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- Companion cells form a functional unit with the sieve elements for long-distance translocation of assimilates, nutrients and signalling molecules and play indispensable roles throughout the life cycle of plants.
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Aug 4, 2015 · Companion cells are parenchymal cells found within the phloem of flowering plants that manage the flow of nutrients through sieve tubes. Companion cells deliver ATP, proteins and other nutrients to sieve elements.
Nov 3, 2016 · Introduction. Phloem tissue connects the aerial photosynthetic organs to heterotrophic structures such as roots and fruits, distributing nutrients for adequate plant growth and fitness. In addition to transporting photoassimilates, it also influences plant development, since it distributes plant hormones, mRNA, small RNAs, and proteins.
- Sofia Otero, Ykä Helariutta, Ykä Helariutta
- 2017
Jul 11, 2023 · Phloem transports organic nutrients, particularly sugars synthesized during photosynthesis, from the leaves to all other cells of the plant, including the roots. Phloem tissue is composed of sieve-tube elements, companion cells, phloem fibers, and phloem parenchyma.
- Phloem
- Xylem
- Xylem and Phloem in Leaves
- Xylem and Phloem in Stems
- Xylem and Phloem in Roots
The phloem carries important sugars, organic compounds, and minerals around a plant. Sap within the phloem simply travels by diffusion between cellsand works its way from leaves down to the roots with help from gravity. The phloem is made from cells called ‘sieve-tube members’ and ‘companion cells’.
The xylem is responsible for keeping a plant hydrated. Xylem sap travels upwards and has to overcome serious gravitational forces to deliver water to a plant’s upper extremities, especially in tall trees. Two different types of cells are known to form the xylem in different plant groups: tracheids and vessel elements. Tracheids are found in most gy...
Photosynthesis in leaves requires a lot of water from the xylem and produces a lot of sugar for the phloem. The xylem and phloem enter a plant’s leaves via their petiole – a short stalk that connects a leaf to a branch. With the exception of lycophytes, veins divide multiple times in a leaf which creates a good spread of veins and makes it easier t...
Xylem and phloem travel entire length of stems in discrete threads called ‘vascular bundles’. In eudicots, vascular bundles are arranged in a ring within the stem. Each vascular bundle is orientated with the xylem on the interior and the phloem on the outside of the xylem. In monocots, the vascular bundles are scattered throughout the stem rather t...
The xylem and phloem are grown within the central section of a root called a ‘stele’. In eudicots, the xylem usually forms a cross of cells within the stele which runs the length of the root. Four independent phloem strands grow between each bar of the xylem cross. In monocots, the center of the stele is composed of pith. The phloem and xylem form ...
The assimilate, which is rich in sucrose, is actively transported from source cells into companion cells and then into the sieve-tube elements. This reduces the water potential, which causes water to enter the phloem from the xylem.
Nov 22, 2022 · Companion cells support sieve-tube elements in angiosperms, and albuminous cells support sieve cells in gymnosperms. Additionally parenchyma cells and sclerenchyma cells (phloem fibers) are also found in the phloem.
Mar 11, 2023 · Companion cells and sieve elements play an essential role in vascular plants, and yet the details of the metabolism that underpins their function remain largely unknown. Here, we construct a tissue-scale flux balance analysis (FBA) model to describe the metabolism of phloem loading in a mature Arabidopsis (Arabidopsis thaliana) leaf. We explore ...
