ANATOMY OF MUSTARD PLANT (BRASSICA-CAMPESTRIS L) .3. HYPOCOTYL

An anatomical investigation has been made on the hypocotyl of Brassica campestris L. cv. Sonali (Yellow Sarson) at different stages of growth. The lower part is stem-like in structure. Two poles of protoxylem alternate with two poles of protophloem in the lower part of the hypocotyl but towards the upper part, the tracheary elements differentiate abaxially while the sieve elements differentiate adaxially. The transition occurs mostly in the upper part of the hypocotyl. In the 9 days old seedling the cambium appears in the upper part of the hypocotyl but the secondary tissues do not differentiate there till the plants are 12 days old. The cambium extends towards the lower part of the hypocotyl. The epidermis is single layered cosisting of small and large cells. Adaxial to it there are 5-8 layers of cortical cells with conspicuous intercellular spaces. The phellogen appears in the cortex, 4-5 layers beneath the epidermis. It produces 4-6 layers of cork cells abaxially and 1-3 layers of phelloderm adaxially.