Showing 4 results for Cca
S. A. Maybodi, A. R. Amini Hajiabadi, J. Khajeddin,
Volume 6, Issue 2 (7-2002)
Abstract
A number of halophytic species as Salicornia europea, Halocnemum strobilaceum, Aeluropus lagopoides, and Aeluropus littoralis were found to occupy a significant portion of the total vegetation of the surrounding area at the Zayande-Roud inlet to Gavkhoony wetland. However, their ecological demands and bioenvironmental factors by which vegetation community composition has been affected is not undestood. A compehensive knowledge of the establishment is essential for future improvements in using the above species on salanized regions. In this paper, using the ordination method. The establishment pattern of these four species in a range of varied habitats is evaluated based on the recongition of the relative significance of habitat soil chemical properties and vegetion crown cover to the establishment of the four species. For this purpose, 48 plants meansurements were taken along a transect, having more species variation in term of vegetation cover percentage. Furthermore, 48 soil samples were taken from the plot along the same transect in a one-year period in 1999. The soil samples were analysed for PH, EC, available Na, K, Ca and Mg as well as clay, and silt contents. The ground and field vegetation data were analysed using the Principlas Components Analysis (PCA), and Canonical Correspondence Analysis (CCA) to produce summary vectors (PCA axes) of both the soil chemistry and habitat vegetation structure datasets. The summary of ordination method quantified the degree to which soil variables and species cover were related to variability in ground vegetation composition. variation in community composition (type and percentage) was significantly related to gradient of the aforementioned soil factors. Generally, the vegatation community composition in this experiment could be considered as a key component to expand the growth and development patterns of these species to similar salinised regions.
S. M. J. Nazemosadat, A. Shirvani,
Volume 8, Issue 1 (4-2004)
Abstract
In Iran, about 75% of national rice production is supplied in Gilan and Mazandaran proviences which have the highest amount of precipitation. Seasonal prediction of rainfall induces significant improvement on yield production and on preventing climate hazardz over these feritle areas. Canonical correlation analysis (CCA) model was carried out evaluates the possibility of the prediction of winter rainfall according to the states of ENSO events. The time series of (southern oscilation index (SOI) and SST (sea surface temperature) over Nino's area (Nino's SST) are used as the predictors, and precipitation in Bandar Anzali and Noushahr are used as the predictands. Emperical orthogonal functions (EOF) were applied for reducing the number of original predictors variables to fewer presumably essential orthogonal variables. Four modes of variations (EOF1, EOF2, EOF3, EOF4) which account for about 92% of total variance in predictors field were retained and the others were considered as noise. Based on the retained EOFs and precipitation time series, the canonical correlation analysis (CCA) was carried out to predict winter precipitation in Noushahr and Bandar Anzali.
The results indicated that the predictors considered account for about 45% of total variance in the rainfall time series. The correlation coefficents between the simulated and observed time series were significant at 5% significant level. For 70% of events the anomalies of observed and simulated values have the same sign indicating the ability of the model for reasonable prediction of above or below normal values of precipitation. For rainfall prediction, the role of Nino's SST (Nino4 in particular) was found to be around 10% more influential than SOI.
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M. Modaraye Mashhoud, M. Esfahany, M. Nahvi,
Volume 11, Issue 42 (1-2008)
Abstract
In order to reduce the rainfall damages on rice yield at harvest stage, a field experiment was conducted at Rice Research Institute of Iran, Rasht, in 2004 by using Sodium Chlorate as a chemical desiccant. Five seed moisture contents of Dorfak rice cultivar were considered as experimantal treatments [24 - 28% (M1), 22 - 24% (M2), 20 -22% (M3). 18 - 20% (M4) and control (M5= conventional harvesting)]. The experiment was carried out in a randomized complete block design with three replications and the effects of treatments on grain yield, head rice yield,seed germination rate and percentage, kernel breakage, kernel cracking, amylose content, gelatinization temperature and gel consistency were evaluated. Results showed that the whole plant and grain moisture contents were significantly reduced in all experimental treatments compared with control. M2 and M3 both cosiderably reduced the plant moisture content in which harvesting occurred 12 and 8 days respectively sooner than the control. In M1, due to high grain moisture and non - simultaneous grain filling in different tillers, many of panicles desiccated prior to maturity lost their quality. In M4, the crop harvested was only 2 days earlier than the control. Analysis of variance showed that there were no significant effects of treatments on evaluated traits. It seems that rice plant could be reliably desiccated by Sodium Chlorat and harvested earlier without any adverse effects on its quality and quantity.
M Ebrahimi, S.m Khayam Nekoei, S Kadkhodaei,
Volume 12, Issue 46 (1-2009)
Abstract
Somatic embryogenesis is affected by several factors. In this research project, we studied the effect of explant size, wounding and desiccation treatments on somatic embryogenesis and their conversion into plantlet among three genotypes of soybean. The explants were sampled from immature embryos of soybean in three different sizes (3, 5 & 7 mm) with wounding treatment on half of each, and then were cultured on the somatic embryogenesis medium. In order to determine desiccation effect on conversion amount of embryos into plantlets, the produced embryos were affected by three levels of desiccation treatments (2, 4 & 6 days). The increase ratio of callus mean weight, percentage of embryogenic calli, embryo number per explant and percentage of embryo conversion to plantlet were used for treatment evaluation. Variance analysis of the data showed significant differences (P<0.01) between treatments regarding the variables. The results indicated that BP was a superior genotype with embryogenic capability (24.19 %) and the best explant size for somatic embryogenesis was immature embryo with 3 mm length. The six day desiccation treatment caused highest percentage of embryo conversion into plantlet (74.7 %). Wounding increased callus production on explants and number of embryos per explant (20.28), but it did not show any significant effect on percentage of embryogenic calli. Germinated somatic embryos were transferred to pots containing peat-moss. Somatic embryogenesis is an efficient method for the plant regeneration and genetic transformation. However, this method still offers low percentages of plant regeneration, and is perhaps related to the maturation process and high morphological abnormalities of the matured embryos. This study aimed to find some solutions for soybean somatic embryogenesis problems.
