Question 1
Which of the following best describes the soil water potential gradient and its role in water movement from soil to tree roots?
A. The soil water potential gradient is the difference in water potential between the soil and the atmosphere, driving water movement into the atmosphere. B. The soil water potential gradient is the difference in water potential between the soil and the root, driving water movement from the soil into the root. C. The soil water potential gradient is the difference in water potential within the root xylem, driving water movement upwards within the plant. D. The soil water potential gradient is the difference in water potential between the root and the leaves, driving water movement towards the leaves.
Question 2
How does the soil's redox potential ($E_h$) primarily influence the availability of iron (Fe) for tree roots?
A. A high redox potential ($\displaystyle E_h$) increases the solubility of iron, making it more available to roots. B. A low redox potential ($\displaystyle E_h$) promotes the reduction of ferric iron ($\displaystyle Fe^{3+}$) to ferrous iron ($\displaystyle Fe^{2+}$), which is more soluble and available to roots. C. Redox potential ($\displaystyle E_h$) directly controls the chelation of iron by organic acids, thus increasing its availability. D. Redox potential ($\displaystyle E_h$) primarily affects the uptake of iron by influencing the activity of iron-transporting proteins in the root membranes.
Question 3
Which of the following is a primary mechanism by which trees can actively regulate stomatal aperture to conserve water during drought, involving the hormone abscisic acid (ABA)?
A. ABA directly increases the turgor pressure in guard cells, causing stomata to open wider. B. ABA promotes the efflux of potassium ions ($\displaystyle K^+$) from guard cells, leading to a decrease in turgor pressure and stomatal closure. C. ABA stimulates the synthesis of new guard cells, increasing the overall number of stomata on the leaf surface. D. ABA enhances the photosynthetic rate, thereby reducing the need for stomatal opening to take up $\displaystyle CO_2$.
Question 4
The pressure bomb technique is commonly used in plant physiology to measure which of the following parameters related to tree water status?
A. The rate of transpiration from the leaves. B. The osmotic potential of the root cells. C. The xylem water potential ($\displaystyle \Psi_x$) in a detached shoot. D. The hydraulic conductivity of the soil.
Question 5
Which of the following best describes the role of suberin in the endodermis of tree roots, specifically in forming the Casparian strip?
A. Suberin facilitates the active transport of water and nutrients into the stele. B. Suberin forms a permeable barrier that allows unrestricted movement of water and solutes through the apoplast. C. Suberin is a waxy, hydrophobic substance that forms the Casparian strip, forcing water and solutes to pass through the cell membranes (symplast pathway) of endodermal cells. D. Suberin acts as a storage compound for carbohydrates within the endodermal cells.
