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Anatomically fairly old dicotyledonous r...

Anatomically fairly old dicotyledonous root is distinguished from the dicotyledonous stem by
1 absence of secondary xylem
2 absence of secondary phloem
3 presence of cortex
4 position of protoxylem

A

absence of secondary xylem

B

absence of secondary phloem

C

presence of cortex

D

position of protoxylem

Text Solution

AI Generated Solution

The correct Answer is:
To determine how an anatomically fairly old dicotyledonous root is distinguished from a dicotyledonous stem, we need to analyze the options given in the question. ### Step-by-Step Solution: 1. **Understanding Secondary Growth**: Both dicotyledonous roots and stems undergo secondary growth, which means they both develop secondary xylem and secondary phloem. Therefore, options 1 and 2, which mention the absence of secondary xylem and secondary phloem, are incorrect. 2. **Cortex Presence**: The cortex is a tissue found in both dicot roots and stems. Thus, option 3, which states the presence of cortex, cannot be used to distinguish between the two. 3. **Protoxylem Position**: The key difference lies in the position of protoxylem in the xylem structure. In dicot roots, the protoxylem is located at the periphery (this is known as exarch xylem), while in dicot stems, the protoxylem is located at the center (this is known as endarch xylem). 4. **Conclusion**: Based on the analysis, the correct answer is option 4, which refers to the position of protoxylem. This anatomical feature allows us to distinguish between a dicotyledonous root and a dicotyledonous stem. ### Final Answer: The anatomically fairly old dicotyledonous root is distinguished from the dicotyledonous stem by the **position of protoxylem**. ---
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