What are the "properties" of Xylem and Phloem ?
Xylem are hollow/elongated dead cells with no end walls, so water can pass through it easily.
Phloem has sieve tube elements to transport solutes which have no nucleus and few organelles so more can be transported. Companion cell carry out living functions for sieve tube, providing them energy.
Xylem- dead organelles, no cells or living content, basically one hollow tube with pits for horizontal water movement,strong spiral thickenings of lignin give it a strong and stable structure- water moves through like a column according to cohesion tension theory
Phloem answer pretty much given above
Heyo! I see this question was already answered, however based on your syllabus you may need to know about Tracheids, Vessels, etc. I'll just add a tiny bit about that.
Tracheids are thinner, imperforate and as such have a lower capacity for water to pass through. They're an adaptation for gymnosperms (i.e. Conifers, good thing to know, some questions for WJEC are on that) in a xeric habitat. They're generally one unit. The walls of the tracheids consist of lignified cells, where lignification occurs in a spiral or circular pattern (annular) to allow continuous elongation of the cells.
Vessels are wider and perforated, and built up in segments known as vessel elements (sound similar?) and are a huge force for angiosperms, which is often quoted as being a reason to their dominance. The strong transpiratory stream that can form enclosed by the vessels is far stronger than the tracheid transpiratory stream, and hence allows taller plants to grow as higher levels wont be devoid of water.
I'd think you'd also want to know about how water moves up the column, at the least the factors pertaining to the tracheids/vessels themselves... so...
Adhesion occurs between the water moving up the column and the lignin in the cell walls, and this force helps to prevent the water falling down the column.
Root pressure over short distances, i.e. 1-2 metres, whereby water brought in to the root via osmosis 'pushes' for lack of a better word the water in the plant, forcing it up the transpiratory stream.
Another point to add would be cellular structure of the sieve tube element...
It almost exclusively consists of a large vacuole surrounded by some cytoplasm, with plasmodesmata that extend through the sieve tube plates, allowing continuous flow of its contents up the phloem tissue. The companion cell regulates onloading and unloading of sugars in to the sieve tube.
Is this OCR or aqa?Do we need to know it for aqa?