Question

Tyloses are found in
A. Sclereids
B. Sclerenchyma fibres
C. Secondary phloem
D. Secondary xylem

Answer 1

Hint:-Tyloses is nothing but a physiological process that results in occlusion in the xylem of large woody plants in response to injury which protects the plant from further damage or decay in heartwood. They are protruding from the parenchyma cells of xylem vessels.

Complete Answer:-Tyloses are outgrowths which are coming out from the parenchyma cells of xylem vessels, its main function is to protect the heartwood of a plant during the condition of drought or infection. It forms the occlusion in the xylem of large woody plants which results in protection from the further damage or spread of infection within the plant. The blocked vessels which are the result of occlusion provide a defence against the radial spread of pathogens, limits their spread horizontally in the plant stem, this protection is stronger at boundaries. It helps in the process of converting the sapwood of the plant into heartwood in large and hard trees. The heartwood has no active defence mechanism of its own against the infection, so the process of blockage is needed which blocks the xylem vessels with tyloses and other substances like resins, gums and sometime waxes that is rich in highly volatile organic compounds such as ‘Terpenes’ which is toxic to insects and tree pathogens such as bacteria or fungi. This helps in making a stronger heartwood by slowing the progress of rot in the plant.

Hence we can easily conclude that the correct option is (D) Secondary Xylem.

Note:- In many plants and species of plants the older wood which is the centre of the tree becomes less important in context with physiological processes like nutrient and water transportation. Thus, this is converted to ‘Heartwood’ by the tree. This has no active defence mechanism of its own.