Chapter 36 Flashcards
Resource Acquisition and Transport in Vascular Plants
Water & minerals:
Pulled from roots to shoots via xylem (negative pressure from transpiration).
Sugars:
Pushed from sources (leaves) to sinks (roots/fruits) via phloem (positive pressure).
Early land plants evolved xylem and phloem for long-distance transport.
Early land plants evolved xylem and phloem for long-distance transport.
Root Architecture:
oots adjust growth based on
local nitrate availability
Phyllotaxy (leaf arrangement)
alternate, opposite, whorled.
Leaf area index affects l
light access and shading
Vertical leaves reduce
horizontal leaves absorb
light damage
absorb more light in low-light.
Transport Pathways:
- Apoplast:
- Symplast:.
- Transmembrane:
Cell walls + extracellular spaces + dead cells.
Cytosol + plasmodesmata
Repeated plasma membrane crossings.
H+ pumps generate
membrane potential (not Na+/K+ as in animals).
Determines direction of water flow.
WATER potential
Plasmolysis: Water loss
cell shrinks
Turgid: Water gain
firm cell
Xylem Transport (Bulk Flow):
- Driven by transpiration
evaporation from leaves).
strip regulate mineral entry into xylem.
- Endodermis and Casparian
Cohesion-tension hypothesis:
Water pulled upward via cohesion and surface tension.
Stomata Regulation: in guard cells opens/closes pores.
Turgor
drives turgor changes.
K+ ion movement
Transpiration Effects:
Causes wilting if excessive.
Phloem sap (sucrose-rich) moves f
from source to sink.
Active transport loads
sucrose into phloem.
Stress (e.g., drought) modifies
transport routes
Stress (e.g., drought) modifies
transport routes.
hloem as Information Superhighway:
- Transports
macromolecules, viruses, and signals
Summary:
- Transport in plants involves coordinated mechanisms of xylem, phloem, membranes, and tissues.
- Adaptations balance photosynthesis, growth, and water conservation.
