Transcript Plant Transport

Plant Transport
Transport Overview
Water and
minerals
Sugars
Vascular Tissue
• Xylem
– Water
– Dissolved minerals
• Phloem
–
–
–
–
Water
Sugars
Amino acids
Hormones
Uptake of Minerals and Water
• Lateral movement – soil to xylem
– Diffusion and active transport of minerals
• Increased surface area
– Root hairs
– Mycorrhizae
• Symplastic and apoplastic movement
– All minerals must pass through a selective membrane
– Casparian strip prevents direct apoplastic movement
into the xylem
Lateral Transport of Minerals and Water from Roots
Bulk Flow Transport Through Xylem
• Root pressure – pushing water
– Active transport of minerals into root creates lower
water potential
– Water enters cells and is pushed up xylem
• Transpiration – pulling water
– Water evaporates from leaves
– Water pulled up xylem because of cohesion of water
molecules
– Transpiration controlled by openings in leaf called
stoma
Transpiration
Control of Transpiration
• Stoma open
– K+ enter guard cell
– Cell becomes turgid
from influx of water
• Stoma closed
– K+ pumped out of
guard cell
– Cell becomes flaccid
from efflux of water
Photorespiration
• Response to high heat and low water
• Stoma close to prevent water loss causing
low CO2 and high O2 levels in leaf
• Carbon fixation low
– Carbon is removed from RuBP to produce CO2
– Rubisco runs in reverse
Loading of Sucrose into
Phloem
• Transport is in either
direction at different times
• Transport from sugar
source to sugar sink
• Sugar is pumped from
source to sieve tube
member
Mass Flow in a Sieve Tube