Physiological Responses of Leaves of Rumex obtusifolius to Damage by a Leaf Miner

Abstract

1. Larvae of the leaf-mining fly Pegomya nigritarsis cause blotch mines on leaves of Rumex obtusifolius. 2. Effects of mines on net photosynthesis, water vapour conductance and stomatal functioning were measured. 3. Net photosynthesis of mined tissue was on average 20% of healthy tissue. 4. Water vapour conductance was significantly higher from the abaxial surface than the adaxial. Conductance from the adaxial surface of younger (smaller) mines was significantly lower than from adjacent healthy adaxial epidermis. For older (larger) mines, conductance was higher from the mined area than from adjacent healthy lamina. 5. Water loss from detached leaves with mines occurred at a faster rate than from undamaged leaves. 6. Stomata in the epidermis above mines did not function properly. In smaller mines stomata tended to remain closed whereas in older mines stomata tended to remain open. 7. Consequences arising from insect damage in the field are discussed.