Question

A few drops of sap were collected by cutting across a plant stem by a suitable method. The sap was tested chemically. Which one of the following test results indicates that it is phloem sap ?

• A. Acidic
• B. Alkaline
• C. Low refractive index
• D. Absence of sugar

Answer 1

Answer: (B)

Alkaline

Answer 2

The correct option is (B): Alkaline

Explanation:

Phloem sap is spread throughout the plant; it delivers nutrients (mainly sugars) produced during photosynthesis to various parts of the plant. When phloem sap is collected and tested, it will have an alkaline pH due to the presence of amino acids and organic acids, which can contribute to a slightly basic solution.

Here are the other options and why they are incorrect:

A) Low refractive index: Phloem sap may contain sugars as well as other substances. The presence of other solutes can affect the refractive index, making it difficult to identify.

C) Absence of sugar: Sugar is a key component of phloem sap as it transports the products of photosynthesis throughout the plant.

D) Acidic: Phloem sap typically has a slightly alkaline pH due to the presence of amino acids and organic acids.

Thus, the right answer to this question is alkaline.