nobiru ni turete, sityuu ga hituyou ni naru.

に つれて means as something happens, in proportion as, or along with.

So 伸びる に つれて means:

• as it grows
• as it gets longer
• as growth progresses

This pattern is used when one change happens alongside another change.

In this sentence:

• the plant or stem grows
• and, as a result, a support becomes necessary

So the sentence describes two linked changes happening together.

Before に つれて, verbs normally appear in the plain dictionary form.

So:

• 伸びる に つれて = as it grows
• not 伸びて に つれて

This is just the standard grammar pattern:

• verb dictionary form + に つれて
• noun + に つれて

Examples:

• 年を取るにつれて = as one gets older
• 日本語が上手になるにつれて = as one gets better at Japanese

So 伸びる is not especially informal here; it is just the required form for this grammar.

伸びる literally means things like:

• to stretch
• to grow
• to extend
• to get longer

In this sentence, the most natural meaning is to grow or to get taller/longer.

Because the sentence also mentions 支柱, it strongly suggests a plant. So 伸びる here probably means that a plant is growing upward, and as it grows, it needs support.

This is the intransitive verb 伸びる. It describes something growing or extending on its own.

Compare:

• 枝が伸びる = the branch grows
• 髪が伸びる = hair grows
• 手を伸ばす = to stretch out one’s hand

The last example uses 伸ばす, the transitive counterpart.

The subject is omitted, which is very normal in Japanese.

Something is understood to be growing, but the sentence does not explicitly say what. From context, it is probably something like:

• a plant
• a vine
• a stem
• a crop

Japanese often leaves out information that is obvious from the situation. So instead of saying:

• 植物が伸びるにつれて、支柱が必要になる

it simply says:

• 伸びるにつれて、支柱が必要になる

This is natural if the topic has already been established.

支柱 means support pole, stake, or prop.

In gardening or farming, it is the stick or pole used to support a plant as it grows. For example:

• tomato plants
• climbing plants
• tall flowers

So in this sentence, 支柱が必要になる means that a support stake becomes necessary.

Breaking down the kanji:

• 支 = support
• 柱 = pillar, post

So the meaning is very literal: a supporting post.

Because 必要になる means becomes necessary, while 必要だ means is necessary.

That difference matters here.

The pattern に つれて often describes change over time, so なる fits well:

• 伸びるにつれて、支柱が必要になる
• As it grows, a support becomes necessary

This suggests a progression:

1. at first, maybe no support is needed
2. then the plant grows
3. eventually, support becomes necessary

If you said 支柱が必要だ, it would sound more like a general statement of fact:

• 伸びるにつれて、支柱が必要だ
• As it grows, a support is necessary

That is not impossible, but 必要になる better expresses the idea of changing conditions.

In 必要になる, the に is part of the pattern that marks the result state with なる.

A very common structure in Japanese is:

• noun / な-adjective + に なる = to become ...
• い-adjective + く なる = to become ...

Examples:

• 静かになる = to become quiet
• 元気になる = to become healthy / energetic
• 必要になる = to become necessary

Since 必要 behaves like a な-adjective / nominal adjective, it uses に before なる.

So:

• 必要だ = is necessary
• 必要になる = becomes necessary

Because 支柱 is the thing that is necessary.

In Japanese, with 必要だ and 必要になる, the thing needed is often marked with が:

• お金が必要だ = money is necessary
• 許可が必要です = permission is required
• 支柱が必要になる = a support becomes necessary

This may feel different from English, where we often say need a support. Japanese often frames it as:

• a support is necessary

So が marks the item that is necessary.

You might also see は in some contexts for contrast or topic marking, but が is the basic, neutral choice here.

Yes, they can be similar, but they are not always interchangeable.

Both can mean something like:

• as
• along with
• together with

But に つれて strongly emphasizes gradual change that happens in step with another change.

That makes it especially suitable here:

• the more it grows, the more support becomes necessary

とともに can sound a bit more formal and can also mean together with in a broader sense, not only gradual change.

So in this sentence, に つれて is a very natural choice because it highlights a developing process.

Yes, that is a very natural English rendering.

Even though the Japanese literally says something closer to:

• As it grows, a support becomes necessary

in natural English, you could say:

• The more it grows, the more it needs support
• As it grows, it needs a stake
• As it gets taller, a support stake becomes necessary

So this is a good example of how natural English translation may shift the structure a little, even when the Japanese grammar is different.

The comma helps readability, but it is not grammatically essential.

It separates:

• the condition/change part: 伸びるにつれて
• the main result part: 支柱が必要になる

So it makes the sentence easier to read:

• As it grows, a support becomes necessary

In Japanese writing, punctuation is somewhat flexible, especially in shorter sentences. So you may see both:

• 伸びるにつれて、支柱が必要になる。
• 伸びるにつれて支柱が必要になる。

Both are fine.

The overall pattern is:

• Verb dictionary form + に つれて、B
• As A happens, B changes along with it

In this sentence:

• A = 伸びる = it grows
• B = 支柱が必要になる = a support becomes necessary

So the structure expresses a linked change over time.

A good way to remember it is:

• one thing changes
• another thing changes along with it

That is exactly what this sentence is doing.