Plant Transport and Mechanisms

Study Notes

Plant Transport

Water is transported upwards in the xylem, a unidirectional process.
Water movement is driven by transpiration, the evaporation of water from leaves, creating a pulling force.
Minerals are transported with water. This process is called translocation.
Xylem cells are dead at maturity, enabling efficient water movement.
Xylem cells have thick, lignin-rich walls for structural support.

Water Adhesion and Cohesion in Xylem

Cohesion: Water molecules stick together due to their polarity, forming a continuous chain.
Adhesion: Water molecules stick to the xylem walls, resisting downward pull of gravity.

Transport Mechanisms

Passive Transport: Movement of molecules along a concentration gradient (no energy needed).
Active Transport: Movement of molecules against a concentration gradient (requires energy).

Translocation (Phloem Transport)

Phloem transports sugars from sources (production sites, like leaves) to sinks (areas needing resources, like roots or developing fruits).
This is an active process.
Companion cells use active transport to load sugars into sieve tube elements, creating a pressure difference driving transport.

Asexual Reproduction (Mitosis)

Asexual reproduction produces clones (genetically identical offspring).
Advantages include adaptation to specific environments and fewer energy requirements.
Disadvantages include limited adaptability to changing conditions due to lack of genetic diversity.
Examples include runners in strawberries, root fragments in dandelions and modified stems in potatoes.

Sexual Reproduction (Meiosis)

Sexual reproduction involves meiosis.
Flowers are the reproductive organs.
Advantages include adaptability to new environments and enhanced resilience during stress.
Disadvantages include the high energy expenditure for meiosis and pollination.
Example: Pollination in flowering plants.

Flower Anatomy

Sepals: Protect the flower bud.
Petals: Attract pollinators.
Stamen (male): Anther (pollen producer) and filament.
Carpel/Pistil (female): Stigma, style, and ovary.

Pollination

Self-Pollination: Pollen transfer within the same flower or plant.
Cross-Pollination: Pollen transfer between different flowers or plants (usually by wind or animals).

Seed Dispersal

Seeds disperse to prevent competition and expand the plant's range.
Methods include:
- Fruit (transport by animals)
- Lightweight seeds (wind dispersal)
- Sticky seeds (animal dispersal)

Leaf Structure

Upper epidermis/cuticle: Protect against water loss and pathogens.
Chloroplasts: Carry out photosynthesis.
Palisade mesophyll: Maximize light absorption.
Veins: Contain xylem and phloem for transport.
Spongy mesophyll/air spaces: Facilitate gas exchange.
Guard cells: Regulate stomata opening/closing.
Stomata: Allow gas exchange (CO2 in, O2 out) and transpiration (water out).

Osmosis

Osmosis is the movement of water across a selectively permeable membrane from a high water concentration to a low water concentration.
Key terms include:
- Solute: Dissolved substance
- Hypertonic: Higher solute concentration
- Isotonic: Equal solute concentration
- Hypotonic: Lower solute concentration

Description

Test your knowledge on the processes of water and nutrient transport in plants. This quiz covers xylem and phloem functions, water adhesion, and cohesion, as well as passive and active transport mechanisms. Perfect for students studying plant biology or related topics.