Maize morphology and shoot CO2 assimilation after root damage by western corn rootworm larvae

Knowledge of the physiological stress mechanisms triggered by corn rootworm larval feeding damage may suggest new ways of maintaining maize (Zea mays L.) productivity in plants damaged by this important insect pest. Western c orn rootworm [Diabrotica virgifera virgifera (LeConte)] larval feeding dama ge to maize roof systems causes complex changes in leaf CO2 assimilation. T he objective of our study was to further explore the relationships between plant morphology and CO2 assimilation in rootworm-damaged maize. The effect s of moderate or severe root damage caused by larval feeding or by mechanic al damage on roof system morphology, shoot dry weight, leaf area, stomatal conductance, and CO2 assimilation were investigated in greenhouse experimen ts. Rootworm larval feeding, which removed about 75% of the total root syst em volume, or mechanical cutting treatments imposed at the V12 leaf stage, which removed about 30% of the total root system volume, had no effect upon leaf CO2 assimilation hut significantly reduced stomatal conductance when measured at the tassel development stage; During the time when larvae were damaging root systems or when specific root node axes were mechanically cut , however, leaf CO2 assimilation was less in root-damaged plants than in un damaged plants. Larval-damaged root systems had accelerated adventitious ro ot axis growth and development in the nodes located immediately above the d amaged nodes. This compensatory root growth was more pronounced under the m oderate root feeding damage treatments than in the severe root damage treat ments. Total leaf area and shoot CO2 assimilation were less in plants with severe larval feeding damage than in plants with moderate damage or in cont rol plants, Thus, the severity of root damage plus the level of root compen satory growth play important roles in mediating shoot growth and CO2 assimi lation responses to stress imposed by rootworm larval feeding.