shokubutsu ni mizu o yaruno o wasurenaide kudasai.

Please don't forget to water the plants.

Breakdown of shokubutsu ni mizu o yaruno o wasurenaide kudasai.

• を: direct object particle
• 水みず: water
• に: indirect object particle
• 〜の: verb nominalizer

Questions & Answers about shokubutsu ni mizu o yaruno o wasurenaide kudasai.

Why are there two を particles in 水をやるのを忘れないでください?

In Japanese, each を marks the object of a different verb.

• The first を marks 水 as the object of やる (to give).
• Then you nominalize 水をやる with の, making 水をやるの (“the act of watering”).
• The second を marks that whole noun phrase as the object of 忘れる (to forget).
  So the structure is literally “Don’t forget (忘れないでください) the act of giving water (水をやるのを).”

What is the function of の after 水をやる? Could we use こと instead?

の here is a nominalizer—it turns 水をやる into a noun-like phrase meaning “the act of watering.”
You can often swap の for こと to sound more formal or written:
植物に水をやることを忘れないでください。
Generally, の feels more conversational, while こと is a bit more formal or stiff.

Why is 植物 marked with に rather than を? Isn’t the plant what you’re watering?

You’re actually giving 水 to the plant, so 水 is the direct object (with を). 植物 is the recipient or target of that giving action, so it takes the indirect-object particle に. In English it’s like “give water to the plant.”

What’s the difference between やる and あげる when talking about giving water to plants?