Background

Abstract

This experiment was designed to find out if the growth and development of aquatic plants was affected by the pH values of the water they were grown in. This was investigated via the modifying of the pH levels of the water of the water hyacinths using the addition of acids and bases respectively.

The investigation showed that the water hyacinths tend to grow better in water of approximately pH 7 (distilled water). The water hyacinths were sensitive and reacted to the changes in pH differently.

This means that water pollution, which causes changes in pH of water bodies, can easily break the ecosystem of an environment by killing off the population of the autotrophs (trophic level one organisms).

Introduction

The experiment investigated the reaction of water hyacinths to acidic, neutral and basic liquids. It was done so in order to mirror the effects of water pollution in the environment.

The experiment was carried out in order to mimic the effects of water pollution on plants, specifically that regarding pH values. The change of pH values was meant to show the effect of pollutants changing the pH of the groundwater to a value that was either excessively acidic or alkaline.

The experiment was thus done using variations of different liquids the water hyacinths were grown in. The liquids’ pH ranged from acidic to neutral, then neutral to alkaline. This was done in order to show the different effects acids and bases have on the growth and development of plants.

Our hypothesis was that the more acidic or alkaline the liquid the water hyacinths were grown in, the less healthily the water hyacinths would grow.

The independent variable involved in the experiment was the pH of the water used to grow the water hyacinths in; and the dependent variables were the conditions of the water hyacinths’ leaves, roots and general state was in.

Methods

The experiment was set up with five containers, each with an individual water hyacinth. 200ml of liquid (tap water (pH 7.5), distilled water (pH 6), dilute hydrochloric acid (pH 1), sodium hydroxide (pH 14) and toothpaste mixed with distilled water (pH 10)) was added to each of the containers. The water hyacinths were then left to grow over a period of seven days.

The control set-up was made with the exact same water hyacinths in a container filled with pond water that the water hyacinths were originally grown in. This was to ensure that any changes observed in the water hyacinths were not caused by factors excluding the changed variable (pH of liquids).