• Which will decay faster if exposed freely to air
• soft wood
• heart wood
• sap wood
• wood with lots of fibers

ANSWER (3)

In wood with a lot of fibres, the fibres are thick-walled walled dead cells, so resist microbial action.

 

The region which comprises of dead elements with highly lignified walls is called heartwood.It has deposition of organic compounds like tannin, resins, oils, gum, aromatic substances and essential oil at the central or innermost layers. Heartwood is the one that would decay the slowest as these deposited substances make it hard, durable and resistant to microbial action and insects.

 

The peripheral region of the secondary xylem is known as sapwood and is lighter in colour. It involves conduction of water and minerals hence more prone to microbial attack. So sap wood is the one that decays the slowest. 

Please approve ^_^

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