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Physiology - Translocation

	How does water move through tissues on its way from the soil to the atmosphere - when must it pass through cells?
	Between root hairs and endodermis, water can go between cells, through cell walls or through cells. At the endodermis, it must pass through the cytoplasm; then into lumen of xylem cells and need never enter another living cell.

	How does root pressure occur and how important is it in water movement?
	Endodermis can actively (ATP energy) accumulate ions leading to osmotic uptake of water which can be pushed up the plant. This is important in spring and recovery (often at night) from blockage of xylem by gas bubbles.

	Do mineral elements just move passively with the water - what problems could this cause for the plant?
	In the xylem, yes, and then tend to build up in the leaves, possibly causing toxicity. Endodermis can be a filter for unwanted ions.

	How could mycorrhizae help in nutrient uptake?
	help get P and micronutrients into solution for movement into plant roots

	Which ions can move from the xylem to the phloem and which cannot?
	K+ and phosphate can Ca2+ cannot

	What decides the direction of movement in the phloem - how is this different from the situation in the xylem?
	supply and demand or source and sink, so it can be up or down the stem since leaves or roots can be sources stem apex, flowers, fruits and roots can be sinks xylem is a one way street from root to leaf

	What plant structures constitute sources and sinks - how does this change through the year?
	•In the spring roots may be the only source. •When leaves develop, they become a source and roots may be a sink.

	What is a possible driving force for the phloem movement, and what should move in the phloem?
	Energy (ATP) driven (active) loading of ions and organic molecules into sieve elements leads to osmotic uptake of water (from xylem) and pressure flow of water with solutes through phloem to sink where active unloading occurs.

	How does movement in the xylem differ from the phloem in terms of the possibility of: simultaneous movement up and down the same stem?
	It's possible in phloem, but not in xylem.

	How does movement in the xylem differ from the phloem in terms of the possibility of: movement through a section of stem killed by localized heating?
	possible in xylem but not in phloem

	How does movement in the xylem differ from the phloem in terms of the possibility of: movement past a partial cut in the stem?
	by-pass of cut area in both xylem and phloem.

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