**Author details**

As introduced in this chapter, the use of biostimulants has potential as a powerful countermeasure for improving crop production under conditions of environmental stress. Traditional methods for enhancing yield, such as fertilizer and irrigation support, enable a basal level of production to be maintained (**Figure 4**). However, when crops are subject to unusual abiotic and/or biotic stresses, the transient use of adequate biostimulant(s) helps to overcome these stresses, sustaining production to at least the basal level, and sometimes bringing about an increase in crop production, as explained in **Figure 3**. Some biostimulants are already commercially available, and their use will become increasingly popular. However, there is still a lack of technical information for each biostimulant, such as the application period, concentration, and target plant species; these points must be established if biostimulant application is to become a reliable technique. Moreover, the combined use of biostimulants and traditional pesticides must be examined in order to realize the integrated chemical control of abiotic/biotic stress tolerance. In addition to the chemical biostimulants that are the focus of this chapter, other types of biostimulants that are derived from natural materials, such as microorganisms and algae, are also useful in reducing damage caused by abiotic stress [14, 15]. While the mode of action in chemical biostimulants can be explained scientifically, this is not the case for natural biostimulants. Therefore, more details on scientific analyses of the mechanisms used by biostimulants are necessary to support their avail-

traditional countermeasures and biostimulants are indicated by white and black arrows, respectively.

**Figure 4.** Integrated chemical control of abiotic stress tolerance using biostimulants. Traditional countermeasures, such as irrigation and fertilizers, contribute to improving the basal level of crop production. On the other hand, unusual losses in crop yield caused by biotic and abiotic stress can be mitigated by pesticides and biostimulants, respectively. In this figure, unusual adverse events and biostimulants are boxed and underlined, respectively. The stresses targeted by

A part of unpublished data introduced in this chapter was generously provided by Phyto-

ability for widespread use in the field.

140 Plant, Abiotic Stress and Responses to Climate Change

**Acknowledgements**

chrome Inc. (Tokyo, Japan).

Yasuo Yamauchi Address all correspondence to: yamauchi@kobe-u.ac.jp Graduate School of Agricultural Science, Kobe University, Kobe, Japan
