Plönturnar lifa ekki lengi án vatns.

In Icelandic, the definite article the is usually attached to the end of the noun instead of being a separate word.

• planta = plant
• plöntur = plants
• plönturnar = the plants

So -nar is part of the definite ending here.
Also notice the vowel change:

• singular: planta
• plural: plöntur

That change is just part of how this noun forms its plural.

Because the subject is plural: plönturnar = the plants.

The verb lifa means to live, and in the present tense it changes depending on the subject:

• ég lifi = I live
• þú lifir = you live
• hann/hún lifir = he/she lives
• við lifum = we live
• þið lifið = you (plural) live
• þeir/þær/þau lifa = they live

Since the plants is a plural subject, Icelandic uses the plural form lifa.

In a normal Icelandic statement, the finite verb usually comes early in the sentence, and ekki often follows it.

So:

• Plönturnar lifa ekki lengi án vatns.

literally follows the pattern:

• subject + verb + not
  • adverbial material

This is very normal Icelandic word order.

Compare:

• Hann kemur ekki. = He is not coming / He does not come.
• Við skiljum ekki. = We do not understand.

English puts not with an auxiliary verb, but Icelandic usually just uses ekki after the main finite verb.

Lengi means for a long time or long in this kind of sentence.

So:

• lifa lengi = live a long time
• ekki lengi = not for long / not long

In this sentence, ekki lengi means the plants do not survive for very long.

Because the preposition án always takes the genitive case in Icelandic.

The noun is:

• vatn = water

But after án, it must become genitive:

• án vatns = without water

This is a very important pattern to remember:

• án + genitive

More examples:

• án matar = without food
• án bíls = without a car
• án hjálpar = without help

So án vatn would be incorrect.

Because Icelandic usually does not use a separate word like English the. Instead, definiteness is often built into the noun itself.

But in this sentence, vatns is being used in a general sense: without water, not without the water.

That is why you just get:

• án vatns = without water

If you wanted a more specific meaning like without the water, Icelandic could express that, but in this sentence the general, uncountable idea water is the natural choice.

Here it is being treated as a substance, like English water in without water.

So Icelandic uses the singular noun:

• vatn = water
• án vatns = without water

This does not mean without one water. It means the plants lack the substance water.

Yes. Even though lifa literally means live, in this context English often says:

• The plants don’t live long without water
• The plants don’t survive long without water

Both are natural translations of the Icelandic sentence.

A rough learner-friendly guide is:

• plönturnar ≈ PLUHN-tur-nar

A few notes:

• ö is not the same as English o. It is closer to the vowel in French peur or German schön, though not exactly.
• Stress in Icelandic almost always falls on the first syllable, so: PLÖN-
• The ending -nar is pronounced clearly.

You do not need perfect pronunciation right away, but it helps to notice that ö is a distinct Icelandic vowel.

Yes, Icelandic allows some flexibility, but the verb still usually stays in the second position in main clauses.

The basic sentence is:

• Plönturnar lifa ekki lengi án vatns.

You could also say:

• Án vatns lifa plönturnar ekki lengi.

That version emphasizes without water more strongly.

So Icelandic word order is more flexible than English, but it still follows important rules, especially the tendency for the finite verb to come early.

Here are the basic forms:

• plönturnar → dictionary form: planta = plant
• lifa → dictionary form: lifa = to live
• ekki → not
• lengi → for a long time / long
• án → without
• vatns → dictionary form: vatn = water

This is useful because Icelandic words often appear in changed forms depending on number, case, and grammar.