How do sieve tubes adapt to their functions?
The cells that make up the phloem are adapted to their function: Sieve tubes – specialised for transport and have no nuclei . Each sieve tube has a perforated end so its cytoplasm connects one cell to the next. Sucrose and amino acids are translocated within the living cytoplasm of the sieve tubes.
What is the function of the phloem sieve tube?
sieve element, in vascular plants, elongated living cells of the phloem, the nuclei of which have fragmented and disappeared and the transverse end walls of which are pierced by sievelike groups of pores (sieve plates). They are the conduits of food (mostly sugar) transport from the leaves to the rest of the plant.
How are sieve tubes supported and kept alive?
Companion cells provide sieve tube members with proteins necessary for signaling and ATP in order to help them transfer molecules between different parts of the plant. It is the companion cells that helps transport carbohydrates from outside the cells into the sieve tube elements.
How are companion cells adapted for their function?
Among other adaptations, companion cells therefore contain many mitochondria. This allows them to carry out cellular respiration at a high rate and, hence, release lots of energy.
How are sieve plates adapted for mass transport?
Sieve cells have few organelles, very little cytoplasm, large vacuole, and thick walls. This leads to more flow because strong walls resist pressure so flow is unrestricted. They contain mitochondria which releases energy for active transport.
How are the xylem and phloem adapted for their function?
Adaptations: Made of living cells (as opposed to xylem vessels, which are made of dead cells) that are supported by companion cells. Cells are joined end-to-end and contain holes in the end cell walls (sieve plates) forming tubes which allow sugars and amino acids to flow easily through (by translocation)
Which of the following statements best describes the special features of phloem sieve tubes?
Which of the following statements best describes the why phloem sieve tubes have special cell wall adaptations? Phloem have perforated cell walls to aid the flow of cytoplasm from cell to cell.
Are sieve tubes living or dead?
Sieve tube elements, also known as sieve tube members in plant anatomy, are highly specialised types of elongated cells found in flowering plants’ phloem tissue. Sieve elements are living cells, as opposed to water-conducting xylem vessel elements, which are dead when mature.
Why do phloem have sieve plates?
These thin plates, which separate neighboring phloem cells, are perforated by a large number of tiny sieve pores and are believed to play a crucial role in protecting the phloem sap from intruding animals by blocking flow when the phloem cell is damaged.
Why phloem sieve tubes have special cell wall adaptations?
What controls the flow of materials through phloem sieve tubes?
Within the lumen of sieve elements are cytoplasmic filaments/strands which are continuous rom cell to cell to enable continuous flow of materials. The companion cells have nuclei and other organelles. They control the flow of materials through the phloem sieve tubes.
What are the sieve elements of phloem?
Phloem cells. The sieve elements are elongated, narrow cells, which are connected together to form the sieve tube structure of the phloem. The sieve element cells are the most highly specialized cell type found in plants.
How are the sieve tube and companion cells connected?
The sieve tube and companion cells are connected via a plasmodesmata, a microscopic channel connecting the cytoplasm of the cells, which allows the transfer of the sucrose, proteins and other molecules to the sieve elements.
How does the phloem move photoassimilates?
Through the system of translocation, the phloem moves photoassimilates, mainly in the form of sucrose sugars and proteins, from the leaves where they are produced by photosynthesis to the rest of the plant. The sugars are moved from the source, usually the leaves, to the phloem through active transport.