A buttress root.
A buttress-root is a root growing from the above-ground stem or trunk, providing support.
A taproot
acacia is a taproot
The HI2 answer is taproot.
Fibrous root
The carrot plant's root system is a taproot
There are two types of root systems. taproot system and the fibrous root system.
Taproot.
Taproot!
I think you are refering to a taproot coming from the center of the root structure this is the main root for tree to live
taproot
It is called a taproot.