Don't kill anything!

Once I asked a Zen Master Seung Sahn question: "Seung Sahn Sunim, we vow not to take someone else's life, but the plants are sentient beings. They react to light, sound, touch, but we kill them for food. How it is connected with the vow?" Zen master replied: "One day an old Zen Master who lived in the mountains washed in the morning, and his disciple was pouring water into his arms from the jar. When the master washed, the jar still had some water, and the student emptied it. Master cried: 'Do not kill water, do not kill water!Do not kill water!'" Then DM Seung Sahn, pointed his finger at me and said: "Do not kill anything! If there is no need for that".