Science practice 59

Air permeability is defined as the ability of soil to transmit air through interconnected air-filled pores under an imposed air pressure gradient. Air permeability is a function of volumetric water content, porosity, pore size distribution, and pore geometry. Scientists used a soil corer air permeameter (SCAP) to digitally measure the flow rates of air through desert soil under low-pressure gradients. The SCAP measured air permeability both in situ, with the instrument inserted in the soil and ex situ, after the soil corer had been removed from the soil. Figures 1 and 2 display the results of field testing conducted at two of the four sites in Arizona, over the course of three months. The porosity of the soil at each site is displayed in Figure 3. Figure 4 shows the relationship between the air pressure used and the flow rate of the air for each site.

Figure 1

Figure 2

Figure 3

Figure 4

Scientists studying sucrose examined oranges and lemons to determine how the two fruits form and synthesize sucrose. Studies were conducted both on extractions from the fruits and on small, intact fruits.

Study 1

Mature lemon and orange fruits were obtained and then juiced by hand. Formation of fructose was determined using two portions of the fruits: the juice, and the particulate sediment. The results are shown in Table 1.

Table 1—Formation of Sucrose by Fructose Reaction

Study 2

Scientists found lemons of varying ages from the same fruit grove. Each piece of fruit was cut into sections, and various tissue samples were isolated for testing. The three tissue types tested were the flavedo (colored, outer layer of the peel), the albedo (white peel layer), and the vesicle (fleshy part of the fruit). The results of the formation of sucrose in lemons are shown in Figure 1.

Figure 1

Study 3

Whole fruits (each weighing approximately 5 g) were tested and then cut into sections to measure sucrose activity in the various tissues. Figure 2 displays the results.

Figure 2