Effects of defoliation on growth of cauliflower

Three experiments were performed with defoliation of young cauliflower plan ts in the field. The leaves were removed 3-6 weeks after planting and about 65% of the leaf area were removed. After defoliation, several plant proces ses contributed to compensate for the loss of leaf area. Right after defoli ation, the ratio of leaf area to plant weight was strongly decreased. Howev er, during further growth the ratio of leaf area to plant weight was increa sed in defoliated plants. Together with an increase in net assimilation rat e it contributed to the increase in plant relative growth rate after defoli ation. Due to higher rates of leaf growth relative to stem growth, the biom ass allocation pattern was re-established. Specific leaf area was increased in defoliated plants due to depletion of reserves, and contributed to the restoration of the relationship between leaf area and plant dry weight. Con centrations of non-structural carbohydrates were reduced after defoliation, showing that reserves were mobilised to support re-growth. We found that c auliflower through a number of mechanisms re-established the basic relation ships in the plants after damage, and this observation and the estimated re lationships can be used for modelling effects of pest damage on crop growth . (C) 2001 Elsevier Science B.V. All rights reserved.