Head of Plant, Ear Of Plant
The part of the grain people favor the most is the head of the plant. You don't eat the stems and leaves of rice or wheat plants, right? You eat the head where the grains are.
Imagine yourself walking through a field of rice plants. Now look very closely at the head of the plant in front of you. See the rice bunched up there? That's the good stuff.
すい
ほ
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When you want to harvest the head of the plant you'd like to eat, you need to use a hoe (ほ). Using a hoe, you can dig up the bottom of the plant without injuring the head.
Imagine working in a field of rice and using a hoe so you don't injure the head of the plant. You're sweating and it's hot, but you keep at it.