NEET Biology question
Not in NEET syllabus
Consider the following statements and choose the correct option from the codes given below. I. Loading of phloem is related to an increase of sugar in phloem II. Active loading of sugar in sieve tube of phloem is driven by a proton pump III. Pressure may be positive or negative in sieve tube cells IV. Water and solutes move through the sieve tube against the pressure gradient V. Cytoplasmic strands pass through the holes in sieve plates and form continuous filaments
Solution
Statements I, II and V are correct: phloem loading does increase sugar concentration in the sieve tube; active loading at the source is driven by a proton (H⁺) gradient established by a proton pump (and coupled sucrose-H⁺ symport); and sieve tube cytoplasmic strands pass through sieve-plate pores
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