Water Balance
Water is essential to the survival of all plant species so the supply of water needs to be managed by plants. Water balance is when water moves in and out of a system, such as plants. Plants need to balance water to ensure that there is enough water to sustain a healthy life but that there is also enough gas exchange occurring, and that there isn’t a large amount of excess water. In plants, water is used for multiple purposes. The main use of water in plants is for photosynthesis. Water is also used to keep cells turgid by ensuring the vacuole is full, for efficient gas exchange, nutrients (hydrophytes), and temperature regulation by reducing the rate at which transpiration in occurring and ensuring that enzymes will not denature and stop the plant from carrying out life processes (L2 Biology Class Notes - Ms. Jones).
Plants get water through their roots [17]. This results in the root systems of many plants being extensively developed, and complex. Water in the surrounding soil enters the roots hair through osmosis, a passive process involving the transportation of water across a semi-permeable membrane, travelling from a region of high water potential – the surrounding soil - to a region of low water potential – the plant roots.
After entering the plant through the roots, the water is then able to more through the plants, so travels up the stem of the plant through the xylem tube. The water molecules then reach the leaves of the plant, where it is required as the leaves contain chloroplasts, in which photosynthesis takes place, and the water can also be used to ensure the turgidity of the cells. The passive process of transpiration is what cause this water movement, and allows for the water molecules to travel upward against the pull of gravity.
Banner photo source: Tiang, M 2015 Biology Field Trip