Explain the changes in dry weight of a germinating seedling over a 10-day period.

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Here are the changes in dry weight of the whole seedling and their explanations:

State the initial change in dry weight.
The dry weight of the whole seedling initially decreases from 43 mg on Day 0 to 35 mg on Day 8.
Account for the initial decrease.
This decrease occurs because the germinating seedling relies on stored food reserves from the endosperm. These reserves are broken down through respiration to provide energy for growth and development. Respiration consumes organic matter, releasing carbon dioxide and water, which leads to a net loss of dry mass. During this initial period, the rate of respiration is greater than the rate of photosynthesis.
State the subsequent change in dry weight.
After Day 8, the dry weight of the whole seedling increases from 35 mg to 43 mg on Day 10.
Account for the subsequent increase.
This increase is due to the seedling developing leaves and beginning to perform photosynthesis. Photosynthesis produces new organic compounds, which are incorporated into the seedling's biomass. At this stage, the rate of photosynthesis exceeds the rate of respiration, resulting in a net gain of dry mass.

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