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5. (a) Describe in detail how a named plant builds up a reserve of food in a tap root system - Leaving Cert Agricultural Science - Question 5 - 2014
Question 5
5. (a) Describe in detail how a named plant builds up a reserve of food in a tap root system. (b) Explain each of the following terms as used in the context of pla... show full transcript
Worked Solution & Example Answer:5. (a) Describe in detail how a named plant builds up a reserve of food in a tap root system - Leaving Cert Agricultural Science - Question 5 - 2014
Step 1
Describe in detail how a named plant builds up a reserve of food in a tap root system.
Answer
A named plant with a tap root system, such as a carrot (Daucus carota), builds a reserve of food primarily through the process of photosynthesis. In the green parts of the plant, chlorophyll captures sunlight, converting carbon dioxide and water into sugars, which are vital for energy and growth. These sugars are transported through the phloem to the tap root, where they are stored as starch. This method enables the plant to retain energy, especially during unfavorable conditions, ensuring its survival and regrowth.
Step 2
Explain each of the following terms as used in the context of plant growth in the soil: (i) field capacity
Answer
Field capacity refers to the amount of water that can be retained in the soil after excess water has drained away due to gravitational forces. At this point, the soil is saturated with water, and the remaining moisture is held by soil particles, making it available for plants to absorb.
Step 3
Explain each of the following terms as used in the context of plant growth in the soil: (ii) permanent wilting point
Answer
The permanent wilting point is the critical level of soil moisture at which plants can no longer extract water from the soil. Beyond this point, all capillary water is depleted, leading to plant stress or death, as the plant is unable to maintain turgor pressure and wilts irreversibly.
Step 4
Explain each of the following terms as used in the context of plant growth in the soil: (iii) available water.
Answer
Available water is defined as the portion of water present in the soil that can be absorbed by plants. It is the difference between the field capacity and the permanent wilting point, indicating the water that plants can use for transpiration and growth.
Step 5
Explain any three effects of drought on the development of crop plants.
Answer
Drought can have several detrimental effects on crop plants, including:
- Poor development: Limited moisture results in inadequate growth, leading to stunted plants.
- Low yield: Drought stress significantly impairs photosynthesis and can reduce the number of flowers and fruits, thereby lowering crop yields.
- Reduced transpiration: Insufficient water in the soil leads to reduced transpiration rates, affecting nutrient uptake and causing physiological stress, which can result in leaf turgidity loss and wilting.
Step 6
Step 7
Explain your answer. (ii)
Answer
Soil C's higher percentage of water at field capacity means that it retains more water for plant use compared to soils A and B. This additional moisture can support plants during dry periods, thereby reducing the likelihood of wilting. In contrast, soil A only retains 8% water, making it less capable of sustaining plant hydration during drought conditions.