The plant tissues become woody by a process of

The correct option is D Lignification

• The plant tissues become woody by a process of lignification.
  
• Lignification is a complex process which occurs in vascular plants to strengthen the plant body.
• In this process, the complex organic molecule lignin fills the intercellular spaces between the cell wall with cellulose, hemicellulose and pectin components (in vascular tissues).
  
• This compound is covalently linked to hemicellulose thus, the cross-links are formed between different plant polysaccharides which provide mechanical strength to the cell wall or plant as a whole.
• They are abundantly found in the wood of plants.
• Lignin is hydrophobic in nature and thus, impermeable to water.
• So, the correct answer is 'Lignification'.