**1. Introduction**

Rapidly increasing population in the world, limitless industrialization process, poor urbaniza‐ tion activities, regional wars, pesticides which are used to increase crops, and unconscious use of fertilization and chemicals such as detergents have started to contaminate the environ‐ ment, which results in damage for living beings as a result of extensive air, water, and soil pollutions. The use of fossil fuels has been on the increase since the industrial revolution. With the addition ofrapid deforestation,these factors have yielded a serious situation nearly beyond prevention [1, 2].Throughout history,the amount of CO2 concentration in the airdidnot exceed 320 ppm. However, current concentration is above 385 ppm and it keeps on increasing [3]. This situation has led to a concern and long debates in relation to the effects of global warming [1].

It is inevitable that climate change manifests its effects all around the world due to global warming. The increase in temperature and changing precipitation are expected to increase water problems, which are already felt in certain regions. It is estimated that there will be changes in the frequency and severity of droughts and floods, which may lead to serious loss of lives and properties throughout Europe [4].

Drought is a phenomenon resulting from certain variables such as precipitation, temperature, humidity, evaporation, and transpiration. Basically, drought refers to water deficit resulting from below‐average emergence of natural water assets, which are used by various systems, in some regions for a particular time period [5]. When drought is mentioned, precipitation and water deficit come to one's mind first. It can be defined as having higher levels of water loss due to evaporation than the water supplied by precipitation in a certain region [6].

Twenty‐eight percentage of usable territories on the world are affected by drought [5]. Due to greenhouse gas accumulation in the atmosphere, a climate change will take place in the upcoming years, which is likely to leave us with arid and sub‐arid territories. These, in turn, will add to the water problems in urban areas, and there will be an increase in the demand for water for both agricultural and drinking purposes. Hence, in addition to the expansion of arid and sub‐arid territories, there will be an increase in summer drought period and severity accompanied by desertification, salinization, and erosion processes [7]. Undoubtedly, one of the most vulnerable territories to drought is green and outdoor spaces in cities.

The drought increasing day by day and the thirstiness as a result of this make their destructive effects felt in green fields as it is in all parts of our lives. Almost all of the green fields constituted with the approach of classical landscaping design, which requires great amounts of water especially in our metropolitan cities, were damaged greatly in a few months in which water usage was restricted [8–11].

While the purpose was healing the environment‐ambience quality in the applications of landscaping architecture and repairing the damaged environment conditions in previous years, the wise usage of water for the worries depending on the climate change and herbal applications resistant to drought have come to the fore recently [12–16]. The plants used in landscaping fields are desired to be resistant to drought, and this becomes the most important criterion, which affects the choice of plants in some regions even [17–21]. It is of great impor‐ tance for the wise usage of water that species and origins resistant to drought are identified first and these kinds of species and origins is used for the landscaping designs.

Different methods are used for identifying the resistances of species against drought. One of these methods is to conduct PEG applications on the seeds in different concentrations. PEG applications have been used in many species for identifying their resistance to drought, and it has given very successful results [22, 23].

In this study, it was aimed at identifying the water stress tolerance for some plants, which are used in landscaping works. Trials have been conducted on nine species chosen for this purpose, and the water stress reactions of the species in different levels were determined.
