BIS 2C Lecture Notes - Lecture 17: Sieve Tube Element, Vascular Plant, Archegonium
23 Feb 2018
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Major cell types are sieve ubes & companion cells. Both are alive transports sugars, amino acids cells are alive thin-walled plasmodesmatal connection can ow up or down, depends on concentration of solute in the column source cell : produce sucrose and load it in - starts pump. Can also be root cells with large stores of carbs) sink cell: unload sucrose from phloem. Need carbs: water enters from any surrounding tissues, osmosis: water moves from low solute to high solute, pressure increases and forces solution to regions of lower pressure. 3. turgor pressure increases and forces sugar to regions with lower pressure: sugar goes into sink cells, as sugar is unloaded, water moves out which decreases pressure. Atp is used in movement of sugar into and out of the sieve tubes. Rhyniophytes had a simple vascular system and dichotomous (branches split up into two equal parts) branching but lacked leaves and roots. Sporophyte that was branched with terminal sporangia.
