Social Function: To explain the processes involved in the formation or working of natural or sociocultural phenomena.
- A general statement to position the reader
- A sequenced explanation of why or how something occurs.
Significant Lexicogrammatical Features
- Focus on generic, non-human Participants
- Use mainly of Material Processes and Relational Processes
- Use mainly of Temporal and causal Circumstances and Conjunctions
The United States of America is where the Venus’s fly trap has its origins. The Venus’s fly trap is a unique plant. It belongs to a group of plants called ‘carnivorous plants’. These plants feed on insect. The Venus’s fly trap has a special mechanism by which it traps its prey. This is how it works.
At the end of each leaf – which grows from the base of a long, flowering stalk – there is a trap. The trap is made up of two lobes and is covered with short, reddish hairs which are sensitive. There are teeth like structures around the edge of the lobes.
The trap contains nectar which attracts insect. When an insect comes in contact with the nectar, the trap snaps shut. There are certain digestive juice inside the trap which digest the insect. It takes about ten days for a trapped insect to be digested. We can tell when this digestion is complete, for then the walls automatically open to wait for another victim.
There are two hundred species of carnivorous plants. Another kind of these well- known species is the pitcher plant. What differentiates this plant from the Venus’s fly trap is the shape; the mechanism to catch insects is the same in both plants.
The pitcher plants which cling to other plants by means of tendrils. At one end of the tendril, there is a pitcher –shaped vessel with an open lid. The mouth and the lid of the pitcher contain glands which produce nectar to attract insect. When an insect settles on the nectar, the lid of the pitcher shuts, trapping its victim. The digestive juices inside the pitcher then begin to work.
Soils with a pH of less than 7.0 are acid. The lower the pH, the more acid the soil. When soil pH falls below 5.5, plant growth is affected. Crop yields decrease, reducing productivity
Soils provide water and nutrients for plant growth and development. Essential plant nutrients include phosphorus, nitrogen, potassium and sulfur. Plants require other elements such as molybdenum, in smaller quantities. Some elements eg aluminium and manganese, are toxic to plants.
Nutrients become available to plants when they are dissolved in water. Plants are able to take up phosphate, nitrate, potassium and sulfate ions in solution.
The solubility of nitients changes with pH. In acid soils (low pH), molybdenum becomes less soluble and aluminium becomes more soluble. Therefore, plant growth may be affected by either a deficiency of molybdenum or too much aluminium.
Both crop and pasture plants are affected by acid soils. there may be a range of symptoms. Crops and pastures may be poorly established resulting in patchy and uneven growth. Plant leaves may go yellow and die at the tips. The root system of the plant may be stunted. Crops may yield less.
Plants vary in their sensitivity to low pH. Canola and lucerne are very sensitive to acid soils so do not grow well. Lupins and triticale are tolerant to soils of low pH so they still perform well.
Land can become unproductive if acid soil is left untreated. Incorporating lime into the soil raises the pH. Therefore, liming soil can reverse the effects of acid soil on plants and return a paddock to productivity.