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Water Wise Gardening Poster 1 Lesson Notes RAND WATER RAND WATER Water Wise Gardening Poster 1. HOME/SOIL 2. LIGHT 3. WATER 4. FOOD 5. AIR 1 2 5 3 4 POSTER 1 Lesson 1 LIMITING FACTOR PRINCIPLE Not only do plants need a home/soil (habitat), light, water, air and food, but they also need to have these factors in the correct amounts. They need the right balance of each in order to grow efficiently. This is called the LIMITING FACTOR PRINCIPLE which states that, “too much or too little of any biotic factor can limit or prevent the growth of an organism, even if all other factors are at or near the optimum level”. So, for example, if a gardener plants a plant in an area where it receives too little light, it will not grow, even if there is enough water, air, food and soil (warmth/home environment) for the plant. If the plant receives enough light, water, air, and soil but too little food, it will also not grow to its full potential. If a plant is given lots of water, but has too little food, it will be unable to use all the water. This is because its growth will be limited by the amount of food available, and the water has been wasted! The principles of caring for plants should not be overwhelming. Humans and plants have many areas of common ground. On the following page are a few examples, can you find more? Water Wise Gardening - Poster 1 - Lesson 1 - Page 1 NEW HOME For survival a plant needs... For survival we need... A home or habitat with the right combination of environmental factors (like temperature and moisture) in w h i ch t h e p l a n t c a n g r o w a n d reproduce. A home which provides us with shelter and security. Light - sunlight is the energy source that plants use to produce carbohydrates through the process of photosynthesis. The sun’s energy provides warmth. The action of sunlight on the skin produces Vitamin D. Sunlight can improve people’s moods. Water - makes up about 90% of plant cells. It provides mechanical support to cells and tissues. Water is needed for all metabolic reactions. Water is the solvent in which other molecules can dissolve and be moved around the plant. Plants lose water through transpiration. Water makes up 70% of the human body. It is needed for digestion and absorption of food and for getting rid of wastes. People also use water for bathing, washing and cleaning and carrying wastes away from their homes. People lose water through respiration. Air - contains a mixture of gases including carbon dioxide and oxygen. Carbon dioxide is absorbed by plants through their leaves and is used to make food t hrough t he process of photosynthesis. Oxygen is produced during photosynthesis and is released into the air through the leaves. Plants also use oxygen to break down food molecules like sugars (this process is called respiration). When we inhale, our lungs absorb the oxygen in the air and this is used to break down the food stored in our cells, releasing the food energy (this process is called respiration). The carbon dioxide that is produced dur ing respiration is released into the air when we exhale. Plants are essential in cleaning the air for humans and thus air is cycled between man and plants. Water Wise Gardening - Poster 1 - Lesson 1 - Page 2 Food - Plants are called producers because they make their own food using t h e s u n’ s e n e rg y. P l a n t s m a ke carbohydrates in their leaves and stems during photosynthesis. But they need to get other nutrients like nitrates and phosphates from the soil. Soils contain a mixture of nutrients that plants take up though their roots. Plants are at the bottom of the food chain. No other life could exist if there were no plants. Humans cannot make their own food like plants can. Humans are consumers, meaning that they get their energy by consuming either plants or animals. The food that we humans eat is broken down in our bodies releasing energy. This is used for work, growth, and repair of the body. Humans are at the top of the food chain. Note: If we applied too much fertilizer (food to the roots) at one time and then left it for a long time, the plant would die. People are similar eg. a baby will require small amounts of food at a regular time. Giving a baby a week’s supply of food at one time will kill it as the baby is not able to make use of it all at once. ACTIVITY 1. Imagine you are stranded at the back of the moon. Draw up a list of things you would need to survive. See which of these things correspond to plant requirements. 2. Can you find any other similarities between plants and humans. Water Wise Gardening - Poster 1 - Lesson 1 - Page 3 RAND WATER For information and ideas on Water Wise gardening call the Rand Water customer service centre on 0860 10 10 60, or visit the home and garden section of their website at www.randwater.co.za RAND WATER