To solve this problem, we need to understand where the deficiency symptoms of nitrogen and potassium first appear in plants.$\newline \bullet$Nitrogen and potassium are both mobile nutrients in plants.$\newline \bullet$Mobile nutrients can be translocated from older tissues to younger tissues when there is a deficiency.$\newline \bullet$As a result, deficiency symptoms of mobile nutrients like nitrogen and potassium typically appear first in older or senescent leaves.$\newline$Therefore, the correct answer is that the deficiency symptoms of nitrogen and potassium are visible first in senescent leaves.$\newline$This corresponds to Option 1.