321: Topic 2 - Roots and Fungi

What is the zone of maturation?

When the area of newly formed cells for elongation stops expanding and begins to differentiate into the epidermis, cortex, or stele of a root

How do lateral roots grow out of the main tap root?

Pericycle cells become meristematic and divide to form lateral primordium which grow into lateral roots

What are the three components of root systems?

The main root, first order lateral roots, and second order lateral roots

How do lateral root branches become woody long roots?

They undergo secondary thickening, which forms a woody structure

What factors affect root growth?

Species, genotype, age, season, site, and other conditions

What is feedback growth ?

When roots of a tree release metabolites into the soil, which enhances microbial growth, and then furthers roots growth

What is the seasonal growing behaviour for roots in heterophyllous species?

They grow throughout the entire growing season

What is the relationship that forms between mycorrhizal fungi and plant roots? Why?

Symbiotic --> Plant provides sugars for the fungus --> fungus provides P and N, water uptake, and protection

What are hyphae?

Extremely small threads produced by mycorrhizal fungi that are all interconnected into a net-like web called mycelium

What is the role of mushrooms in relation to mycorrhizal fungi?

They are the fruiting bodies (sporocarps) that are used by basidiomycete (common fungi and toadstools) fungi for reproduction

What approx. percentage of plants form mycorrhizal associations? What are the exceptions?

95% (exceptions include Brassicaceae, Cyperaceae, and Juncaeae families)

What are the three types of mycorrhizae?

Ectomycorrhizae, endomycorrhizae, and ectendomycorrhizae

What is ectomycorrhizae?

Fungal hyphae that does not penetrate individual root cells

What is endomycorrhizae?

Fungal hyphae that penetrate root cells, producing vesicles or branching invaginations (arbuscules)

What is ectendomycorrhizae?

Fungal hyphase that displays characteristics pof both endomycorrhizal and ectomycorrhizol fungi

What is the Hartig Net?

Highly branched ectomycorrhizal hyphae that forms between epidermal and corical root cells

What is the Mantle?

A dense ectomycorrhizal hyphal sheath that surrounds a root's surface

Where is ectomycorrhizae most commonly found in the world?

In temperate and boreal biomes in the northern hemisphere

What is the main function of endomycorrhizae?

Nutrient uptake (by the ever-increasing surface area between arbuscles and invaginated cell wall)

What is vesicular arbuscular mycorrhiza?

A type of endomycorrhiza that increases the contact surface area between hypha and protoplasts in order to transfer nutrients

What compound do the hyphae of arbuscular mycorrhizal fungi produce?

Glomalin (a glycoprotein that may be one of the major stores of carbon in the soil)

What is the overall function of mycorrhizae?

Increasing the absorption of a tree's root system, mobilizing limited nutrient sources, excreting chelating compounds or ectoenzymes, and protecting roots from heavy metals and other stresses