HORTICULTURE

Detailed explanation-1: -A high concentration of organic substances, particularly sugar, inside cells of the phloem at a source, such as a leaf, creates a diffusion gradient (osmotic gradient) that draws water into the cells from the adjacent xylem. This creates turgor pressure, also known as hydrostatic pressure, in the phloem.

Detailed explanation-2: -Water from surrounding tissues, enters the sieve tube members by osmosis following a concentration gradient.. The water absorbed into the sieve tube creates hydrostatic pressure that forces the phloem sap to flow (bulk flow) towards the sink.

Detailed explanation-3: -Water moves into the phloem by osmosis, which increases the hydrostatic pressure. There is a pressure gradient with high hydrostatic pressure near the source cell and lower hydrostatic pressure near the sink cells. Solutes move down the pressure gradient towards the sink end of the phloem.

Detailed explanation-4: -The Pressure-Flow Hypothesis The pressure is created by the difference in water concentration of the solution in the phloem and the relatively pure water in the nearby xylem ducts. At their “source”-the leaves-sugars are pumped by active transport into the companion cells and sieve elements of the phloem.

Detailed explanation-5: -Figure 25.12: The Transpiration–Cohesion–Tension Mechanism Transpiration causes evaporation from mesophyll cell walls, generating tension on the water in the xylem.