Two Light Sources Differentially Affected Ferric Iron Reduction and Growth of Cotton

Abstract

In growth chambers, low pressure sodium (LPS) plus incandescent (Inc) lamps and fluorescent cool-white (FCW) plus Inc lamps were used to determine their effects on growth of cotton (Gossypium hirsutum L.) and on the reduction of Fe³⁺ to Fe²⁺. Cotton plants grown under LPS + Inc light developed chlorosis and grew poorly, whereas plants grown under FCW + Inc lights were green. The chlorophyll concentration and top and root weights of cotton grown under LPS + Inc were lower than those under FCW + Inc. In solution, FCW + Inc lamps reduced about eight times more Fe³⁺ to Fe²⁺ than did LPS + Inc lamps. Fe³⁺ is transported to plant tops as Fe³⁺ citrate and if we assume that FCW + Inc light reduces Fe³⁺ to Fe²⁺ in plant foliage as it did in the solutions, then reduction of Fe³⁺ by the light environment will make Fe²⁺ in the tops more available for biochemical reactions.