ABSTRACT
The experiment was carried out in one of the green houses of the research station A of the Department of Horticulture and Landscape Design during fall season 2020/2021 This study was aimed to reducing the amount of irrigation water using factorial experiment with in split plot designed by The study included three factor , First factor, the quality of irrigation water (main plots) and at three levels: (irrigation with water from the Tigris River 0.92 dm s-1(I0), alternating irrigation (one irrigation with saline water followed by irrigation with the water of the Tigris River(I1), Alternating irrigation (two irrigations with saline water, followed by irrigation with the water of the Tigris River(I2), Second factor was the addition of Polyacrylamide (0, 1.5,2.5) g of soil-1 his symbol(P0,P1.P2). Third factor was spraying with selenium with three concentrations (0, 10,20) mg L-1 his symbol (S0,S1,S2) The results showed The addition of polymers led to decrease in the amount of irrigation water used to irrigate Iris, as the amount of irrigation water decreased with an increase in the concentrations of added polymers. Also, the polymers contributed at a concentration of 2.5 g kg of soil-1 percentage of dry matter in leaves, percentage of carbohydrates in leaves, N, P, K, percentage the water potential in the leaves, relative water content, stomata area and the reduction in the activity of the enzyme Superoxide dismutase led to an increase in the salinity of the irrigation water to a decrease in all characteristics and an increases in the activity of the sod and spraying with selenium at a concentration of 20 mgL-1 increased all study parameters and reduced enzyme activityed.
Keyword: Polyacrylamide,water salinity, sodium selenite, water potential.
INTRODUCTION
Iraq and most other countries of the world suffer from a lack of rainfall and scarcity of water resources, and in light of the decreasing water supplies coming to Iraq from neighboring countries, so it is necessary to follow a scientific irrigation practice to rationalize water consumption, and since water is one of the most important factors that limit plant growth and agricultural productivity in many areas of the world, therefore, has recent need have emerged to find scientific methods used to ration irrigation water. One of these methods used is super water-absorbing polymers, as this is one of the modern methods of treating the agricultural soils physical properties of such as their benefits in improving the properties of sandy soils and the ability to retain water and reduce Irrigation water consumption and thus improving water use efficiency (11) There are other means used to rationalize the consumption of fresh water, which is the use of saline water in agriculture through alternating irrigation with fresh water, especially if we know that fresh water does not exceed 1%, so efforts in various parts of the world have been directed to the use of more saline water sources such as springs, wells and agricultural drainage water (8) Therefore, the alternating irrigation strategy is important to save quantities of fresh water and thus use it to irrigate plants that are highly sensitive to salinity (9) Selenium is one of the rare and useful elements of the plant and has a role in raising the activity of enzymatic antioxidants such as peroxidase, glutathione peroxidase and superoxide, which increases the plant's tolerance to abiotic stress conditions, including water and salt stress through its association with amino acids and the formation of complexes of selenium proteins (1) The study aimed to reduce the quantities of added water by adding polymers, and to know the effect of the interaction between polymers and spraying with selenium in reducing stress.
MATERIALS AND METHODS
The experiment was carried out in one of the greenhouses of the research station A of the Department of Horticulture and Landscape Design / College of Agricultural Engineering Sciences / University of Baghdad during fall season 2020/2021 If the research was carried out as factorial experiment according to split plot designed and with three replications to study the effect of three factors: The first factor is the quality of irrigation water (the main plots) at three levels: (irrigation with the water of the Tigris River 0.92 dms-1, alternating irrigation (one irrigation with saline water followed by irrigation with river water), alternating irrigation (two irrigations with saline water, followed by irrigation with the water of the Tigris River, Sodium chloride salt was used at a concentration of 10 dms"1, The second factor was the addition of Polyacrylamide (0, 1.5 and 2.5) gm of soil-1, the third factor was spraying with selenium at three concentrations (0, 10 and 20) mg L'1. Foliar application was repeated every 3 weeks (1) and until the end of the experiment Irrigation treatments were distributed within the main plots and the treatments for spraying with selenium and polymers were distributed within the secondary plots The averages of the treatments were compared with the least significant difference (L.S.D) test and at a significant level of 0.05 Iris bulbs were planted in Iris white excelsior dated 1/ October /2020 In plastic bags of 10 kg of soil, a layer of gravel was placed inside the bags. The planting bags were filled with 7 kg of soil, which was brought from one of the banks of the Tigris River, and the irrigation process was done up to field capacity. Irrigation was repeated when Soil drained 35% of Prepared water until the end of the experiment 1/ May/2021 and on the basis of the weighted method the amount of irrigation was calculated water by multiplying the number of irrigations by the amount of water used to irrigate one seedling and for each month of the planting month Percentage of dry matter in leaves .(%) Leaves were collected from each plant, after which the fresh weight was measured , leaves were then dried using an electric oven at a temperature of 70 degrees Celsius until the stable weight was obtained and the ratio was calculated as follows- :
Percentage of dry matter in leaves = dry weight of leaves / wet weight of leaves x 100 The percentage of carbohydrates in the leaves (%).The carbohydrates in the leaves were estimated according to the method described by (18). Water potential in leaves. The water potential was estimated by the flow drop method, as different concentrations of sugar solutions of known voltage were prepared in test tubes and a few drops of methylene blue dye were added Placed inside tubes without dye, a piece of known area was taken from the leaves of the iris plant for 30 minutes, then the leaves were lifted and a drop was taken from the tubes of the colored solutions and added to the uncolored tubes of similar concentration. The drop diffusion indicates that the concentration remains the same, meaning that the solution is diffusion-neutral (34). The relative water content of the leaves. Calculations were carried out according to (5). as the leaves were cleaned of dirt , weighed and then immersed for 3 hours in water and weighed after extracting them from the water (weight when saturated with water) after which they were dried in the oven and their dry weight was taken as follows, Relative water content = leaf wet weight - dry weight / weight after saturation - dry weight
Percentage of Nitrogen in leaves (%): Nitrogen is estimated by Kejldahl-Micro(17).
Percentage of phosphorous in leaves (%).Phosphorus was estimated using ammonium molybdate and Absorption was measured using Spectrophotometer at 882 nm according to the method used by (26).
Percentage of Potassium in leaves(%): Potassium is estimated by Flamephotometer (3!).
Determination of the activity of the enzyme superoxide dismutase. The effectiveness was estimated by riboflavin and nitrobutyrate according to the method used by (32).
Stomach area (µ2) The paper was fully expanded and the bottom surface of the paper was cleaned to remove dust and coated with a light layer of colorless nail polish because it contains cellulose acetate. It is left for a period of time to dry and a transparent adhesive is fixed on it to make a stomata imprint. This layer is then removed and fixed on glass slides to be examined under a microscope using the eyepiece with a magnification of (40x) and the objective with a magnification of lOOx) (30) and Calculation of stomata area were done according to the ellipse equation are:
A = a · b · π
a represents the radius of the length of the gap b is the radius of the stoma width
RESULTS AND DISCUSSION
Amount of irrigation water (liters)
Table (1) shows that the irrigation treatments did not record a difference between them in the amount of irrigation water needed by Iris.As for the addition of polymers, treatment Po was significantly superior in recording the highest amount of irrigation water to 28.86 liters compared to treatment P2, which recorded the lowest amount of irrigation water amounting to 18.07 liters.When spraying with selenium, treatment So was significantly superior in recording the highest amount of irrigation water amounting to 23.83 liters compared to treatment S2, which recorded the lowest amount of irrigation water amounted to 23.01 liters .The results of the binary interaction between irrigation factors and the addition of polymers indicated that I0P0 treatments were superior in recording the highest amount of irrigation water amounting to 28.95 liters compared to treatment I1P2 which recorded the lowest amount of irrigation water amounting to 18.06 liters.The interaction effect between irrigation and selenium spray resulted in the moral superiority of I0S0 treatment in recording the highest amount of irrigation water amounted to 23.96 liters compared to treatment I2S2which recorded the lowest amount of irrigation water amounted to 22.99 liters.In the bilateral interaction between the addition of polymers and spraying with selenium, treatment P0S0 significantly outperformed in recording the highest amount of irrigation water amounting to 29.35 liters compared to treatment P2S2, which recorded the lowest amount of irrigation water amounting to 17.74 liters Also, treatment I0P0S0 was significantly superior in the triple interaction between the studied factors, as it recorded the highest amount of irrigation water amounting to 29.74 liters compared to treatment I2P2S2 which recorded the lowest amount of irrigation water amounting to 17.74 liters.
Percentage of dry matter in leaves(%).
The results in Table 1 indicate the moral superiority of the irrigation treatments fi and Io in giving them the highest percentage of dry matter in the leaves, which amounted to (26.86, 26.71%) respectively, while the percentage of dry matter in the leaves decreased when treatment I2 reached 22.75%.As for the addition of polymers, it had a positive effect in increasing the percentage of dry matter, as treatment P2 was significantly superior in giving the highest percentage of dry matter amounting to 25.87%, while the percentage decreased when treatment P0 reached 24.95%. And when spraying treatments with selenium, treatment S2 was significantly superior in recording the highest characteristic of 26.86% compared to control treatment So, which recorded the lowest dry matter percentage of 23.59%. also, treatments I1P1 and I0P2 were significantly superior, as they recorded (27.42 , 27.30)%, respectively, which did not differ significantly from I1P2 treatment, which scored 26.88%, while treatment I2P0 recorded the lowest percentage of dry matter amounted to 22.29% in the bilateral interaction treatments between irrigation and addition of polymers. As for the bilateral interaction between the quality of irrigation water and spraying with selenium, the treatment I1S2 was significantly superior, which scored 28.72%, compared to the treatment I2S0, which recorded the lowest percentage of dry matter that reached 21.17% in regard to the binary interaction between the addition of polymers and spraying with selenium, the two treatments P2S2 and P1S2 which did not differ significantly between them outperformed them in giving the highest percentage of dry matter of the leaves reaching (27.20,26.80)% while the percentage decreased to reach 23.17% in the treatment P0S0. the triple interaction between the effect of irrigation water quality, the addition of polymers and spraying with selenium showed the significant superiority of the two treatments I1P2S2 and I1P2S1, which recorded (28.83, 28.79)%, which did not differ significantly from the treatments I1P1S2,I1P0S2 and I1P1S1 as they recorded (28.70, 28.65 ,28.49 The percentage of dry matter in the treatment I2P0S0 reached 20.43%.
Percentage of carbohydrates in the leaves(%).: The results in Table 2 show the effect of irrigation water quality on the percentage of carbohydrates in the leaves. Treatment f was significantly superior in recording the highest percentage of carbohydrates, which amounted to 3.834%, while the percentage of carbohydrates decreased to 3.665% in treatment l2.and the addition of polymers affected the percentage of carbohydrates, so the treatment of adding P2 polymers recorded 3.985%, significantly superior to the treatment of no addition Po which recorded 3.555% also spraying with selenium had a significant effect on the percentage of carbohydrates, as the spraying treatment S2 recorded 3.917% compared to the treatment So, which recorded 3.555%.The bilateral interaction between the quality of irrigation water and the addition of polymers showed the significant superiority of I1P2 treatment in increasing the percentage of carbohydrates, which amounted to 4.103%, while the percentage of carbohydrates decreased to 3.476% in the I2P0 treatment, in the bilateral interaction between irrigation and spraying treatments with selenium, treatment I1S2 was significantly superior in giving the highest percentage of carbohydrates in leaves, which amounted to 4,000%, while this percentage decreased in treatment I2S0, which recorded 3.476%.with regard to the bilateral interaction between the addition of polymers and spraying with selenium, the treatment P2S2 affected the percentage of carbohydrates, which recorded 4.150%, significantly superior to the treatment P0S0, which recorded the lowest percentage of carbohydrates, which amounted to 3.305%. The results of the triple interaction between the studied factors showed the significant superiority of the two treatments I1P2S2 and I0P2S2 in giving them the highest percentage of carbohydrates, which amounted to (4.283 and 4.266)%. respectively, and the percentage of carbohydrates in the leaves decreased when the treatment I2P0S0 recorded 3.270%.
Percentage of nitrogen(%).
It is clear from the results of the statistical analysis in Table 2 that the quality of irrigation water had a negative impact on reducing the percentage of nitrogen, as the treatment I2 recorded the lowest percentage of nitrogen, which amounted to 1.08% compared to the treatment I0, which recorded 1.17% .The results of adding polymers also showed the significant superiority of treatment P2 in the percentage of nitrogen, as it gave 1.22%, superior to the comparison treatment P0, which gave 0.99%. Spraying plants with selenium was accompanied by a significant increase in the percentage of nitrogen, as S2 spraying treatment gave 1.21%, while the non-spraying treatment So recorded 1.01 %. When the bilateral interaction between irrigation and the addition of polymers was applied the treatment I0P2 was significantly superior by giving them 1.25%, which did not differ significantly from the treatments I1P2 and I2P2 which gave (1.22 , 1.21)%, while the percentage of nitrogen decreased to reach 0.93% when the treatment I2P0. The results of the binary interaction between irrigation and spraying treatments with selenium showed the significant superiority of I0S2 treatment in giving the highest nitrogen percentage, which amounted to 1.30% compared to treatment I2S0, which recorded the lowest percentage, which amounted to 0.98%, as for the effect of the bilateral interaction between the addition of polymers and spraying with selenium, the treatment P2S2 was significantly superior, as it recorded 1.32%, superior to the treatment P0S0, which recorded the lowest percentage of nitrogen amounted to 0.83%.the results of the triple interaction between the quality of irrigation water and the addition of polymers and sprinklers with selenium indicated that the treatment I0P2S2 was superior in recording the highest nitrogen content, which amounted to 1.37%, which did not differ significantly from the treatments I0P1S2,I2P2S2,I1P2S2,I0P2S1 and I1P2S1 as they scored (1.32, 1.30, 1.29 , 1.25,1.23) respectivy While the percentage of nitrogen decreased in the treatment I2P0S0, which recorded 0.76%.
Percentage of phosphorus(%).
The results of the analysis in Table 3 show the percentage of phosphorous to the significant superiority of the comparison treatment Io in recording the highest percentage of phosphorous, which amounted to 0.272%, while the irrigation treatment I2 reduced the percentage of phosphorus, which amounted to 0.230% and the treatments of adding polymers significantly affected this trait as the P2 treatment gave 0.292% superior to that of Po which gave 0.212%. The effect of spraying the plant with selenium on the percentage of phosphorous the S2 spraying treatment was significantly superior, as it scored 0.277%, compared to the non-spray treatment S0, which recorded 0.228%. As for the bilateral interaction between irrigation and the addition of polymers, the treatment I0P2 which recorded 0.314% was significantly superior to the treatment I2P0 which recorded 0.192%. As for the results of the bilateral interaction between irrigation and spraying agents with selenium, the treatment I0S2 outperformed the rest of the treatments by giving the highest phosphorous percentage of 0.296% compared to I2S0 treatment which gave the lowest phosphorous percentage of 0.204%. The binary interaction between the addition of polymers and spraying with selenium was significantly superior to the treatment P2S2 in giving the value of 0.322% compared to the comparison treatment P0S0, which recorded the lowest percentage of phosphorus of 0.186%. In regard to the triple interaction between the studied factors, the treatment I0P2S2 was significantly superior in giving the highest phosphorous ratio of 0.346%, while the I2P0S0 treatment recorded the lowest phosphorous ratio of 0.163%.
Percentage of potassium(%).
The results in Table 3 show that irrigation treatments led to a clear decrease in potassium, as the percentage of potassium decreased in treatment I2 to 1.151% compared to treatment I0, which recorded the highest potassium percentage of 1.213%.the addition of polymers achieved the highest percentage of potassium, as the treatment P2 was significantly superior in recording 1.320% compared to treatment P0, which recorded the lowest percentage of potassium, which amounted to 1.034%. When spraying with selenium, treatment S2 scored 1.260%, significantly superior to the comparison treatment S0, which recorded 1.108%. The bilateral interaction between irrigation treatments and the addition of polymers, the treatment I0P2 outperformed, as it recorded the highest percentage of potassium, which amounted to 1.347%, while the treatment I2P0 gave the lowest percentage of potassium, which amounted to 0.991 %. The bilateral interaction between irrigation and spraying with selenium showed significant superiority of I0S2 treatment, which scored 1.287%, compared to treatment I2S0, which recorded the lowest percentage of potassium, which was 1.081%. The dual interaction between the addition of polymers and spraying with selenium showed a significant superiority for the treatment P2S2 to record 1.384%, while the treatment P0S0 gave the lowest percentage of potassium, which amounted to 0.946%. The results of the triple interaction between the quality of irrigation water, the addition of polymers and spraying with selenium indicated that the treatment I0P2S2 was significantly superior by giving 1.416 % compared to the treatment I2P0S0 which recorded the lowest percentage of potassium which was 0.886%.
Table 4 that irrigation treatments affected the effectiveness of Sod enzyme, as treatment I2 recorded the highest concentration of the enzyme amounted to 10.13 Absorption unit.mg-1, compared to treatment I0, which recorded the lowest concentration of enzyme reaching 8.37 Absorption unit.mg-1. While the addition of polymers led to a decrease in the enzyme's activity, as the treatment P2 recorded the lowest activity of the enzyme amounting to highest activity of the enzyme amounting to 9.49 Absorption unit.mg-1. The Spraying selenium effected the effectiveness of Sod enzyme, as the treatment S2 reduced the enzyme's effectiveness, amounting to 9.09 Absorption unit.mg-1, compared to the treatment of not spraying with selenium S0, which led to an increase in the activity of the enzyme, which amounted to 9.47 Absorption unit.mg-1.as for the bilateral interaction between irrigation treatments and the addition of polymers, treatments I2P0 and I2P1 excelled in recording the highest concentration of the enzyme, reaching (10.20 , 10.14) Absorption unit.mg-1 compared to treatment I0P2 which led to a decrease in enzyme activity, which recorded 8.03 Absorption uniting-1. In the bilateral interaction between irrigation and spraying with selenium, the treatments I2S0, I2S1 and I2S2 were superior in giving them the highest activity of Sod enzyme, which amounted to (10.18, 10.13 , 10.9 Absorption uniting-1), respectively, while the enzyme activity decreased when treated with I0S2 to record 8.16 Absorption unit mg-1. Whereas, the binary interaction between adding polymers and spraying with selenium recorded the significant superiority of treatment P0S0 in recording the highest activity of the enzyme amounting to 9.65 Absorption uniting-1 compared to the treatment P2S2 which led to a decrease in the enzyme activity as it recorded 8.83 Absorption uniting-1. The results of the triple interaction in the same table showed that treatment I2P0S0 was significantly superior in increasing the enzyme activity, which amounted to 10.24 Absorption uniting-1, which did not differ significantly from the treatments I2P1S0, I2P0S1, I2P0S2, I2P1S1 and I2P2S0, as they scored (10.19, 10.19, 10.16, 10.14,10.13) Absorption uniting-1 compared to the treatment I0P2S2, which recorded the lowest activity of Sod enzyme, which was 7.80 Absorption uniting-1.
Water potential in leaves (bar).
It is shows from Table 4 that the irrigation treatments had a significant effect on the water potential of the leaf, as the irrigation treatment I0 achieved the highest rate (the least negative) that amounted to -0.44 bar, compared to the irrigation treatment I2, which gave the lowest rate (the most negative) that amounted to -5.75 bar. Also, the addition of polymers had a significant effect, as treatment P2 gave the highest rate (less negative) which amounted to -2.09 bar compared to the comparison treatment P0, which recorded the lowest rate (more negative) which amounted to -3.63. Spraying with selenium had a significant effect on this trait, as the spraying treatment S2 at concentration (20) mg L-1 gave the highest rate (less negative) of -2.59 bar compared to the treatment of no spray which recorded the lowest rate (most negative) of -3.12 bar .It is noted from the same table the results of the binary interaction between irrigation treatments and the addition of polymers to the superiority of treatment I0P2 significantly in recording the highest rate (less negative) of - 0.30 bar compared to treatment I2P0 which recorded the lowest rate (more negative) of - 6.96 bar. when the two interactions between the irrigation and spraying treatments with selenium, the results indicate the moral superiority of the treatment I0S2 in giving it the highest rate (the least negative) amounting to - 0.37 bar compared to the treatment I0S0 which gave the lowest rate (the highest negative) amounting to-6.13bar. The bilateral interaction between the addition of polymers and spraying with selenium, the treatment P2S2 was significantly superior in recording the highest (lowest negative) rate of -1.80 bar compared to treatment P0S0 which recorded the lowest rate (highest negative) of -3.89 bar. Also, treatment I0P2S2 was significantly superior in the triple interaction between the study factors, as it recorded the highest rate (less negative) -0.24 bar compared to treatment I2P0S0 which recorded the lowest rate (more negative) of - 7.29 bar.
Relative water content (%).
Table 5 shows that no differences were recorded among the irrigation parameters in the relative water content. As for the addition of polymers, treatment P2 was significantly superior in recording the highest relative water content of 70.30% compared to treatment P0, which recorded 57.75%.when spraying with selenium, treatment S2 was significantly superior in recording the highest relative water content of 69.30% compared to treatment without spraying So, which recorded the lowest relative water content of 54.80%. The results of the binary interaction between irrigation factors and the addition of polymers indicated that the treatments I2P2,I1P2 and I0P2 were superior in recording the highest relative water content of (70.57, 70.50 , 69.83)%, respectively, compared to treatment I0P0, which recorded the lowest relative water content of 57.57%. interactions between irrigation and spraying factors with selenium resulted in significant superiority of the treatments I2S2, I1S2 and I0S2 in giving them the highest relative water content, they scored (70.01, 69.33,68.56)% sequentially compared to the treatment I0S0, which gave the lowest relative water content of 54.77%. The bilateral interaction between the addition of polymers and spraying with selenium, the treatment P2S2 was significantly superior in recording the highest relative water content of 80.93% compared to treatment P0S2, which recorded the lowest relative water content of 52.69%. Also, the treatments I1P2S2,I2P2S2 and I0P2S2 were significantly superior in the triple interaction between the studied factors, as they scored (81.17, 81.12 ,80.52)% sequentially compared to the treatment I2P0S0 which recorded the lowest relative water content of 52.02%.
Stomata area(micron2).
The results in Table 5 indicat a significant effect of irrigation treatments on stomata area, as treatment I1 excelled in recording the highest stomata area of 15.07 microns2, which did not differ significantly from treatment I0, which recorded 14.84 microns2, and the stomata area decreased to 11.87 microns2 in treatment I2. While the addition of polymers led to the significant superiority of treatment P2 in recording the highest stomata area of 15.85 microns2 while the stomata area decreased in treatment P0 to 12.21 microns2 .When spraying with selenium, treatment S2 was significantly superior in giving the highest stomata area of 15.21 microns2 compared to treatment So which recorded the lowest stomata area of 12.55 microns2. In the bilateral interaction between the irrigation treatments and the addition of polymers, the two treatments I1P2 and I0P2 were significantly superior in recording the highest stomata area of (17.37 , 16.55) microns2 compared to the I2P0 treatment, which recorded the lowest stomata area of 10.08 microns2. The binary interaction between irrigation and spraying treatments with selenium showed the significant superiority of I1S2 treatment, which recorded 16.62 microns2, which did not differ significantly from treatments I0S2 and I1S1, which recorded 16.14 and 15.33 microns2, while the treatment I2S0 recorded the lowest stomata area of 10.90 microns2. As for bilateral interactions between the addition of polymers and spraying with selenium, the treatment P2S2 was significantly superior in recording the highest stomata area of 17.00 microns2 compared to the treatment P0S0 which recorded the lowest stomata area of 10.18 microns2. The triple interaction between the study factors, the treatment I1P2S2 was significantly superior, which recorded 18.40 microns2, which did not differ significantly from the treatments I0P2S2 and I1P2S1, which recorded (17.36,17.30) microns2, and the stomata area was reduced in the treatment I2P0S0 to reach 9.20 microns2.
It is noted from the results of Tables (1,2,3) that the amount of irrigation water decreased with an increase in the concentrations of added polymers, and this is due to the ability of polymers to improve the physical properties of the soil and increase the effectiveness and ability of the soil to retain water, and thus reduce watering rates and have the ability to retain water 400 times its weight in addition to giving what It is estimated to be about 95% of water goes to growing plants, and thus increases the efficiency of the plant to obtain water, and the main and most prominent factor in these materials is their ability to release water instead of holding water (10,24). The spraying with selenium also reduced the amount of added water due to the ability of selenium to reduce the impact of water stress through its role in getting rid of free radicals, including the cleavage of hydrogen peroxide into two water molecules, the extraordinary ability of cellular membranes to withstand water stress and prevent the denaturation of plant protein metabolism compounds, and this mechanism is one of the most successful biological means through which the plant works to withstand stress in the presence of selenium (15). Notes from table (2,3) The percentage of dry matter and carbohydrates in the leaves were significantly superior in the flow concentrations of saline water in treatment I1 (irrigated with saline water followed by irrigation with river water) This increase may be appropriate for the continuation of the growth process and improving its indicators It was also explained by the plant's need for small amounts of salt represented by nutrient ions that contribute to increasing growth and increasing salinity levels. A significant decrease in the percentage of dry matter and carbohydrates in leaves was observed. This may be due to the effects of treatment salinity in reducing leaf area and chlorophyll in leaves and the effect of this in inhibiting The efficiency of the photosynthesis process, and its effect on the activity of the enzymes responsible for reducing carbon dioxide, especially the enzyme RUBP carboxylase (Rubisco) (19). These results agree with what was obtained (22). The increase in the salinity of the irrigation water led to a decrease in the plant's nutrient content, because the concentration of sodium chloride in the soil solution led to an increase in the osmotic potential of the soil solution, which made it difficult for the plant to absorb water and ions, and there was inhibition in the growth and division of cells, as well as damage to cell membranes, which affects negatively in its selective permeability (2). Results show that the addition of polymers has significantly outperformed in improving all vegetative growth indicators, due to its role in preventing water infiltration into the depths of the soil away from the root system and thus maintaining the readiness of water and the moisture content in the soil for a longer period when plants are exposed to Lack of water (28). these materials have the ability to retain large amounts of water and nutrients when added to the soil, making it ready for plant growth whenever it is needed (25). It is also noted that the addition of polymers to the soil leads to an improvement in the physical properties of the soil, including aeration, and thus leads to the presence of nutritional elements (6, 7, 25). Polymers can also reduce salt stress on plants directly by improving soil properties or indirectly through their role in increasing the metabolism of plants to tolerate salt.lt is noted that selenium has a significant effect on increasing the concentration of nitrogen, phosphorous and potassium ions in the leaves, and the concentration increased by increasing the concentration of selenium (tables 2,3) foliar applied to on the plant. Absorption of nutrients in the growth medium (3,14). It is also believed that the increased absorption of nutrients is due to the role of selenium as an antioxidant for cytochromes, which has a role in the cytochrome pump to absorb salts (27). and this result agrees with what was obtained by(33) as they noticed an increase in the total soluble carbohydrates concentration the tubers and the concentration of nitrogen and potassium ions the leaves by treating the potato leaves with selenium at a concentration of 20 gm ft-1 compared to the no-spray treatment. It is noted from the results of Table (4,5) that the reason for the decreasing water potential in the leaf by the increase in the salinity of irrigation water may be due to the high osmotic effort in the soil, which impedes the plant's absorption of water, which leads to a decrease in its water effort (Table 4) and this led to a decrease in cell swelling and weakness in the processes of division and elongation (21), the reason for the increase in the stomata area in the low concentrations of the salinity of the irrigation water may be attributed to its role in increasing the levels of antioxidant enzymes, including superoxide dismutase (Table 4), which prompted the plant to resist stress, while the area stomata significantly decreased. The stomata by increasing the salinity level of the irrigation water may be due to the increase in the free gusts and the closure of the stomata and the synthesis of quantities of ABA acid in the cells of the epidermis of the leaf, and then it accumulates in the guard cells and works to influence the area and size of the stomata (Table 5) and this is consistent with (20,12).It is noticed that the water stress, the relative content of the leaves and the area of the stomata increase, as in (Tables 4 , 5), when adding polymers to the soil. It reduces the number of watering times in addition to improving the plant characteristics and reducing the total amount of water required for irrigation in addition to improving the aeration in the root zone and increasing the microbial activities in the soil (13).It is believed that selenium works to cleave the oxidizing factors inside the plant, turning the hydrogen peroxide molecule into two water molecules through its cleavage (16). It also contributes to the formation of Aquaporins, which contributes to increasing the efficiency of cellular transport of water within the plant tissues and increasing the relative water content inside the leaf This contributes to resistance to environmental stresses (23,4). Perhaps the reason for the decrease in water stress (the most negative) is due to the high levels of stress, which in turn will affect the stomata area (Table 5). The reason for increasing the stomata area may be due to an increase in selenium concentrations sprayed on the plant indicates the role of selenium in resisting water stress and these results agree with what was obtained (29).
*Part of Ph.D., Dissntation of the 1st author
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Abstract
The experiment was carried out in one of the green houses of the research station A of the Department of Horticulture and Landscape Design during fall season 2020/2021 This study was aimed to reducing the amount of irrigation water using factorial experiment with in split plot designed by The study included three factor , First factor, the quality of irrigation water (main plots) and at three levels: (irrigation with water from the Tigris River 0.92 dm s-1(I0), alternating irrigation (one irrigation with saline water followed by irrigation with the water of the Tigris River(I1), Alternating irrigation (two irrigations with saline water, followed by irrigation with the water of the Tigris River(I2), Second factor was the addition of Polyacrylamide (0, 1.5,2.5) g of soil-1 his symbol(P0,P1.P2). Third factor was spraying with selenium with three concentrations (0, 10,20) mg L-1 his symbol (S0,S1,S2) The results showed The addition of polymers led to decrease in the amount of irrigation water used to irrigate Iris, as the amount of irrigation water decreased with an increase in the concentrations of added polymers. Also, the polymers contributed at a concentration of 2.5 g kg of soil-1 percentage of dry matter in leaves, percentage of carbohydrates in leaves, N, P, K, percentage the water potential in the leaves, relative water content, stomata area and the reduction in the activity of the enzyme Superoxide dismutase led to an increase in the salinity of the irrigation water to a decrease in all characteristics and an increases in the activity of the sod and spraying with selenium at a concentration of 20 mgL-1 increased all study parameters and reduced enzyme activityed.
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