What is the main idea of the passage?

Some mangroves grow upward roots that admit air and carry oxygen into tissues buried in waterlogged mud. (The passage connects oxygen-poor mud with upward roots, openings, internal spaces, and tidal exposure.)

Why does falling water help the special roots?

It exposes their openings to air again. (The third paragraph states that lower tide exposes the root surface for gas exchange.)

What does “waterlogged” mean here?

soaked and filled with water (The opening describes muddy ground flooded by tides, establishing the saturated condition.)

What are the upward roots called?

pneumatophores (The second paragraph gives the name immediately after introducing the special roots.)

How a Mangrove Root Breathes: Level 1 Reading Comprehension Questions

Mangrove trees can grow in muddy ground flooded by tides. The mud holds much less oxygen than loose, dry soil. Yet the tree's buried cells still need oxygen for respiration.

Some mangroves send special roots upward from the mud. These roots, called pneumatophores, have small openings that let gases enter when the surface is exposed. Air moves through spongy spaces inside the root toward tissues below.

The roots do not breathe with lungs, and they cannot take in air while every opening is deeply covered. Tides matter because falling water exposes the surface again. Mud should not be packed tightly around these roots, since blocked openings reduce gas exchange.

A mangrove's upward roots solve a boundary problem. The tree stands in waterlogged ground, but part of its root system reaches the air above it.

Comprehension questions