A pure tall plant was grown in nutrient limited soil and became dwarf. If this plant was selfed then the genotype in the F₁ generation are

A pure tall plant was grown in nutrient-limited soil and became a dwarf. If this plant was selfed then the genotype in the F₁ generation are all tall plants.
A pure tall plant has genes TT, whereas in limitation of nutrients its phenotype is affected. If the plants with dominant and pure genes (TT) are selfed then all tall plants will only be developed as there is the absence of any dwarf or recessive genes.