Test: Transportation In Plants - 1

The xylem tracheary elements consist of cells known as tracheids and vessel members, both of which are typically narrow, hollow, and elongated. Tracheids are less specialized than the vessel members.

Xylem cells form long tubes that transport materials, and the mixture of water and nutrients that flows through the xylem cells is called xylem sap. These substances are transported through passive transport, so the process doesn’t require energy. The phenomenon that allows xylem sap to flow upwards against gravity is called capillary action. This occurs when surface tension makes liquid move upward. Water is also aided in moving up through the xylem by adhering to the xylem cells. However, it gets harder to work against gravity to transport materials as a plant grows taller, so xylem sets an upper limit on the growth of tall trees.

Osmosis is the concept that involves in the moment of solutions inside and outside of the cell. If the cell is placed in isotonic solution, the net change will be zero.

Substance transported through phloem tissue​ are sucrose and amino acid.

Water is passively transported into the roots and then into the xylem.The forces of cohesion and adhesion cause the water molecules to form a column in the xylem.

Steroid hormones are made up of fats and they are not soluble in water. They are hydro phobic in nature. Hence they can easily pass through the plasma membrane by simple diffusion.

Raisins when soaked in water swell up due to imbibition. As a result of absorption or imbibition of water, the size of the raisins increases. The difference in mass between the swollen and dry raisins gives the amount of water imbibed by the raisins.

In spring, new buds are formed. These buds need more energy to grow than other parts of the plant. This energy comes from the sugar stored in the root or stem tissue to the buds by phloem. Thus. buds need the sugars in springs. 

Tracheids and vessels are vessels have perforations at the end plates which make them a tube-like, long structure while tracheids do not have end plates.

Higher temperatures cause the plant cells which control the openings (stoma) where water is released to the atmosphere to open, whereas colder temperatures cause the openings to close.

Root pressure, in plants, force that helps to drive fluids upward into the water-conducting vessels (xylem). It is primarily generated by osmotic pressure in the cells of the roots and can be demonstrated by exudation of fluid when the stem is cut off just above ground. It is partially responsible for the rise of water in plants.
The root-pressure hypothesis of sap rise holds that pressures in trees are several times atmospheric pressure, not nearly enough to transport water to the top of the tallest trees. Furthermore, root pressures tend to be lowest when water loss from leaves (transpiration) is highest, exactly when trees most need water.
The lifting force generated by evaporation and transpiration of water from the leaves and the cohesive and adhesive forces of molecules in the vessels, and possibly other factors, all contribute to the rise of sap in plants

The opening and closing of the stomata is controlled by the guard cells. In light, guard cells take up water by osmosis and become turgid. Because their inner walls are rigid they are pulled apart, opening the pore. In darkness water is lost and the inner walls move together closing the pore.

The loss of water in the form of vapour from living plants, particularly from the aerial parts, is known as transpiration. The process is in principle one of evaporation and diffusion. Loss of water vapour may occur from any part of the plant which is exposed to the air.

Plants: Plants do not move. They have a large proportion of dead tissues. Some plants are very tall. So, plants generally have relative slow transport system.

The phloem is arranged in long, continuous strands called vascular bundles that extend through the roots and stem and reach into the leaves as veins. vascular bundles also contain the xylem, the tissue that carries water and dissolved minerals from the roots to the shoots.