Based on the given information about the genotypes and the outcomes of the Punnett squares, let's analyze the statements one by one.
1. Plants with short stems are homozygous for that trait.
- Short stems are represented by the genotype 'tt', which means the plant must have two recessive alleles. Only plants with the genotype 'tt' will exhibit short stems. Therefore, plants with short stems are indeed homozygous for that trait.
- This statement is true.
2. Plants with tall stems are always homozygous for that trait.
- Tall stems are represented by the presence of at least one dominant allele (T). Plants with the genotypes 'TT' or 'Tt' will have tall stems. Since tall stems can result from both a homozygous dominant (TT) and a heterozygous (Tt) genotype, plants with tall stems are not always homozygous for that trait.
- This statement is false.
3. Both parent plants in the second generation are heterozygous.
- Looking at the second Punnett square:
[tex]\[
\begin{array}{|c|c|c|}
\hline
\text{Second Generation} & T & t \\
\hline
T & TT & Tt \\
\hline
t & Tt & tt \\
\hline
\end{array}
\][/tex]
The parents for the second generation are represented by the alleles on the top row (T, t) and the leftmost column (T, t), which means their genotypes are both 'Tt'. Thus, both parent plants in the second generation are heterozygous.
- This statement is true.
4. Both parent plants in the second generation are homozygous.
- As previously identified, the parents' genotypes in the second generation are 'Tt', which means they are heterozygous, not homozygous.
- This statement is false.
Thus, the two statements that are true are:
- Plants with short stems are homozygous for that trait.
- Both parent plants in the second generation are heterozygous.
