Final answer:
The trait for achlorophyllous or albino plants is recessive; it manifests when the plant inherits two recessive alleles for the trait. This trait is lethal for plants if the entire plant expresses the recessive albino phenotype because it cannot perform photosynthesis.
Step-by-step explanation:
If we consider achlorophyllous or albino plants, where the entirety of the plant lacks chlorophyll, this trait is typically recessive. A plant must receive two copies of the gene causing albinism (one from each parent) to exhibit this characteristic. As mentioned, if it is the entire plant that is albino, this would be lethal since chlorophyll is necessary for photosynthesis, the process by which plants produce their own food.
Based on the information provided, plants with white flowers (bb) represent the recessive trait, while those with purple flowers (BB or Bb) have the dominant trait. This is supported by the inheritance patterns discovered by Gregor Mendel in his pea plant experiments, where he noted that the dominant trait is expressed in hybrids. For instance, Mendel observed that in monohybrid crosses involving two true-breeding pea plants with contrasting traits, the F1 offspring always exhibited the traits of one parent—the dominant trait—and the recessive trait reappeared in the F2 generation with a 3:1 dominant to recessive ratio.
To sum up, the albino phenotype of a plant is recessive and only manifests when two recessive alleles are present. This is important to understand in genetics and can also be connected to other examples of recessive traits in organisms, such as the allele for albinism in humans.