Chemical composition of rosemary ( Rosmarinus officinalis L . ) leaves under salt stress

Rosmarinus officinalis L. is an important plant due to its chemical constituents, medicinal properties and commercial use. The present study was carried out to determine the change in concentration of chemicals in salt stressed R. officinalis. Plants were treated with 50, 100 and 150mM NaCl to determine the change in moisture content level and concentrations of carbohydrates, alkaloids, flavonoids and phenols. Results revealed that moisture content and carbohydrates decreased with increased salinity. Maximum values of moisture content (60.39%), insoluble carbohydrates (2.25 g) and soluble carbohydrates (24.5 ml), found in control treatment, while the minimum values of moisture content (48%) and 1.47 g and 21 ml for insoluble and soluble carbohydrates respectively were recorded for 150 mM NaCl treatment. Maximum values for alkaloids 0.9 g and flavonoids 0.82 g were recorded for 50 mM NaCl treatment while minimum values, alkaloids 0.76 g and flavonoids 0.32 g were recorded for 150 mM NaCl treatment. Quantitative analysis of phenols expressed that phenols increased with increased salinity i.e for control lowest 3.02% and for 150 mM NaCl highest value 4.24% obtained. It concluded that phenols might release the oxidative stress caused by NaCl applications but their increase is also beneficial because they are natural antioxidants.


Introduction
Salinity is now becoming threatens environmental issue and its adverse effects are more on agriculture [1].As more than 25% of the total area of the terrestrial land is saline also the fresh water supply is becoming a major problem and 97% water is saline, this necessitates investigation into use of saline areas for agricultural cultivation as salinity causes changes in plant growth, resistance to environmental conditions and yield of carbohydrates, protein and fatty acids as well as proline and phenols [2].It was found that salt stressed plants had higher concentrations of phenolic compounds and antioxidants, but lower levels of photosynthetic pigments [3]

Sample preparation
For the determination of moisture content fresh leaves were taken.For all other quantitative tests air dried leaves (grounded to a fine powder using an electrical grinder) were used.

Statistical analysis
Statistical analysis was carried out to find whether the different treatments (salt stress levels) have significant (different) or nonsignificant effects on the concentration of investigated chemicals.For this purpose standard error bars were added to the graphs after calculating the standard error of the means for each quantitatively analyzed chemical.The bars are also helpful in finding that how much uncertainty there is in the data [10].

Results
Highest moisture content 60.39%, was noted in control treatment followed by the 50 mM NaCl treatment (57.64%).The lower moisture content 48% was found in 150 mM NaCl treatment (Figure -1).Highest carbohydrates amount of insoluble sugars (polysaccharides) 2.25 g and soluble sugars (monosaccharides and disaccharides) 24.5 ml were determined from controlled plot (Figure-2 & 3).Maximum amount of alkaloids was 0.9 g calculated for the 50 mM NaCl plot.The results showed that alkaloids increased at 50 mM NaCl salinity, they also increased up to some extent at 100 mM NaCl treatment, but when salinity increased up to 150 mM NaCl, the alkaloids amount became lower than that of control one (Figure -4).The result for flavonoids was same as that for alkaloids.The For almost all the treatments in all investigated chemicals, the obtained bars were of short length, indicated that the means were not so dispersed rather they were concentrated over the small area.The study indicated that that rosemary can tolerate moderate applications of salinity.The increasing salinity caused increase in oxidative stress, and it may be a mechanism for protecting plants from salt stress rather than causing damage to plants.

Conclusion
Rosemary presents efficient mechanism for tolerating salinity.The moisture content and carbohydrates were decreased with the increased salinity.The alkaloids and flavonoids were highest at 50 mM NaCl salinity but decreased at higher salinity.On the other hand phenols increased when salinity levels were raised.This increase of phenol may be due to release the oxidative stress caused by the applied salinity, because the phenols of rosemary have good antioxidant role.The findings suggested that rosemary can be cultivated under specific salinity for production of phenols (antioxidants), alkaloids and flavonoids.
50 mM NaCl treated plants were have highest amount 0.82 g, while 150 mM NaCl treated rosemary plants have lowest amount 0.32 g of flavonoids (Figure-5).Increased salinity caused increase in phenol concentration, highest phenol 4.24% found in 150 mM NaCl while the lowest phenol 3.02% was found in Control (Figure-6).Overlap standard error bars demonstrate that the two treatments on average do not cause different effects while the non-overlap bars revealed that two treatments have different effects.Error bars of moisture content indicated that 150 mM NaCl salinity treatment have entirely different effect (Figure-1).In case of polysaccharides two treatments (50 and 100 mM NaCl) denoted non-significant results while control and 150 mM NaCl treatments showed significant effects.All the treatments produced significant effects in case of mono and disaccharides (Figure-2 & 3).For alkaloids highest salinity treatment (150 mM NaCl) expressed significant results (Figure-4).Significant results were obtained for flavonoids at 50 mM NaCl treatment (figure-5).In case of phenols all salinity treatments (50, 100 and 150 mM NaCl) produced significant effects as compared to control (Figure-6).Lengths of error bars show the concentration of means over the area.