Marjan Diayanat
Abstract
Introduction The presence of broadleaf weeds not only reduces the aesthetic quality of the turfgrass, but more importantly they compete with desired turfgrass for water, nutrients, and light. Weed management after seeding is an important component to successfully establishing a healthy stand of cool ...
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Introduction The presence of broadleaf weeds not only reduces the aesthetic quality of the turfgrass, but more importantly they compete with desired turfgrass for water, nutrients, and light. Weed management after seeding is an important component to successfully establishing a healthy stand of cool season turfgrass. Weed seed germination is a key process because determines both the number of weeds that could potentially emerge and the timing of their appearance in the turfgrass. Temperature is of the most important factor regulating germination of non-dormant seeds in irrigated, annual agroecosystems at the beginning of the growth season where light, nutrients, and moisture are typically not growth limiting. Also prostrate knotweed (Polygonum aviculare L.) and annual sowthistle (Sonchus oleraceus L.) are two annual common broad leaf weeds in cool season turfgrass. Prostrate knotweed is very competitive in infertile and compacted soils and often invades turfgrasses along driveways, sidewalks, and beaten paths across lawns. Annual sowthistle is found in open habitats that include waste areas, turf, and roadsides. The aim of this study was to evaluate different nonlinear regression models to describe response of germination rate to different temperatures in perennial ryegrass (Lolium perenne L.), fescue (Festuca rubra L.), prostrate knotweed and annual sowthistle.
Materials and Methods This experiment was based on completely randomized design with 4 replications at Islamic Azad University in the laboratory of Science Research Branch in 2015. The seeds were treated with different temperatures (2, 5, 10, 15, 20, 25, 30, 35, 40 and 45oC) Twenty five seeds were placed in each petri dish for each species in per replication. Ten milliliters of distilled water were added to each petri dish and the filter papers were regularly moistened to ensure saturation throughout the germination tests. Petri dishes were placed in germinator with 16 hour day, 8 hour night and 60% relative humidity. Seeds were considered germinated when the radicle protruded at least 2 mm from the seed coat. Germinated and rotted seeds were counted and discarded at 24 hour intervals until no germination had occurred over four consecutive days. The germination percentage was obtained by dividing the number of germinated seeds at any time by the total number of seeds germinated multiplied by 100. Data from this experiment were first subjected to analysis of variance and means of treatments were compared using the least significant difference at the 5% level of probability. The following nonlinear regression models were used to quantify the response of the germination rate to temperature and to determine cardinal temperatures.
Results and Discussion The analysis of variance showed that temperature had a significant effect on all seed germination percentage and germination rates. Seed germination percentage and rate increased to a point with increasing the temperature. Germination model based on temperature can be used for the prediction of cardinal temperatures. Cardinal temperatures are required because a portion of the crop model is developed for prediction of the timing of germination. Non-linear regression models have been used to quantitatively describe development rate in many plants. Three regression models (Intersected-lines, Dent-like and Quadratic Polynomial) used to predict germination rate and cardinal temperature. Root mean square of error (RMSE) and R2 adjusted were used to find the appropriate model(s). Intersected-lines model was superior compared to other models in perennial ryegrass, fescue and annual sowthistle and Dent-like model was superior for prostrate knotweed. It was concluded that this model can be used to quantify response of turfgrass and common weeds of turfgrass germination to temperature and to obtain cardinal temperature of germination. Also base, optimum and maximum temperatures were for perennial ryegrass 4.12, 24.66 and 43.27oC; fescue 2.0, 24.86 and 43.48oC ; Prostrate knotweed 2.95, 19.94-22.21 and 44.97oC and annual sowthistle 2.0, 17.77 and 44.86oC, respectively.
Conclusions These results show that fescue germinated earliest among the studied species, because it had the lowest base temperature. In comparison to perennial ryegrass, using turfgrass seed with more fescue seed causes sooner turfgrass establishment and less weed competition. Because of their narrow leaves, young seedlings of prostrate knotweed grow upright and appear at first glance to be grass seedlings. With maturity, most plants grow prostrate, especially with traffic or mowing, so mechanical control of this species in turfgrass is impossible andit could be controlled with pre-emergence herbicide. Pre-emergence herbicides are applied prior to the germination of weeds; thus, predication of timing germination help us in decreasing prostrate knotweed competition with turfgrass and its proper management.
Azadeh Mousavi Bazaz; Ali Tehranifar; Mohammad Kafi; Ali Gazanchian; Mahmood Shoor
Abstract
Introduction: Worldwide, more than one-third of irrigated land is salinized, and in many regions, fresh water shortage has resulted in restrictions on the use of potable water for landscape irrigation. On the other hand, rapidly expanding population growth is occurring in many arid regions, where soil ...
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Introduction: Worldwide, more than one-third of irrigated land is salinized, and in many regions, fresh water shortage has resulted in restrictions on the use of potable water for landscape irrigation. On the other hand, rapidly expanding population growth is occurring in many arid regions, where soil and water salinity are problems and there are increased demands on limited fresh water resources (9). In the turf grass industry, with the increased use of saline and non-potable water, the development of turf grass landscapes in arid and seashore regions where saline soil is common, and with the use of salt for deicing roadways, the need for salinity tolerant turf grasses is very important (16).Seed germination and early seedling growth is usually the most critical stage in plant establishment, and determining successful crop production (23). Tall fescue (Festuca arundinacea Schrub.) is an important perennial cool-season grass in temperate regions and it is widely used for both forage and turf purposes (25). There is no study on the evaluation of salinity on tall fescue native populations in Iran. The major objective of this study is to determine the relative salt tolerance and growth response of native populations of tall fescue to salinity in germination stage.
Materials and Methods: In this experiment, seeds of some native populations of tall fescue (TF) (F. arundinacea Schreb) including: Semirom, Mashhad, Sanandaj, Sanajan, Yasuj, Yazd Abad, Daran, Kamyaran, Gandoman, Borujen, Nasir Abad, Alborz and commercial TF (C. TF) seeds were used. Four replicates of 25 seeds were germinated on filter papers with 5 ml of NaCl concentrations placed in 9 cm Petri dishes. NaCl concentrations included: 0, 45, 90 and 135 milimolar. The Petri dishes were transferred to germinator at 23°C.Germinated seeds were counted on the3rd, 5th, 8th, 11th and 14th days. Germination was considered to have occurred when the root length was 2 mm long. The seedling with short, thick, and spiral formed hypocotyls and stunted primary root were considered as abnormally germinated. Then, the total germination percentage, germination rate, root length and shoot length were calculated on Day 15. The vigor index was calculated as VI= (RL+SL)×GP, where for the VI, RL is the root length, SL is the shoot length and GP is the germination percentage. Root length and shoot length were measured manually with a ruler. The experimental design was a completely randomized design with 4 replications and 25 seed per replicate. The data were statistically analyzed by JMP 8.0. The difference between the means was compared using LSD values (P < 0.01).
Results and Discussion: The results indicated that the increase of salinity level leads to a significant decrease in germination percentage, germination rate, length of shoot, root and vigor index in all genotypes. Also, interaction of salinity and genotype was significant for germination percentage, germination rate, and vigor index. The highest germination percentage was related to Mashhad population at 45 milimolar, and Daran population at 90 and 135 milimolar. Also, the lowest germination percentage was related to Kamyaran population at 45 and 90 milimolar and Commercial tall fescue at 135 milimolar. Mashhad population at 135 milimolar, Daran population at 90 and 135 milimolar had the highest germination rates. The lowest germination rate was recorded at 45, 90 and 135 milimolar in Commercial tall fescue, Kamyaran and Sanandaj populations, respectively. The highest root length was seen in Commercial tall fescue at 90 and 135 milimolar, and Mashhad population at 45 milimolar. For shoot length factor, Mashhad population, Commercial tall fescue and Mashhad population had the highest lengths at 135, 90 and 45 milimolar, respectively. The highest vigor index was related to Mashhad, Daran and Mashhad populations, at 45, 90 and 135 milimolar, respectively. NaCl has an inhibitory effect on seedgermination and its effect on germination showed time course dependence for absorption of Na and Cl by thehypocotyls (28).Increasing salinity levels caused delays in seedlingemergence as a result of reducing cell division and plant growth metabolism (28). The negative effect of salinity on seed germination and early growth could be due to the toxic effects of NaCl on seeds, or to the osmotic effect, that prevents the seeds from imbibitions (21).
Conclusion: Major grasses mentioned above could tolerate 45 milimolar salinity without noticeable changes in germination traits. Mashhad and Brujen populations were least affected by 135 Mm Nacl at germination rate and percentage. Also, Daran and Mashhad populations were least affected by different salinity levels in all germination factors compared to other populations and could be suggested as salt-tolerant genotypes at germination stage.
