Amino Acid Concentrations in Extrafloral Nectar of Impatiens Sultani Increase after Simulated Herbivory

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. In many plants, extrafloral nectars attract ants that protect the plant from herbivory. Previous work indicates that both sugars and amino acids contribute to ant attraction and that herbivory may affect nectar production or composition. This study was designed to measure the effect of defoliation on sugar and amino acid concentrations in the extrafloral nectar of Impatiens sultan. Twenty-nine fall-raised plants and 45 springraised plants were subjected to varying degrees of defoliation in which 25, 50, or 75% of each leaf was removed. Extrafloral nectar was collected immediately before and 24 h after defoliation for the fall-raised plants; additionally, nectar was collected 24 h before and 48 and 72 h after defoliation in the spring-raised plants. Nectars were analyzed for sugar and amino acid content by means of high-pressure liquid chromatography (HPLC). Twentyfour hours after defoliation, amino acid content increased dramatically in plants subjected to all three levels of defoliation; amino acid concentrations of nectars 72 h after defoliation were indistinguishable from predefoliation levels. No change in sugar concentrations or nectar volumes was detected. Additional work is needed to determine if the increase in amino acids is adaptive and serves to attract more plant protectors.

Extrafloral nectar production of the ant-associated plant, Macaranga tanarius, is an induced, indirect, defensive response elicited by jasmonic acid

“…Similar effects were found in two field experiments that were conducted in different years. These results are in line with earlier reports indicating that EFN flow might be induced by herbivory (10,(13)(14)(15), and that this reaction does not require herbivore-specific elicitors (16,17). Exogenous application of the plant stress hormone JA led to a comparable increase in EFN flow ( Fig.…”

“…Given a choice, ants forage preferentially on plants with extrafloral nectaries (5-7), and several ant and wasp species directly defend the nectary-bearing plant parts against other insects (8). Both insect groups reduce numbers of herbivorous insects on plants possessing extrafloral nectaries and thus lessen damage by herbivores (5,6,(8)(9)(10)(11)(12).Several studies have already indicated that EFN secretion or amino acid concentrations in EFN may increase in response to herbivory (10,(13)(14)(15) and that this reaction does not require herbivore-specific elicitors (16,17). However, most of these studies have suffered from methodological problems (discussed in ref.…”

“…Several studies have already indicated that EFN secretion or amino acid concentrations in EFN may increase in response to herbivory (10,(13)(14)(15) and that this reaction does not require herbivore-specific elicitors (16,17). However, most of these studies have suffered from methodological problems (discussed in ref.…”

Recruitment of predators and parasitoids by herbivore-injured plants

“…He diluted the nectar of individual nectaries with water and demonstrated that the diluted nectar collected from sphingid-damaged leaves was richer in solutes compared with nectar collected from undamaged leaves. Smith et al (1990) point out that this does not resolve whether C. speciosa actually increased its nectar volume or whether it produced the same volume with an increased solute concentration. Koptur (1989) reported that mechanical damage of Vicia sativa leaves increased the volume of extrafloral nectar production by a factor of 2.5.…”

“…In addition to carbohydrates, extrafloral nectar may contain variable amounts of proteins, amino acids, and lipids (Baker et al, 1978;Smith et al, 1990). The particular amino acid composition can increase the attractiveness of extrafloral nectar as a food source (Lanza, 1988).…”