Question

You are given a fairly old piece of dicot stem and a dicot root which of the following anatomical structures will you use to distinguish between the two..
A) Secondary phloem
B) Proto xylem
C) Cortical cells
D) Secondary xylem

Answer 1

Hint:Old dicot root and step both are of strong wooden piece. And the inner anatomical structure can be seen easily for detail study. Some structures have different type orientation in the stem and the root which plays an important role in the transportation process in plants.

Complete answer:
Secondary phloem :-The secondary phloem helps in the secondary growth of the dicot plants ,without the secondary phloem secondary growth can not proceed, and the position of the secondary phloem is same in both stem and the root.

Proto xylem :- Protoxylem is developed from the procambium but it’s orientation in both the stem and the root is different in the stem the proto xylem is present towards the centre which is known as pith where as in roots it is present towards the periphery . Orientation of structure is different in stem and root.

Secondary xylem :- Secondary xylem and the secondary phloem are combined to form the vascular cambium which results in the secondary growth.

Cortical cells :- They contain the stored food in the plant cells in the form of carbohydrates, tannins etc.

So from the above we know that the orientation of the proto xylem is different in root and the stem so we will differentiate them with the help of protoxylem.

Hence the correct answer is option ‘B’.

Note:
i) When proto xylem is present towards the periphery then it is known as exarch
ii) When proto xylem is present towards the pith then it is known as end arch.