As sessile organisms, plants must adapt to variations in the environment. Environmental stress triggers various responses, including growth inhibition, mediated by the plant hormone abscisic acid (ABA). The mechanisms that integrate stress responses with growth are poorly understood. Here, we discovered that the Target of Rapamycin (TOR) kinase phosphorylates PYL ABA receptors at a conserved serine residue to prevent activation of the stress response in unstressed plants. This phosphorylation disrupts PYL association with ABA and with PP2C phosphatase effectors, leading to inactivation of SnRK2 kinases. Under stress, ABA-activated SnRK2s phosphorylate Raptor, a component of the TOR complex, triggering TOR complex dissociation and inhibition. Thus, TOR signaling represses ABA signaling and stress responses in unstressed conditions, whereas ABA signaling represses TOR signaling and growth during times of stress. Plants utilize this conserved phospho-regulatory feedback mechanism to optimize the balance of growth and stress responses.

Surface plasmonic with its unique confinement of light is expected to be a cornerstone for future compact radiation sources and integrated photonics devices. The energy transfer between light and matter is a defining aspect that underlies recent studies on optical surface-wave-mediated spontaneous emissions. But coherent stimulated emission, being omnipresent in every laser system, remains to be realized and revealed in the optical near fields unambiguously and dynamically. Here, we present the coherent amplification of Terahertz surface plasmon polaritons via free electron stimulated emission. We demonstrate the evolutionary amplification process with a frequency redshift and lasts over 1-mm interaction length. The complementary theoretical analysis predicts a 100-order surface wave growth when a properly phase-matched electron bunch is used, which lays the ground for a stimulated surface wave light source and may facilitate capable means for matter manipulation, especially in the Terahertz band.

The miscellaneous applications of terahertz have called for an urgent demand of a super intense terahertz source. Here, we demonstrate the capability of femtosecond laser-driven wires as an efficient ultra-intense terahertz source using 700 mJ laser pulses. When focused onto a wire target, coherent THz generation took place in the miniaturized gyrotron-like undulator where emitted electrons move in the radial electric field spontaneously created on wire surface. The single-cycle terahertz pulse generated from the target is measured to be radially polarized with a pulse energy of a few milijoule. By further applying this scheme to a wire-tip target, we show the near field of the 500 nm radius apex could reach up to 90 GV/m. This efficient THz energy generation and intense THz electric field mark a substantial improvement toward ultra-intense terahertz sources.

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