This is for R3102 June ‘18.
Q6 a) Describe ONE role of EACH of the following elements in plant metabolism:
i) phosphorus (P);[ 2 marks]
ii) boron (B). [2 marks]
b) State how the mobility of EACH of the following nutrients within the plant influences their deficiency symptoms:
i) magnesium (Mg;) [ 2 marks]
ii) calcium (Ca); [ 2 marks]
iii) phosphorus (P). [ 2 marks]
This question relates to the following part of the syllabus:
4.1 Explain how specific nutrients affect plant growth.
Describe ONE role of EACH of the elements in plant metabolism: NPK nitrogen, potassium, phosphorus, sulphur, calcium, magnesium, iron and boron – expected level of detail: phosphorus required in ATP for energy transfer.
State how the mobility of nutrients in soils (nitrogen, phosphorus and potassium) and in the plant (nitrogen, phosphorus, potassium, magnesium, calcium and iron) influence plant deficieNitrogen: describe symptoms of deficiency and excess, and explain the causes to include: protein and chlorophyll synthesis, the effects on water uptake/osmosis and vegetative growth.Phosphorus: describe symptoms of deficiency and explain the causes, to include the effect on seedling growth.
Potassium: describe symptoms of deficiency and excess, and explain the
causes, to include: the effects on water uptake/osmosis, vegetative growth and
Magnesium: describe symptoms of deficiency and excess, and explain the
causes, to include: chlorophyll synthesis, the effect on potassium availability
and vegetative growth.
Calcium: describe symptoms of deficiency (bitter pit, blossom end rot),
excess and explain the causes, to include: vegetative growth, watering and
Iron: describe symptoms of deficiency and explain the causes to include
Copper: state the horticultural situations where possible toxicity may occur (hydroculture, pesticide residue).
This is a question that relates directly to the syllabus, just selecting two particular plant nutrients for part a) from the list, and three for part b).
For part a) only one role is needed for each, so it is important to read the question carefully and only give the required information. As the question asks you to ‘describe’, a reasonable amount of detail is needed.
The examiners’ comments state that ‘The role of phosphorus with regard to ATP and energy was well described, however candidates were less familiar with the role of boron, which includes dormancy, the uptake of phosphorus, its role in regulating pollen tube growth and the production of viable pollen’.
For part b) you need to know the deficiency symptoms of the nutrients as well as whether the nutrients are mobile in the plant. The examiners’ comments mention that sometimes the mobility of the nutrient in the soil was discussed which wasn’t what was asked for. This is another example of the importance of reading through the question well so you only spend time writing the information that is required.
One suggested answer in the examiners’ comments was:
‘calcium is not very mobile in the plant so deficiency symptoms of stunted growth/necrosis appear in youngest leaves and shoot tips’.