mass transport in plants

• What are the main substances transported en masse in plants?

  Water and organic substances
• How are water and organic substances transported in plants?

  By xylem and phloem in vascular bundles
• How is water absorbed by plants?

  Through osmosis via root hair cells
• Why can water move against gravity in plants?

  Due to transpiration creating a pulling force
• What is transpiration?

  Evaporation of water through stomata
• How does temperature affect transpiration?

  Higher temperatures speed up evaporation
• What environmental factors increase the rate of transpiration?

  Less humidity and more wind
• What controls the opening of stomata?

  Guard cells
• What happens to guard cells when a plant has a lot of water?

  They swell and bend, opening stomata
• When do stomata typically open more?

  When it is light and cells are turgid
• What is the Cohesion-Tension Theory?

  It explains water movement in plants
• What property of water creates cohesion?

  Dipolar nature of water
• What is created when water evaporates from stomata?

  A pulling force known as transpiration pull
• How does the diameter of the xylem change during transpiration?

  It becomes narrower and longer
• Why are xylem cells hollow?

  They are dead cells without organelles
• What does a potometer measure?

  The rate of transpiration
• How is a plant sample prepared for a potometer experiment?

  Cut underwater to prevent air entry
• What is the purpose of introducing an air bubble in a potometer?

  To measure the distance moved for transpiration rate
• How is the transpiration rate calculated from the potometer?

  Distance moved divided by time
• What environmental conditions can be tested using a potometer?

  Light, wind, and humidity
• What is the function of phloem in plants?

  Transporting organic substances like sugars
• What is translocation in plants?

  Transport of organic substances in phloem
• What are sieve tube elements?

  Long, thin cells in phloem
• How do sucrose molecules enter sieve tube elements?

  By facilitated diffusion into companion cells
• What is required for sucrose to enter sieve tube elements?

  A co-transport protein involving hydrogen ions
• What happens to water potential when sucrose enters sieve tube elements?

  It becomes more negative
• How does water move from xylem to phloem?

  By osmosis due to water potential differences
• What creates hydrostatic pressure in phloem?

  Increased volume from water movement
• How does sucrose transport relate to respiration in cells?

  Sucrose is transported to maintain respiration rates
• What is the pressure gradient in phloem?

  Higher near leaves, lower near respiring cells
• What is the purpose of ringing experiments?

  To prove phloem transports sugars
• What happens when phloem is removed in ringing experiments?

  The trunk swells above the removed section
• How is radioactive labeling used in tracing experiments?

  To track sugars produced in photosynthesis
• What happens to the stem slices in tracing experiments?

  They turn black where sugars are located
• At what time of day are transpiration rates highest?

  Midday
• At what time of day is the diameter of a tree smallest?

  Midday
• What property of water results in cohesion?

  Dipolar nature
• What are the two cells that make up phloem tissue?

  Companion cells and sieve tube elements
• Xylem

  A type of vascular tissue in plants that transports water and minerals
• Transpiration

  The process of water movement through a plant and its evaporation from aerial parts, like leaves