Evaluation of some physiological characteristics of Thymus fedtschenko under different levels of water stress

IntroductionWater is the most basic ecological factors in arid and semiarid environments which determine the rate of plant growth and development. Therefore, the effective use of water resources for optimum growth should always be considered. Abiotic environmental stresses such as drought stress are the most important problems in these areas that have a negative impact on growth and development of the plants. Water stress, permanently or temporarily, is the most limitative environmental factors in the development and distribution of natural vegetation. Drought stress occurs in plants when the received water is less than the casualties. Given the importance of medicinal plants, especially in the pharmaceutical industry, and deficiencies in various aspects of agricultural nature of this plant is very important. Given the importance of medicinal plants, especially in the pharmaceutical industry and their rarity in the nature, investigating on various aspects of these types of plants is recommended. Diversity and abundance of the plants in different parts of the earth, more than any other environmental factor, depends on the amount of water available to the plants. Drought stress is the most important abiotic plays an important role in reducing the production of the plants’ crops in the world.
Materials and methodsIn order to determine the evaluate the effects ofdifferent levels of drought stress on some physiological characteristics of Thymus fedtschenkoi a complete randomized block design is carried out in the greenhouse of the University of Yazd in 2014. For seeding cultivation,the pots with a height of 21 cm and the diameter of 20 cm including drains are used. In order to reduce the heat exchange between the soil inside and the outside surface, the pots are isolated perfectly.Using some gravel at the bottom of the pots and placing some dishes under them to egress the extra water was recommended in order to improve drainage. To fill the pots, a mixture of the sandy soil and leaf soil was used.The treatment of drought stress includes 100, 75, 50 and 25% of field capacity (fc)for which the number of four replication are applied.
Results and discussionThe results showed that chlorophyll a and total chlorophyll contents were affected by water deficit at 1% level of probability where chlorophyll b, proline contents and relative water content (RWC) significantly were affected at 5% level of probability. The results also showed that water stress had not a significant effect on soluble sugars content. Drought stress significantly affected the amount of prolines, so that, minimum amount of this factor was observed in 100% Field capacity (FC). Maximum a, b and total chlorophyll contents of Thymus fedtschenko (by 0.48, 0.167 and 0.633 mg/g, respectively) were obtained, at 25% of field capacity whereas the minimum amounts of these factor were obtained at 100% of field capacity. Overall, results indicate that increasing of prolin accumulation as well as chlorophyll contents are primary strategies of Thymus fedtschenkoagainst drought stress. The maximum level of proline is related to the Thymus fedtschenko of 25%, 50% and 75%. However, the minimum quantity is observed in the Thymus fedtschenko of 100%.