The joining of nuclei and chromosomes is known as incubation fertilization inoculation gestation

The answer is fertilization.

Among the given choices, fertilization is the closest answer. Generally, fertilization occurs when the nucleus both reproductive cells called gametes from a male and a female combines. And the result of the fertilization is the combination of the chromosomes from the male and the female.

The joining of nuclei and chromosomes is known as fertilization. 

The reactants are co_{2} aka carbon dioxide and h_{2}o aka water along with light energy