Stomata: Gatekeepers of Uptake and Defense Priming by Green Leaf Volatiles in plants
Plants adapt to balance growth-defense tradeoffs in response to both biotic and abiotic stresses. Green leaf volatiles (GLVs) are released after biotic and abiotic stresses and function as damage-associated signals in plants. Although, GLVs enter plants primarily through stomata, the role of stomatal regulation on the kinetics of GLVs uptake remain largely unknown. Here, we illustrate the effect of stomatal closure on the timing and magnitude of GLVs uptake. We closed stomata by either exposing plants to darkness or applying abscisic acid, a phytohormone that closes the stomata in light. Then, we exposed maize seedlings to Z-3-hexen-1-ol and compared the dynamic uptake of Z-3-hexen-1-ol under different stomatal conditions. Additionally, we used E-3-hexen-1-ol, an isomer of Z-3-hexen-1-ol not made by maize, to exclude the role of internal GLVs in our assays. We demonstrate closed stomata effectively prevent GLVs entry into exposed plants, even at high concentrations. Furthermore, our findings indicate that reduced GLV uptake impairs GLVs-driven induction of sesquiterpenes biosynthesis, a group of GLV-inducible secondary metabolites, with or without herbivory. These results elucidate how stomata regulate the perception of GLV signals, thereby dramatically changing the plant responses to herbivory, particularly under water stress or dark conditions. We elucidate the role of stomata, small pores on plants leaf surface, in regulating the entry of green leaf volatiles, damage-associated signals, into plants, and thus influencing their signaling functions.