Maryam Sisakht Nejad , Roghayeh Zolfaghari ,
Volume 1, Issue 2 (3-2015)
Abstract
Drought is the major environmental stresses that it can have a negative impact on plant growth. The study of gas exchange under drought stress can help to identify factors affecting stress resistant. Due to this fact that Zagros forests has Mediterranean and dry climate, with the aim of this study was to assess the impact of drought on leaf gas exchange in two oak species (Quercus brantii and Quercus libani). Water stress consisted of four levels of water stress (100%, 70%, 50% and 30% FC) in the greenhouse situations. Those seedlings were intended for water stress weren’t irrigated to reach to the desired field capacity (70%, 50% and 30% of field capacity), but control seedlings were irrigated every day in order to soil water content at field capacity shall be kept 100%. Results showed that water stress treatment has a significant reduction of stomatal conductance, photosynthesis, conduct mesophilic, carbon dioxide emission, and transpiration. Also Quercus libani showed higher level of photosynthesis, water use efficiency and transpiration than Quercus branti. Overall, results in both species, showed stomatal and non-stomatal limitation would cause of photosynthesis reduction. Also, due to higher water efficiency and lower gas parameter variations, Quercus libani would gain better mechanism of waster stress and Quercus brantii would gain the use drought avoidance mechanism.
Leila Ranjbar, Payam Fayyaz, Ebrahim Adhami, Hamidreza Owliaie, Roghayeh Zolfaghari,
Volume 4, Issue 1 (12-2024)
Abstract
Background and objectives. By accelerating of the intensity and duration of the drought periods in the Zagros forests, the revival of native tree species, including the brant’s oak (Persian oak), is diminished. Despite the knowledge of the importance of phosphorus in increasing drought resistance in different species, there is little information about the role of this element in brant’s oak seedlings in facing drought.
Materials and methods: For this purpose, the main and interactive effects of two factors of soil phosphorus (at five levels of zero, 25, 50, 75 and 100 mg/kg) and soil moisture regime (at three levels of 60, 30 and 10 percent of field capacity) on performance traits of one-year-old brant’s oak seedlings, with six replications, have been examined. The studied traits include morphological traits (root and stem length, number and area of leaves, fresh weight of roots, stems and leaves), physiological traits (relative water content and electrolyte leakage rate in different organs of leaves, stems and roots, and optimum and maximum yield of photosystem II, and chlorophyll index) and nutrition uptake (concentration of potassium and phosphorus elements in leaves).
Results: The results revealed that with the decrease in soil water content, the traits of leaf number, root and leaf fresh weight, relative water content, photosystem II performance, leaf chlorophyll index and leaf potassium and phosphorus content decreased and root length and electrolyte leakage rate increased. The increase of soil phosphorus in the high irrigated seedlings (60 percent of field capacity) caused the development of aerial organs and leaf surface, and in the seedlings that were in water deficit conditions, it caused the maximum performance of photosystem II to be maintained. Increasing soil phosphorus in all water conditions increased phosphorus, potassium and chlorophyll index, in the leaves of brant’s oak, but it had no effect on reducing membrane damage caused by oxidative stress.
Conclusion: In general, application of phosphorus increased the resistance of brant’s oak seedlings to drought stress by improving nutritional status and protecting the photosynthetic apparatus. Implementing higher concentrations of phosphorus is suggested for future research in order to study the possibility of improving water relations and protecting against plasma membrane injury.
