Se vi lasos la planton sen akvo, ĝi baldaŭ ne plu estos bela.

to be

Breakdown of Se vi lasos la planton sen akvo, ĝi baldaŭ ne plu estos bela.

• vi: you
• bela: beautiful
• akvo: the water

Questions & Answers about Se vi lasos la planton sen akvo, ĝi baldaŭ ne plu estos bela.

Why is lasos used here instead of lasus?

Because this sentence is a real future condition, not a hypothetical one.

• Se vi lasos... = If you leave...
• lasos is the future tense of lasi.

In Esperanto, -os is used when something is expected to happen in the future.
You would use -us for a more hypothetical or unreal situation:

• Se vi lasus la planton sen akvo, ĝi ne plu estus bela.
  = If you were to leave the plant without water, it would no longer be beautiful.

So lasos fits a normal, likely future situation.

Why does planton have -n at the end?

The -n marks the direct object.

Here:

• vi lasos = you will leave
• la planton = the plant (the thing being left)

So la planton is what receives the action, which is why it takes -n.

Compare:

• La planto kreskas. = The plant grows.
  No -n, because it is the subject.
• Mi akvumas la planton. = I water the plant.
  -n, because it is the object.

Why is it la planton and not just planton?