Info

The experimental trace spiked immediately after the injection of K+ solution.

" Return to H2O alone

K+ solution injected

" Return to H2O alone

K+ solution injected

The control trace (H2O only) showed little variation in flow rate.

1000 2000 3000 Time (seconds)

1000 2000 3000 Time (seconds)

The control trace (H2O only) showed little variation in flow rate.

Conclusion: K+ increases the rate of flow in the xylem.

36.10 Potassium Ions Speed Transport in the Xylem This experiment showed that the rate of fluid ascending through the xylem spiked when a solution with a known concentration of potassium ions was injected. Repeating the experiment with solutions of different concentrations of K+ showed that the higher the K+ concentration, the greater the flow rate.

temperature, light intensity, and wind velocity affect the transpiration rate, and hence the rate of sap flow, more directly.

Although transpiration provides the impetus for the transport of water and minerals in the xylem, it also results in the loss of tremendous quantities of water from the plant. How do plants control this loss?

dioxide. This poses a problem: How can the leaf balance its need to retain water with its need to obtain CO2 for photosynthesis?

Plants have evolved an elegant compromise in the form of stomata (singular, stoma), or pores, in the epidermis of their leaves. A pair of specialized epidermal cells, called guard cells, controls the opening and closing of each stoma (Figure 36.11a). When the stomata are open, CO2 can enter the leaf by diffusion—but water vapor is lost in the same way.

Was this article helpful?

0 0
Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

Get My Free Ebook


Post a comment