A leathery-tan color on the edges of recently matured leaves is the first symptom to appear. This marginal discoloration progresses between the veins to the mid-rib. The tanning is intensified by bright sunlight to a brown scorch. As deficiency increases, the older leaves are affected, leaving the young, center leaves free of symptoms, even when deficiency becomes extreme. Apparently, potassium is translocated from older to younger leaves in the plant center, and at times the newly absorbed potassium may be sufficient to provide for a fair amount of new leaf growth. Some- times, the center leaves may also develop calcium deficiency symptoms, probably because potassium is involved directly or indirectly in calcium utilization. Large leaf blades with potassium-deficiency symptoms have a faint, but distinct odor of putrescene, reminiscent of decaying vegetable matter.

Sodium within the plant tends to replace potassium when potassium is in short supply. It enhances the growth of tops and roots and reduces the intensity of the, deficiency symptoms, particularly that of leaf scorch. Much of this sparing action of sodium appears to be associated with the displacement of potassium from the petiole to the growing point, or to the corresponding blade where it is used for further growth. Sodium also appears to enhance growth slightly, even when potassium is present in ample supply within the plant.