10-Plant Transport and Carbon consequences II (2)

Page 1: Introduction

• Title: Pine stem art by 10-Plant Transport and Carbon Consequences

Page 2: Today's Lecture

• Announcements:

  • REU programs are currently running.

  • Federal grant funding executive order has been rescinded; encourage applications.

  • Upcoming Conservation Career panel.

  • Lab next week will focus on Project Design; no alcohol or nicotine treatments allowed.

  • Exam scheduled for Friday; bring your computer and sign in/out with TAs.

  • Student Showcase from 4-6 at Connelly Art Gallery; highlight: Faith Yost won award for Science-Art creation.

  • Science News topics:

    • Rewilding successes.

    • Drought implications for agriculture.

    • Topics covered include cavitation and plant adjustments for light and drought, phloem transport, and tree rings.

Page 3: Rewilding and Conservation

• Takehome Message:

  • Rewilding and conservation efforts, while slow, are effective.

  • Example: Tapirs rediscovered in Brazilian forest after being locally extinct for a century; their presence as seed dispersers enhances the ecosystem.

  • Other species like hyenas and pumas are re-establishing themselves where they were previously extirpated, promoting ecosystem health through cascading effects.

  • Hyenas recently expanded into Egypt due to a once-in-5000-years unusually wet period.

  • Evidence of the fisher cat's return in Pennsylvania this year.

Page 4: Water Potential Gradient

• Xylem sap movement:

  • Water potential values:

    • Outside air: -100.0 MPa

    • Leaf (air spaces): -7.0 MPa

    • Leaf (cell walls): -1.0 MPa

    • Trunk xylem: -0.8 MPa / -0.6 MPa

    • Soil: -0.3 MPa

Page 5: Transpiration Effects

• Effects of Transpiration on Plants:

  • Plants lose substantial water via transpiration.

  • Insufficient water absorption through roots results in wilting.

  • Drought conditions lower photosynthesis, reducing crop yields due to stomatal closure.

Page 6: Evaporative Cooling

• Transpiration also serves to:

  • Cool leaves, preventing enzyme denaturation.

  • Importance for photosynthesis and metabolic processes.

Page 7: Understanding Cavitation

• Cavitation Process:

  • Air bubbles (embolisms) disrupt xylem water flow.

  • Impact on xylem tracheids, causing inactivation.

Page 8: Plant Water Tolerance

• Plant species exhibit different tolerances to low water potentials:

  • Example species:

    • Hoaryleaf ceanothus

    • Wyoming sagebrush

    • Cottonwood

  • Data illustrates % loss of xylem conductance relative to xylem MPa.

Page 9: Drought Adaptations

• Plant adaptations include:

  • C4 and CAM evolutionary strategies.

    • CAM plants (e.g., cacti) take up CO2 at night to minimize day-time transpiration.

    • C4 plants enhance CO2 concentration, allowing stomata to remain partially closed.

  • Stomata of xerophytes located on lower leaf surface, often sheltered in depressions.

  • Xylem size varies with environmental conditions, influencing water transportation effectiveness.

Page 10: Leaf Arrangements

• Leaf design maximizes:

  • Light capture while minimizing water loss.

  • Arrangement prevents self-shading.

Page 11: Leaf Angles and Light Conditions

• Leaf angle adjustments based on light conditions:

  • Horizontal leaves in low light conditions.

  • Vertical leaves in high light conditions.

Page 12: Phloem Transport

• Phloem Functionality:

  • Phloem sap is primarily sucrose, facilitating movement from sugar sources to sinks (translocation).

  • Sugar sources: mature leaves; Sugar sinks: growing roots, expanding leaves, or fruits.

  • Energy consumption is necessary for phloem transport.

  • Importantly, thinning of sinks has horticultural implications.

Page 13: Phloem as an Information Highway

• Phloem's role includes:

  • Transport of proteins and RNA.

  • Communication for flowering from leaves to meristems and across plant parts via electrical signals.

Page 14: Measuring Phloem Contents

• Technique: Using aphids to gauge phloem content.

  • Girdling (cutting off phloem) will kill a tree, showcasing the critical nature of phloem transport.

Page 15: Tree Growth and Aging

• Tree aging dynamics:

  • Older secondary xylem layers (heartwood) cease to transport water/minerals.

  • Sapwood remains active in material transport, leading to the formation of tree rings.

Page 16: Dendrochronology

• Dendrochronology focus:

  • Study of tree rings to infer past climates/environmental conditions.

  • Wider rings correlate with improved growth conditions (warmer, wetter climates).

  • Exploration into other factors influencing tree ring growth is encouraged.