ABSTRACT
The aerial and soil environments surrounding plants control the quality, speed and effectiveness of seed germination and subsequent growth, flowering and fruiting. A series of simple, safe practical tests are described, using easily available domestic items which demonstrate the importance of water, warmth, light, nutrition, support and the air for plant functioning. Using broad bean seed grown in drinking cups, tests demonstrate the need for light, warmth and water. Cress or mustard seed grown in food trays demonstrates how nutrients and physical support of root systems permit the growth of healthy seedling. Growing seedlings in the absence of nutrients reduces growth and vigour compared with seedlings of cress or mustard which are provided with these essential supplies. The effects of an absence of carbon dioxide which inhibits photosynthesis is demonstrated using seedlings of cress or mustard grown in redundant plastic drinks bottles. Carbon dioxide is removed from the atmosphere of bottles by reacting it with soda-lime or absorbed onto activated charcoal. Production of carbon dioxide during respiration is demonstrated using living and heat-treated soil. Microbes in living soil respire, producing carbon dioxide which reacts with lime water, a very dilute suspension of calcium hydroxide, producing solid calcium carbonate (chalk) deposits.
These tests offer a platform for understanding how green plants capture energy from sunlight and use it in the conversion of aerial carbon dioxide into sugars and other essential components used in growth and development. Underpinning knowledge sections explain the processes of energy capture from sunlight (photosynthesis) and energy release (respiration). The unique capability, termed photosynthesis, places green plants as the essential base for the existence of all life on the planet. Energy contained in the products of photosynthesis is used by plants and animals in respiration using atmospheric oxygen. Plant growth requires transport systems which distribute the products of photosynthesis from the sites of manufacture to those where they are utilised. The transport systems bring water and nutrients from the soil into roots, and from there they are taken to the tops of even the tallest trees. Green plants have carefully evolved integrated systems for producing complex, energy-rich substances, transporting them into sites where they are broken down for use in growth and reproduction. Plants grow from seed into seedlings and eventually mature garden products as a result of these intricately integrated mechanisms. These growth stages are illustrated using green broccoli (calabrese). Gardeners make use of these systems in controlling plant growth and productivity. Learning achievements are listed at the end of the chapter.
