Select all the correct answers.

A particular plant has two alleles that control the length of its stem. T represents the dominant allele that codes for a tall stem, and t represents the recessive allele that codes for a short stem. Based on the Punnett squares, which two statements are true about the genotype of the plant's stem length?

\begin{tabular}{|c|c|c|}
\hline First Generation & [tex]$t$[/tex] & [tex]$t$[/tex] \\
\hline [tex]$T$[/tex] & [tex]$Tt$[/tex] & [tex]$Tt$[/tex] \\
\hline [tex]$T$[/tex] & [tex]$Tt$[/tex] & [tex]$Tt$[/tex] \\
\hline
\end{tabular}
\begin{tabular}{|c|c|c|}
\hline Second Generation & [tex]$T$[/tex] & [tex]$t$[/tex] \\
\hline [tex]$T$[/tex] & [tex]$TT$[/tex] & [tex]$Tt$[/tex] \\
\hline [tex]$t$[/tex] & [tex]$Tt$[/tex] & [tex]$tt$[/tex] \\
\hline
\end{tabular}

1. Plants with short stems are homozygous for that trait.
2. Plants with tall stems are always homozygous for that trait.
3. Both parent plants in the second generation are heterozygous.
4. Both parent plants in the second generation are homozygous.

The question pertains to determining the genotype of the plant's stem length based on two Punnett squares.

Let's analyze the information step-by-step:

1. First Generation Punnett Square:
```
| | t | t |
|---|---|---|
| T | Tt| Tt|
| T | Tt| Tt|
```
- This shows the crossing between a homozygous dominant plant (TT) and a homozygous recessive plant (tt).
- All offspring have the genotype Tt, which means they are all heterozygous tall plants.

2. Second Generation Punnett Square:
```
| | T | t |
|---|---|---|
| T | TT| Tt|
| t | Tt| tt|
```
- This shows the crossing between two heterozygous plants (Tt).
- The genotypes of the offspring are as follows:
- TT: Homozygous dominant (tall stem)
- Tt: Heterozygous (tall stem)
- tt: Homozygous recessive (short stem)

Based on these Punnett squares, we can identify the correct statements:

1. "Plants with short stems are homozygous for that trait."
- True. Plants with short stems have the genotype tt, which is homozygous recessive.

2. "Plants with tall stems are always homozygous for that trait."
- False. Plants with tall stems can have the genotype TT (homozygous dominant) or Tt (heterozygous).

3. "All the offspring plants in the second generation are heterozygous."
- False. The second-generation offspring include TT (homozygous dominant), Tt (heterozygous), and tt (homozygous recessive).

4. "Both parent plants in the second generation are homozygous."
- False. The parents in the second generation are heterozygous (Tt).

Given the analysis, the two true statements are:
- Plants with short stems are homozygous for that trait.
- This statement is true based on the Punnett squares: Plants with short stems have the genotype tt, which is homozygous recessive.