Effects of mineral nutrient de®ciencies on leaf development, visual symptoms and shoot±root ratio of Spathiphyllum

Effects of de®ciencies in N, P, K, Ca, Mg, B and Fe on leaf development, visual symptoms and shoot±root dry weight ratio were studied in Spathiphyllum `Sensation' grown hydroponically. Leaf nutrient contents of treated plants were analyzed to con®rm suspected de®ciencies. Leaf number, leaf area and chlorophyll content were all signi®cantly reduced in the nitrogen-de®cient plants similar to plants grown in distilled water. The phosphorus-de®cient plants grew slowly but no de®ciency symptoms were visible on leaves. Many small yellow specks, usually 2 mm or less in diameter, developed on the adaxial surface of lower leaves in the potassium-de®cient plants. Leaf area, but not leaf number, was signi®cantly suppressed by the calcium-de®cient treatment and the young leaves developed necrotic margins on the middle and basal leaf blade. Fully expanded leaves in the magnesium-de®cient plants were distorted and had lower chlorophyll contents than the controls. The iron-de®cient plants showed interveinal chlorosis on younger leaves. The boronde®cient plants showed two types of de®ciency symptoms: a marginal necrosis at the leaf apex and distorted and crinkled petioles break at the leaf blade. Shoot±root dry weight ratio was decreased under N, P and Fe de®ciencies but was increased under de®ciencies of Ca and B. A key was developed for the identi®cation of mineral nutrient de®ciencies. # 2000 Elsevier Science B.V. All rights reserved.