Question

Loading of phloem is related
A. Increase of sugar of phloem
B. Elongation of phloem cell
C. Separation of phloem parenchyma
D. Strengthening of phloem fibre

Answer 1

Organic solutes such as sucrose are transported from the supply end to the consumption end via sieve tube elements of the phloem. However, soluble sugars must first be transferred from mesophyll cells to leaf sieve tube elements before this sugar translocation can occur.
Phloem loading is the transfer of sugars (photosynthesis) from mesophyll cells to sieve tube elements in the leaf. Phloem unloading, on the other hand, is the transport of sugars (photosynthetic) from sieve tube elements to the receiver cells of the consumption end (i.e., sink organs). Both procedures necessitate the use of energy.

Complete answer:
Option A: The process of phloem loading occurs when phloem cells near the source, such as green leaves, achieve a higher sugar concentration. Sucrose is produced in the chloroplasts of leaves' mesophyll cells. Mesophyll cells communicate with one another via plasmodesmata. Plasmodesmata can be seen between mesophyll cells and companion cells, as well as between mesophyll cells and sieve tubes. There are plasmodesmata, which are sucrose-passing 'channels'.
So option A is correct.
Option B: Phloem movement is bidirectional, but xylem cell movement is unidirectional. Because sap cannot easily travel between adjacent sieve tubes, it is not uncommon for sap in sieve tubes to flow in the other direction as a result of the multidirectional flow.
So option B is not correct.
Option C: Phloem loading occurs when the sugar concentration in phloem cells near the source, such as green leaves, rises. Plasmodesmata allow mesophyll cells to communicate with one another. Between mesophyll cells and companion cells, as well as between mesophyll cells and sieve tubes, plasmodesmata can be recognised.
So option C is not correct.
Option D: Sugars are transported into the phloem sieve components at the source end of the phloem. This increase in solute lowers the cell's water potential, allowing water to flow in from the surrounding environment via osmosis. As a result, phloem loading is linked to an increase in sugar in the phloem rather than elongation of the phloem cell, separation of the phloem parenchyma, or phloem fibre strength.
So option D is not correct.

So option A is the correct answer.

Note:
Plants' xylem and phloem are conducting tissues that, when combined, create a vascular bundle and are thus referred to as vascular tissues. Tracheophytes are plants that have vascular tissues. Xylem and phloem are the two primary types of vascular tissues.
Phloem is the vascular tissue that transports sugars from source tissues to sink tissues (such as non-photosynthetic root cells or growing flowers) (e.g. photosynthetic leaf cells). Other compounds, such as proteins and mRNAs, are also transported by phloem throughout the plant.