The translocation of organic solutes in sieve tube members is supported by:

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, 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. Protcins has a role as defence against phloem feeding insects and sealing of damaged sieve tubes. Protein is absent in monocots and gymnosperms.