La radiko kreskas kaj la tigo fariĝas longa.

La is the Esperanto definite article, meaning the.

So:

• la radiko = the root
• la tigo = the stem

It appears twice because Esperanto normally uses la separately before each noun that is definite. English often does the same: the root and the stem.

In Esperanto, nouns end in -o.

So:

• radik- = the idea of root
• radiko = a/the root
• tig- = the idea of stem
• tigo = a/the stem

This -o ending is one of the most basic and regular parts of Esperanto grammar.

Kreskas is the present-tense form of kreski, which means to grow.

Breakdown:

• kreski = to grow
• kresk- = grow
• -as = present tense

So kreskas means grows or is growing, depending on the context.

Because it contains more than one meaningful part:

• far- = do / make
• -iĝ- = become / get into a state
• -as = present tense

So fariĝas means becomes or is becoming.

This is a very common Esperanto pattern. The suffix -iĝ- often shows that something changes into a new state.

For example:

• longa = long
• fariĝas longa = becomes long

Because they mean different things:

• estas longa = is long
• fariĝas longa = becomes long / is getting long

So in your sentence, la tigo fariĝas longa emphasizes a change: the stem was not long before, but now it is becoming long.

Because longa is describing the subject la tigo, not acting as a direct object.

In la tigo fariĝas longa:

• la tigo is the subject
• longa is a predicate adjective, describing what the stem becomes

Predicate adjectives normally do not take -n in Esperanto.

So:

• La tigo estas longa. = The stem is long.
• La tigo fariĝas longa. = The stem becomes long.

In both cases, longa stays without -n.

Yes. In Esperanto, adjectives agree with the nouns they describe in number and case.

Here:

• tigo is singular
• it is not accusative
• so the adjective is also singular and not accusative: longa

If the noun were plural, the adjective would also be plural:

• la tigoj fariĝas longaj = the stems become long

If it were accusative in some other structure, the adjective would also take -n.

Kaj means and.

So the sentence joins two clauses:

• La radiko kreskas
• kaj la tigo fariĝas longa

This is exactly like English and.

Because Esperanto often repeats the noun instead of replacing it with a pronoun, especially in simple teaching sentences.

So:

• la radiko kreskas kaj la tigo fariĝas longa

is perfectly natural and very clear.

You could use pronouns in other contexts, but here repeating la tigo makes the sentence easier to understand.

The normal word order is subject-verb, just like in English:

• La radiko kreskas
• la tigo fariĝas longa

Esperanto word order is fairly flexible, but this standard order is the most natural and easiest for learners.

For example, Longa fariĝas la tigo is possible in a poetic or emphatic style, but much less neutral than la tigo fariĝas longa.

Ĝ is pronounced like the j in judge.

So fariĝas is pronounced approximately:

fa-REE-jas

More carefully:

• fa as in father
• ri with a rolled or tapped r if possible
• ĝas with ĝ = English j sound

The stress in Esperanto always falls on the second-to-last syllable, so here the stress is on ri:

fa-RI-ĝas

They are two different plant parts:

• radiko = root
• tigo = stem

So the sentence is describing two related but different things happening in a plant:

• the root grows
• the stem becomes long

This kind of sentence is common in basic science or nature vocabulary.

Yes. Esperanto -as is a general present tense, so kreskas can mean:

• grows
• is growing

The exact English translation depends on context.

So this sentence could be understood as either:

• The root grows and the stem becomes long
• The root is growing and the stem is becoming long

Both are compatible with the Esperanto.