Final answer:
Heritability for flower color intensity in a group of pea plants homozygous for the purple color is low or estimated at 0, because the variation in color intensity, given the identical genetic makeup, is due to non-genetic factors such as environmental influences or polygenic effects.
Step-by-step explanation:
When a group of peas homogenous for purple flowers is grown, and despite the uniformity in genotype, there is still variability in the flower color intensity, the estimated heritability for flower color intensity would be low. Heritability is a measure that examines how much variation in a trait is due to genetic factors as opposed to environmental influences.
In Mendel's experiments, he noticed that flower color in pea plants was controlled by a single gene, with purple being dominant over white. However, the intensity of the purple color, which varies among the plants, suggests that although the flower color (purple versus white) follows a simple Mendelian inheritance pattern, the intensity of the color is most likely influenced by other factors.
These could include environmental effects or polygenic inheritance, where multiple genes may play a role in determining the precise shade of purple, despite the plants being homozygous for the purple color allele. Since the examined plants all have identical genetic makeup regarding the purple color allele, and yet show variability in color intensity, the heritability for the intensity of flower color would be estimated at 0, indicating no genetic variance is responsible for the observed phenotypic variation in this case.