Let's check and improve the grammar of your sentences step by step.
Original sentences:
1. Long roots help plants find water
2. pointy needles are better at saving water than leaves.
Corrections:
1. The first sentence is correct as it is. "Long roots help plants find water." The sentence starts with a capital letter and ends with a period.
2. The second sentence needs a capital letter at the start and punctuation at the end. It should be: "Pointy needles are better at saving water than leaves."
So, the corrected sentences are:
"Long roots help plants find water. Pointy needles are better at saving water than leaves."