Showing 3 results for Drought
Volume 10, Issue 1 (3-2010)
Abstract
One of the fundamental steps in management of drought involves identification and frequency analysis of its properties, e.g. duration and severity of drought. Regarding the high correlation among these factors, one must use a method that shows the relation and effects of these factors on drought analysis. Copula functions can be used to represent the dependency structure of several variables through a model. In this paper, we introduce the appropriate copula families for modeling drought phenomenon modeling. Then, their parameters would be estimated by maximum likelihood and Empirical Bayes methods and the most appropriate copula function for determining bivariate distribution of duration and severity of drought in Tehran stations is determined. Next, this copula function is used to model the drought phenomenon of Tehran for the period of 37 years from 1348 until 1384, Finaly the application of this model is represented in water supply management.
R Ghafari, Fariba Meighani, F Ghasemkhani, H Salimi,
Volume 15, Issue 1 (4-2015)
Abstract
Abstract
Mesquite is one of the invasive, problematic and noxious weeds and special warm and dry areas. This plant in recent years due to high resistance to drought stress level in the vast agricultural lands and orchards spread. Management so it is very important. The following studies were conducted in plant protection of weed research Department Research Institute of during the years 2010: 1- Effect of constant temperature on germination that including 5, 10, 15, 18, 20, 25, 30, 35 and 40° C independent dark and independent light conditions 2- Effect of temperature fluctuations on seed germination: 0/10, 10/20 and 20/30° C 3- Effect of planting depth seed on seed germhnation. All experiments were conducted with 4 replications. mesquite seeds showed no dormancy when detachment from mother plant. Seed germination was strongly influenced by temperature. Light did not play a crucial role on seed germination of this weed. Therefore mesquite seeds were not photoblastic and temperature fluctuations did not increase seed germination of mesquite. The above characteristics are very important in making mesquite an invasive weed. Having precise information of these traits enables us to a better management and control of this troublesome weed.
Keyword: Prosopis farcta, seed germination, seed dormancy, constant and fluctuating temperature, planting depth.
Volume 18, Issue 56 (9-2006)
Abstract
The mechanism of soybean(Glycine max L.cv.Gorgan 3) response to drought stress was evaluated. The plants were grown in pots under 23 ± 2°C temperature and 14000 lux light intensity and 14hr photoperiod. When first leaf appeard, three irrigation treatments occurred that consisted as one every day(control), once in three(mild stress) and in five days(sever stress).During 15 days the plants were irrigated an amount of 150 ml. The effect of irrigation treatment on the soluble sugar, total protein, proline, phenolic compound, chlorophyll content and nitrate reductase activity was studied.The results showed that in the root soluble sugar and proline content in mild and sever stress significantly increased while in the stem and the leaf these compound considarably increased under sever stress the total protein ,chlorophyll a,b and nitrate reductase activity in leaf especially decreased in sever stress. Also the decrease phenolic compound in leaf under this condition was significant
