2 pts. The bubble potometer is generally considered to provide a good assessment

Question

2 pts. The bubble potometer is generally considered to provide a good assessment of the potential for water uptake in a plant over time, whereas a pressure bomb provides a better "snapshot" measurement of the actual water potential of the plant as a function of the water conditions that existed in the field at the moment the stem was cut. Explain why this is so. c. d. 2 pts. Imagine if, after setting up your potometer, you used a blowtorch to seal the end of the pipette trapping the air bubble inside. During transpiration, what would you expect to observe in the sealed pipette over time, and how could such a setup be used to estimate the actual tension and therefore water potential of the plant in MPa?

Explanation / Answer

Answer-c:

A Bubble Potometer is generally considered to provide a good measurement of water potential but a Pressure Bomb gives a better measurement of actual water potential of the plant as a function of water conditions that existed the field. This is so because when a plant is fully saturated (that is, solute concentration is high due to dissolved salts and minerals), then the value for water potential is zero; and if the water concentration decreases further then the value becomes negative. Since pressure bomb applies the measured value of pressure, then the amount of water oozed out is observed and measured. So, higher the pressure applied, more water would be oozed out that will ultimately gives an idea about the tension (turgor pressure) experienced by a leaf. However, if a plant if growing the field whose soil is very rich is minerals and salts. So, automatically solute concetration inside the plant will be hight but water concentration will be low, due to hypertonic conditions. Therefore, when the pressure is applied, comparably lesser amount of water will be oozed out as compared with the condition of some other plant that is growing in the soil having mineral inadequacy. Thus, if Water concentration is low, the the value of water potential is negative, stating that the plant is growing in mineral rich environment.

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