IMPACT OF ELEVATED LEVELS OF ATMOSPHERIC CO2 AND HERBIVORY ON FLAVONOIDS OF SOYBEAN (Glycine max LINNAEUS)

O'NEIL, B.; ZANGERL, A.; DERMONDY, O.; BILGIN, D.D; CASTEEL, C.L.; ZAVALA, J.A.; DE LUCIA, E.H.; BERENBAUM, M.R.

JOURNAL OF CHEMICAL ECOLOGY

Springer

Lugar: Berlin; Año: 2010 p. 35 - 45

0098-0331

Atmospheric levels of carbon dioxide (CO2) have been increasing steadily over the last century.  Plants grown under elevated CO2 conditions experience physiological changes that can influence their suitability as food for insects.  Phytochemical levels in particular can influence herbivore feeding, health, and longevity.  In this study, changes in flavonoid content were examined in foliage of soybean (Glycine max Linnaeus) grown under ambient and elevated levels of CO2, and subjected to damage by herbivores in three feeding guilds: leaf skeletonizer (Popillia japonica Newman), leaf chewer (Vanessa cardui Linnaeus), and phloem feeder (Aphis glycines Matsumura).  Flavonoids are important plant defense compounds and antioxidants and can have a large effect on leaf palatability and herbivore longevity.  The presence of the isoflavones genistein and daidzein and the flavonols quercetin and kaempferol was confirmed in all plants examined, as were glycosides of these compounds.  All compounds significantly increased in concentration as the growing season progressed.  Concentrations of quercetin glycosides were significantly higher in plants grown under elevated levels of CO2.  The majority of compounds in foliage were induced in response to leaf skeletonization damage but remained unchanged in response to non-skeletonizing chewing damage or phloem-feeding damage.  Insects feeding on G. max foliage growing under elevated levels of CO2 may derive additional antioxidant benefits from their host plants as a consequence of the presence of elevated flavonoid levels.  This nutritional benefit could lead to increased herbivore longevity and increased damage to soybean (and perhaps other crop plants) in the future.