the stem
A tomato is a fruit.
The tomato fruit is edible, the rest of the plant is not.
Because the seeds of the tomato plant form inside the tomato. That's what a fruit is, the part of the plant that contains the seeds.
The fruit.
The most obvious answer is that Tomato plants have to photosynthesise using in part energy from the sun. If they did not have this energy from the sun and photosynthesis the plant would not be able to grow. Another way a tomato plant can be traced back to the sun is that when the earth was created it was essentially spat out by the sun. In this way all tomato plants are made of matter that was once part of the sun.
the roots
No, they are poisonous. The only edible part of the plant is the tomato(fruit).
The pistil (not 'pistol'; if a plant had that we would be living in a dangerous world).
The fruit. The fruit of any plant is the part that carries the seed. So that means a pumpkin is a fruit so is a cucumber and a tomato
The stalk of a tomato plant is commonly referred to as a stem. It is the main part of the plant that supports the leaves, flowers, and fruits.
The part of the sweet potato plant that you eat is the root. The entire root is edible.
The flower becomes the fruit. As hard as it may seem, to have larger, healthier fruits it is recommended that you pick some of the flowers off of the plant to thin and encourage growth in those fruits instead of many small fruits.