جستجوی مقالات مرتبط با کلیدواژه « درصد بقاء » در نشریات گروه « اکولوژی »

Tall festuca (Festuca arundinacea) belongs to Poaceae family and is a cool-season perennial plant native to Europe. Festuca species are broadly adapted to different climate conditions. To date, 9 different species of Festuca have been identified in Iran. These species are growing naturally in different regions of Iran such as Golestan, Mazandaran, Lorestan, Khorasan, Fars, Isfahan, Karaj, Dorood, Damaneh, Alvand and Firoozkooh. Festuca reduces soil erosion due to its fibrous, thick and deep roots. Such roots reduce soil density and improve soil structure and reduce soil erosion, and thus, this plant plays a crucial role in reducing water and wind erosion. Tall fescue is a long-lived perennial species with medium to large leaves. The plant is grown as turf and is considered as an important animal fodder, thus is widely grown in pastures and grasslands. Tall festuca is among the 27 identified species of festuca in Iran. The species is well spread across Iran and has a high potential for growth and production in pastures or mountainous areas, especially in the central, western and northern regions of the country. Tall festuca is a perennial plant, so it is often exposed to cold and freezing stress. Therefore, the successful production of this plant requires the use of cold-tolerant varieties. According to previous studies, although tall festuca has good tolerance to a wide range of environmental stresses (cold and drought), different ecotypes show different cold tolerance, accordingly further studies on growth characteristics and cold tolerance of this plant is necessary, especially in winter type varieties. The field experiment was carried out in Parks and Green Space Organization, Mashhad Municipality located in the Islamic Republic of Iran Blvd., and Crop Physiology Laboratory, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran in 2013- 2014. The experimental design was a randomized complete block design arranged in a split plot with three replicates. In order to expose the tall festuca plants to winter cold stress, 23 ecotypes were sown on the 7th of October and 6th of November. Dimensions of each plot were 100 × 150 cm and after seed sowing, seeds were covered with composted cattle manure and then irrigated. After emerging the seedlings, the plots were thinned to reach final plant density of 400 plants per square meter. Weeds were manually controlled and irrigation was carried out according to the need of the plants. The data were analyzed using MSTAT-C. The comparison of means was performed through the LSD test at 5% probability level. The results showed that the effects of sowing date and ecotype were significant on a number of days until emergence, survival percentage, plant dry weight, seed yield, and total dry weight. The phenological investigations and plant height measurement indicated that there was a genetic difference between the ecotypes. In all studied ecotypes, the survival percentage in the second sowing date was higher than that in the first sowing date. However, a number of days until emergence, plant dry weight, seed yield and total dry weight in the first sowing date were found to be higher in comparison to tens second sowing date. In addition, among the studied ecotypes, the highest traits stability with an emphasis on survival percentage and yield components were observed in Isfahan, Boroujen, Daran, Daran-Damaneh, Gandoman, Sanaajan, Mashhad, Sari, Golestan, and Quchan-Seyyed Abad ecotypes. Therefore, these ecotypes were selected as genetic reserves for future studies. In general, the effect of sowing date and ecotype was significant on most of the studied traits such as a number of days until seedling emergence, survival percentage, plant dry weight, seed yield, and total dry weight. In addition, in phenology related traits such as a number of days from flowering to maturity, total growing period length and plant height genetic difference between ecotypes was investigated. Although in most of the traits such as a number of days until seedlings emergence, plant dry weight, seed yield, and total dry weight, the obtained values were higher in the first sowing date compared with the second sowing date, survival percentage showed unlike results so that late sowing increased this index.

In order to evaluation of freezing tolerance in viola (Viola gracilis L.) under controlled conditions, a trial carried out in completely randomized design with six replications at college of agriculture, Ferdowsi University of Mashhad, Iran, during 2008-2009. Seeds were planted in bed and seedlings were acclimated during natural conditions in autumn and at 5-7 leaves stage plants transferred to the thermo-gradient freezer to apply 12 freezing temperatures (0, -2, -4, -6, -8, -10, -12, -14, -16, -18, -20 and -22°C). Leaf cell’s membrane integrity was measured through electrolyte leakage (EL) after the freezing and survival percentage and plant recovery (e.g. plant height and dry weight, number of branches and flowers and flower’s diameter) were determined after three weeks of plant re-growth in the cold frame. As temperature decreased, EL% increased significantly and reached to the maximum in -20oC. Survival percentage did not affected by temperatures between 0oC to -18oC but all plants killed in -22oC. LT50el and LT50su were -20.0°C and -19.4°C, respectively. Decreasing the temperature lower than -18 oC reduced plant dry matter severely and RDMT50 was -19.2°C.