Mycorrhiza | Difference between endo- and ectomycorrhiza | Benefits to plants | Symbiosis

Summary

The lecture discusses mycorrhizae, a symbiotic association between fungi and plant roots, introduced by A.B. Frank in 1885. It highlights the different types of mycorrhizae, primarily endomycorrhizae (arbuscular) and ectomycorrhizae, explaining their structures and functions. Endomycorrhizae penetrate plant root cells, aiding nutrient absorption, while ectomycorrhizae form external fungal layers that protect against pathogens. Mycorrhizal associations benefit plants by improving water, nutrient uptake, and resistance to environmental stress. Over 95% of plant species rely on these associations for growth and survival.

Takeaways

• 🌿 Mycorrhizae is a symbiotic relationship between fungi and the roots of higher plants, first identified by A.B. Frank in 1885.
• 🍄 The term 'mycorrhizae' combines Greek words: 'mykes' (fungus) and 'rhiza' (root), indicating a fungal-root association.
• 🤝 Mycorrhizae is mutualistic, benefiting both the plant and fungi. Over 95% of plant species have mycorrhizal associations.
• 🔍 Soil contains a vast, unseen network of fungal mycelia that interact with plant roots, playing a vital role in agriculture.
• 🌱 Two primary types of mycorrhizae exist: Endomycorrhiza (arbuscular mycorrhiza) and Ectomycorrhiza, each with unique characteristics.
• 🌾 Endomycorrhizae, also known as AM (arbuscular mycorrhizae), form intracellular vesicles and arbuscules in the root cells to exchange nutrients.
• 🌐 Ectomycorrhizae remain extracellular, forming a protective fungal sheath (mantle) around the root and creating a Hartig net inside the root cortex.
• 🔬 Endomycorrhizae are found in most vascular plants, while Ectomycorrhizae are primarily associated with woody plants like oak and pine.
• 💧 Mycorrhizae enhance water and nutrient uptake, especially phosphorus, and increase plant resistance to drought, frost, and soil-borne pathogens.
• 🛡 The fungal mantle in ectomycorrhizae acts as a barrier, protecting plants from nematodes and other root pathogens, offering significant agricultural benefits.

Q & A

Who coined the term 'mycorrhizae' and when?

The term 'mycorrhizae' was coined by a German forest pathologist, A.B. Frank, in 1885.

What is mycorrhizae and what is the origin of the term?

Mycorrhizae is a symbiotic association between fungus and the roots of higher plants. The term originates from the Greek words 'mykes' (fungus) and 'rhizo' (root).

What percentage of plant species have mycorrhizal associations?

More than 95% of plant species have mycorrhizal associations.

What is the difference between endomycorrhizae and ectomycorrhizae?

Endomycorrhizae involve fungi that penetrate the root cells, forming vesicles and arbuscules. In contrast, ectomycorrhizae form a mantle around the root surface and remain in the intercellular space without entering the root cells.

What are vesicles and arbuscules, and what are their functions in endomycorrhizae?

In endomycorrhizae, vesicles are storage organs for the fungi, while arbuscules act as absorptive organs, helping the fungi to extract nutrients from the plant roots.

Which fungi form endomycorrhizae, and what are some examples?

Endomycorrhizae are formed by fungi from the Glomeromycota group. Examples include Glomus, Gigaspora, and Acaulospora.

What is the role of the fungal mantle in ectomycorrhizae?

In ectomycorrhizae, the fungal mantle forms a thick layer around the root surface, preventing direct contact with the rhizosphere. It acts as a barrier against pathogens, such as nematodes.

What is a 'Hartig net' in ectomycorrhizae?

A Hartig net is a network of fungal mycelia that occupies the intercellular space in the root cortex in ectomycorrhizal associations.

What are the main benefits of mycorrhizae to plants?

Mycorrhizae help plants by enhancing nutrient uptake (e.g., phosphorus, nitrogen, calcium), increasing drought and frost resistance, providing protection against pathogens, and producing growth hormones and antibiotics.

How do mycorrhizal associations help protect plants from nematodes?

In ectomycorrhizae, the fungal mantle acts as a mechanical barrier that prevents nematodes from reaching the root surface, thereby protecting the plant from nematode attacks.