The highly conserved core circadian clock component TIMING OF CAB EXPRESSION1 (TOC1) contextualizes environmental stress responses in plants, for example by gating abscisic acid signaling and suppressing thermoresponsive growth. Selective interaction of TOC1 with PHYTOCHROME B under far-red–enriched light suggests a connection between circadian gating of light responses and sensitivity to ABA, an important regulator of growth and stress responses, including under drought. However, the fitness consequences of TOC1 function, particularly in the root, are poorly understood. Here, we used the desert annual, Nicotiana attenuata, to investigate the function of TOC1 in shoots and roots for maintaining fitness under drought, in both field and glasshouse experiments. Despite marked decreases in leaf water loss, TOC1-deficient lines failed to maintain fitness in response to drought stress as measured by total seed capsule production. Restoring TOC1 transcript levels in shoots via micrografting was sufficient to restore wild-type drought responses under field conditions. Microarrays identified a coexpression module in leaves strongly linking red and far-red light signaling to drought responses in a TOC1-dependent manner, but experiments with phytochrome-deficient lines revealed that the effects of TOC1 deficiency under drought cannot be attributed to changes in red/far-red light perception alone. Taken together, these results elucidate the sophisticated, tissue-dependent role of the circadian clock in maintaining fitness in the face of long-term abiotic stresses such as drought.

The essential oils obtained by steam distillation of leaves of Piper species have found several applications in bioeconomy due to their various biological properties. Nevertheless, the analysis of essential oils does not provide information regarding the ecologically relevant volatile organic compounds (VOCs) emitted by metabolically active leaves under real-world conditions, challenged or not by herbivore damage. In this study, P. arboreum growing in a highly diverse area was observed as the host of two generalist caterpillars—Gonodonta maria (Erebidae) and Dysodia spissicornis (Thyrididae)—and one Piper-specialist from the genus Eois (Geometridae). The effect of the leaf attack caused by the three different caterpillars on VOCs emission indicated significant and herbivore-specific changes in leaf-induced responses. The profiles of undamaged leaves showed that the two generalist herbivores induced a higher number of single VOCs and of total VOCs emissions by P. arboreum when compared to the herbivory of the specialist caterpillar. Many of the VOCs emitted by herbivore-damaged leaves contained terpenoids that have been previously shown to attract parasitoids, such as (E)-β-ocimene, linalool, DMNT and (E)-β-caryophyllene. All three herbivores significantly altered the VOC profile of P. arboreum leaves compared to undamaged controls, but specific composition signatures were observed, highlighting the complexity of chemical communication at multitrophic levels.