Why Are There Two Types Of Potato 'Lateral Roots'?

TWO TYPES OF 'ROOTS'

Something else interesting about the new laterals developing from the potato root we saw last week are the two apparently different types of 'root': thick ones (pink) and thin ones. Are they both roots or just the thicker ones with the root hairs? Can't see how they could be tuber* rhizomes, since these arise from stems. I know adventitious roots also come from stems. But not from the same source, surely. But the two types seem to be attached to the parent at different angles.

Too soon to determine any of this. Not even clear whether each of these types of 'root' is attached to the main root. See what develops.

* A potato tuber is a bulky short terminal part of an underground stem (rhizome) whose 'eyes' are really buds at nodes. Shoots and roots grow from these eyes upon planting. We often see these on old potatoes in the cupboard which have started to grow. The main bud is at the end of the tuber and exerts dominance over the other lesser 'eyes' in the way expected in stem terminal buds.

Why Are Potato Lateral Roots Mostly At Surface?

This is the same root you saw last week, rising and falling beneath the soil surface. More interesting developments this week:

Secondary (lateral) roots have suddenly developed, but only where the original root is nearest to the surface. It's hard to get a photo because of the shape of the pot, but the root is almost devoid of laterals either side where it is lower in the soil, so farther away from the surface. Why?

• Perhaps laterals responding belatedly (it takes lateral roots some time to appear, because they have to grow from the 'pericycle', deep inside the root) to the water applied to the surface some time back.
• or Perhaps, being principally feeder roots, they just grow when roots come up near the surface (feeder roots do this to gather water from rain showers, among other things)

Just out of interest, I inserted some water around the lower root (where it is furthest from the surface) with a syringe, so that the soil is just moist. Will this water induce lateral roots to form?