Biology 2601A/B Lecture Notes - Lecture 15: Sieve Tube Element, Phloem, Water Potential
Document Summary
Lecture 15: water and fluid transport moving fluids in plants ii. Living cells (sieve elements) connected by sieve plates. Transport the products of photosynthesis: also hormonal and rna signals. Number of sieve elements make a sieve tube pores on sieve plate and pores on the sides of the cell wall that connects the cells. Usually connected to companion cell some of the needs of the cell are supplied by this companion cell. No nucleus, vacuole, filaments, microtubules, or ribosomes. Under high turgor pressure (lots of solute) large drive for water to enter cells due to high sugar content. Sieve plates: holes in cell wall between sieve elements, covered by smooth er. Phloem loaded with sucrose by companion cells at source tissues: may be symplastic (via plasmodesmata) or apopplastic (active transport) Osmotic gradient in phloem creates pressure differential and moves both water and solutes.