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Phloem loading: Sink/ source vs. Productivity

Phloem loading: Sink/ source vs. Productivity. Symplast vs. apoplast pathways: distinguish at near the sieve element-companion cell complex.  s -1.3 MPa.  s -3.0 MPa. or transfer cells. apoplast: suc major selective transporter energy required: respiratory inhibitors,

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Phloem loading: Sink/ source vs. Productivity

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  1. Phloem loading: Sink/source vs. Productivity Symplast vs. apoplast pathways: distinguish at near the sieve element-companion cell complex s -1.3 MPa s -3.0 MPa or transfer cells apoplast: suc major selective transporter energy required: respiratory inhibitors, active loading Organic acids, hormones  passive symplast: suc and others, such as raffinose and stachyose

  2. Sucrose-H+ symporter  in the apoplast of phloem loading  in the membrane of company cells or sieve elements  dissipate proton energy to couple the uptake of sucrose CC SE

  3. Regulating sucrose loading by the sucrose-H+ symporter — are not completely clear  The turgor pressure of the sieve elements below a threshold level, a compensatory increase loading?  Sucrose concentration in the apoplast [Suc]apoplast?  The available No. of symporter molecules feed Suc  SUT1 transcription, SUT1 and itsmRNA rapidly degrade, protein phosphorylation involved a diurnal regulation  Nutrient supply— potassium availability enhance sucrose efflux into apoplast  sink growth

  4. Intermediary cellsin thesymplastof phloem loading ¤ diffusion ¤ raffinose, stachyose, in addition to sucrose ¤ apolymer-trapping model

  5. The type of phloem loading is corrected withplant familyand withclimate herbaceous trees, shrubs, vines temperate and arid tropic and subtropic exceptions Coexist New loading ? Symplastic loading advantages?

  6. Phloem unloading and short-distance transport — via symplast or apoplast PCMB: inhibit sucrose across membrane

  7. The transition of a leaf from sink to source Squash Feed 14C on source leaf for 2 h source leaf sink leaf The base still a sink sink  source depend on species, 25% → 40-50% The cessation of import and the initiation of export are independent events. The extent of maturation and sampling position

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