Final answer:
The most probable result when crossing two violet petunias is a combination of violet and possibly the parent colors, depending on the genotype. With four-o'clock flowers, offspring of RR and rr parents are pink with the genotype Rr, showing incomplete dominance.
The growth order for plants under colored lights, assuming only chlorophyll a and b are used, would be blue, orange, then green corresponding to the effectiveness of light absorption.
Step-by-step explanation:
In genetics, petunias exhibit certain inheritance patterns when crossed. According to the information provided:
- When a blue flower is crossed with a red flower, all resulting flowers are violet, suggesting violet is a phenotype produced by the dominant alleles of both blue and red flowers.
- When two violet petunias are crossed, if violet is dominant, the most probable result of the cross would likely be a mix of violet and potentially the parent colors (blue and/or red), depending on the underlying genotype.
- If violet is indeed a trait caused by the combination of two dominant alleles (one from each parent), crossing violet (heterozygous) flowers can result in approximately a 3:1 ratio of violet to non-violet offspring.
Then for four-o'clock flowers, if the red parent has the genotype RR and the white parent has rr, and all offspring are pink, this suggests incomplete dominance. Therefore, the offspring would have the genotype Rr. For the keyword genotype, the pink offspring have one red allele (R) and one white allele (r), resulting in their phenotype being pink.
Regarding plant growth under different colored lights, assuming plants only use chlorophyll a and chlorophyll b, the predicted order of growth from most to least would likely be: Plant A under blue light, Plant C under orange light, and Plant B under green light. This is because chlorophyll absorbs blue and red light most effectively, and green light the least.