The translocation of organic solutes in sieve tube members is supported by
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root pressure and transpiration pull
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P-proteins
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mass flow involving a carrier and ATP
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cytoplasmic streaming
C.
mass flow involving a carrier and ATP
According to mass flow hypothesis, the transport of organic solutes takes place from source to sink this transport also depends on metabolic energy.
According to cytoplasmic streaming hypothesis (put forward by de Vries 1885) the transport of organic solutes takes place by combination of diffusion and cytoplasmic streaming.
Cytoplasmic streaming carry organic solutes from one end the other end of sieve tube.
P proteins has a role as defence against phloem-feeding insects and sealing of damaged sieve tubes.
Protein is absent in monocots and gymnosperms.
