Write a note on Bark and Wood?
Bark: -
i) The cork cambium, a special layer of cells in the outer region, produces layers of cells with thickened water proof walls called cork.
ii) All cells outside cork die due to lack of food supply.
iii) Cork together with dead epidermis and cortex collectively form bark.
iv) Cork cambium also produces spongy tissues called lenticels. Exchange of gases takes place through lenticels.
Wood: -
The rate of secondary growth in a stem varies with seasonal changes. This result in the formation of growth rings or annual rings, which may have a
i) Autumn wood as the xylem cells formed during autumn and winter (during the period of slow growth)
ii) Spring wood as the xylem cell formed during spring and summer are large and have thinner walls during the fast growth.