RootsRoots

RootsRoots

• Originally deemed the part of the plant that grew underground, but with the evolution of aerial roots (ones that grow above ground) and aerating roots (ones that grow upward especially above water), the definition has changed.

RootsRoots

• The better definition of a root is the part of the plant body that bears no leaves and therefore has no nodes (places where branches come up).

Root FunctionsRoot Functions

• The major functions of roots are:

1) Anchor the plant

2) Absorb water and inorganic nutrients

Root FunctionsRoot Functions

• Roots also can act as storage organs for the plant

• They also enter into a symbiotic relationship with fungi and/or bacteria in the soil in order to obtain nutrients easier.

Root MorphologyRoot Morphology

• The tip of each root has a conical covering of tissue known as the root cap.

• Underneath the root cap lies the apical meristem, which is the root region undergoing mitosis in order to grow and push the root through the soil.

Root MorphologyRoot Morphology

• The outer surface of the root is known as the epidermis.

• The epidermis produces outgrowths known as root hairs that increase the surface area for absorption.

• Root hairs typically only live a few days before they are replaced by new ones.

Root MorphologyRoot Morphology

• Under the epidermis lies the cortex whose primary role is starch storage.

• The innermost layer of the cortex is the endodermis (containing Casparian Strips) which acts as a barrier to nutrients, preventing them from passively entering the vascular tissue.

• This allows the plant to accumulate lots of minerals in its roots.

Root MorphologyRoot Morphology

• Inside the endodermis lies the vascular tissue.

• This is where water and nutrients start their journey up the plant.

• It is also an area of sugar movement or storage depending on the environmental conditions.

Dicot RootsDicot Roots

Monocot RootsMonocot Roots

Root GrowthRoot Growth

• Roots will grow in the direction of the correct oxygen, moisture and nutrient levels for plant growth.

• Primary growth is elongation whereas secondary growth is an increase in diameter.

Root SystemsRoot Systems

• There are two main types of root systems:

1) Taproot system where there is a large primary root with lots of smaller, secondary roots emerging from it. It is found mostly in dicots where starch storage is key.

Root SystemsRoot Systems

• 2) Fibrous System where there is no primary root and all roots are similar in size. They jut out in all directions. Found commonly in monocots. The main function is anchorage.