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    • #1118
      Navin
      Participant

      Hi

      I want to know is there is Starch present in the phloem.

      From what I know, the phloem transports sucrose.

      So, would the phloem turn blue-black when flooded with iodine solution?

      Also, would the pith of a stem turn blue-black when added with iodine solution?

    • #24115
      James
      Participant

      Sucrose is transported in the phloem, and converted to starch at sink cells. The phloem doesn’t contain starch, but the pith does.

    • #24124
      ERS
      Participant

      they should stain blue-black or thereabouts.
      ERS

    • #24138
      MrMistery
      Participant

      Actually it is a bit more complicated than that… Starch can not disolve into water, so it is moved around under the form of sucrose(or zaharose). Now the floem contains 25% organic substances and 75% water. From the total of organic substances, 90% is sucrose, the other 10% is made up of other sugars, aminoacids and lipids. So it is false to say that the role of the phloem is to transport sucrose, as some textbooks say.
      Now, the phloem does not contain starch, if you put Lugol on it it will not turn blue.
      I tried to do the experiment to test this last year, but no book tells us how to isolate the phloem from the plant. The pith will no doubt turn blue as there is starch present there

    • #24162
      lohita
      Participant

      and also phloem doesn’t carry only starch. it carries all the products of photosynthesis, this process is called translocation.

    • #24165
      Navin
      Participant

      Hey thanks a bunch!

    • #24227
      MrMistery
      Participant
      quote lohita:

      and also phloem doesn’t carry only starch. it carries all the products of photosynthesis, this process is called translocation.

      Actually the phloem doesn’t carry starch at all because starch is not water-soluble. The stuff stranslocated through the phloem is called sucrose or sacharose

    • #24279
      b_d_41501
      Participant

      It carries disaccharides, correct? It doesn’t carry polysaccharides (starches) due to this insolubility, right?

    • #24340
      MrMistery
      Participant

      Yes that is true… It also carries fructose(something like 0.000001% but it is there) and other molecules such as aminoacids

    • #24370
      b_d_41501
      Participant

      I thought so

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