Variations in the timing, speed and pattern of senescence (seen in their most dramatic and extreme forms in mutants) are often heritable.  That is, offspring of a plant that senesces in a particular way will tend to behave in the same fashion as their parent.

This is because the genes controlling senescence pass from generation to generation according to the rules of genetics.

Genes are arranged linearly along the chromosomes.  The nucleus of just about every cell in an organism contains a set of chromosomes, usually in pairs.  Thus a cell of a pea plant (and rye grass, as shown here) will contain 14 chromosomes, representing two sets of 7 (in genetic studies, this would be represented as 2n = 14).  Humans are 2n = 46.

Let's look at the cell of an imaginary plant with just two pairs of two chromosomes (2n = 4).  And let's follow the inheritance of three genes (call them G1, G2 and G3) controlling different aspects of senescence.

Here we see that G1 and G2 are in different locations on chromosome 1, while G3 is on chromosome 2.  Remember that chromosomes come in pairs (here the two sets of chromosomes are indicated by two different colours) and so each gene also exists as a pair (also colour-coded in the illustration).