how can the absence of starch in the elaborated sap be explained knowing that it is produced by photosynthesis?
This qualitative study aimed at exploring whether students' successful use of analogy in learning curriculum complex science concepts was related: (a) to the level of their understanding of a specific analogy and (b) to their metacognitive awareness of how the analogy was to be used and of the changes produced in their own conceptual structures. In implementing a biological curriculum unit, students' prior knowledge has been taken into account in order to examine its conceptual growth and change via a not completely introduced analogy to 15 fifth graders as they were engaged in understanding the ways in which the new concepts (on photosynthesis) were similar to a familiar source (making a cake). Qualitative data present the children's mapping processes in elaborating the analogy and their metacognitive awareness of the meaning and purpose of the analogy itself, and their personal use of the analogy in changing initial conceptions. As hypothesised, the results showed a high positive correlation among the level of conceptual understanding of the new science topic, the level of understanding of the analogy, and the level of effective use of the analogy in integrating the new information into the pre-existing conceptual structures. Key implications on the use of analogy for conceptual change in the classroom are outlined.
To explain the absence of starch in the elaborated sap despite it being produced by photosynthesis, we need to understand the process of photosynthesis and the way plants store and transport energy.
Photosynthesis is a process by which plants convert light energy from the sun into chemical energy in the form of glucose. Glucose is the primary source of energy for plants, and excess glucose can be stored in the form of starch.
However, not all glucose produced during photosynthesis is converted into starch. Some of it is immediately used for energy by the plant's cells or transported to different parts of the plant for immediate energy needs. This glucose, which is utilized or transported, is referred to as "elaborated sap" or "assimilates."
Now, coming back to your question, the absence of starch in the elaborated sap can be explained by the fact that not all glucose produced during photosynthesis is stored as starch. Some possible reasons for this could be:
1. Immediate energy needs: Plants constantly require energy for metabolic activities, growth, and maintenance. Hence, glucose produced during photosynthesis may be used immediately for energy, rather than being stored as starch.
2. Transport: Glucose is transported throughout the plant via a complex network of phloem vessels. These vessels supply glucose to different parts of the plant, where it is utilized for various purposes. Therefore, the elaborated sap may contain glucose but not starch since the glucose is in transit rather than being stored.
3. Seasonal variations: The production and storage of starch can vary depending on the plant's stage of growth, environmental conditions, and the availability of nutrients. During certain seasons or growth stages, plants may prioritize immediate energy usage over starch storage.
In summary, the absence of starch in the elaborated sap can be attributed to the dynamic energy needs of the plant, the immediate utilization of glucose, and the transport of glucose to various plant parts.