Vascular plants obtain water through their roots and non-vascular plants absorb moisture through all their parts. Non-vascular plants must live in moist environments, and lack the ability to move water through their system. In vascular plants, the root hairs, part of the epidermis, act as a wick to absorb water from the ground.
The water travels into and through the plant by osmosis. The water absorbs due to the surrounding area having a higher water potential, or wetness. The plants transpire, or release water, through their leaves. This happens when the stomates (microscopic pores) open.
Carbon dioxide enters when the stomates open and the moisture escapes. This creates lower water potential and moves the water up the stem and into the cells of the plant.
Plants manufacture their own food from raw materials using photosynthesis. They require light, air and water to perform photosynthesis. The light provides energy and the air give the plant carbon dioxide. Water has several roles. Plant cells, primarily made of water, need adequate water to grow.
The water provides turgor pressure that keeps the cell's shape. The plant breaks the water into hydrogen and oxygen and releases the oxygen. The plant uses the hydrogen to make food, in the form of carbohydrates.
When the water absorbs into the plant roots, it contains minerals from the soil. These minerals promote growth of plant tissue. Without water, plants cannot survive.
Growing and maintaining a garden requires knowledge of how much water plants need and when to provide it for them. Many places experience dry spells that damage or kill plants.
You can use two ways to check if plants have adequate water. First, a rain gauge measures how much rain you receive. Most plants need 1-2 inches of rain per week for optimal health. When less rain falls, you should provide supplemental water.
The other method uses the soil moisture as the measurement. Stick your finger into the soil the soil at least 3 inches. Water if the soil is dry in the top 3 inches.
If you must water your plants, do so in the early morning. This prevents evaporation during heat and the development of mold or diseases. Supply the water directly to the soil, if possible. Evaporation causes a portion of the water to be lost if you use a hose or sprinkler. Drip irrigation, watering cans, spray wands and watering reservoirs work well.