Apedia

A-Level Biology OCR A

Xylem Evidence Cohesion Tension Cut Shoot Transpiration Dye Diameter

Evidence for the cohesion-tension theory includes poisons not stopping transpiration (not an active process), dyes showing xylem as the main water pathway, and tree trunk diameter narrowing during the day due to negative xylem pressure.

Evidencia de la teoría de cohesión-tensión incluye que los venenos no detienen la transpiración (no es un proceso activo), los tintes muestran que el xilema es la vía principal del agua, y el estrechamiento del diámetro del tronco del árbol durante el día se debe a la tensión negativa en el xilema.

Front Describe 3 sources of evidence for cohesion-tension theory.
Back Evidence for cohesion-tension theory:
  • Poisons - if cut shoot is placed in cyanide water, uptake and transpiration continues as usual showing that transpiration does not rely on live cells and therefore isnt an active process
  • Dyes - if leafy shoot is cut and dipped into dye the dye will visibly be taken into the xylem vessels supporting that major water pathway is thru xylem
  • Diameter of tree trunk over 24 hour period is narrowest at midday and widest at midnight - cohesive forces in xylem cause negative pressure that draws tissues in and reduces diameter bc highest rate of photosynthesis is at midday & lowest around midnight

Learn with these flashcards. Click next, previous, or up to navigate to more flashcards for this subject.

Next card: Guard cells explain open/close stomata turgor low asymmetric

Previous card: Draw label annotate diagram show transport water plant

Up to card list: A-Level Biology OCR A