sieve-tube element

Examples of sieve-tube element in the following topics:

• Transportation of Photosynthates in the Phloem

  • Photosynthates move through plasmodesmata to reach phloem sieve-tube elements (STEs) in the vascular bundles.
  • Phloem is comprised of cells called sieve-tube elements.
  • Neighboring companion cells carry out metabolic functions for the sieve-tube elements and provide them with energy.
  • Lateral sieve areas connect the sieve-tube elements to the companion cells.
  • Sucrose is actively transported from source cells into companion cells and then into the sieve-tube elements.

• Stem Anatomy

  • Phloem tissue is composed of sieve-tube cells, companion cells, phloem parenchyma, and phloem fibers.
  • A series of sieve-tube cells (also called sieve-tube elements) are arranged end-to-end to create a long sieve tube, which transports organic substances such as sugars and amino acids.
  • The sugars flow from one sieve-tube cell to the next through perforated sieve plates, which are found at the end junctions between two cells.
  • Although still alive at maturity, the nucleus and other cell components of the sieve-tube cells have disintegrated.
  • Companion cells are found alongside the sieve-tube cells, providing them with metabolic support.

• Vascular Tissue: Xylem and Phloem

  • These cells are joined end-to-end to form long tubes.
  • The substances travel along sieve elements, but other types of cells are also present: the companion cells, parenchyma cells, and fibers.
  • These porous connections are called sieve plates.
  • Despite the fact that their cytoplasm is actively involved in the conduction of food materials, sieve-tube members do not have nuclei at maturity.
  • The activity of the sieve tubes is controlled by companion cells through plasmadesmata.

• Morphology of Sponges

  • In some sponges, ostia are formed by porocytes: single, tube-shaped cells that act as valves to regulate the flow of water into the spongocoel.
  • Meanwhile, food particles, including waterborne bacteria and algae, are trapped by the sieve-like collar of the choanocytes, slide down into the body of the cell, are ingested by phagocytosis, and become encased in a food vacuole.

• Primary and Secondary Growth in Stems

  • The cells of the vascular cambium divide and form secondary xylem (tracheids and vessel elements) to the inside and secondary phloem (sieve elements and companion cells) to the outside.
  • This alternation of early and late wood is due largely to a seasonal decrease in the number of vessel elements and a seasonal increase in the number of tracheids.

• Plant Tissues and Organ Systems

  • It includes three different cell types: vessel elements and tracheids (both of which conduct water) and xylem parenchyma.
  • Phloem tissue, which transports organic compounds from the site of photosynthesis to other parts of the plant, consists of four different cell types: sieve cells (which conduct photosynthates), companion cells, phloem parenchyma, and phloem fibers.

• Intermediate Filaments and Microtubules

  • As their name implies, microtubules are small hollow tubes.
  • Microtubules are the largest element of the cytoskeleton.
  • Microtubules are also the structural elements of flagella, cilia, and centrioles (the latter are the two perpendicular bodies of the centrosome).
  • Intermediate filaments contribute to cellular structural elements and are often crucial in holding together tissues like skin .
  • The left image shows the molecular structure of the tube.

• Characteristics of Chordata

  • It is located between the digestive tube and the nerve cord, providing skeletal support through the length of the body.
  • In vertebrates, the notochord is present during embryonic development, at which time it induces the development of the neural tube which serves as a support for the developing embryonic body.
  • The dorsal hollow nerve cord derives from ectoderm that rolls into a hollow tube during development.
  • The tail contains skeletal elements and muscles, which provide a source of locomotion in aquatic species.

• Phylum Chordata

  • A notochord, or a longitudinal, flexible rod between the digestive tube and the nerve cord .
  • A dorsal nerve cord which develops from a plate of ectoderm that rolls into a tube located dorsal to the notochord.
  • In chordates, the tail has skeletal elements and musculature, and can provide most of the propulsion in aquatic species.