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

http://www.purchon.com/biology/flash/leaf.swf