Post on 24-Feb-2016
description
Leaf Structure
Aquaponics
Leaf Structure-Dermal layers• Cuticle-The thin waxy
covering on the outer surface of the leaf has a thin waxy covering This layer's primary function is to prevent water loss within the leaf. (Plants that live entirely within water do not have a cuticle).
• Directly underneath the cuticle is a layer of cells called the epidermis (upper and lower)
Leaf Tissues• Mesophyll
– Ground tissue between upper and lower epidermis
– Two types:• Palisade parenchyma (mesophyll) cells
– Lots of chloroplasts in these cells– Most photosynthesis occurs here
• Spongy parenchyma (mesophyll) cells– Lots of air spaces where O2 and CO2
circulate– Near stomata (Think: sponges have lots
of air spaces)
• Veins– Xylem and phloem are continuous from
roots through stem to leaves
Vascular Tissue• Transports materials in roots,
stems, & leaves.• Xylem– Carry water & minerals up from
roots– Tube-shaped dead cells
• Their walls are used as water pipes
• Phloem– Carry nutrients (food) throughout
plant• SUGARS (sucrose), amino acids….
– Tube-shaped living cells
http://wps.prenhall.com/wps/media/objects/838/858365/ch03anim/3_1_6_1a.swf
Stomata and Guard Cells• The underside portion of a leaf has stomata and is the site of
transpiration (water movement) and gas exchange.
Stomata help regulate the rate of transpiration
• Guard cells –2 cells on either side of stomata
(surrounds stomata)–regulate water loss
• What conditions will promote closing of guard cells?–Hot, dry, windy conditions
Stoma Opening/Closing
• http://academic.kellogg.edu/herbrandsonc/bio111/animations/0021.swf
VeinH2O
Leaf cross section
Mesophyll (leaf tissue)
CO2 O2Stomata
CO2 O2Stomata; Stoma (pl)
30-40 chloroplasts
Cross Section