**Preface to "Regulation of Central Carbon and Amino Acid Metabolism in Plants"**

Over the past few decades, a considerable amount of effort has been dedicated to understanding plant primary metabolism. While the biochemistry and the underlying genetics of central carbon and nitrogen metabolism have been thoroughly studied, there is still a lack of knowledge on how these metabolic branches are regulated, in addition to how they regulate and interact with each other. Improving our current understanding of such regulatory loops is of particular interest given that all oxygenic phototrophs are frequently exposed to environmental changes, including periods of unfavorable conditions that distinctly lower plant growth and yield. Understanding how adjustments of metabolism towards a fluctuating environment are achieved in both shortand long-term timescales will also facilitate genetic engineering approaches. One major goal of such attempts is to produce more robust plant varieties that are able to sustain high photosynthetic efficiencies and yields during persistent phases of abiotic stresses.

This Special Issue of plants aims to highlight the metabolic acclimation and signaling mechanisms of plant central carbon and nitrogen metabolism towards environmental changes, particularly involving alterations in CO<sup>2</sup> and O<sup>2</sup> concentrations, light availability and intensity, as well as fluctuations in temperature and water supply during different stages of plant development. Thus, the major focus will be on the acclimation and the regulatory interplay that—among others—involve the operation and interaction of photosynthesis, photorespiration and respiration.

> **Stefan Timm, St ´ephanie Arrivault** *Editors*
