In this IBDP Biology post, we will look into the structure of phloem, and the differences between phloem and xylem, let's get to it!
The Structures and their Functions of Phloem
Phloem is made of living cells
Sieve elements: Elongated living cells that form from the phloem tissue
1. Phloem sieve tube: Develop from sieve tube elements (coloumns of cells) that break down nuclei and organelles. It has lumen for easy flow of sap
Sieve tube: Several sieve elements that are connected end to end
Sieve plate: Cross walls within the sieve tubes that are perforated (pores)
2. Sieve plate: Cross wall that strengthens the sieve tube, the plate has pores which allows sap to flow through
3. Cell membrane: Inside of wall that holds sap inside the sieve tubes and has pumps to load and unload sucrose
4. Cell wall: Resists high pressure within the sieve tubes
Phloem and Transport
Translocation: The process of transporting organic compounds (sugars and amino acids) made during photosynthesis in the phloem sieve tubes
Plant cells need organic compounds to function
- Many organic compounds are made in the chloroplasts
- The phloem transports the organic compounds around the plant
Comparing Xylem and Phloem
Phloem
- Coloumns of living cells
- Transports sugars, amino acids and plant hormones
- Companion cells carry out cell functions with many mitochondria that provide ATP for Active Transport
- Sieve tubes have sieve plates that controls the flow of sap
Xylem
- Coloumns of dead cells
- Transports water and minerals
- Thickened cell wall consisting of lignin
- Continuous tube which allows for an unbreakable coloumn of water
That's all for this post!
References:
- https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.vedantu.com%2Fquestion-answer%2Fdraw-and-label-the-diagram-of-phloem-class-11-biology-cbse-5f59a9536e663a29cca585f3&psig=AOvVaw3Gix0MVnCoyz6loK_g7fEm&ust=1626977048896000&source=images&cd=vfe&ved=0CAsQjRxqFwoTCPiAzvrf9PECFQAAAAAdAAAAABAD
- https://www.google.com/url?sa=i&url=http%3A%2F%2Fib.bioninja.com.au%2Fhigher-level%2Ftopic-9-plant-biology%2Funtitled%2Fxylem-versus-phloem.html&psig=AOvVaw3N8Jqn8mlgmAcg4ViP9EEd&ust=1626976973547000&source=images&cd=vfe&ved=0CAsQjRxqFwoTCMCMpeXg9PECFQAAAAAdAAAAABAD
Drafted by Venetia (Biology)