Lec8Translocationnotes

Honeydew httpwwwyoutubecomwatchvi6ovyj9ia2y it

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Unformatted text preview: – Phloem system under positive pressure aphid • Use of aphids Watch it! – "honeydew" http://www.youtube.com/watch?v=i6OVYj9Ia2Y it sticks and works to find the sieve element and sucks out Translocation Translocation Characteristics • Translocated substances – Xylem versus phloem Translocation Translocation Characteristics • Non-reducing sugars – Less reactive than reducing sugars • Have exposed aldehyde or ketone group – Specific and selective • Only certain non-reducing sugars are translocated Translocation Translocation Characteristics • Organic acids, proteins, mineral ions Translocation Translocation Characteristics • Rates of movement – 1 meter per hour • Gravity does not govern transport • Substances move from sources to sinks – Sources • Leaves, storage organs – Sinks • Meristems, rapidly growing organs – Leaves, roots, flowers, fruits, adventitious organs Translocation Diffusion vs Osmosis vs Mass flow • Diffusion is thermal motion of molecules equalizing differences in concentration of substance (i.e. a gradient in partial pressure) • Osmosis is thermal motion of solvent (water) equalizing effective differences in concentration of the solvent across a semipermeable membrane – The effective difference in concentration is formed by a solute (e.g. sucrose) diluting the solvent on one side of the semipermeable membrane • Mass flow is the movement of solute and solvent...
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