Difference Between Parasitic Roots and Mycorrhizae

The key difference between parasitic roots and mycorrhizae is that parasitic roots are the roots of non-photosynthetic parasitic plants while mycorrhizae are a type of mutualistic association that exists between the roots of photosynthetic higher plant and a fungus.

Parasitism and mutualism are two symbiotic associations existing between two different species that live together. Parasitism is beneficial only to parasite since the parasite obtains foods and other requirements from the host while harming it. On the other hand, mutualism benefits both partners that are in the association. Mycorrhizae are a type of mutualistic association occurring between a higher plant and a fungus. The fungus lives in the roots of higher plants. Higher plants provide foods to the fungus while fungus absorbs water and nutrients from the soil to plant.

CONTENTS

1. Overview and Key Difference
2. What are Parasitic Roots
3. What are Mycorrhizae
4. Similarities Between Parasitic Roots and Mycorrhizae
5. Side by Side Comparison – Parasitic Roots vs Mycorrhizae in Tabular Form
6. Summary

What are Parasitic Roots?

Parasitic roots are the roots of parasitic plants. These plants are not photosynthetic since they do not possess chlorophylls, which are necessary to carry out photosynthesis. Hence, they cannot make their own foods. Therefore, they depend on another photosynthetic plant, which is the host plant, to obtain foods. Parasitic plants obtain food from the host plant via parasitic roots. Parasitic plants form adventitious roots from their nodes. They are a type of modified roots. These roots penetrate the host plant tissues through haustoria, which are peg-like projections. These haustoria reach the conducting tissues of the host plant and absorb nutrients. However, some parasitic plants connect only with the xylem; hence, they are xylem feeding plants. In contrast, some parasitic plant roots connect only with the phloem and are known as phloem feeders.

Parasitic plants such as Cuscuta, pinedrops, broomrapes, Pedicularis densiflora and mistletoes possess parasitic roots and are some examples of total parasitic plants.

What are Mycorrhizae?

Mycorrhizae are a type of symbiotic relationship that occurs between a fungus and the roots of a higher plant. The association is an example of mutualism. Mutualistic interaction is beneficial for both partners. Therefore, the mycorrhizal association provides benefits to both plant and fungus. Fungal hyphae penetrate into the soil and bring nutrients to the plant. On the other hand, the plant assimilates carbohydrates and shares with the fungus. Hence, it is an ecologically important relationship. Most importantly, when the plant roots do not have access to nutrients, fungal hyphae can grow several meters and transport water and nutrients, especially nitrogen, phosphorus, potassium, to the roots. Hence, nutrient deficiency symptoms are less likely to occur in plants which are in this symbiotic association. About 85% of the vascular plants possess endomycorrhizal associations. Also, fungus protects the plant from root pathogens. Therefore, mycorrhizae are very important associations in the ecosystems.

There are two types of mycorrhizae as ectomycorrhizae and endomycorrhizae. Ectomycorrhizae do not form arbuscules and vesicles. Moreover, their hyphae do not penetrate into the cortical cells of the plant root. However, ectomycorrhizae are really important since they help plants to explore nutrients in the soil and protect plant roots from root pathogens. In endomycorrhizae, fungal hyphae penetrate into the cortical cells of the plant roots and form vesicles and arbuscules. Endomycorrhizae is more common than ectomycorrhizae. Fungi from Ascomycota and Basidiomycota are involved in forming ectomycorrhizal association while fungi from Glomeromycota form endomycorrhizae.

What are the Similarities Between Parasitic Roots and Mycorrhizae?

• Parasitic roots and mycorrhizae show two types of symbiotic associations.
• Parasitic roots connect with the host plant. Similarly, a mycorrhizal association exists between a plant and a fungus.

What is the Difference Between Parasitic Roots and Mycorrhizae?

Parasitic roots are roots of the parasitic plant that penetrate into host plant tissues. Meanwhile, mycorrhiza is a type of symbiotic relationship between a fungus and the roots of a higher plant which is beneficial to both partners. So, this is the key difference between parasitic roots and mycorrhizae. Parasitic roots are adventitious roots that form haustoria to penetrate the host tissues. But, mycorrhizae form arbuscules, vesicles and hyphae mantle during the association. Therefore, we can consider this also as a difference between parasitic roots and mycorrhizae.

Below is a side by side comparison to make clear the difference between parasitic roots and mycorrhizae.

Summary – Parasitic Roots vs Mycorrhizae

Mycorrhiza is an important symbiotic relationship that occurs between higher plant roots and a fungus. It is a mutualistic association in which both partners receive benefits from their interaction. In contrast, parasitic plants are a type of symbiotic relationship that exists between two different plant species. In this relationship, parasite receives benefits at the expense of the host plant. Parasite obtains foods from the host plant via parasitic roots known as haustoria. These parasitic roots penetrate the host conducting tissues and exploit nutrients. Thus, this summarizes the difference between parasitic roots and mycorrhizae.

Reference:

1. “Parasitic Plants.” Parasitic Plants – an Overview | ScienceDirect Topics, Available here.
2. “Mycorrhizae – Definition, Examples, Types and Quiz.” Biology Dictionary, 18 May 2017, Available here.

Image Courtesy:

1. “Dodder wrapped around green plant” By PookieFugglestein – Own work (CC0) via Commons Wikimedia
2. “Arbuscular mycorrhiza microscope” By Msturmel – MS Turmel, University of Manitoba, Plant Science Department (Public Domain) via Commons Wikimedia