Final answer:
In pea plants, the dominant traits for tall stalk and blue flowers mask the recessive traits for short stalk and orange flowers. When two plants with contrasting traits are crossed, the F1 generation will have all dominant traits. The F2 generation will have a phenotypic ratio of 3:1 for the dominant and recessive traits.
Step-by-step explanation:
In pea plants, the trait for tall stalk (T) is dominant over the trait for short stalk (t). The trait for blue flowers (B) is dominant over the trait for orange flowers (b).
When two pure-breeding plants with contrasting traits are crossed (Tall Stalk and Short Stalk & Blue Flowers and Orange Flowers), the F1 generation will all have the dominant traits (Tall Stalk and Blue Flowers). This is because the dominant traits mask the recessive traits.
In a Punnett square, the F1 generation can be represented as:
TB x tb
where TB represents the Tall Stalk and Blue Flowers trait, and tb represents the Short Stalk and Orange Flowers trait.
The F2 generation resulting from crossing the F1 plants will have a phenotypic ratio of 3 Tall Stalk and Blue Flowers : 1 Short Stalk and Orange Flowers. This is because the recessive traits have a 25% chance of being expressed in the F2 generation.