Topic: Factors affecting photosynthesis· Plant Physiology

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?

1. Alkaline

2. Low refractive index

3. Absence of sugar

4. Acidic

Doubtly Asked 30 Oct 2026 NEET UG 2016 Phase 2 neet Save WhatsApp Report

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Answer: 1. Alkaline

Phloem sap is rich in sugar (mainly sucrose), has a high refractive index because of dissolved solutes, and is alkaline (pH about 8 to 8.5).

Xylem sap, in contrast, is slightly acidic with very little sugar. Hence "alkaline" is the test result for phloem sap; "absence of sugar" and "low refractive index" do not fit phloem.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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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?

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