what is xylem ?? define briefly .
how is my account pic ?? 10/_
Answers
Explanation:
Xylem, plant vascular tissue that conveys water and dissolved minerals from the roots to the rest of the plant and also provides physical support. Xylem tissue consists of a variety of specialized, water-conducting cells known as tracheary elements.
Definition
Xylem is a type of tissue in vascular plants that transports water and some nutrients from the roots to the leaves
___________________________________________
Function
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.
___________________________________________
Structure
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.
___________________________________________
Types
Primary Xylem
Primary xylem forms with primary growth of a plant. This is the growth that occurs at the tips of stems, roots, and flower buds. It allows the plant to grow taller and the roots to grow longer. This growth is called primary because it occurs first in the growing season, before secondary growth. Both primary and secondary xylem transport water and nutrients.
Secondary Xylem
Secondary xylem is formed with a plant’s secondary growth; this is the type of growth that allows the plant to get wider over time. Wide tree trunks, for example, show a lot of secondary growth. It occurs each year after primary growth. Secondary xylem is what gives the inside of tree trunks dark rings that are used to determine the age of the tree.
___________________________________________