Question

Heartwood differs from sapwood in

• A. being susceptible to pests and pathogens
• B. presence of rays and fibres
• C. absence of vessels and parenchyma
• D. having dead and non-conducting elements

Answer 1

The correct option is D having dead and non-conducting elements

The older woody stems tend to show two distinct regions, the outer light coloured and functional sapwood (or alburnum), and the inner darker and non-functional heartwood (or duramen).

The inner zone gets dark due to progressive deposition of organic compounds like resins, gums, tannins, etc and essential oils in vessels and tracheids of older secondary xylem (wood). The cells of the heartwood are lignified which makes it stronger and durable. Some of these substances can also function as antiseptics which makes it furthermore resistant to pathogens. These depositions result in blockage of xylary elements due to which water is not conducted. So, vessels are present that become non- functional and parenchyma dies soon after heartwood formation. The formation of heartwood often causes the death of ray cells. The conduction of water and minerals dissolved in it is performed by peripherally located younger sapwood. Sapwood shows the presence of ray cells and fibres. A part of the sapwood has conducting function and a part has storage function.