Vegetative, physiological and genetic responses of two Zagros oak species (Q.brantii and Q.libania) under drought stress. Vegetative responses

Master's thesis in forestry

Vegetative, physiological and genetic responses of two Zagros oak species

(Q. brantii and Q. libania) under drought stress

Abstract

The forests of Zagros occupy about 40% of the total forests of Iran and have the greatest impact on water supply, soil conservation, climate adjustment and economic-social balance in the whole country. Due to the Mediterranean climate, these forests have a long dry season during the vegetation period throughout the year, and the amount of water available in these forests is a primary limiting factor in the regeneration of species in these areas. Non-biological stresses such as drought are important phenomena and affect the health, productivity and fitness of our forests, so it is necessary to understand the genomic and ecophysiological response of forest trees to changing weather conditions. By using morphological, physiological and molecular studies, we can identify different breeding methods that exist for drought resistance. In this experiment, the seeds of the three studied oak species (Q.brantii, Q.libania and Q.infectoria) were planted inside plastic pots in open space (each pot contains 1-2 seeds). Seedlings of Q. infectoria species were not included in this experiment due to not growing. In order to apply the stress, the seedlings were transferred to the greenhouse space and the healthy seedlings of each species were divided into 4 groups of control treatment and water shortage stress at three levels. The seedlings considered for water shortage stress were not irrigated until they reached the desired field capacity (70%, 50% and 30% of the field capacity), but the control seedlings were irrigated every day to keep the soil water content of the pots at about 100% of the field capacity. After harvesting the seedlings, vegetative and morphological parameters (seedling height, root length, weight of leaf, stem and root, total number of leaves, ratio of green leaf to total leaf, biomass, ratio of root to stem, dry weight of leaf, root and stem) and physiological parameters (relative water content of leaf, stem and root (RWC), electrolyte leakage rate (EL), photosystem II performance and gas exchange) were measured and finally RNA extraction was performed from frozen leaf and root samples. took The results of this study showed that drought stress had negative effects on the vegetative, morphological and physiological parameters of oak, so that most of the vegetative and physiological parameters decreased, but the electrolyte leakage rate of the organs increased. Based on the results obtained, the absorption of the drought stress element increased the amount of potassium in the root and stem. Also, the results showed that the amount of tolerance index in the Iranian oak species is higher than the weevil species in all the studied parameters except fresh and dry leaf weight. In this study, the Iranian oak species was able to show better tolerance compared to the weevil species with less sodium absorption in the leaves and as a result, a lower sodium-to-potassium ratio and a reduction in the number of leaves. The parameters related to gas exchanges showed that the water deficit stress treatment caused a significant decrease in stomatal conductance, photosynthesis, mesophilic conductance and carbon dioxide below stomata to the environment and transpiration. Also, weevil species had higher photosynthesis, water consumption and transpiration efficiency than Iranian oak. In general, it can be concluded that in both species stomatal and non-stomatal limitations caused a decrease in photosynthesis. Also, the Iranian oak species uses the mechanism of avoiding drought during stress due to its lower water consumption efficiency and greater reduction in the percentage of changes in gas parameters compared to the weevil species. However, in the case of molecular studies, RNA extraction was performed and the sample was run, but in the electrophoresis stage, molecular studies were not successful due to the absence of bands related to RNA.

Key words: gene expression, elements, gas exchange and molecular marker.

- Introduction and purpose

Zagros forests from The most extensive forest ecosystems are being destroyed in Iran, and they are considered the second natural ecosystem after the northern forests, which is of great importance in terms of water and soil protection and economic and social issues (Hosseini et al., 2017). Therefore, it is necessary to restore and enrich these forests with different species of the oak genus, which is the most important species (Zulfaqari, 2017).But due to the Mediterranean climate, the Zagros forests have a long dry season during the period of plant growth and irregular distribution of rainfall throughout the year, and as a result, the amount of water available in these forests is considered as a primary limiting factor in the regeneration of species, especially oak. According to researchers, oak forests of the West are among terrestrial forests. There are three species of oak in the whole of Zagros, all three species are native to Iran and are accepted by most Iranian botanists. These species include Quercus infectoria, Quercus libania, and Quercus brantii (Jazihai and Ebrahimi, 1382).

Based on the vegetation areas, the habitats of different species of Zagros have been divided into two distinct parts called North Zagros and South Zagros. North Zagros is the special habitat of Quercus libani Olivier, which, of course, is mixed with Q. infectoria Olivier or Lindl Q. brantii or both in some parts of this area. However, South Zagros, which has a drier climate than North Zagros, is a special habitat for Q. brantii species (Jazihai and Ebrahimi, 2012).

Abiotic stresses such as drought are important phenomena and affect the health, productivity and fitness of our forests, so it is necessary to understand the genomic and ecophysiological response of forest trees to changing weather conditions (Rajura et al.[1], 2011). Water scarcity is a growing global problem. Lack of water limits the production of many natural ecosystems, especially in dry climates. In addition, water stress, as the most important abiotic stress, plays an important role in reducing the genetic diversity and performance of plants in the world (Kocheki et al., 2014).  Although the forests of the west of Iran have the largest area of ??the country's forests in terms of size, but economically (wood production) it is after the forests of the north of the country, and the main role of these forests is the protection of water and soil, which should not be ignored. Therefore, in order to restore the forests of the west of the country, it is necessary to use the adapted and native species of the Zagros forests (Fattahi, 2008). Until now, few studies have been conducted in the field of environmental stress on forest trees, whose main goal is to identify and create varieties that can resist stress well and produce more produce. Therefore, the use of new techniques to study environmental stresses is inevitable and economically justifiable (Khoideki, 2018). By using morphological, physiological and molecular studies, we can identify different breeding methods for drought resistance (Nowrozi, 1383).

Studies have shown that the natural reproduction of the oak species often faces problems (Tadani[3] et al., 1995) and the low quality of oak seedlings has also made afforestation with this species difficult. (Clark [4] et al., 2000), therefore, the study of morphological and vegetative characteristics (Rich [5] et al., 1992) as well as physiological characteristics (absorption, transport, and photosynthesis) on plant resistance to drought is very important, and it is based on the fact that there are differences in drought resistance strategies in plants in different species or ecotypes (Loya and Fernandez [6], 1998).

Today, methods are used that can identify the different expression of genes among test samples. One of the best of these methods is cDNA-AFLP, which is widely used due to its reproducibility and high sensitivity (Bachem[7] et al., 1996). The cDNA-AFLP method allows us to detect the different expression of the transcripts using PCR.

According to the above and the increasing importance of dryness and destruction of the Zagros forests and the lack of success in afforestation, the present research intends to investigate and study the morphological, physiological and genetic responses using cDNA-AFLP molecular markers, seedlings of three species of Iranian oak, Darmazo and Viol. To deal with drought stress in order to understand the reactions of different oak species with water deficit stress.