johtokudoksiin

Johtokudoksiin, or vascular tissues, are the tissues in plants responsible for the transport of water and nutrients. These tissues are crucial for the survival and growth of all vascular plants. The two main types of vascular tissue are xylem and phloem.

Xylem is primarily responsible for transporting water and dissolved minerals from the roots to the rest of the plant. It also provides structural support. Xylem is composed of several cell types, including tracheary elements (tracheids and vessel elements), xylem parenchyma, and xylem fibers. Tracheary elements are the main water-conducting cells, and they are dead at maturity, forming hollow tubes.

Phloem, on the other hand, transports sugars produced during photosynthesis, primarily from the leaves to other parts of the plant where they are needed for growth or storage. Phloem is composed of sieve elements (sieve cells and sieve-tube elements), companion cells, phloem parenchyma, and phloem fibers. Sieve-tube elements are the primary conducting cells in phloem and are living at maturity, though they lack a nucleus. Companion cells are closely associated with sieve-tube elements and play a vital role in their function.

Together, xylem and phloem form the vascular system, which is a continuous network throughout the plant, from the tips of the roots to the highest leaves. This intricate system ensures that all plant cells receive the necessary resources for their metabolic activities, enabling plants to thrive in diverse environments. The arrangement and development of these tissues can vary between different plant groups, reflecting their evolutionary adaptations.