An insect countermeasure impacts plant physiology: midrib vein cutting, defoliation and leaf photosynthesis

• Published in: Plant, cell and environment Vol. 29; no. 7; pp. 1245 - 1258
• Main Authors: DELANEY, KEVIN J., HIGLEY, LEON G.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.07.2006; Blackwell
• Subjects: Analysis of Variance; Animals; Apocynaceae; Asclepiadaceae; Biological and medical sciences; dogbane; Fabaceae; Fundamental and applied biological sciences. Psychology; Gases; herbivory; injury; Insecta - physiology; Metabolism; milkweed; Models, Biological; Photosynthesis - physiology; Photosynthesis, respiration. Anabolism, catabolism; Plant Leaves - physiology; Plant physiology and development; Polygonaceae; vascular tissue; dogbane; Cardenolide; Polygonaceae; vascular tissue; Asclepiadaceae; Plant leaf; Latex; Apocynaceae; Defoliation; Leguminosae; Dicotyledones; Angiospermae; herbivory; Spermatophyta; Habitat; Gas exchange; injury; Photosynthesis; milkweed; Petiole
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/j.1365-3040.2006.01504.x

ABSTRACT One type of specialised herbivory receiving little study even though its importance has frequently been mentioned is vein cutting. We examined how injury to a leaf’s midrib vein impairs gas exchange, whether impairment occurs downstream or upstream from injury, duration of impairment, compared the severity of midrib injury with non‐midrib defoliation, and modelled how these two leaf injuries affect whole‐leaf photosynthesis. Leaf gas exchange response to midrib injury was measured in five Asclepiadaceae (milkweed), one Apocynaceae (dogbane), one Polygonaceae and one Fabaceae species, which have been observed or reported to have midrib vein cutting injury in their habitats. Midrib vein injury impaired several leaf gas exchange parameters, but only downstream (distal) from the injury location. The degree of gas exchange impairment from midrib injury was usually more severe than from manually imposed and actual insect defoliation (non‐midrib), where partial recovery occurred after 28 d in one milkweed species. Non‐midrib tissue defoliation reduced whole‐leaf photosynthetic activity mostly by removing photosynthetically active tissue, while midrib injury was most severe as the injury location came closer to the petiole. Midrib vein cutting has been suggested to have evolved as a countermeasure to deactivate induced leaf latex or cardenolide defences of milkweeds and dogbanes, yet vein cutting effects on leaf physiology seem more severe than the non‐midrib defoliation the defences evolved to deter.