En primer lugar, reviso la plántula.

En primer lugar is a very common way to say first, first of all, or in the first place when you are listing steps or points.

In this sentence, it signals that this is step one in a process.

Other common sequencing expressions are:

• Primero = first
• Luego = then
• Después = afterward / later
• Por último = lastly / finally

So en primer lugar sounds a little more formal or structured than just primero.

This is because primero shortens to primer before a singular masculine noun.

Here, the noun is lugar, which is masculine and singular, so Spanish uses:

• primer lugar = first place / first position

Compare:

• el primero = the first one
• el primer paso = the first step
• el primer lugar = first place

This shortening is very common with primero and tercero before singular masculine nouns:

• el tercer capítulo
• el tercer día

Reviso is the first-person singular present tense form of the verb revisar.

That means it means:

• I check
• I review
• I inspect
• sometimes I examine

The ending -o tells you the subject is I.

Conjugation of revisar in the present:

• yo reviso = I check
• tú revisas = you check
• él/ella revisa = he/she checks
• nosotros revisamos = we check
• ustedes revisan = you all check
• ellos revisan = they check

Spanish often leaves out subject pronouns when they are not necessary.

So instead of saying:

• Yo reviso la plántula

it is very natural to say:

• Reviso la plántula

The verb form reviso already tells you the subject is I, so yo is usually omitted unless you want emphasis, contrast, or clarity.

For example:

• Yo reviso la plántula y tú riegas la tierra.
  = I check the seedling and you water the soil.

There, yo helps create contrast with tú.

Spanish usually uses a definite article more often than English does.

Here, la plántula means:

• the seedling
• or sometimes the plantlet, depending on context

The article la is used because plántula is:

• singular
• feminine

So:

• la plántula = the seedling
• una plántula = a seedling

Even if English might sometimes say I check seedling growth or use no article in some contexts, Spanish often prefers an article with a specific noun.

The article tells you: la plántula.

Also, nouns ending in -a are very often feminine, though not always. In this case, plántula is feminine, so it takes:

• la plántula
• una plántula

If you wanted to describe it with an adjective, the adjective would also normally match in gender and number:

• la plántula pequeña = the small seedling
• la plántula saludable = the healthy seedling

Plántula has a written accent because of Spanish stress rules.

The natural stress in the word is on the first syllable:

• PLÁN-tu-la

Without the accent mark, Spanish spelling rules would suggest a different stress pattern, so the accent is needed to show the correct pronunciation.

That accent mark is also important in writing, because Spanish uses accents to show where the stress falls when it is not predictable from the normal rules.

A helpful approximation is:

• PLAHN-too-lah

with the stress on the first syllable:

• PLÁN-tu-la

A few pronunciation notes for Latin American Spanish:

• a sounds like the a in father
• u sounds like oo in food
• t is a clean dental t, softer than many English t sounds
• every vowel is pronounced clearly

Yes. Primero, reviso la plántula is completely natural.

The difference is mostly style:

• Primero, reviso la plántula. = simpler, more conversational
• En primer lugar, reviso la plántula. = a bit more formal or structured

Both work well if you are describing a sequence of actions.

Revisar is a good choice if the idea is check, inspect, or look over carefully.

Depending on context, other verbs could also appear:

• observar la plántula = observe the seedling
• examinar la plántula = examine the seedling
• ver la plántula = see/look at the seedling
• inspeccionar la plántula = inspect the seedling

But revisar often suggests a practical check, such as looking for condition, progress, or problems.

This is the present tense.

In Spanish, the present can describe different things depending on context:

• something happening now
  Reviso la plántula. = I’m checking the seedling.
• a habitual action
  Cada mañana reviso la plántula. = Every morning I check the seedling.
• a step in instructions or narration
  En primer lugar, reviso la plántula. = First, I check the seedling.

So the same verb form can cover both I check and I am checking, depending on the situation.