Chemical correlates of ?-tocopherol (Vitamin E) alteredMalacosoma disstria herbivory inFraxinus pennsylvanica var.Subintegerrinia, green ash

Abstract

The antioxidant α-tocopherol (vitamin E), applied in a basal trunk band to the green ash tree,Fraxinus pennsylvanica var.subintergerrinia, elicited an alteration of foliar feeding byMalacosoma disstria larvae (Lepidoptera: Lasiocampidae). The bioassayed effects were dependent on the dosage of elicitor, the time after elicitation, and the position in the tree. Leaves for chemical analysis were collected from trees receiving two dosages and at two intervals after elicitation. Compounds in the ethyl acetate extractables from the ash tree leaves were separated by TLC and HPLC. TLC separations showed differences in the nonhydrolyzed extractables attributable to elicitor dosage and time after elicitation. TLC-resolved differences were also evident among acid-hydrolyzed samples. HPLC-resolved profiles revealed eight peaks in the nonhydrolyzed extractables that were quantitatively negatively correlated with larval feeding preference between elicited versus control foliage on at least one of the two sampling dates. Results from this study and other investigations reported in the literature indicate that the antioxidantα-tocopherol (vitamin E) can function as an environmental-stress elicitor of alterable defensive chemistry in green ash and other plants.

Gypsy moth (Lymantria dispar) larval development and survival to pupation on diet plus extractables from green ash foliage

“…The filtrate was reduced to about 15 ml by rotoevaporation at 42 2 C. The concentrated MeOH extractables were partitioned three times in a separatory funnel with 1000 ml of ethyl acetate (EtOAc). The three EtOAc fractions per MeOH sample were combined, rotoevaporated to dryness and then redissolved in an excess of EtOAc (Markovic et al, 1993). Each sample was then placed in a preweighed screw-cap vial, dried under a stream of nitrogen and weighed.…”

Dynamics of forest herbivory: quest for pattern and principle.

“…Such reaction, or interaction, between a sulfhydryl reagent and a sulfhydryl protein (i.e., receptor) at the plasma membrane level may trigger significant alterations in the defensive chemistry of elicited plant cells (Liu et al 1992(Liu et al , 1994Norris 1994). Third, the essential mechanism by which sulfhydryl reagents and other proven elicitory entities, both biotic and abiotic, function in altering defensive phytochemistry is apparently oxidative-reductive Norris 1991b, 1992;Markovic et al 1993;Norris and Liu 1992). The classical antioxidants, L-ascorbic acid (vitamin C) and o_-tocopherol (vitamin E), have proven to be effective elicitors when applied to whole plants Norris 1991b, 1992).…”

“…The insect's feeding option thus was between a comparable leaf disk from an elicited versus a solvent-control tree. The quantitation of insect feeding was detailed by Markovic et al (1993).…”

“…Three compound leaves from each tree were immediately put individually into a glass jar containing 80% methanol, and then stored in darkness at -20°C until chemical analysis. Procedures used to extract chemicals from ash leaves; hydrolyze extracted chemicals; and analyze the chemicals by high performance thin layer chromatography (HPTLC) and high performance liquid chromatography (HPLC) were as detailed by Markovic et al (1993).…”

“…Forest tent caterpillar herbivory was altered on leaf disks from green ash trees elicited with either of the two dosages of c_-tocopherol as compared to disks from solvent-treated ash trees (Table 1). High performance thin layer chromatography (HPTLC) revealed distinct differences in both the non-hydrolyzed and hydrolyzed portions of the ethyl acetate extractables from elicited versus control ash trees (Markovic et al 1993). Reduced insect preference for foliage due to tocopherol elicitation was accompanied by an increased mean total HPLC-resolved peak area of ethyl acetate extractables from the nonhydrolyzed leaf sample as compared to control foliage.…”