Chitosan and salty irrigation water affect morphological and physiological characteristics of rosemary herb

Abstract

There are numerous uses for rosemary essential oil (Rosmarinus officinalis), including aromatherapy, antioxidant activity, antimicrobial and antitumour properties. High salinity of irrigation water is one of the main barriers inhibiting the growth of rosemary cultivation in Egypt's new reclamation zones. Chitosan is a natural biopolymer which is obtained from the deacetylation of chitin and has a high potential to improve plant productivity under stressful conditions. So, this study aimed to minimize the negative effects of salty irrigation water on rosemary plants by assisting them in adjusting to salt stress through foliar application of chitosan to determine the potential for increasing their cultivation in the new reclamation zones as a natural supply of essential oil. Rosemary plants were subjected to different doses of salty irrigation water (0, 25.7, 51.3, 77.0, 102.6 mM) without or with chitosan (6 mg L-1). Plants irrigated by salty water with spraying chitosan resulted in higher values of plant aerial parts, photosynthetic pigments, carbohydrates, protein, phenols, flavonoids, antioxidant enzymes (peroxidase and superoxide dismutase), essential oil, nitrogen, phosphorous and potassium than those irrigated by salty water without chitosan. In contrast, lower amounts were found in free radical scavenging, sodium and chloride of plant treated with salty water x chitosan than those treated with saline water only. Saline water, chitosan, and their interactions caused a number of changes in detected amino acids and essential oil components. It may be summarized that productivity of rosemary plants can be improved with adapting them under saline irrigation conditions by adding chitosan. This trial benefits the producers of rosemary to alleviate the hurtful effects of saline water in reclaimed regions with adding chitosan.