5. [2pt] 5.1 The figure shows a pair of guard cells with an open stomatal pore. Which condition best explains this state? ((A) Guard cells have low (more negative) solute potential (Us), water enters guard cells, and the stomata open. ((B) Guard cells have high (less negative) solute potential ('s), water leaves guard cells, and the stomata open. ((C) Guard cells have high (less negative) water potential (Ww) than surrounding cells, so water exits guard cells and the stomata open. ((D) Guard cells have low (more negative) pressure potential (p), which directly forces the stomatal pore to open.

[2pt] 11. A fertilizer label "16-16-16" indicates the percentage by mass of N, P2O5,and K₂O. Which statement is the most accurate interpretation for plant growth? (A) A 16-16-16 fertilizer maximizes growth because all three nutrients are present in equal amounts. (B) The fertilizer provides equal amounts of elemental N, P, and K, so deficiencies are impossible. (C) Plant growth response depends on which nutrient is limiting; adding a balanced fertilizer may not increase growth if another nutrient (e.g., Fe) is limiting. (D) Phosphorus and potassium are not essential nutrients because they can be replaced by nitrogen. (E) The numbers indicate the soil pH required for optimal uptake.

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