Topic2_WaterTransport_2025v2

CELL BIOLOGY and VASCULAR TRANSPORT

• Course Title: Biology 186

• Instructor: Dr. Jürgen Ehlting

• Contact: je@uvic.ca

Page 1: Introduction to Plant Physiology

• Overview of key topics

  • Cell structure

  • Tissues and organs

  • Vascular transport mechanisms

  • Exploiting light as an energy and information source

• Preparation for lab sessions

Page 2: Water Transport in Plants

1. Advantages and Challenges of Life on Land

   • Advantages:

     • More abundant light

     • Increased availability of oxygen and carbon dioxide

   • Challenges:

     • Overcoming gravity (early plants were simple; lacked lignin)

     • Maintaining moisture

     • Water and nutrients are spatially separated from gaseous exchange sites

     • Challenges in gamete/offspring dispersal and environmental stressors

Page 3: Diversity in Plant Size

• Factors influencing plant height:

  • Primary and secondary growth

• Water transport mechanisms in plant structures:

  • Water potential drives transport in roots, leaves, and stems

• Transport of sugars through the plant

• Reference Material: Chapter 36 (pg. 842-862) from Campbell's Biology (4th Canadian Edition)

Page 4: Evolution of Land Plants

• Transition from algae to terrestrial plants emphasizing the significance of water

• Examples of aquatic and land plants: Cabomba (fanwort) and Zostera (sea grass)

Page 5: Perspectives on Living on Land

• Advantages:

  1. Enhanced light availability

  2. More abundant gases (O2, CO2)

• Challenges:

  1. Needs to combat gravity (early plants relied only on cellulose)

  2. Scarcity of water requiring moisture maintenance

  3. Water/nutrient location differs from gas site

  4. Gamete/offspring dispersal complexities

  5. Exposure to environmental stressors like UV and temperature changes

Page 6: Adaptations for Terrestrial Life

1. Moisture Maintenance: Water transport systems and cuticle/stomata for regulation.

2. Reproduction: Adaptations for animal pollination and specialized fruit for seed dispersal.

3. Resource Acquisition: Larger leaves and differentiated root and shoot systems to maximize photosynthesis.

4. Structural Support: Development of thicker cell walls and lignin for gravity resistance.

5. Abiotic Stress Protection: Production of secondary metabolites.

Page 7: Growth in Plants

• Questions on evolutionary developments:

  • Photosynthetic surface area vs water transport systems

  • Reference: Research from 2011 about plant growth traits from ancient plants like Psilophyton.

Page 8: Water Transport Mechanisms

• Gas Exchange: Oxygen uptake and CO2 release mechanisms

• Water/mineral uptake at the root

• Upward transport via xylem and photosynthesis sugar transport through phloem

• Key Terminology: Transpiration, source-sink dynamics in phloem

Page 9: Key Differences in Plant Types

• Vascular vs. Non-vascular plants

  • Mosses lack vascular structure leading to height limitations

Page 10: Plant Growth Types

• Primary Growth: Involves growth at tips (shoots and roots).

• Secondary Growth: Involves widening due to lateral meristems (cambium).

Page 11: Tree Growth and Structure

• Thickness Growth: Achieved through vascular and cork cambium, contributing to wood formation.

• Discussion on seasonal tree bark issues.

Page 12: Tree Rings

• Formation of annual rings indicating growth patterns: early and late wood analysis through dendrochronology.

Page 13: Mechanisms of Tree Growth

• An exploration of how height impacts tree growth and localizes sign placement over years.

Page 14: Understanding Bark

• Differentiation in plant structures based on yearly growth pamphlets for annual versus perennial plants.

Page 15: Vascular Bundle Structuring

• Eudicot vascular bundle arrangement

• Primary phloem outside, xylem inside layer denotation for structural integrity.

Page 16: Cork and the Bark

• Identification of cork cambium as secondary protective layer and factors affecting debarking timing.

Page 17: Water Transport and Pressure

• Identification of mechanisms for transporting water and nutrients through differing hydraulic pathways.

Page 18: Yields of Transport Mechanisms

• Different speeds and effectiveness of transport depending on the physiological challenges placed on trees.

Page 19: Functionality of Aquaporins

• Functionality of aquaporins in allowing bidirectional transport of water, achieving higher rates than diffusion through membranes.

Page 20: Water Use in Trees

• Exemplifies extreme daily water needs for larger trees like Western Red Cedar

• Interesting comparison to weightlifting as a transport analogy.

Page 21: Xylem and Bulk Flow

• Bulk flow relies on pressure gradient generated from transpiration to transport water and minerals efficiently through xylem.

Page 22: Cohesion and Adhesion Mechanisms

• Phenomena influencing water transport and driving mechanisms including cavitation considerations.

Page 23: Stomatal Dynamics

• Gas exchange and transpiration through stomata impacted by potassium ion regulation

• Dependency on external environmental factors like light.

Page 24: Stomatal Operations

• Stomata typically open during the day and close at night in response to CO2 uptake needs, light, and potential environmental stress factors.

Page 25: Phloem Transport Dynamics

• Understanding source to sink concepts in phloem as well as the concept of mineral nutrient transport.

Page 26: Maple Syrup Production

• A question raising about the source (phloem or xylem) of this popular product elaborating on transport in trees.