IRON-DEFICIENCY STRESS RESPONSE OF TOLMIEA-MENZIESII

The popular foliage houseplant, Tolmiea Menziesii (piggyback plant), grown in an all NO3-N, half-strength Hoagland Solution No. 1 without Fe or with 0.5 g/liter Fe2O3 became severely Fe chlorotic and caused the nutrient solution pH to rise from 5.1 initially to above 7. Plants supplied 90-mu-M Fe-EDTA also raised solution pH but did not become chlorotic. When Fe chlorotic plants were transferred to a solution with 0.5 g/liter Fe2O3, modified to contain 25 to 100% of the N as NH4, the solution pH dropped to between 4.3 and 3.1, and the chlorotic plants regreened. However, if the pH of the modified solution was buffered above 7 with 1 g/liter CaCO3, no regreening occurred. Solution pH also dropped if the solution lacked N, and there was a temporary regreening of Fe chlorotic plants before N deficiency chlorosis appeared. These solution culture results indicate that Tolmiea should be classified as an Fe inefficient plant.