Relative Water Content (RWC %)

Data presented in Table (2) clearly indicate that the RWC of rosemary leaves was gradually increased as the irrigation level or AA increased and this increment was significant among the treatments. The effect of combination between FC and AA was superior than applying each of them alone. The trend of RWC was in the same line of vegetative growth as well as herb yield as affected by different water regimes as AA treatments. Similar findings were reported by Munne-Bosch and Alegre (2000).

3.4. Volatile Oil Content

As shown in Table (2), deficit irrigation improved the volatile oil percentage since it was gradually increased by decreasing the irrigation level. In the second cut the volatile oil percentage was higher than in the first one. An opposite trend was observed for volatile oil yield per plant in both cuts and hence for total oil yield since they increased with increasing the irrigation level. Considering that obtaining oil yield by 100% FC treatment equal 100%, the reduction in total oil yield per plant was 1.73 and 5.78% for the treatment of 80 and 60% FC, respectively.

Table 2: Combined effects of different water regimes and amino acids application on herb yield, relative water content (RWC) and volatile oil content of rosemary plant.

Treatments Total herb yield (g) RWC (%) Volatile oil (%) Volatile oil yield ml/plant

Table 2: Combined effects of different water regimes and amino acids application on herb yield, relative water content (RWC) and volatile oil content of rosemary plant. - continued

60 X AA 2 142.32 30.38 69.33 71.00 1.18 1.20 0.65 1.05

60 X AA 4 154.67 31.47 72.00 73.67 1.21 1.23 0.71 1.18

LSD 5% 6.03 0.52 1.95 1.42 0.16 0.05 0.04 0.06

On the other hand, the volatile oil percentage was gradually increased with increasing the AA level and reached its maximum value by applying AA at 4 ml L^-1 and this increment was significant compared to the control or the other AA levels. The total oil yield followed the same trend of its percentage and the highest oil yield was obtained by using AA at 4 ml L^-1 treatment (Table 2).

Compared to the untreated control, the increment in total oil yield was 14.38, 28.05 and 43.88% for the treatments of AA at 1, 2 and 4 ml L^-1. The volatile oil percentage was significantly affected by the interaction between irrigation and AA levels. The highest percentages were obtained by the treatment of 60% FC and 4 ml L^-1 in both cuts, respectively. However, the maximum oil yield was obtained by the treatment of 100% FC combined with 4 ml L^-1 AA in both cuts. From the previous results it could be concluded that, deficit irrigation increased the volatile oil percentage of rosemary however oil yield was negatively affected. The increase in the essential oil ratio and the decrease in oil yield with the increase in water stress have also been documented (Khalid, 2006; Moeini Alishah et al., 2006).

Antioxidant producer crops like rosemary may increase antioxidant phenolic compound production, and may lead to an economic advantage over regular water irrigation (Bernstein et al., 2009). In addition, plants use these antioxidants to protect themselves against drought damage (Munne-Bosch et al., 2001). It has been suggested that under stress a higher density of oil glands due to the reduction in leaf area results in an elevated amount of volatile oil accumulation (Simon et al., 1992). Increasing volatile oil ratio with water deficit may be also due to the increment in total carbohydrates as our data indicated since volatile oils are formed as secondary metabolites.

3.5. Volatile Oil Composition

The results of GC-MS analysis of rosemary volatile oil show that the main components of volatile oil were α-pinine, camphine, 1,8-cineol, verbinone and borneol (Table 3) and Figs. (1 and 2) and were affected by deficit irrigation. Decreasing the irrigation level enhanced the accumulation of α-pinine, verbinone and borneol components. However, 1,8-cineol and camphine were reduced by deficit irrigation. AA treatments also affected the volatile oil composition since the main components of α-pinine, 1,8-cineol and borneol were increased with increasing AA levels. On the other hand, camphene and verbinone components were decreased by applying AA treatments. To the best of our knowledge this is the first study investigate the chemical composition of rosemary volatile oil as affected by deficit irrigation. Deficit irrigation not only affected volatile oil percentage but also affected its composition as presented in Table (3) and Figs. (1 and 2). These results support the others obtained by Khalid (2006) and Ekren et al., (2012) who revealed that the essential oil content and composition of basil were affected by different water treatments.

Table 3: The main components of rosemary volatile oil as affected by water regimes and amino acids (AA) treatments.

Main components of volatile oil (%)

Treatments α-pinine Camphine 1, 8-cineol Verbinone Borneol

Control 13.32 5.14 18.83 8.75 3.26

FC 80 % 18.33 4.23 16.00 11.36 4.21

FC 60 % 24.37 3.97 17.33 10.15 7.26

AA 1 mlL^-1 18.44 3.98 15.66 10.20 6.16

AA 2 mlL^-1 19.81 4.30 17.10 9.17 7.05

AA 4 mlL^-1 19.23 4.12 17.37 10.18 7.38

Figure 1: The main components of rosemary volatile oil as affected by deficit irrigation treatments. A, B and C are treatments of 100, 80 and 60 % FC, respectively. The components were 1: α-pinine, 2:

camphine, 3: 1, 8-cineol, 4: verbinone and 5: borneol.

A

1

2 3

4 5

A

2 3

5

4 B

1

1

2 3

4

C 5

.

Figure 2: The main components of rosemary volatile oil as affected by amino acids treatments (AA). A, B and C are treatments of AA at 1, 2 and 4 mlL^-1, respectively. The components were 1: α-pinine, 2:

camphine, 3: 1, 8-cineol, 4: verbinone and 5: borneol.

1

2 3

4 5 A

1

2 3

4 5 B

1

2 3

4 5 C

Interestingly, our results show that the camphor component was not detected in the oil composition although different authors observed it (Singh and Guleria, 2013; Yosr et al., 2013). The volatile oil composition of rosemary may vary according to geographical and climatic regions because the oil contains mainly monoterpenes and sesquiterpenes which easily change by environmental conditions and geographic origin (Angioni et al., 2004).

In this experiment, AA treatment enhanced oil yield through the increment in both herb yield and oil percentage. It is very interesting here to indicate that the volatile oil composition was affected by AA treatment as well. This information has not been previously reported on rosemary volatile oil composition as affected by AA. Several authors reported that, AA application improved plant growth and production (Tantawy et al., 2009; Khan et al., 2012). Moreover, AA modulated the growth, yield and biochemical quality of different plants (Abo Sedera et al., 2010; Shehata et al., 2011).