Water Movement Up a Plant
When water moves from the root towards the upward direction of the plant is called the ascent of sap. The upward transport of water in plants which are in some cases as tall as 400ft. Posses a serious problem.
Root pressure
When a plant that is well watered is cut near the base, through the cut end xylem sap flows out with pressure. This process is mostly seen in herbaceous plants. The water flows slowly out through a small opening due to bleeding or exudation. This exudation of water is due to hydrostatic pressure inside the root hence, known as root pressure. If roots are provided with hypertonic or isotonic solution root pressure disappears. Stephen Hales (1727) coined the term root pressure.
Transpiration Pull
The theory was originally proposed by Dixon and Joly (1894) and supported by Renner (1911,1915), Curtis and Clark (1951 ), Bonner and Golston (1952), and Kramer and Kozlowski (1960).
A transpiration pull is a process in which, inside the xylem tissue the force of pulling is produced. This force helps water to move in an upward direction into the xylem vessels. In this process, the loss of water in the form of vapors takes place.
Transport System in Plants Class 11 Biology
Plants obtain a variety of inorganic elements (ions) and salts from their surroundings, especially from water and soil. The movement of these nutrients from the environment into the plant as well as from one plant cell to another plant cell essentially involves movement across a cell membrane. Transport across cell membranes can be through diffusion, facilitated transport, or active transport. Xylem and phloem are the two components by which transportation takes place in a plant. Xylem transports water and minerals in plants. It is a vascular tissue. Whereas, phloem transports food prepared by the leaves to the other parts of the plant.
Plants lack both interstitial fluid as well as a regular circulation system. Even then they have to move various types of substances not only to short distances but also to very long distances.