tā lián gēnbù dōu kàn le.

Because 都 is part of the pattern 连 + X + 都 + verb.

In this pattern:

• 连 marks the item being emphasized
• 都 helps complete the emphasis
• together they mean even X...

So:

• 她连根部都看了。 = She even looked at the roots/base part.

By itself, 都 often means all or both, but in this construction it helps express surprise or emphasis.

连……都…… is a very common Chinese pattern meaning:

• even...
• to the extent that even...
• not excluding even...

It highlights something that is unexpected, extreme, or surprisingly included.

Structure:

• Subject + 连 + emphasized item + 都 + verb

So in this sentence:

• 她 = she
• 连根部都 = even the root/base part
• 看了 = looked at / examined

The speaker is emphasizing that she looked at everything so carefully that she even looked at the root/base.

Because in the 连……都…… pattern, the thing being emphasized usually comes before the verb.

So the order is:

• 她 + 连根部都 + 看了

not:

• 她看了连根部都 ❌

Chinese often puts the emphasized object before the verb in this structure. You can think of 连根部都 as a kind of emphasis block:

• even the root/base part

Then the verb comes after it:

• 看了 = looked at it

根部 literally means root part or base part.

Depending on context, it can refer to:

• the roots of a plant
• the base of hair
• the bottom/base of an object
• the root area of something

So the exact English translation depends on what is being talked about. The sentence itself just says she even looked at the root/base part.

Here 了 marks the action as completed.

So:

• 看 = look / examine
• 看了 = looked / examined

In this sentence, 了 shows that she actually carried out the action. It is not just a habit or general statement.

Compare:

• 她连根部都看。 = She even looks at the roots/base part.
  This sounds more like a habitual action or a general description.

• 她连根部都看了。 = She even looked at the roots/base part.
  This refers to a completed action.

看 literally means look or look at, but in many contexts it can also mean:

• inspect
• examine
• check

So in this sentence, 看 may sound more natural in English as:

• She even checked the roots/base part
• She even examined the roots/base part

rather than only looked at, depending on context.

Chinese often uses simple verbs like 看 in places where English might choose a more specific verb.

Yes, it is very natural.

A basic pattern is:

• Subject + 连 + object/focus + 都 + verb + 了

So this sentence fits perfectly:

• 她
  • 连根部都
    • 看了

This word order is standard for emphasis.

A more expanded sentence could be:

• 她连根部都看了一遍。
• She even looked over the roots/base part once.

But the original sentence is already complete and natural.

Usually, 连 and 都 go together in this pattern.

Most natural:

• 她连根部都看了。

If you remove 连:

• 她根部都看了。
  This sounds odd or incomplete in most contexts.

If you remove 都:

• 她连根部看了。
  This is also not the normal standard pattern.

In everyday Chinese, the pair 连……都…… is the usual way to express even.

There is also a similar pattern with 也:

• 她连根部也看了。

This can also mean She even looked at the roots/base part, but 连……都…… is often stronger or more typical.

The emphasized part is 根部.

The sentence suggests that looking at the root/base part is somehow:

• unexpected
• unusually thorough
• surprisingly detailed
• something that might normally be skipped

So the feeling is not just she looked at it, but:

• she was so thorough that she even looked at the root/base part

That is the main effect of the 连……都…… structure.

Yes. That can be a very good translation.

Because 看 is broad in meaning, the best English version depends on context. Possible translations include:

• She even looked at the roots/base part.
• She even checked the roots/base part.
• She even examined the roots/base part.

If the context is careful inspection, checked or examined may sound more natural than a literal looked at.

Chinese often expresses meanings through patterns rather than one single matching word.

English uses:

• even

Chinese often uses:

• 连……都……
• sometimes 甚至
• sometimes 连……也……

So instead of looking for one word that always equals even, it is better to learn the whole structure:

• 连 + emphasized item + 都 + verb

That will help you understand many similar sentences, such as:

• 他连饭都没吃。 = He didn’t even eat.
• 我连她的名字都不知道。 = I don’t even know her name.