Transplantei o rebento.

Transplantei is the 1st person singular form of the verb transplantar in the pretérito perfeito (the simple past used for a completed action).

So:

• transplantar = to transplant
• transplantei = I transplanted

The ending -ei shows that the subject is eu (I).

Portuguese often leaves out subject pronouns when the verb ending already makes the subject clear.

So:

• Transplantei o rebento. = I transplanted the shoot/sprout.
• Eu transplantei o rebento. = also correct, but eu adds emphasis, contrast, or clarity

In neutral sentences, leaving out eu is very common in European Portuguese.

O is the masculine singular definite article, meaning the.

So:

• o rebento = the sprout / the shoot
• um rebento = a sprout / a shoot

Using o suggests that the speaker means a specific rebento, one already known in the context.

Because rebento is a masculine noun in Portuguese.

That means it takes masculine articles:

• o rebento = the sprout
• um rebento = a sprout

If it were feminine, you would expect a or uma, but that is not the case with rebento.

Here, rebento is a masculine singular noun and it is the direct object of the verb transplantei.

In other words:

• transplantei = the action
• o rebento = the thing that was transplanted

This is a very standard verb + direct object structure.

Not always. Rebento can have a few meanings depending on context, such as sprout, shoot, offshoot, and in some contexts even descendant/offspring.

But in this sentence, because the verb is transplantar, the plant-related meaning is the natural one. So a learner should understand it here as something like sprout, shoot, or young plant growth.

This is the normal order for a simple statement in Portuguese:

• verb
• direct object

Since the subject eu is omitted, the sentence begins directly with the verb:

• Transplantei o rebento.

If you include the subject, you get:

• Eu transplantei o rebento.

Both are correct. The version without eu is more natural in many everyday contexts.

This is the pretérito perfeito, which usually refers to a completed action in the past.

So Transplantei o rebento means the action is seen as finished: the transplanting happened and is complete.

Compare:

• Transplantei o rebento. = I transplanted the sprout.
• Transplantava o rebento. = I was transplanting the sprout / I used to transplant the sprout.

The second one gives a more ongoing, habitual, or background sense, while transplantei presents the action as a finished event.

Yes. Transplantar is a regular -ar verb.

That is helpful because its forms follow the normal pattern. For example:

• eu transplanto = I transplant
• tu transplantas = you transplant
• ele/ela transplanta = he/she transplants
• eu transplantei = I transplanted

So if you know regular -ar verb patterns, transplantar is straightforward.

Normally, no. In Portuguese, singular countable nouns usually need a determiner such as an article or demonstrative.

Natural options would be:

• Transplantei o rebento. = I transplanted the sprout.
• Transplantei um rebento. = I transplanted a sprout.
• Transplantei este rebento. = I transplanted this sprout.

A bare singular noun like rebento without any article sounds unnatural here.

A rough approximation for a native English speaker is:

trãsh-plan-TAY u r(uh)-BEN-tu

A few European Portuguese points to notice:

• o often sounds more like u when unstressed
• the r in rebento is typically a Portuguese r, not an English one
• unstressed vowels are often reduced more than in Brazilian Portuguese

This is only an approximation, but it helps you avoid reading every letter in a fully English way.

No, not wrong at all. It is fully correct.

The difference is mainly one of style and emphasis:

• Transplantei o rebento. = neutral, very natural
• Eu transplantei o rebento. = more explicit, possibly emphatic

For example, eu might be used if you are contrasting yourself with someone else:

• Eu transplantei o rebento, não foi ele.
  I transplanted the sprout, not him.