Quantitative patterns between plant volatile emissions induced by biotic stresses and the degree of damage

Abstract

Plants have to cope with a plethora of biotic stresses such as herbivory and pathogen attacks throughout their life cycle. The biotic stresses typically trigger rapid emissions of volatile products of lipoxygenase (LOX) pathway (LOX products: various C6 aldehydes, alcohols, and derivatives, also called green leaf volatiles) associated with oxidative burst. Further a variety of defense pathways is activated, leading to induction of synthesis and emission of a complex blend of volatiles, often including methyl salicylate, indole, mono-, homo-, and sesquiterpenes. The airborne volatiles are involved in systemic responses leading to elicitation of emissions from non-damaged plant parts. For several abiotic stresses, it has been demonstrated that volatile emissions are quantitatively related to the stress dose. The biotic impacts under natural conditions vary in severity from mild to severe, but it is unclear whether volatile emissions also scale with the severity of biotic stresses in a dose-dependent manner. Furthermore, biotic impacts are typically recurrent, but it is poorly understood how direct stress-triggered and systemic emission responses are silenced during periods intervening sequential stress events. Here we review the information on induced emissions elicited in response to biotic attacks, and argue that biotic stress severity vs. emission rate relationships should follow principally the same dose–response relationships as previously demonstrated for different abiotic stresses. Analysis of several case studies investigating the elicitation of emissions in response to chewing herbivores, aphids, rust fungi, powdery mildew, and Botrytis, suggests that induced emissions do respond to stress severity in dose-dependent manner. Bi-phasic emission kinetics of several induced volatiles have been demonstrated in these experiments, suggesting that next to immediate stress-triggered emissions, biotic stress elicited emissions typically have a secondary induction response, possibly reflecting a systemic response. The dose–response relationships can also vary in dependence on plant genotype, herbivore feeding behavior, and plant pre-stress physiological status. Overall, the evidence suggests that there are quantitative relationships between the biotic stress severity and induced volatile emissions. These relationships constitute an encouraging platform to develop quantitative plant stress response models.

Effect of pretreatments and modified atmosphere packaging on the shelf life and quality of fresh- cut green bell pepper

“…During the non MA packed storage, sesquiterpenes accumulation was high; indicating the elevated metabolic stress in produce as a result of injury by cutting in aerobic environments. Also oxidative pathway initiated by the lipoxygenase (LOX) enzyme results in aldehydes and alcohols synthesis from C18 polyunsaturated fatty acids in various fruits and vegetables upon tissue disruption (Niinemets et al 2013). The observed changes in the volatiles in the present study also largely support these findings.…”

<sup>13</sup>C labelling study of constitutive and stress-induced terpenoide missions from Norway spruce and Scots pine

“…At the example of S1, the emission 10 fluxes of the individual terpenoids are listed as well. The classification of the constitutive and the stress-induced emissions was based on previous studies (Guenther et al, 2012;Niinemets et al, 2013) and on the comparison of the compounds detected for all individual plants and those found only for the infested ones.…”

“…However, many recent studies have shown that de novo biosynthesis, which 10 is regulated by both temperature and light (Guenther et al, 1993), also contributes to a certain amount of the total emissions from conifers (Shao et al, 2001;Ghirardo et al, 2010;Taipale et al, 2011). Furthermore, biotic stresses such as insect outbreaks, may significantly increase stress-induced emissions, including novel monoterpenes and sesquiterpenes (Blande et al, 2009;Ghimire et al, 2013;Niinemets et al, 2013;Ghimire et al, 2016).…”

Secondary organic aerosol from atmospheric photooxidation of indole

“…Such compounds can also be emitted by vegetation; for example, indole is produced by wide variety of plants (Cardoza et al, 2003;De Boer et al, 2004;Gols et al, 1999;McCall et al, 1993;Turlings et al, 1990;. Indole is emitted in response to physical or herbivore-induced stress (Erb et al, 2015;Frey et al, 2004;Misztal et al, 2015;Niinemets et al, 2013;Schmelz et al, 2003;Turlings et al, 2004) and during flowering events (Gentner et al, 2014). Once emitted, indole performs critical roles in plant ecology, for example in attracting pollinators (Zito et al, 2015).…”