Senescence as an active development cellular process in the growth and functioning of a flowering plant is indicated in 

• vessel and tracheid differentiation

• leaf abscission

• annual plants

• floral parts

B.

leaf abscission

Senescence can be defined as ' the sum of deteriorative processes, which naturally terminate the functional life of an organism'. Senescence is not confined only to the whole plant, it may be limited to a particular plant organ such as leaf and flower or cells such as phloem and xylem. Abscission is the natural shedding of leaves, foliage branches, fruits, floral parts etc. According to Leopold (1967) abscission is a Senescence phenomenon. Senescence as an active development cellular process in growth and functioning of a flowering plant is indicted in leaf abscission.
Whole plant senescence also known as overall senescence occur in annulas (eg, rice, wheat, gramme, mustard) biennials (eg, henbane or perennials.)