Changes in growth and chemical defences upon defoliation in maize

The effect of defoliation on growth and on levels and allocation patterns o f hydroxamic acids (Hx) in maize seedlings was evaluated 6 days after treat ment. No significant differences were found between defoliated and nondefol iated plants for the Hx concentration, relative Hx content and Hx-aglucone to Hx-glucoside ratio in shoots, roots and root exudates, with the exceptio n of Hx concentration in shoots, which decreased upon defoliation. However, growth of defoliated seedlings was considerably higher than that of nondef oliated ones. These results indicate that maize responds to defoliation by allocating its resources mainly to growth rather than to defence. Since pre vious work described the opposite strategy in rye, responses to defoliation in both species are discussed in relation to current theories of plant def ence. (C) 1998 Elsevier Science Ltd. All rights reserved.