Final answer:
The genotypes of parental plants producing the observed 9:3:3:1 offspring ratio for the traits tall/dwarf and violet/white are DdWw x DdWw, demonstrating a dihybrid cross consistent with Mendelian genetics. Option number 1 is correct.
Step-by-step explanation:
The parental plants in the given cross that result in offspring with a 9/16 tall, violet: 3/16 tall, white: 3/16 dwarf, violet: 1/16 dwarf, white ratio are heterozygous for both traits (DdWw x DdWw). This is determined by the dihybrid cross which follows Mendel's principles, showing a phenotypic ratio of 9:3:3:1 in the F2 generation for two traits that segregate independently.
A Punnett square can be used to predict the outcomes of genetic crosses, and when it is applied to this scenario, the observed ratio matches the expected results according to Mendelian genetics. Consequently, option 1) DdWw x DdWw correctly represents the genotypes of the parental plants with the traits tall (D) dominant over dwarf (d) and violet (W) dominant over white (w).