Document Type : Full Paper

Authors

• Meysa Raoof ¹
• Vahideh Nazeri ²
• Leila Tabrizi Raeini ³
• Majid Shokrpour ³

¹ Department of Horticultural Science and Landscape Architecture, Faculty of Agriculture, College of Agriculture and Natural Resources, University of Tehran, Karaj.Iran.

² , Department of Horticultural Science and Landscape Architecture, Faculty of Agriculture, College of Agriculture and Natural Resources, University of Tehran, Karaj. Iran

³ Department of Horticultural Science and Landscape Architecture, Faculty of Agriculture, College of Agriculture and Natural Resources, University of Tehran, Karaj. Iran.

Abstract

Keywords

• Ecotype
• Essential oil
• GC-Mass
• Medicinal plants
• Pulegone

Main Subjects

• Medicinal plant science

Extended Abstract

Introduction

Ziziphora clinopodioides known as Kakootie-koohi is one of the important medicinal plants in treatment of cardiac disorders, high blood pressure, and respiratory disease in traditional medicine of Iran. It has a wide distribution throughout Iran particularly in mountainous area, rocky slops and deposits of steppe regions of Hyrcanian and Irano- Touranian regions. Kakootie-koohi shows obvious morph-physiological variation in different natural habitats. The most abundant components of its essential oil are pulegone, isomentol, cineole and piperiton. Drought stress has adverse effects on plants growth and development and consequently upon the amounts of yields and quality of agricultural crops. In water shortage condition, leaf wilting take place following reduction in leaf water content, increasing evaporation and decreasing water absorption by root system. Disruption in the electron transport chain produces reactive oxygen species, leading to oxidative damage in proteins, nucleic acids, and membrane lipids. This ultimately causes instability in cell membranes. Meanwhile, by reduction in synthesis of riboluse biphosphate and rubisco activity, photosynthetic capacity is decreased and plants growth and development are limited. This study evaluates the impact of water stress and ecotypes on morpho-physiological traits. The enhanced production of essential oil yield during water stress also will be discussed.

Material and Methods

Seeds of five different ecotypes of Kakootie-koohi collected from their natural habitats were sown in trays containing cocopite and perlit (75:25) and kept in the greenhouse. After acclimation of seedlings having 5-6 leaves to outdoor environment, they were transferred to the field. The field was located in the research center of horticultural department of the  University of Tehran in Karj, Iran. Plots were drop irrigated to 90-100% plant water availability until complete establishment of plants, and then irrigation was withheld from selected plots at two developmental stages of vegetative and flowering stage. The experiment was performed as a split plot in a randomized complete block design with three replications. Different levels of irrigation were assigned to first factor including irrigation at 90-100% available water, stop irrigation at vegetative stage (two months after planting in the field) and stop irrigation at the beginning of flowering stage, and different ecotypes assigned to second factor named as Galoogah, Taleghan, Kaboodarahang, Shazand and Velian. At the 50% flowering stage, the plants were harvested and the responses of plants subjected to water stress was evaluated by measuring growth and phytochemical traits. The constituts of essential oils were also detected and measured by GC/ GC- Mass apparatus.

Results and discussion

Water stress affected a few morphological and biochemical traits, showing potential of Ziziphora clinopodioides to resist to drought stress. Stop irrigation at both vegetative and flowering stages decreased leaf dry weight. Leat area was declined when irrigation was stoped at vegetative stage. The amount of chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, ion leakage and relative water content were not affected by water shortage but the amount of total phenol increased under this condition. Water stress at both stages significantly increased the percentage of essential oil.

Comparing ecotypes showed that the shortest plants belonged to Galoogah ecotype and no significant difference was observed among other ecotypes. Kaboodarahang, Shazand and Velian showed the highest values for leaf length, while Galoogah had the lowest value. The largest leaves were observed in Velian, Taleghan and Shazand ecotypes. Interaction effect of ecotype and water stress on plant dry weight was significant. While, the highest amount of plant dry weighet was obtained in ecotypes of Kabodarahang, followed by Galoogah, both at normal condition, no significant difference was observed in plant dry weight under water stress conditions.

It has been shown that decrease in leaf area in plants subjected to water stress may occur as a result of decline in turgor pressure, inhibition of cell division and cell enlargement. Additionally, plant dry weight usually reduces because of stomatal closure which limits Co2 uptake and hence photosynthetic activity.

Phenolic compounds were also increased in plants under the water deficit condition. These compounds have fundamental role in plants resistance to water stress by regulating physiological activities. In the current research, the amount of electrolyte leakage in plants subjected to water stress did not show significant difference with untreated plants, indicating the high resistance of the cell membrane of Kakootie-koohi against the water stress. Inducing water stress at both vegetative and flowering stages caused a significant increase in percentage of essential oil. The GC-MS analysis of essential oil identified 23 compounds with pulegone as a major component. The highest amount of pulegone, 39.9%, obtained in plants of Taleghan ecotype exposed to drought stress at vegetative stages. Ecotype Kabodarahang was the only ecotype with high percentage of 1,8- cineol, a cyclic monoterpene compound that is renowned for its antioxidant properties.

Conclusion

Considering that many studied traits were not affected negatively by water shortage, while phenol content and essential oil percentage were increased, it is possible to achieve the highest amount of essential oil and pulegone in area exposed to water shortage by stopping irrigation either at vegetative or flowering stage in Taleghan and Galoogah ecotypes.

Author Contributions

1. Nazeri, M. Shokrpour and L. Tabrizi conceived and planned the experiments. M. Raoof carried out the experiments. M. Shokrpour and M. Raoof analyzed data. M. Raoof and V. Nazeri wrote the first manuscript. V. Nazeri, M. Shokrpour and L. Tabrizi contributed to the interpretation of the results. All authors provided critical feedback and helped shape the research, analysis and manuscript.

Data Availability Statement

Data available on request from the authors.

Acknowledgements

The authors would like to thank the research council of the University of Tehran, Iran for the financial support of this research.

Ethical considerations

The authors avoided data fabrication, falsification, plagiarism, and misconduct.

Conflict of interest

     The author declares no conflict of interest.