Download Answers to Biological Inquiry Questions – Brooker et al ARIS site

Answers to Biological Inquiry Questions – Brooker et al ARIS site
Chapter 38
Figure 38.4
BIOLOGICAL INQUIRY QUESTION: If a cell of each of these types is placed into a solution of pure
water (whose water potential Ψw, is defined as 0 MPa) in which direction will water move in each
case?
ANSWER: When placed in pure water, a turgid cell having a water potential of 1.0 will lose water,
because 1 is greater than 0. When placed in pure water, a plasmolyzed cell having a water potential
of –1.0 MPa will gain water. When placed in pure water, a flaccid cell having a water potential of -0.5
MPa will gain water. This is because water moves from a region of higher water potential to a region
of lower water potential, and 0 is greater than -0.5.
Figure 38.8
BIOLOGICAL INQUIRY QUESTION: Where in most plants would you expect to find the highest
concentration of Al3+?
ANSWER: In most plants, most Al3+ will remain in the roots, because the ions can move through
outer root tissues, but cannot cross the endodermis. However, some aluminum may be able to get
into root vascular tissues by seeping into root tips where the endodermis has not yet formed or at
places where the endodermis has been broken by the emergence of branch roots. These processes,
together with the fact that aluminum ions are very abundant in soils, explain why plant tissues may
contain some aluminum even though it is not a plant nutrient.
Figure 38.13
BIOLOGICAL INQUIRY QUESTION: Which structural features of a vessel element explain the
vulnerability of vessels to embolism, that is, blockage by air bubbles?
ANSWER: The large perforations in vessel element end walls allow an air bubble to extend from one
element to another, thereby clogging vessels and preventing water flow through them. In contrast,
the much smaller pores in the end walls of tracheids do not allow water to flow as efficiently as it
does through vessels, but these smaller pores also retard the movement of air bubbles. Thus air
bubbles are confined to a single tracheid where they do little harm.
Figure 38.17
BIOLOGICAL INQUIRY QUESTION: Why does evaporation of water have such a powerful cooling
effect?
ANSWER: The evaporation of water has a powerful cooling effect because it disperses heat so
effectively. Water has the highest heat of vaporization of any known liquid.