Blossom Your Green Thumb: Cengage Horticulture Exam 1 Practice 2026 – Cultivate Success!

Nitrogen is a mobile nutrient in plants, essential for chlorophyll and many proteins. When nitrogen is deficient, the plant moves available nitrogen from older leaves to developing tissues. This leaves the older leaves yellowed (chlorosis) while the growth slows because photosynthesis and protein synthesis are limited. The result is yellowing of the older leaves accompanied by overall slowed, stunted growth.

Other patterns don’t fit nitrogen deficiency as well. Yellowing of newer leaves points to immobile nutrients (like iron), where deficiency shows up first in new growth. Dark green leaves usually signal ample or excess nitrogen, not a deficiency. Purple stems are more commonly associated with phosphorus deficiency or other stress. So the described signs align best with nitrogen deficiency.