From the HORT402 manual
Plants that are deficient in nitrogen have stunted growth, depending on the severity of the deficiency. Leaf growth is inhibited; younger leaves are inhibited in particular. Longitudinal shoot growth is inhibited, as is the increase in thickness. Deficient plants often become pale green to yellowish-green due to inhibited chloroplast and chlorophyll synthesis. Leaves start to wither and dry out, turning yellowish brown to brown.
- The whole plant looks pale to yellowish green
- Early senescence of older leaves
- Increased root growth and stunted shoot growth results in a low shoot/root ratio
- Nitrogen is very mobile in both soil and the plant.
- Nitrogen uptake may be reduced at low pH (<4)
- Nitrogen deficiency is common in nature. Plants have developed response mechanisms to nitrogen deficiency which include hormonal up regulation of root growth, and closing of aqua pores which results in shoot water stress and stunted shoot growth.