Water is very important for plant growth so its deficiency weakens the plant.
When plants do not get sufficient water, they do not grow to their expected height, have reduced photosynthetic activity, and produce much less harvest than expected.
Without enough water, plants will also be susceptible to diseases, which can eventually lead to the death of the plant.
This may result in no food, no oxygen, and no rains and eventually end of all forms of life on the Earth.