You carefully measured the average wet mass and dry mass* of samples of plant se

Question

You carefully measured the average wet mass and dry mass* of samples of plant seedlings collected at sundown and the following sunrise from water-saturated soil:

*Plants were initially weighed immediatly after collection (wet mass) and then again after being completely dried in an oven (dry mass).

Assuming the seedlings were all of the same size, how do you expect those numbers to differ, if at all? In other words, will wet and/or dry masses be higher or lower at sunrise by a little or a lot, or will they be the same as at sundown? Explain.

How would your previous answer differ if you were to compare the results of trials done in dry soil? Explain.

Explanation / Answer

Assuming that all the seedlings were of same size the numbers would differ. The difference would be such that wet mass tends to be more than the dry mass because wet mass varies as per the uptake of water on that day and does not constitute part of biomass. When dried water will evaporate and dry mass will be obtained which will be less but represents the actual biomass of the plant.

Wet mass will be more at sunrise due to the dew in the night which causes soil to uptake water and it will lessen at sundown as the water will be evaporated due to the heat from sun.

If trials were done in dry soil then the results will differ in the context as to when dry mass will be higher or lower. For example: During growth of plant from seedling the dry mass decreases slightly during germination due to various respiratory processes taking place in plant. The dry mass then increases as the plumule starts photosynthesizing.

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