Question

Tyloses an outgrowth from ray or axial parenchyma cell into the lumen of vessel, which partially or completely blocks the cavity, are present in:
A. Periderm
B. Heartwood
C. Sap wood
D. Secondary cortex

Answer 1

Hint: Plants have specialized cells or tissues that perform specific functions. The plant tissues are divided into two groups: meristematic and permanent tissues. The meristematic tissues are the specialized tissues which are actively dividing cells present in the region of active cell division called meristems. Some cells in plants lose their ability to divide and these are termed as permanent tissues.

Complete answer:
The complex tissues are those which have specialized cells that are made of more than one type of cells, but work as a single unit. These are xylem and phloem; xylem is the tissue that is responsible for the conduction of water, minerals and nutrients from roots to the other parts as well as mechanical support to the plant body. And phloem transports the food throughout the plant. The xylem tissue has four types of cells which are: Xylem tracheids (elongated tube cells having tapering ends), Xylem vessels (cells with long and large central cavity and have perforated plates through which these are interconnected with the other units of the xylem tissue), Xylem fibers (have thickened walls and obliterated central lumens) and Xylem parenchyma (cells which are used to store food in form of starch and help in conduction of water in peripheral region).
In woody plants like heartwood, an extension of parenchymatous cells into the lumen of vessels is observed, this is called as Tyloses. When there is any injury or infection, the cavity is blocked by Tyloses as a dam so that no further damage or destruction can occur in the plant, specifically the heartwood.

Therefore, the correct answer for this question is option B- heartwood.

Note: In old trees, the secondary xylem becomes darker in color due to the deposition of various organic compounds such as tannins, resins, oils, gums, aromatic substances and essential oils in the central layers of stem. These substances make the stem durable and resistant to various infections.