POPULATION-LEVEL COMPENSATION AFTER LOSS OF VEGETATIVE BUDS - INTERACTIONS AMONG DAMAGED AND UNDAMAGED COTTON NEIGHBORS

Population-level compensation occurs ''when herbivore attack on one in dividual allows another individual to grow more rapidly''. This form o f compensation was investigated in high and low density cotton crops s ubjected to three treatments: (i) undisturbed controls, (ii) uniformly damaged, in which all plants were damaged, and (iii) non-uniformly da maged, in which every second plant was damaged. Damaged plants had the ir vegetative buds manually removed to simulate damage by Helicoverpa spy. (Lepidoptera). Removal of vegetative buds did not reduce seed cot ton production per unit ground area. In uniformly damaged crops? compe nsation was essentially the result of profuse branching after release of apical dominance and activation of axilary buds. In non-uniformly d amaged crops, population level mechanisms acted that involved strong p lant-plant interactions. At both plant densities, undamaged plants gro wn alongside damaged neighbours accumulated more root and shoot biomas s and produced more seed cotton than undamaged plants in uniform crops . Different degrees of symmetry in the relationship between damaged an d undamaged neighbours lead to different degrees of compensation, viz. seed cotton production of non-uniformly damaged crops ranged from 98 to 125% of that in controls. At high plant density, neighbour status a lso affected flowerbud initiation and/or retention. Changes in competi tive relationships as well as early detection of and response to neigh bour status were likely involved in these responses.