Write the merits and demerits of mass flow hypothesis.

Explanation

### Step-by-Step Solution

**Step 1: Define Mass Flow Hypothesis**
- The mass flow hypothesis, proposed by Ernst Munch in 1930, explains the movement of sap through the phloem in plants. It suggests that sap flows from areas of high sugar concentration (source) to areas of low sugar concentration (sink) due to pressure differences.

**Step 2: List the Merits of Mass Flow Hypothesis**
1. **High Sugar Exudates**: When a woody or herbaceous plant is griddled (cut through the bark), the sap collected from the cut end contains high concentrations of sugar. This observation supports the idea that sap movement is driven by sugar concentration.

...