Leaves - II

Corn leaves show Kranz anatomy

Photosynthesis

• Light Reactions produces ATP and NADPH

• Carbon fixation reaction incorporates CO2 into sugars– Normal fixation is by Calvin Cycle: C-3

pathway• CO2 + Ribulose-1,6-bisphosphate forms 2

molecules of PGA

– C-4 plants prefix CO2 into oxaloacetic acid and malic acid prior to the Calvin Cycle

Calvin Cycle (C-3)

C-3 plant leaves

C-4 pathway

Sugar Cane Leaf

Grama grass leaf (C-4)

Corn leaf

Amaranth Leaf (C-4 dicot)

Schematic of Atriplex leaf (a C-4 dicot)

1 = vascular bundle

2 = bundle sheath cell

3 = radially arranged palisade mesophyll (Kranz-mesophyll) cell

4 = water-storage parenchyma cell

5 = stomatal complex

6 = sub-stomatal cavity

7 = cuticle of adaxial epidermis 

Adaptations to Xeric Environments

Thickened cuticle

Sunken stomata

Beach grass

Yucca

Oleander has many xeromorphic adaptations

Ficus

Succulency

Succulents

Lithops

Saguaro cactus

Hydrophytes

Nymphae spp

Nymphae leaves

Elodea

Potamogeton

Floating leaf Submerged leaf

Submerged Vallisneria leaf

Gymnosperm leaves

Pine needles

Pine

Cooksonia earliest vascular plant

Evolution of microphylls as enations

Evolution of Megaphylls by

•Overtopping

•Plannation

•Webbing