Control & Regulation

Control & Regulation Effects of Chemicals on Growth Mr G Davidson

The Importance of macro-elements in Plants • A macro-element is one which is required by an organism in small but significant quantities for healthy growth and development. • Plants get macro-elements Nitrogen, Potassium, Phosphorous and Magnesium from the soil in which they are growing. G Davidson

The Importance of macro-elements in Plants • They enter the plant through tiny extensions of the root called root hairs. • Since root hairs are single cells, substances enter by diffusion or active transport. G Davidson

The Importance of macro-elements in Plants • If one macro-element is missing or in short supply, the plant will not be healthy. • The symptoms it shows will be caused by the lack of that element. G Davidson

Water Culture Experiments • The importance of these macro-elements can be investigated using water culture experiments. • This involves growing plants in a mineral solution from which one element has been removed. • The control contains all the necessary elements for growth and a comparison can therefore be carried out. G Davidson

Tube to aerate the solution. SEEDS Polystyrene beads to float the seeds. Glass beaker with an opaque cover to prevent algal growth. Mineral solution containing all the elements except the one being investigated. Water culture experiment G Davidson

Water culture experiment • When this experiment is set up, the glass beaker is rinsed in concentrated nitric acid to remove all traces of mineral elements which may be present. • The beaker has an opaque cover put round it to keep light out which prevents growth of algae which could deprive the plant of oxygen or compete for minerals. G Davidson

Water culture experiment • After growth for a few weeks, the plants show certain deficiency symptoms which quite often are an indication of the part played in the metabolism by particular elements. G Davidson

Elements in Plants G Davidson

The importance of Calcium and Iron in animals • Animals need small amounts of elements for healthy growth and development: • They get this supply from the food they eat. • Calcium is found in dairy products and helps form bones and teeth. • As with macro-elements in plants, we can infer the role of calcium by looking at animals with a deficiency. G Davidson

The importance of Calcium and Iron in animals • Animals also require a supply of iron, especially during gestation. • A small mass of iron is lost everyday in urine, bile and dead skin cells. • A single atom of iron is a key part of every haemoglobin atom in the blood. • Iron is required for growth and menstruation which use up the supplies. G Davidson

Elements in Animals G Davidson

The effect of Vitamin D deficiency in humans • Vitamins are groups of organic substances which are necessary for a healthy diet. • They were named by letters before their chemical nature was known. G Davidson

The effect of Vitamin D deficiency in humans • Vitamin D is known as the sunshine vitamin because, when the body is exposed to sunshine, vitamin D can be synthesised in the lower layers of the skin. G Davidson

The effect of Vitamin D deficiency in humans • The main food sources of vitamin D are fish oils. • In children, a deficiency of vitamin D leads to the development of rickets. • In Scotland, as early as the 18th Century, cod-liver oil was regarded as a traditional remedy to cure rickets. G Davidson

The effect of Vitamin D deficiency in humans • In children, the ends of the bones are actively growing and where there is a lack of vitamin D, they continue to grow. • However, they don’t harden because calcium phosphate cannot be absorbed and the bones bend under the weight of the child. G Davidson

The effect of Vitamin D deficiency in humans • In adults, lack of vitamin D causes a disease known as osteomalacia. • In this disease, the problem is one of lack of absorption of calcium from the diet. • In an attempt to maintain blood calcium levels, calcium is withdrawn from the bones which then become soft, weak and painful. G Davidson

The effect of Vitamin D deficiency in humans • Osteomalacia often affects women who have had numerous pregnancies and is quite common in elderly women in Scotland who are housebound and therefore unable to make up dietary deficiencies from sunlight. G Davidson

The effect of Vitamin D deficiency in humans • One study has shown that 34% of women over fifty years old who have suffered fractures of the femur also showed symptoms of osteomalacia. G Davidson

The effect of Vitamin D deficiency in humans • Vitamin D is the most toxic of all vitamins when taken excessively. • There is a narrow gap between its nutritional requirement and its toxic dose. G Davidson

The effect of Vitamin D deficiency in humans • If too much vitamin D is taken over a prolonged period, calcium can be deposited in the soft tissues of the body, e.g. kidneys, heart, lungs, breasts, etc. G Davidson

The effect of Vitamin D deficiency in humans • Some cases of rheumatoid arthritis have been helped by vitamin D but the doses required are high and only available on prescription under medical supervision. G Davidson

The effect of Vitamin D deficiency in humans • The usual reason for toxicity of vitamin D in infants is parental error. • A parent may make a mistake in the dose given to their child, e.g. a teaspoonful of calciferol (a vitamin D preparation) is 50 times more potent than the same amount of cod liver oil G Davidson

The inhibiting effect of lead on enzyme activity • As well as small amounts of substances sustaining healthy growth and development, there are other substances which in small amounts can inhibit growth and development. • Lead is one such toxic substance. G Davidson

The inhibiting effect of lead on enzyme activity • Lead inhibits the reaction of the enzyme catalase which breaks down hydrogen peroxide into water and oxygen in living cells. • Lead taken into the body by any number of methods, e.g. lead water pipes, car exhaust fumes, etc. can lead to lead poisoning. G Davidson

The inhibiting effect of lead on enzyme activity • Lead poisoning has many symptoms such as headaches, vomiting, clumsiness etc. • If large intakes continue, acute lead poisoning results. • Thiscan result in a swelling of the brain and damage which can lead to mental retardation. G Davidson

The inhibiting effect of lead on enzyme activity • Tests have been carried out which show that lead levels and intelligence questioning in children are linked. • The children with higher lead levels show poorer performance and are easily distracted, more so than children with lower lead levels. G Davidson

The effect of drugs on foetal development • Some drugs can adversely affect growth and development. • Foetal growth occurs in the uterus and food materials reach the foetus in the maternal blood. G Davidson

The effect of drugs on foetal development • However, the maternal blood also carries other substances to the foetus. • Pregnant women have to be careful about any drugs they take during pregnancy, especially in the early stages of pregnancy when foetal organs are beginning to develop. G Davidson

The effect of drugs on foetal development • In the 1960s, thalidomide was a popular drug used to prevent morning sickness but produced severe deformities in babies. • If the drug was taken early in the pregnancy, then the limbs of the foetus failed to develop properly. G Davidson

The effect of drugs on foetal development • Alcohol can also be passed on to developing babies. • Birth defects known as Foetal Alcohol Syndrome (FAS) can result if a mother drinks excessively during pregnancy. • The effects can be growth retardation, facial deformities, heart defects, abnormal joints and limbs and mental retardation. G Davidson

The effect of drugs on foetal development • These can be the result of alcohol crossing from the maternal blood system to the foetal blood. • This can result in the blood vessels of the umbilical cord, temporarily collapsing, resulting in oxygen starvation. G Davidson

The effect of drugs on foetal development • Nicotine can result in a high foetal and infant mortality rate and in foetal abnormalities of the heart and nervous system. • Infants nursing from smoking mothers may also have an increased risk of gastrointestinal problems. G Davidson

Effects of drugs on foetal development G Davidson

Control & Regulation