Q. Consider the following statements and choose the correct option from codes given below I. Loading of phloem is related to increase of sugar in phloem II. Active loading of sugar in sieve tube of phloem is driven by proton pump III. Pressure may be positive or negative in sieve tube cells IV. Water and solutes move through the sieve tube against pressure gradient V. Cytoplasmic strand passes through the holes in sieve plates and form continuous filaments
A) I, II, V are incorrect, while III and IV are correct
B) III and IV are incorrect while I, II and V are correct
C) I, II and III are incorrect while IV and V are correct
D) IV and V are incorrect while, I, II and III are correct
Explanation
Transport of organic nutrients from source to sink can be summarised as the osmotic movement of water into sugar loaded sieve tube from adjacent xylem. This creates a higher hydrostatic pressure or turgor pressure in the sieve tube (source) than the sink. Organic nutrients are transported from the region of higher turgor pressure to the region of lower turgor pressure. Organic nutrient are transported along the concentration gradient and pressure gradient. Sieve tubes and sieve cells of phloem are the channels of transport in flowering plant and non-flowering plant, respectively
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.