Question

Amount of secondary xylem as compared to secondary phloem formed every year is
A. Equal
B. 8 - 10 times
C. Half
D. Depends on season and region where the plant grows

Answer 1

Hint: The secondary xylem is the xylem which is formed from secondary growth, whereas the secondary phloem is the phloem tissue produced from secondary growth. Secondary tissues are formed on the outside of the vascular cambium and contain complex tissues which include an axial and a ray system.

Complete answer:
During intra-stellar secondary growth in dicotyledonous stems, a ring of cambium known as vascular cambium is formed. The vascular cambium forms more amount of secondary xylem towards the inner side and comparatively less amount of secondary phloem towards the inner side.
In the plants which are found in temperate regions, the activity of the vascular cambium is affected by the existence of extreme seasonal variations in these regions. Due to the favourable conditions in the spring or early summer, a large amount of secondary xylem is formed which is known as Springwood or earlywood. It is lighter in colour and has a lower density. During the autumn season, because of the presence of adverse conditions, less amount of wood is produced which is known as autumn wood or latewood. It is darker in colour and has a higher density.

Hence, the correct answer is option (D)

Note: Some similarities between Primary Xylem and Secondary Xylem are:
A)Both contain vessels, xylem fibres and xylem parenchyma.
B)Both conduct water from the root to the upper part of the plant.
C)Both are differentiated from the cambium.