Question

types of xylem and their function

Answer 1

Xylem is one of the two types of transport tissue in vascular plants, phloem being the other. The basicfunction of xylem is to transport water from roots to shoots and leaves, but it also transports nutrients.
The most distinctive xylem cells are the longtracheary elements that transport water. Tracheids and vessel elements are distinguished by their shape; vessel elements are shorter, and are connected together into long tubes that are called vessels. Xylem also contains two other cell types: parenchyma and fibers.The most distinctive xylem cells are the long tracheary elements that transport water. Tracheids and vesselelements are distinguished by their shape; vessel elements are shorter, and are connected together into long tubes that are called vessels

Answer 2

Here is your answer..

Xylem is a type of tissue in vascular plants that transports water and some nutrients from the roots to the leaves. Phloem is the other type of transport tissue; it transports sucrose and other nutrients throughout the plant. Xylem and phloem give vascular plants their classification; they are the vascular tissues that transport substances throughout the plant.

Function of Xylem

The main function of xylem is to transport water, and some soluble nutrients including minerals and inorganic ions, upwards from the roots to the rest of the plant. 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.

Xylem evolved in plants over 400 million years ago. In order to make food through photosynthesis, plants need to absorb carbon dioxide from the atmosphere and water from the soil. However, when the stomata—small holes in a plant’s leaves—are open to allow CO2 in, a lot of water evaporates, much more than the amount of CO2 taken in. Plants that developed systems to transport water to the sites of photosynthesis on leaves had a better chance of survival.

Structure of Xylem

Xylem is made up of several types of cells. Tracheids are long cells that help transport xylem sap and also provide structural support. Vessel elements are shorter than tracheids, but also help conduct water. They are found in flowering plants, but not in gymnosperms like pine trees. Vessel elements have perforation plates that connect each vessel element to form one continuous vessel. Xylem also contains parenchyma, a tissue that makes up most of the soft parts of plants, and long fibers that help support the plant. In a cross section of a plant, under a microscope, xylem appears star-shaped.

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