The simultaneous senescence which is also known as the synchronous senescence is the process in which the leaves of temperate deciduous tree undergo senescence and falls off in the late autumn season of the year. This type of senescence is controlled by the environmental factors. In this process only leaves fall off and root and shoot remain as it is.

Senescence refers to a number of controlled processes which finally culminate in the death of the plant part. There are different forms of senescence which are observed in the plants during ageing. Progressive senescence is the form in which there is the gradual death of all the parts of the plant. The parts above the ground are affected first. This type of senescence is observed in the perennial plants.

Senescence also known as aging refers to the decrease in the functional capacity of an organism. This results in a cellular breakdown followed by metabolic failure. The death of cells followed by the death of plant is seen in senescence. Thus the correct answer is option C.

Ageing is the result of a sequential switching on and off of certain genes. Ageing results in senescence. Senescence refers to a number of controlled processes which finally culminate in the death of the plant part. The senescence is considered as the last phase in the process of ageing. 

When a plant part undergoes senescence, nutrient resources(minerals and carbohydrates) shift away or are translocated from the senescened part to other parts. In leaves at the time of senescene we observe loss of chlorophyll, RNA and protein, transport of nutrients and then abscission.

Senescence in plants is a process of aging. During process of senescence, cells undergo differentiation. It ultimately leads into the death of cells.