*Review* **Response Mechanism of Plants to Drought Stress**

**Xinyi Yang, Meiqi Lu, Yufei Wang, Yiran Wang, Zhijie Liu and Su Chen \***

State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry University, Harbin 150040, China; yangxinyi@nefu.edu.cn (X.Y.); lumeiqi0408@163.com (M.L.); wangyufei@nefu.edu.cn (Y.W.); wangyiran@nefu.edu.cn (Y.W.); hjdyyy69@163.com (Z.L.)

**\*** Correspondence: chensu@nefu.edu.cn

**Abstract:** With the global climate anomalies and the destruction of ecological balance, the water shortage has become a serious ecological problem facing all mankind, and drought has become a key factor restricting the development of agricultural production. Therefore, it is essential to study the drought tolerance of crops. Based on previous studies, we reviewed the effects of drought stress on plant morphology and physiology, including the changes of external morphology and internal structure of root, stem, and leaf, the effects of drought stress on osmotic regulation substances, drought-induced proteins, and active oxygen metabolism of plants. In this paper, the main drought stress signals and signal transduction pathways in plants are described, and the functional genes and regulatory genes related to drought stress are listed, respectively. We summarize the above aspects to provide valuable background knowledge and theoretical basis for future agriculture, forestry breeding, and cultivation.

**Keywords:** drought stress; osmotic regulation; LEA protein; ROS; signaling; drought-responsive gene

**Citation:** Yang, X.; Lu, M.; Wang, Y.; Wang, Y.; Liu, Z.; Chen, S. Response Mechanism of Plants to Drought Stress. *Horticulturae* **2021**, *7*, 50. https://doi.org/10.3390/ horticulturae7030050

Academic Editors: Stefania Toscano, Giulia Franzoni and Sara Álvarez

Received: 20 February 2021 Accepted: 11 March 2021 Published: 13 March 2021

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