Interveinal chlorosis on younger leaves of sweetgum, Liquidambar styraciflua, due to iron deficiency and an older leaf (right) with a healthy appearance.

Because iron is immobile in plants, older basal leaves remain green as younger leaves become increasingly chlorotic between veins. Various soil conditions are usually responsible for making iron unavailable to plants, including a soil pH above 7.0 and cold, wet, or poorly drained soils. Credit: Edward J. Perry, UC Cooperative Extension Stanislaus
Credit: Edward J. Perry, UC Cooperative Extension Stanislaus