If an element increases the growth rate of a plant, can it be defined as an essential element?

(a) Which of the three community locations was least like the other two?

(b) Rank the three variables (community location, developmental stage of roots, and soil type) in terms of how strongly they affect the "species" composition of the bacterial communities.

Imagine yourself as a water molecule in the soil solution of a forest. In a short essay (100- 150 words), explain what pathways and what forces would be necessary to carry you to the leaves of these trees.

The soil in which plants grow teems with organisms from every taxonomic kingdom. In a short essay (100- 150 words), discuss examples of how the mutualistic interactions of plants with bacteria, fungi, and animals improve plant nutrition.

Large brown algae called kelps can grow as tall as 25 m. Kelps consist of a holdfast anchored to the ocean floor, blades that float at the surface and collect light, and a long stalk connecting the blades to the holdfast. Specialized cells in the stalk, although nonvascular, can transport sugar. Suggest a reason why these structures analogous to sieve-tube elements might have evolved in kelps. Explain your thinking.

A Minnesota gardener notes that the plants immediately bordering a walkway are stunted compared with those farther away. Suspecting that the soil near the walkway may be contaminated from salt added to the walkway in winter, the gardener tests the soil. The composition of the soil near the walkway is identical to that farther away except that it contains an additional 50 mM NaCl. Assuming that the NaCl is completely ionized, calculate how much it will lower the solute potential of the soil at $20^{\circ} \mathrm{C}$ using the solute potential equation:

$$\Psi_{\mathrm{S}}=-i C R T$$

where i= the ionization constant $(2$ for $\mathrm{NaCl}), C=$ the molar concentration (in mol/L), $R=$ the pressure constant $[R=0.00831(\mathrm{~L} \cdot \mathrm{MPa}) /(\mathrm{mol} \cdot \mathrm{K})]$, and T= temperature in kelvin $\left(273+{ }^{\circ} \mathrm{C}\right)$. Describe how this change in the solute potential of the soil would affect the water potential of the soil. Explain how the change in the water potential of the soil would affect the movement of water in or out of the roots.

How does the Casparian strip force water and minerals to pass through the plasma membranes of endodermal cells?

Identify plant organs that are sugar sources, organs that are sugar sinks, and organs that might be either. Explain.

How would you change the figure in order to show gas exchanges at night?

If a plant cell immersed in distilled water has a $\Psi_{\mathrm{S}}$ of -0.7 MPa and a Psi of 0 MPa, what is the cell's $\Psi_{\mathrm{P}}$ ? If you put it in an open beaker of solution that has a $\Psi$ of -0.4 MPa, what would be its $\Psi_{\mathrm{p}}$ at equilibrium?

How is the relationship between legume plants and Rhizobium bacteria mutualistic?

Which structure or compartment is part of the symplast?

(A) the interior of a vessel element

(B) the interior of a sieve tube

(C) the cell wall of a mesophyll cell

(D) an extracellular air space

Why do aspen leaves quake?

Based on the data, does the initial uptake of water by radish seeds vary wit h temperature? What is the relationship between temperature and water uptake?