Lack of phosphorus also causes diminutive plants. The
symptoms in young plants are a dark green to purplish color
of the leaves, abnormal stiffness of stalks and leaves, poor root
development, and some discoloration. The roots are longer
than usual but produce few laterals.
Plants absorb an excess of phosphorus under special condi-
tions, such as when nitrogen is lacking in the nutrient solution.
It is difficult to tell the symptoms of phosphorus excess from
those of nitrogen deficiency. In such a case plants are characterized by large root systems, sparse foliage, stiff leaves and
Species having sizable seed, such as many cereals, can repro-
duce without receiving phosphorus from outside sources, that
contained in the seed being enough to produce diminutive
plants. However, plants like lettuce, radish, and turnip, which
have small, seed, must be provided with an additional supply
of this element to reproduce.