Укроп пахнет сильнее, а петрушка выглядит ярче на тарелке.

А often links two ideas that are being contrasted or compared.

In this sentence, the speaker is setting dill and parsley side by side:

• Укроп пахнет сильнее
• а петрушка выглядит ярче

So а is very natural because it suggests as for parsley / whereas parsley.

A rough sense is:

• Dill smells stronger, whereas parsley looks brighter on the plate.

If you used и, it would sound more like simple addition, with less contrast.

Both are in the nominative case because they are the subjects of the two clauses.

• укроп пахнет = dill smells
• петрушка выглядит = parsley looks/appears

Each noun is doing the action of the verb, so nominative is the expected case.

They are comparative forms, and in Russian the simple comparative form can often function in a way that covers both English adjective and adverb uses.

So:

• сильнее can mean stronger or more strongly
• ярче can mean brighter or more brightly

In this sentence:

• пахнет сильнее = smells more strongly
• выглядит ярче = looks brighter

A key point: these comparative forms are indeclinable, so they do not change for gender, number, or case.

They are built from the base adjectives:

• сильный → сильнее = stronger
• яркий → ярче = brighter

Russian comparatives are often formed with endings like -ее / -ей or with forms like -че.

The second one looks less predictable because there is a stem change:

• яркий → ярче

That kind of consonant change is normal in Russian comparatives.

Because яркий forms its comparative irregularly in the standard language:

• яркий → ярче

Russian does not always make the comparative by just adding -ее to the full adjective stem. Some adjectives change the consonant before the ending.

So яркее is not the standard form here; ярче is.

Because the sentence is not built as a direct X is more Y than Z comparison.

Instead, it gives two parallel observations:

• dill smells stronger
• parsley looks brighter on the plate

If you wanted a direct comparison with than, then you would use чем:

• Укроп пахнет сильнее, чем петрушка.
• Петрушка выглядит ярче, чем укроп.

But in the original sentence, the comparison is more stylistic and contrastive, not expressed with чем.

Because на тарелке expresses location: on the plate.

After на:

• Prepositional = location
  
  • на тарелке = on the plate
• Accusative = motion toward a surface
  
  • на тарелку = onto the plate

So here:

• выглядит ярче на тарелке = looks brighter on the plate

There is no movement, only location.

Because а is connecting two separate clauses, each with its own subject and verb:

• Укроп пахнет сильнее
• а петрушка выглядит ярче на тарелке

In Russian, a comma is normally used before coordinating conjunctions like а when they join independent clauses.

Russian present tense is used both for:

• something you notice right now
• a general characteristic

So this sentence could mean either:

• a present observation about herbs on a plate, or
• a more general statement about how dill and parsley tend to seem

That is very normal in Russian.

Yes. Russian word order is flexible, and changing it usually changes emphasis, not the core meaning.

The given order is neutral:

• Укроп пахнет сильнее, а петрушка выглядит ярче на тарелке.

But you could move things around for focus, for example:

• На тарелке петрушка выглядит ярче.
  This puts extra emphasis on on the plate.

• Петрушка на тарелке выглядит ярче.
  This gives a slightly different rhythm and focus.

So the original sentence is a natural, neutral way to say it.

Because Russian has no articles.

So nouns like укроп, петрушка, and тарелка can mean:

• dill / the dill
• parsley / the parsley
• a plate / the plate

Context tells you which one is meant. In this sentence, English naturally uses the plate, but Russian does not need a separate word for that.

A helpful stressed version is:

УкрОп пАхнет сильнЕе, а петрУшка вЫглядит Ярче на тарЕлке.

Key stress points:

• укрОп
• пАхнет
• сильнЕе
• петрУшка
• вЫглядит
• Ярче
• тарЕлке

A few pronunciation notes:

• сильнее has three syllables: силь-не-е
• ярче is pronounced roughly YAR-che
• выглядит begins with вы-, but the stress is on the first syllable: вЫглядит