Are all fibrous roots considered as adventitious roots?

Question

I have just started studying about morphology of angiosperms. I'm learning about roots right now and I came across the following.

In monocots, adventitious roots are a characteristic feature whereas in dicots true roots are a characteristic feature. When I was younger, I had learnt that fibrous roots are a characteristic feature of monocots.

So I studied further to find that, in monocots, the fibrous roots develop from the base of the stem after the radicle goes absent. And since the roots here do not develop from the radicle but the base of the stem, they are called adventitious roots.

So with this information, I have the doubts:

1. Are all fibrous roots adventitious?
2. If all fibrous roots are adventitious, then are all adventitious roots always fibrous?
3. Are all monocots fibrous rooted?

Answer 1

1. Are all fibrous roots adventitious? -Yes. Take note that adventitious roots do NOT originate from a radicle (first root of a germinating seed). Adventitious roots grow primarily from the nodes of the stems and leaf of some documented plant species. In case of germinating monocot seeds, they do have radicle but the embryonic root dies as the monocot plant grows. The dying embryonic root will soon be replaced by new growing roots from the nodes of mature stems of the monocot plant. These thin and numerous roots are now the fibrous roots which are classified as adventitious roots since they now originate from a stem, not from a radicle.

2. If all fibrous roots are adventitious, then are all adventitious roots always fibrous? -No. Example are the plant cuttings of dicot plants. Stem cuttings of a dicot plant will still produce roots that resemble the taproot system yet they NO longer originate from a radicle. Hence, they are now adventitious roots since their new origin is the stem. Therefore, dicot plant cuttings develop adventitious roots that are not fibrous.

3. Are all monocots fibrous rooted? Yes.

Answer 2

Adventitious roots are plant roots that form from any non-root tissue and are produced both during normal development and in response to stress conditions, such as flooding, nutrient deprivation, and wounding.^[1]

Are all fibrous roots adventitious?

As per the definition, yes, the fibrous roots system consists of adventitious roots that arise from the base of the stem.

If all fibrous roots are adventitious, then are all adventitious roots always fibrous?

No.

Are all monocots fibrous rooted?

Yes, a fibrous root system is universal in monocotyledonous plants and ferns.

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References:

1. Bianka Steffens, Amanda Rasmussen, The Physiology of Adventitious Roots, Plant Physiology, Volume 170, Issue 2, February 2016, Pages 603–617, https://doi.org/10.1104/pp.15.01360