Anatomy ReviewBIO 201 - Botany

Herbaceous stems

• Have separate vascular bundles• In each bundle:

- Xylem toward center- Phloem toward outside

• Bundle arrangement important- monocots randomly scattered- dicots in ring

Corn stem – a monocot

Corn with detail of bundles(monkey faces)

Bundle details• Xylem• Phloem• Sclerenchyma• Cortex

Alfalfa stem – a dicot

Sunflower stem – semi-woody(development of a cambium)

TYPICAL TREE TRUNK ANATOMY

• Wood – central largest portion• Cambium – thin area of small dividing cells• Bark – outer layer

TYPICAL TREE TRUNK ANATOMY

• Bark to outside

• Cambium thin!(dark line)

• Xylem to inside(annual rings visible)

• Pith in center

TREE ANATOMY• 2o phloem• Cambium• 2o xylem• 1o xylem• Growth ring• Vascular ray• Pith

CONTRASTING SECTION TYPES

• Cross• Radial• Tangential

Scanning electron micrograph (x60) of the wood of an angiosperm tree, the beech Fagus sylvatica, showing the 'drinking straw' vessels packed in between the narrower tracheids, and oriented parallel to the long axis of the trunk. Conifers have only tracheids. (Image: Brian Butterfield and Brian Meylan)

PINE CROSS SECTION

• Tracheid cells circular• Can see annual rings (cell sizes slowly change)• Vascular rays elongate, but not well developed• Resin canals visible

CROSS SECTION

PINE RADIAL SECTION

• Tracheid cells elongate• Can see annual rings (cell sizes slowly change)• Vascular rays of elongate cells, but area

squared• Resin canals visible

PINE RADIAL SECTION

PINE TANGENTIAL SECTION

• Tracheid cells elongate, pits visible• Cannot see annual rings• Vascular rays elongate with circular cells

within• Resin canals visible

PINE SECTION COMPARISON

Softwood vs hardwood

• Resin canals• Uniformity of xylem

Root anatomy

All roots have• Endodermis• One vascular bundle at center

Monocot vs dicot roots

Corn (monocot) buttercup (dicot)

Root anatomy - details• Epidermis• Cortex• Endodermis• Pericycle• Vascular tissue