water source.

​​Mechanism

​Hydrotropism

​Growth response to water.

​​Function

​Triggered by changes in turgor pressure within specialized cells.

​​Mechanism

​

• Venus Flytrap: Closes rapidly when prey touches its sensitive hairs.

• Mimosa Plant: Folds its leaves when touched or shaken.

​​Examples

​Nastic Movements

​Non-directional responses to stimuli, unlike tropisms, which are directional.

​Protects plants from herbivores or environmental stress.
Helps trap prey (in carnivorous plants) for nutrient acquisition.

Real-World Applications of Tropisms

• Phototropism: Greenhouses use light sources to optimize plant growth.

• Geotropism: Ensures proper orientation of roots and stems during early growth.

• Thigmotropism: Used in agriculture to grow climbing crops like beans and grapes efficiently.

• Hydrotropism: Studied for improving drought-resistant crops.

​Exit Ticket

​Explain one way phototropism and geotropism work together to ensure a plant's survival

Explanation Slide...

produces plants that are genetically identical to the parent plant