The effect of short-term aphid feeding on the partitioning of 14CO2 photoassimilate in three legume species

Abstract

The short-term effects of the feeding of cowpea aphids (Aphis craccivora Koch) and pea aphids (Acyrthosiphon pisum (Harris)), both Homoptera: Aphididae, on 14C translocation and plant growth of broadbean (Vicia faba L. cv. Aquadulce), cowpea (Vigna unguiculata (L.) Walp. cv. Caloona), and garden pea (Pisum sativum L. cv. Victory Freezer) seedlings were investigated, but not all plant–aphid combinations were utilized. Within 10 days of infestation, aphid feeding reduced the flux of translocate to the roots, changed the assimilate partitioning pattern in affected shoots, and apparently induced assimilate sources to become assimilate sinks. Cowpea aphid feeding also caused more lateral branches to be formed in broadbean. Some of these effects may be related to the imbibing of translocate by aphids, while other effects may result from a series of interactions involving substances in the saliva of aphids, plant hormones, and the assimilate ratio of sources–sinks. The amount of radioactivity found per unit weight of aphid tissue increased between days 5 and 10 in all four plant–aphid combinations. This may indicate that the nymphs were incapable of feeding on the larger phloem elements. Except for the decreased rate of translocation to the roots, the effect of aphid feeding on translocation is plant–aphid species specific.