**3. Findings**


**Table 1** shows the end‐of‐study values regarding the change in the germination percentages of species under water stress conditions.

**Table 1.** The change of germination percentages under various water stress conditions.

Considering the values in **Table 1**, the highest germination was observed in *Pinus nigra* with a rate of 81.9% in the control group. It was followed by *Pinus sylvestris* with a rate of 72.6% and *Thuja orientalis* with a rate of 70.2%, respectively. *Cupressus sempervirens* and *Ailanthus altissi‐ ma* yielded germination higher than 60% in the control group. *Cupressus sempervirens'* percentage was 62.6%, while the rate of *Ailanthus altissima* was 60.2%. Germination percentage of *Sophora japonica* was 55.5%, while the rate of *Pyracantha coccinea* was 51.2%. Germination percentages of *Pinus brutia*, *Acer pseudoplatanus*, and *Cedrus libani* remained under 50% in the control groups. *Pinus brutia* yielded a germination percentage of 45.2%, and *Acer pseudoplata‐ nus*' rate was 38.7%. The lowest rate belonged to *Cedrus libani* with 32.3%.

*Pinus nigra*, having the highest germination rate in the control group with a rate of 81.9%, yielded a lower rate, 71%, under -2 Bar water stress level. The rate reduced to 65.5% under -4 Bar, 62.3% under -6 Bar, and 53.1% under -8 Bar. The values in the table show that the highest germination rates belonged to *Pinus nigra* at all experiment levels.

SPSS 17.0 statistics program was used to evaluate the data obtained through experiments. When statistically significant differences (P < 0.05) were found through analyses of variance, Duncan's test was performed to form homogeneous groups. Duncan's test showed that the operations were in the same or different categories in terms of the measured characteristics [26]. Multivariate analysis of variance (ANOVA) employs two or more factors and attempts to reveal significant differences between the mean scores of many groups according to these factors. In other words, multivariate analysis of variance is used to test the difference between the mean scores of k‐dependent groups [27]. In order to interpret study results with more ease,

**Table 1** shows the end‐of‐study values regarding the change in the germination percentages

Considering the values in **Table 1**, the highest germination was observed in *Pinus nigra* with a rate of 81.9% in the control group. It was followed by *Pinus sylvestris* with a rate of 72.6% and *Thuja orientalis* with a rate of 70.2%, respectively. *Cupressus sempervirens* and *Ailanthus altissi‐ ma* yielded germination higher than 60% in the control group. *Cupressus sempervirens'* percentage was 62.6%, while the rate of *Ailanthus altissima* was 60.2%. Germination percentage of *Sophora japonica* was 55.5%, while the rate of *Pyracantha coccinea* was 51.2%. Germination percentages of *Pinus brutia*, *Acer pseudoplatanus*, and *Cedrus libani* remained under 50% in the control groups. *Pinus brutia* yielded a germination percentage of 45.2%, and *Acer pseudoplata‐*

*Pinus brutia* 45,2 40,0 36,3 24,5 21,0 *Pinus nigra* 81,9 71,0 65,5 62,3 53,1 *Cupressus sempervirens* 62,6 54,3 45,8 36,7 19,7 *Ailanthus altissima* 60,2 50,0 12,2 1,2 0,0 *Pyracantha coccinea* 51,2 32,5 26,6 10,2 5,6 *Thuja orientalis* 70,2 65,3 48,0 35,2 15,6 *Pinus sylvestris* 72,6 66,7 41,3 28,6 12,3 *Sophora japonica* 55,5 45,0 30,5 7,1 1,2 *Cedrus libani* 32,3 30,7 18,0 7,2 2,4 *Acer pseudoplatanus* 38,7 28,6 20,2 5,1 0,0

**Control -2 Bar -4 Bar -6 Bar -8 Bar**

Excel program was used to create graphs.

of species under water stress conditions.

**Species Water stress conditions**

**Table 1.** The change of germination percentages under various water stress conditions.

*nus*' rate was 38.7%. The lowest rate belonged to *Cedrus libani* with 32.3%.

**3. Findings**

46 Water Stress in Plants

*Pinus sylvestris* had the highest germination rate following *Pinus nigra* in the control group with a rate of 72.6%. This rate reduced to 66.7% under -2 Bar, 41.3% under -4 Bar, 28.6% under -6 Bar, and 12.3% under -8 Bar. Though *Pinus sylvestris* seeds had the second highest germi‐ nation rate in the control group, it rapidly reduced depending on water stress levels. It had the second highest value under -2 Bar water stress level; however, it ranked the 4th under -4 and -6 Bar water stress levels, while it became the fifth under -8 Bar water stress level. It is possible to say that *Pinus sylvestris* is more vulnerable than other seeds under examination against the increasing water stress conditions.

*Thuja orientalis* seeds had a percentage of 70.2% germination in the control group; however, this rate reduced in parallel with the increasing water stress and became 65.3% under -2 Bar, 48% under -4 Bar, 35.2% under -6 Bar, and 15.6% under -8 Bar.

*Cupressus sempervirens* also experienced a decrease in germination percentage due to increasing water stress. Its germination rate was 62.6% in the control group, but it reduced to 54.3% under -2 Bar, 45.8% under -4 Bar, 36.7% under -6 Bar, and 19.7% under -8 Bar, which was the highest water stress level. *Cupressus sempervirens* ranked 4th in terms of germination percentage in the control group, but it became the 3rd under -8 Bar.

*Ailanthus altissima* ranked 5th in the control group in terms of germination percentage. However, *Ailanthus altissima* experienced a rapid fall in germination percentage particularly after -4 Bar water stress level. The germination percentage which was 50% under -2 Bar reduced to 12.2% under -4 Bar and displayed 1.2% of germination percentage under -6 Bar. The seed did not germinate under -8 Bar. Accordingly, *Ailanthus altissima* had the lowest germination percentage under -4 and -6 Bar water stress levels.

*Sophora japonica* showed a germination percentage of 55.5% in the control group. This rate reduced to 45% under -2 Bar, 30.5% under -4 Bar, 7.1% under -6 Bar, and 1.2% under -8 Bar water stress levels.

Another species experiencing a rapid fall in germination percentage due to increasing water stress level was *Pyracantha coccinea*. Its germination percentage in the control group was 51.2%. It first reduced to 32.5% and then to 26.6% due to increasing water stress and reached 10.2% under -6 Bar and 5.6% under -8 Bar.

Though its germination percentage was below 50% in the control group, *Pinus brutia* was one of the species experiencing one of the lowest fall in germination percentage due to increase in water stress. Germination percentage of *Pinus brutia* in the control group was 45.2%, while this rate reduced to 40% under -2 Bar, 36.3% under -4 Bar, and 24.5% under -6 Bar. Having one of the three lowest germination percentages in the control group, *Pinus brutia* had a germination rate of 21% under -8 Bar water stress level, which was the second highest value.

*Acer pseudoplatanus* was one the species with lower than 50% germination percentage in the control group. Its germination percentage rapidly fell due to increasing water stress. While its percentage in the control group was 38.7%, it reduced to 28.6% under -2 Bar, 20.2% under -4 Bar, and 5.1% under -6 Bar. *Acer pseudoplatanus* was one of the two species which did not germinate under -8 Bar water stress level.

*Cedrus libani* had the lowest germination percentage in the control group (32.3%). While its germination percentage was 30.7% under -2 Bar, this value reduced to 18% under -4 Bar, 7.2% under -6 Bar, and 2.4% under -8 Bar. According to these rates, *Cedrus libani* had the lowest germination percentage in the control group; however, its germination percentage under -8 Bar was the 4th lowest germination percentage. The **Figure 1** shows the change in the germi‐ nation percentages observed in the species due to increasing water stress levels.

**Figure 1.** The changes in the germination percentages of the species due to increasing water stress levels.

The purpose of this study was to reveal the changes in the germination percentages of species depending on the water stress and to determine which species are least influenced by increas‐ ing water stress. However, not only the germination percentages of species but also to what extent they experience a fall in germination depending on the increasing water stress are of importance in order to make an evaluation in this matter. As a matter of fact, the germination percentage of a species may be low due to its biology or environmental conditions. For instance, Khera and Singh [28] studied various origins in their studies. They reported that *Dalbergia sissoo*'s germination percentage varies between 93 and 21% in different origins. Therefore, there is a need to reveal to what extent germination percentage reduces depending on increasing water stress, which is expected to provide a sounder evaluation of tolerance towards water stress among species and facilitate making comparison between them. Hence, the species in the control group were accepted to have a germination percentage of 100%. The rates of reduction depending on the increasing water stress, in other words, cumulative percentages (CGP) are given in **Table 2**.


**Table 2.** The change of the germination percentage compared with the control group.

*Acer pseudoplatanus* was one the species with lower than 50% germination percentage in the control group. Its germination percentage rapidly fell due to increasing water stress. While its percentage in the control group was 38.7%, it reduced to 28.6% under -2 Bar, 20.2% under -4 Bar, and 5.1% under -6 Bar. *Acer pseudoplatanus* was one of the two species which did not

*Cedrus libani* had the lowest germination percentage in the control group (32.3%). While its germination percentage was 30.7% under -2 Bar, this value reduced to 18% under -4 Bar, 7.2% under -6 Bar, and 2.4% under -8 Bar. According to these rates, *Cedrus libani* had the lowest germination percentage in the control group; however, its germination percentage under -8 Bar was the 4th lowest germination percentage. The **Figure 1** shows the change in the germi‐

nation percentages observed in the species due to increasing water stress levels.

**Figure 1.** The changes in the germination percentages of the species due to increasing water stress levels.

The purpose of this study was to reveal the changes in the germination percentages of species depending on the water stress and to determine which species are least influenced by increas‐ ing water stress. However, not only the germination percentages of species but also to what extent they experience a fall in germination depending on the increasing water stress are of importance in order to make an evaluation in this matter. As a matter of fact, the germination percentage of a species may be low due to its biology or environmental conditions. For instance, Khera and Singh [28] studied various origins in their studies. They reported that *Dalbergia sissoo*'s germination percentage varies between 93 and 21% in different origins. Therefore, there is a need to reveal to what extent germination percentage reduces depending on increasing water stress, which is expected to provide a sounder evaluation of tolerance towards water stress among species and facilitate making comparison between them. Hence, the species in

germinate under -8 Bar water stress level.

48 Water Stress in Plants

The values in the table show that the germination percentage reduced in all of the species due to increasing water stress. The minimum change took place in *Cedrus libani*, *Thuja orientalis*, and *Pinus sylvestris* under -2 Bar water stress level. Germination percentage under -2 Bar water stress level in *Cedrus libani* corresponded to 95% of the one in the control group, while germination percentage rate corresponded to 93 and 91.9% of the values in the control group for *Thuja orientalis* and *Pinus sylvestris,* respectively, under the same conditions. The changes in the germination percentage under -2 Bar water stress level compared with the control group are as follows: *Pinus brutia* 88.5%, *Cupressus sempervirens* and *Pinus nigra* 86.7%, *Ailanthus altissima* 83.1%, and *Sophora japonica* 81.1%. For these species, germination percentage under -2 Bar water stress level was higher than 80% of the control group. This rate was 73.9% for *Acer pseudoplatanus* and 63.5% for *Pyracantha coccinea*.

However, most of the species experienced great falls in their germination percentages starting from -4 Bar water stress level. The minimum change under -2 Bar water stress level was observed in *Cedrus libani*, *Thuja orientalis*, and *Pinus sylvestris*. Germination percentage of *Cedrus libani* fell to 55.7% of the control group under -4 Bar water stress level. These rates were 68.4 and 56.9% for *Thuja orientalis* and *Pinus sylvestris,* respectively. The species which were least affected by water stress at this level were *Pinus brutia*, *Pinus nigra*, and *Cupressus semper‐ virens*. The changes in the germination percentages of the species under -4 Bar water stress level compared with the control group percentages were 80.3% for *Pinus brutia*, 80% for *Pinus nigra*, and 73.2% for *Cupressus sempervirens*. The species which experienced the highest change under -4 Bar water stress compared with the control group are as follows: *Sophora japonica* with 55%, *Acer pseudoplatanus* with 52.2%, Pyracantha *coccinea* with 52%, and *Ailanthus altissima* with 20.3%.

Not a big difference occurred in these results under -6 Bar water stress level. The species had similar ranks to the ranks under -4 Bar water stress level. Once again, the highest values in the comparison of germination percentages to the control group percentages were observed in *Pinus nigra* (76.1%), *Cupressus sempervirens* (58.6%), *Pinus brutia* (54.2%), and *Thuja orientalis* (50.1%). The rate was below 50% in all of the other species. Under -6 Bar water stress level, the rate was 39.4% for *Pinus sylvestris* and 22.3% for *Cedrus libani,* while other species went below 20%. *Pyracantha coccinea* had a rate of 19.9%; *Acer pseudoplatanus* had a rate of 13.2%; and *Sophora japonica* had a rate of 12.8%. The highest proportional fall under -6 Bar water stress level was observed in *Ailanthus altissima*, and germination percentage could only reach 2% compared with the control group.

Under -8 Bar water stress, which is the highest water stress level, *Ailanthus altissima* and *Acer pseudoplatanus* did not germinate. Under these conditions, the changes in germination percen‐ tages compared with the control group are as follows 2.2% for *Sophora japonica*, 7.4% for *Cedrus libani*, 10.9% for *Pyracantha coccinea*, 16.9% for *Pinus sylvestris*, 22.2% for *Thuja orientalis*, and 31.5% for *Cupressus sempervirens*. Under the highest water stress level, which is -8 Bar, the highest germination percentages were observed in *Pinus nigra* (64.8%) and *Pinus brutia* (46.5%). The graph showing the reduction rates in the germination percentages of species due to increasing water stress is given in **Figure 2**.

**Figure 2.** The reduction rates in the germination percentages of the species due to increasing water stress.
