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Consider the following statements with respect to plant physiology:
1. C3 plants are twice as efficient as C4 plants in terms of fixing carbon.
2. The direction of movement in the xylem is always unidirectional.
3. Mycorrhizae represent a symbiotic association of rhizobacteria and plant roots.
How many of the statements given above are correct?
- a)Only one
- b)Only two
- c)Only three
- d)None
Correct answer is option 'A'. Can you explain this answer?
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Most Upvoted Answer
Consider the following statements with respect to plant physiology:1. ...
Analysis:
The correct answer is option 'A' - Only one statement is correct. Let's analyze each statement individually to understand why:
Statement 1: C3 plants are twice as efficient as C4 plants in terms of fixing carbon
- This statement is incorrect. C4 plants are actually more efficient than C3 plants in fixing carbon. C4 plants have a specialized mechanism that allows them to minimize photorespiration and maximize photosynthesis, making them more efficient in hot and dry conditions.
Statement 2: The direction of movement in the xylem is always unidirectional
- This statement is incorrect. The movement of water in the xylem can be bidirectional, depending on the physiological needs of the plant. For example, during transpiration, water moves upwards in the xylem, but during the night or when water is needed for metabolic processes, water can move downwards as well.
Statement 3: Mycorrhizae represent a symbiotic association of rhizobacteria and plant roots
- This statement is incorrect. Mycorrhizae are actually a symbiotic association between fungi and plant roots, not rhizobacteria. The fungi help the plant in nutrient uptake, especially phosphorus, in exchange for carbohydrates produced by the plant through photosynthesis.
Therefore, only one statement is correct out of the three given statements.
The correct answer is option 'A' - Only one statement is correct. Let's analyze each statement individually to understand why:
Statement 1: C3 plants are twice as efficient as C4 plants in terms of fixing carbon
- This statement is incorrect. C4 plants are actually more efficient than C3 plants in fixing carbon. C4 plants have a specialized mechanism that allows them to minimize photorespiration and maximize photosynthesis, making them more efficient in hot and dry conditions.
Statement 2: The direction of movement in the xylem is always unidirectional
- This statement is incorrect. The movement of water in the xylem can be bidirectional, depending on the physiological needs of the plant. For example, during transpiration, water moves upwards in the xylem, but during the night or when water is needed for metabolic processes, water can move downwards as well.
Statement 3: Mycorrhizae represent a symbiotic association of rhizobacteria and plant roots
- This statement is incorrect. Mycorrhizae are actually a symbiotic association between fungi and plant roots, not rhizobacteria. The fungi help the plant in nutrient uptake, especially phosphorus, in exchange for carbohydrates produced by the plant through photosynthesis.
Therefore, only one statement is correct out of the three given statements.
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Community Answer
Consider the following statements with respect to plant physiology:1. ...
- An actively photosynthesizing plant has an insatiable need for water. Photosynthesis is limited by available water which can be swiftly depleted by transpiration. The humidity of rainforests is largely due to this vast cycling of water from root to leaf to the atmosphere and back to the soil. The evolution of the C4 photosynthetic system is probably one of the strategies for maximizing the availability of CO2 while minimizing water loss. C4 plants are twice as efficient as C3 plants in terms of fixing carbon (making sugar). However, a C4 plant loses only half as much water as a C3 plant for the same amount of CO2 fixed. Hence statement 1 is not correct.
- Food, primarily sucrose, is transported by the vascular tissue phloem from a source to a sink. Sugar stored in roots may be mobilized to become a source of food in the early spring when the buds of trees, act as a sink; they need energy for growth and development of the photosynthetic apparatus. Since the source-sink relationship is variable, the direction of movement in the phloem can be upwards or downwards, i.e., bi-directional. This contrasts with that of the xylem where the movement is always unidirectional, i.e., upwards. Hence, unlike the one-way flow of water in transpiration, food in phloem sap can be transported in any required direction so long as there is a source of sugar and a sink able to use, store, or remove the sugar. Hence statement 2 is correct.
- Mycorrhizae are a symbiotic association between plant roots and fungi. The fungal filaments form a network around the young root or they penetrate the root cells. The hyphae have a very large surface area that absorbs mineral ions and water from the soil a much larger volume of soil that perhaps a root cannot do. The fungus provides minerals and water to the roots, in turn, the roots provide sugars and Ncontaining compounds to the mycorrhizae. Some plants have an obligate association with the mycorrhizae. For example, Pinus seeds cannot germinate and establish without the presence of mycorrhizae. Hence statement 3 is not correct.
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Consider the following statements with respect to plant physiology:1. C3 plants are twice as efficient as C4 plants in terms of fixing carbon.2. The direction of movement in the xylem is always unidirectional.3. Mycorrhizae represent a symbiotic association of rhizobacteria and plant roots.How many of the statements given above are correct?a)Only oneb)Only twoc)Only threed)NoneCorrect answer is option 'A'. Can you explain this answer?
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Consider the following statements with respect to plant physiology:1. C3 plants are twice as efficient as C4 plants in terms of fixing carbon.2. The direction of movement in the xylem is always unidirectional.3. Mycorrhizae represent a symbiotic association of rhizobacteria and plant roots.How many of the statements given above are correct?a)Only oneb)Only twoc)Only threed)NoneCorrect answer is option 'A'. Can you explain this answer? for UPSC 2024 is part of UPSC preparation. The Question and answers have been prepared according to the UPSC exam syllabus. Information about Consider the following statements with respect to plant physiology:1. C3 plants are twice as efficient as C4 plants in terms of fixing carbon.2. The direction of movement in the xylem is always unidirectional.3. Mycorrhizae represent a symbiotic association of rhizobacteria and plant roots.How many of the statements given above are correct?a)Only oneb)Only twoc)Only threed)NoneCorrect answer is option 'A'. Can you explain this answer? covers all topics & solutions for UPSC 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Consider the following statements with respect to plant physiology:1. C3 plants are twice as efficient as C4 plants in terms of fixing carbon.2. The direction of movement in the xylem is always unidirectional.3. Mycorrhizae represent a symbiotic association of rhizobacteria and plant roots.How many of the statements given above are correct?a)Only oneb)Only twoc)Only threed)NoneCorrect answer is option 'A'. Can you explain this answer?.
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