Plants receive volatile compounds emitted by neighboring plants that are infested by herbivores, and consequently the receiver plants begin to defend against forthcoming herbivory. However, to date, how plants receive volatiles and, consequently, how they fortify their defenses, is largely unknown. In this study, we found that undamaged tomato plants exposed to volatiles emitted by conspecifics infested with common cutworms (exposed plants) became more defensive against the larvae than those exposed to volatiles from uninfested conspecifics (control plants) in a constant airflow system under laboratory conditions. Comprehensive metabolite analyses showed that only the amount of (Z)-3-hexenylvicianoside (HexVic) was higher in exposed than control plants. This compound negatively affected the performance of common cutworms when added to an artificial diet. The aglycon of HexVic, (Z)-3-hexenol, was obtained from neighboring infested plants via the air. The amount of jasmonates (JAs) was not higher in exposed plants, and HexVic biosynthesis was independent of JA signaling. The use of (Z)-3-hexenol from neighboring damaged conspecifics for HexVic biosynthesis in exposed plants was also observed in an experimental field, indicating that (Z)-3-hexenol intake occurred even under fluctuating environmental conditions. Specific use of airborne (Z)-3-hexenol to form HexVic in undamaged tomato plants reveals a previously unidentified mechanism of plant defense.plant-plant signaling | herbivore-infested plant volatiles | green leaf volatiles | defense induction | glycosylation I n response to herbivory, plants emit specific blends of volatiles (1). When undamaged plants are exposed to volatiles from neighboring herbivore-infested plants, they begin to defend against the impending infestation of herbivores (2, 3). This socalled "plant-plant signaling" has been reported in several plant species (4). For example, a study on the expression profiles of defense-related genes when Arabidopsis was exposed to several volatiles, including green leaf volatiles and a monoterpene, showed that the manner of induction varied with the gene monitored or the volatile used, suggesting that the plant responses were specific to the individual volatile compound (5). Kost and Heil (6) reported that the secretion of extrafloral nectar (an alternative food for carnivores) in undamaged lima bean plants was enhanced by volatiles from infested conspecific plants; this reaction was specific to (Z)-3-hexenyl acetate. Recently, Kikuta et al. (7) showed that wound-induced volatile organic compounds from Chrysanthemum cinerariaefolium induced the biosynthesis of pyrethrins in volatile-exposed neighboring plants. In this plant-plant signaling system, a blend of five compounds at specific concentrations was essential for the pyrethrin biosynthesis in receiver plants.These previous studies on plant-plant signaling raise questions about how different airborne volatiles are received by undamaged neighboring plants. Tamogami et al. (8) reported that airborne (E)...

A large portion of the volatile organic compounds emitted by plants are oxygenated to yield reactive carbonyl species, which have a big impact on atmospheric chemistry. Deposition to vegetation driven by the absorption of reactive carbonyl species into plants plays a major role in cleansing the atmosphere, but the mechanisms supporting this absorption have been little examined.Here, we performed model experiments using methacrolein (MACR), one of the major reactive carbonyl species formed from isoprene, and tomato (Solanum lycopersicum) plants. Tomato shoots enclosed in a jar with MACR vapor efficiently absorbed MACR. The absorption efficiency was much higher than expected from the gas/liquid partition coefficient of MACR, indicating that MACR was likely metabolized in leaf tissues. Isobutyraldehyde, isobutyl alcohol, and methallyl alcohol (MAA) were detected in the headspace and inside tomato tissues treated with MACR vapor, suggesting that MACR was enzymatically reduced. Glutathione (GSH) conjugates of MACR (MACR-GSH) and MAA (MAA-GSH) were also detected. MACR-GSH was essentially formed through spontaneous conjugation between endogenous GSH and exogenous MACR, and reduction of MACR-GSH to MAA-GSH was likely catalyzed by an NADPH-dependent enzyme in tomato leaves. Glutathionylation was the metabolic pathway most responsible for the absorption of MACR, but when the amount of MACR exceeded the available GSH, MACR that accumulated reduced photosynthetic capacity. In an experiment simulating the natural environment using gas flow, MACR-GSH and MAA-GSH accumulation accounted for 30% to 40% of the MACR supplied. These results suggest that MACR metabolism, especially spontaneous glutathionylation, is an essential factor supporting MACR absorption from the atmosphere by tomato plants.

RESUMO A busca por medidas alternativas no controle de fitonematoides vem sendo estimulada, e a aplicação de extratos vegetais pode tornar-se uma medida viável para pequenas aéreas. Avaliou-se o efeito da adição ao solo de extratos aquosos de oito espécies vegetais sobre a multiplicação de Rotylenchulus reniformis. O experimento foi conduzido em condições de casa de vegetação com temperaturas máxima e mínima de 34,2º C e 25,6º C, respectivamente. Plantas de algodoeiro foram inoculadas com 4.000 ovos do nematoide e, em seguida, adicionou-se 20 mL dos extratos aquosos obtidos de folhas de Crotalaria spectabilis. Arctium lappa. Plectranthus barbatus. Rosmarinus officinalis. Origanum vulgare. Cajanus cajan. Mucuna aterrima e Momordica charantia. O inoculo foi obtido de populações puras, multiplicadas em plantas de algodoeiro, mantidas em casa de vegetação. Após 60 dias, avaliou-se o número de ovos, altura das plantas, diâmetro do caule e peso fresco da parte aérea e das raízes. Os extratos de C. cajan, O. vulgare, M. aterrima e M. charantia reduziram o número de ovos em 28, 28, 44 e 60%, respectivamente. Para o diâmetro do caule os extratos de M. aterrima e C. cajan diferiram da testemunha e demais tratamentos. Com relação ao peso da parte aérea, os extratos de C. cajan. P. barbatus. M. aterrima e C. spectabilis diferiram da testemunha e demais tratamentos. Portanto, os extratos de Mucuna aterrima. C. cajan. O. vulgare e M. charantia podem ser uma opção para o controle de R. reniformis.