Question

The balloon-shaped structures called tyloses
A. Are extension of xylem parenchyma cells into vessels
B. Are linked to the ascent of sap through xylem vessels
C. Originate in the lumen of vessels
D. Characterize the sap

Answer 1

Tyloses are referred to as an outgrowth. During a stressful condition like drought or any sort of infection, the plant gets stressed and then tyloses will fall from the sides of the cells and dam up in the vascular tissue which prevents the further damage of the plant.

Complete answer:
Tyloses are the balloon-shaped extension or an outgrowth of xylem parenchyma cells of vessels in the heartwood.
These structures are mostly present in drought exposed plants or in infected plants wherein they serve to reduce the surface available for transport in the conducting element and thereby acting as morphological defenses.
Tyloses help in the process of making sapwood and heartwood.
It mainly occurs in some hardwood trees, especially in trees that consist of larger vessels.
These blockages can be used in addition to gum plugs as soon as vessels become filled with air bubbles.
They help us to form stronger heartwood by slowing the progress of rot.
Tyloses are formed because when the protective layer that surrounds the protoplast of the parenchyma cell proliferates into the vessel lumen further the process of degradation and rupture of the vessel parenchyma pit membrane occurs.

So, the correct option is option A. Are extensions of xylem parenchyma cells into vessels.

Note:
Tylosis in the vessels of flowering plants counteracts the axial spread of fungal hyphae and other pathogens by slowing down their vertical spread with a physical barrier.
A similar process occurs in gymnosperms, which block access to tracheids by closing the pits that join them to each other.