Question

Vein loading is the active transport of sugars from-
a. Mesophyll cells to vessels
b. Vessels to mesophyll cells
c. Mesophyll cells to sieve tubes
d. Sieve tubes to mesophyll cells

Answer 1

Hint: The process of loading the veins involved in the transport of food through the plants. It requires the movement of sugar or carbohydrates. The sugar then reaches the phloem from which other parts of the plant can be transported.

Complete answer:
> Option A is incorrect. The food is formed by a leaf's mesophyll cells and it enters the phloem's sieve tubes from there. These phloem tubes are interconnected and then transferred to all other parts of a plant until the food enters the phloem tube of a leaf.

> Option B is incorrect. The xylem vessels transfer water molecules up to the leaves where they exit and transfer from cell to cell. Water passes into the mesophyll cells from the xylem vessels, where it can be used for photosynthesis.

> Option C is correct. The mechanism involved in the transport of food in plants is the loading of veins. The vein loading process requires the movement of carbohydrates or sugar. The sugar moves through the symplast pathway from the mesophyll cells. The sugar then travels forward and reaches the phloem via the apoplast pathway. This procedure is referred to as vein loading. The sugar then reaches the phloem sieve pipes from which it is possible to move them to other parts of the factory.

> Option D is incorrect. Photoassimilates could move intracellularly, moving part of the route via the membrane of the cell wall (apoplasmic phloem loading) by linking plasmodesmata from chloroplasts in mesophyll cells to the lumina of sieve elements (symplasmic phloem loading) or through plasma membranes.

Hence, the correct answer is option (C).

Note: In 1989, Yuri Gamalei first described the various types of phloem-loading mechanisms, correlating the loading strategy with the anatomy of the leaf. He observed that plasmodesmatal abundance was associated with a plant's loading strategy in the minor veins of leaves. Plasmodesmata allow the diffusion of solutes through the symplast.