Question

What are Tyloses?

Answer 1

Hint: A growth on the outside of an animal or plant is known as an outgrowth. Under various stress conditions and during invasion by most xylem-invading pathogens, tyloses form in the xylem vessels of most plants.

Complete answer:
A tylosis is a bladder-like distention of a parenchyma cell into the lumen of neighbouring arteries in woody plants. The word tylosis refers to the physiological process of occlusion in the xylem of woody plants as a reaction to damage or as a defence against decay in the heartwood. It's a crucial step in the compartmentalization of rot in trees and other woody plants. Tyloses show as balloon-like protrusions emerging from axial paratracheal parenchyma cells into xylem vessels through pits connecting the two when observed in section under a microscope. There may be a clear barrier between the tyloses issuing from the pits and the vessels in certain kinds, whilst they may be hardly distinguishable in others.
Tyloses are outgrowths/extra growths on the parenchyma cells of secondary heartwood xylem arteries. When a plant is stressed by drought or infection, tyloses fall from the edges of the cells and "dam" up the vascular tissue, preventing the plant from suffering additional harm. In some hardwood trees, especially those with bigger vessels, tyloses can help with the conversion of sapwood to heartwood. As soon as vessels become filled with air bubbles, these obstructions can be employed in addition to gum plugs to assist build a stronger heartwood by delaying the progression of rot.

Note:
Tylosis in the vessels of flowering plants slows the vertical spread of fungal hyphae and other diseases, preventing them from spreading axially. Gymnosperms use a similar mechanism to prevent access to tracheids by sealing the pits that connect them. The obstructed arteries also act as a barrier to infections spreading radially along the plant stem, restricting their horizontal spread. At the intersections of yearly rings, protection is enhanced. The pace with which tyloses build vertical and horizontal barriers affects their efficacy, with healthier plants usually establishing them faster.