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Decorative foliage plants with a lush appearance are highly valued. One way to achieve this is to use plant growth regulators as plant growth management tools. The study was conducted on Schefflera dwarf (an ornamental foliage plant) treated with foliar sprays of gibberellic acid and benzyladenine hormone in a greenhouse equipped with a mist irrigation system. The hormone was sprayed on the leaves of dwarf schefflera at concentrations of 0, 100 and 200 mg/l in three stages every 15 days. The experiment was conducted on a factorial basis in a completely randomized design with four replications. The combination of gibberellic acid and benzyladenine at a concentration of 200 mg/l had a significant effect on the number of leaves, leaf area and plant height. This treatment also resulted in the highest content of photosynthetic pigments. In addition, the highest ratios of soluble carbohydrates and reducing sugars were observed with benzyladenine at 100 and 200 mg/L and gibberellic acid + benzyladenine at 200 mg/L. Stepwise regression analysis showed that root volume was the first variable to enter the model, explaining 44% of the variation. The next variable was fresh root mass, with the bivariate model explaining 63% of the variation in leaf number. The greatest positive effect on leaf number was exerted by fresh root weight (0.43), which was positively correlated with leaf number (0.47). The results showed that gibberellic acid and benzyladenine at a concentration of 200 mg/l significantly improved the morphological growth, chlorophyll and carotenoid synthesis of Liriodendron tulipifera, and reduced the content of sugars and soluble carbohydrates.
Schefflera arborescens (Hayata) Merr is an evergreen ornamental plant of the Araliaceae family, native to China and Taiwan1. This plant is often grown as a houseplant, but only one plant can grow in such conditions. The leaves have from 5 to 16 leaflets, each 10-20 cm2 long. Dwarf Schefflera is sold in large quantities every year, but modern gardening methods are rarely used. Therefore, the use of plant growth regulators as effective management tools to improve growth and sustainable production of horticultural products requires more attention. Today, the use of plant growth regulators has increased significantly3,4,5. Gibberellic acid is a plant growth regulator that can increase plant yield6. One of its known effects is the stimulation of vegetative growth, including stem and root elongation and increased leaf area7. The most significant effect of gibberellins is an increase in stem height due to lengthening of internodes. Foliar spraying of gibberellins on dwarf plants that are unable to produce gibberellins results in increased stem elongation and plant height8. Foliar spraying of flowers and leaves with gibberellic acid at a concentration of 500 mg/l can increase plant height, number, width and length of leaves9. Gibberellins have been reported to stimulate the growth of various broadleaf plants10. Stem elongation was observed in Scots pine (Pinussylvestris) and white spruce (Piceaglauca) when leaves were sprayed with gibberellic acid11.
One study examined the effects of three cytokinin plant growth regulators on lateral branch formation in Lily officinalis. bend Experiments were conducted in the fall and spring to study seasonal effects. The results showed that kinetin, benzyladenine and 2-prenyladenine did not affect the formation of additional branches. However, 500 ppm benzyladenine resulted in the formation of 12.2 and 8.2 subsidiary branches in the autumn and spring experiments, respectively, compared to 4.9 and 3.9 branches in the control plants. Studies have shown that summer treatments are more effective than winter ones12. In another experiment, Peace Lily var. Tassone plants were treated with 0, 250 and 500 ppm benzyladenine in 10 cm diameter pots. The results showed that the soil treatment significantly increased the number of additional leaves compared to control and benzyladenine-treated plants. New additional leaves were observed four weeks after treatment, and maximum leaf production was observed eight weeks after treatment. At 20 weeks post-treatment, soil-treated plants had less height gain than pre-treated plants13. It has been reported that benzyladenine at a concentration of 20 mg/L can significantly increase plant height and leaf number in Croton 14. In calla lilies, benzyladenine at a concentration of 500 ppm resulted in an increase in the number of branches, while the number of branches was the least in the control group15. The aim of this study was to investigate foliar spraying of gibberellic acid and benzyladenine to improve the growth of Schefflera dwarfa, an ornamental plant. These plant growth regulators can help commercial growers plan appropriate production year-round. No studies have been conducted to improve the growth of Liriodendron tulipifera.
This study was conducted in the indoor plant research greenhouse of Islamic Azad University in Jiloft, Iran. Uniform root transplants of dwarf schefflera 25 ± 5 cm in height were prepared (propagated six months before the experiment) and sown in pots. The pot is plastic, black, with a diameter of 20 cm and a height of 30 cm16.
The culture medium in this study was a mixture of peat, humus, washed sand and rice husk in a ratio of 1:1:1:1 (by volume)16. Place a layer of pebbles at the bottom of the pot for drainage. Average daytime and nighttime temperatures in the greenhouse in late spring and summer were 32±2°C and 28±2°C, respectively. Relative humidity ranges to >70%. Use a misting system for irrigation. On average, plants are watered 12 times a day. In autumn and summer, the time of each watering is 8 minutes, the watering interval is 1 hour. Plants were similarly grown four times, 2, 4, 6 and 8 weeks after sowing, with a micronutrient solution (Ghoncheh Co., Iran) at a concentration of 3 ppm and irrigated with 100 ml of solution each time. The nutrient solution contains N 8 ppm, P 4 ppm, K 5 ppm and trace elements Fe, Pb, Zn, Mn, Mo and B.
Three concentrations of gibberellic acid and the plant growth regulator benzyladenine (purchased from Sigma) were prepared at 0, 100 and 200 mg/L and sprayed onto plant buds in three stages at an interval of 15 days17. Tween 20 (0.1%) (purchased from Sigma) was used in the solution to increase its longevity and absorption rate. Early in the morning, spray the hormones on the buds and leaves of Liriodendron tulipifera using a sprayer. Plants are sprayed with distilled water.
Plant height, stem diameter, leaf area, chlorophyll content, number of internodes, length of secondary branches, number of secondary branches, root volume, root length, mass of leaf, root, stem and dry fresh matter, content of photosynthetic pigments (chlorophyll a, chlorophyll b) Total chlorophyll, carotenoids, total pigments), reducing sugars and soluble carbohydrates were measured in different treatments.
The chlorophyll content of young leaves was measured 180 days after spraying using a chlorophyll meter (Spad CL-01) from 9:30 to 10 am (due to leaf freshness). Additionally, leaf area was measured 180 days after spraying. Weigh three leaves from the top, middle and bottom of the stem from each pot. These leaves are then used as templates on A4 paper and the resulting pattern is cut out. The weight and surface area of one sheet of A4 paper were also measured. Then the area of the stenciled leaves is calculated using the proportions. Additionally, the volume of the root was determined using a graduated cylinder. Leaf dry weight, stem dry weight, root dry weight, and total dry weight of each sample were measured by oven drying at 72°C for 48 hours.
The content of chlorophyll and carotenoids was measured by the Lichtenthaler method18. To do this, 0.1 g of fresh leaves was ground in a porcelain mortar containing 15 ml of 80% acetone, and after filtering, their optical density was measured using a spectrophotometer at wavelengths of 663.2, 646.8 and 470 nm. Calibrate the device using 80% acetone. Calculate the concentration of photosynthetic pigments using the following equation:
Among them, Chl a, Chl b, Chl T and Car represent chlorophyll a, chlorophyll b, total chlorophyll and carotenoids, respectively. Results are presented in mg/ml plant.
Reducing sugars were measured using the Somogy method19. To do this, 0.02 g of plant shoots are ground in a porcelain mortar with 10 ml of distilled water and poured into a small glass. Heat the glass to a boil and then filter the contents using Whatman No. 1 filter paper to obtain a plant extract. Transfer 2 ml of each extract into a test tube and add 2 ml of copper sulfate solution. Cover the test tube with cotton wool and heat in a water bath at 100°C for 20 minutes. At this stage, Cu2+ is converted to Cu2O by reduction of the aldehyde monosaccharide and a salmon (terracotta) color is visible at the bottom of the test tube. After the test tube has cooled, add 2 ml of phosphomolybdic acid and a blue color will appear. Shake the tube vigorously until the color is evenly distributed throughout the tube. Read the absorbance of the solution at 600 nm using a spectrophotometer.
Calculate the concentration of reducing sugars using the standard curve. The concentration of soluble carbohydrates was determined by the Fales method20. To do this, 0.1 g of sprouts was mixed with 2.5 ml of 80% ethanol at 90 °C for 60 min (two stages of 30 min each) to extract soluble carbohydrates. The extract is then filtered and the alcohol is evaporated. The resulting precipitate is dissolved in 2.5 ml of distilled water. Pour 200 ml of each sample into a test tube and add 5 ml of anthrone indicator. The mixture was placed in a water bath at 90°C for 17 min, and after cooling, its absorbance was determined at 625 nm.
The experiment was a factorial experiment based on a completely randomized design with four replications. The PROC UNIVARIATE procedure is used to examine the normality of data distributions before analysis of variance. Statistical analysis began with descriptive statistical analysis to understand the quality of the raw data collected. Calculations are designed to simplify and compress large data sets to make them easier to interpret. Subsequently, more complex analyzes were carried out. Duncan’s test was performed using SPSS software (version 24; IBM Corporation, Armonk, NY, USA) to calculate mean squares and experimental errors to determine differences between data sets. Duncan’s multiple test (DMRT) was used to identify differences between means at a significance level of (0.05 ≤ p). Pearson correlation coefficient ( r ) was calculated using SPSS software (version 26; IBM Corp., Armonk, NY, USA) to evaluate the correlation between different pairs of parameters. In addition, linear regression analysis was performed using SPSS software (v.26) to predict the values of the first-year variables based on the values of the second-year variables. On the other hand, stepwise regression analysis with p < 0.01 was performed to identify the traits that critically influence dwarf schefflera leaves. Path analysis was conducted to determine the direct and indirect effects of each attribute in the model (based on the characteristics that better explain the variation). All the above calculations (normality of data distribution, simple correlation coefficient, stepwise regression and path analysis) were performed using SPSS V.26 software.
The selected cultivated plant samples were in accordance with the relevant institutional, national and international guidelines and domestic legislation of Iran.
Table 1 shows descriptive statistics of mean, standard deviation, minimum, maximum, range, and phenotypic coefficient of variation (CV) for various traits. Among these statistics, CV allows comparison of attributes because it is dimensionless. Reducing sugars (40.39%), root dry weight (37.32%), root fresh weight (37.30%), sugar to sugar ratio (30.20%) and root volume (30%) are the highest. and chlorophyll content (9.88%). ) and leaf area have the highest index (11.77%) and have the lowest CV value. Table 1 shows that total wet weight has the highest range. However, this trait does not have the highest CV. Therefore, dimensionless metrics such as CV should be used to compare attribute changes. A high CV indicates a large difference between treatments for this trait. The results of this experiment showed large differences between low-sugar treatments in root dry weight, fresh root weight, carbohydrate-to-sugar ratio, and root volume characteristics.
The ANOVA results showed that compared to the control, foliar spraying with gibberellic acid and benzyladenine had a significant effect on plant height, number of leaves, leaf area, root volume, root length, chlorophyll index, fresh weight and dry weight.
Comparison of mean values showed that plant growth regulators had a significant effect on plant height and leaf number. The most effective treatments were gibberellic acid at a concentration of 200 mg/l and gibberellic acid + benzyladenine at a concentration of 200 mg/l. Compared to the control, plant height and number of leaves increased by 32.92 times and 62.76 times, respectively (Table 2).
Leaf area significantly increased in all variants compared to the control, with the maximum increase observed at 200 mg/l for gibberellic acid, reaching 89.19 cm2. The results showed that leaf area increased significantly with increasing growth regulator concentration (Table 2).
All treatments significantly increased root volume and length compared to the control. The combination of gibberellic acid + benzyladenine had the greatest effect, increasing the volume and length of the root by half compared to the control (Table 2).
The highest values of stem diameter and internode length were observed in the control and gibberellic acid + benzyladenine 200 mg/l treatments, respectively.
The chlorophyll index increased in all variants compared to the control. The highest value of this trait was observed when treated with gibberellic acid + benzyladenine 200 mg/l, which was 30.21% higher than the control (Table 2).
The results showed that the treatment resulted in significant differences in pigment content, reduction in sugars and soluble carbohydrates.
Treatment with gibberellic acid + benzyladenine resulted in the maximum content of photosynthetic pigments. This sign was significantly higher in all variants than in the control.
The results showed that all treatments could increase the chlorophyll content of Schefflera dwarf. However, the highest value of this trait was observed in the treatment with gibberellic acid + benzyladenine, which was 36.95% higher than the control (Table 3).
The results for chlorophyll b were completely similar to the results for chlorophyll a, the only difference was the increase in the content of chlorophyll b, which was 67.15% higher than in the control (Table 3).
The treatment resulted in a significant increase in total chlorophyll compared to the control. Treatment with gibberellic acid 200 mg/l + benzyladenine 100 mg/l led to the highest value of this trait, which was 50% higher than the control (Table 3). According to the results, control and treatment with benzyladenine at a dose of 100 mg/l led to the highest rates of this trait. Liriodendron tulipifera has the highest value of carotenoids (Table 3).
The results showed that when treated with gibberellic acid at a concentration of 200 mg/L, the content of chlorophyll a significantly increased to chlorophyll b (Fig. 1).
Effect of gibberellic acid and benzyladenine on a/b Ch. Proportions of dwarf schefflera. (GA3: gibberellic acid and BA: benzyladenine). The same letters in each figure indicate that the difference is not significant (P < 0.01).
The effect of each treatment on the fresh and dry weight of dwarf schefflera wood was significantly higher than that of the control. Gibberellic acid + benzyladenine at 200 mg/L was the most effective treatment, increasing the fresh weight by 138.45% compared to the control. Compared to the control, all treatments except 100 mg/L benzyladenine significantly increased plant dry weight, and 200 mg/L gibberellic acid + benzyladenine resulted in the highest value for this trait (Table 4).
Most of the variants differed significantly from the control in this respect, with the highest values belonging to 100 and 200 mg/l benzyladenine and 200 mg/l gibberellic acid + benzyladenine (Fig. 2).
The influence of gibberellic acid and benzyladenine on the ratio of soluble carbohydrates and reducing sugars in dwarf schefflera. (GA3: gibberellic acid and BA: benzyladenine). The same letters in each figure indicate no significant difference (P < 0.01).
Stepwise regression analysis was performed to determine the actual attributes and better understand the relationship between independent variables and leaf number in Liriodendron tulipifera. Root volume was the first variable entered into the model, explaining 44% of the variation. The next variable was fresh root weight, and these two variables explained 63% of the variation in leaf number (Table 5).
Path analysis was performed to better interpret the stepwise regression (Table 6 and Figure 3). The greatest positive effect on leaf number was associated with fresh root mass (0.43), which was positively correlated with leaf number (0.47). This indicates that this trait directly affects yield, while its indirect effect through other traits is negligible, and that this trait can be used as a selection criterion in breeding programs for dwarf schefflera. The direct effect of root volume was negative (−0.67). The influence of this trait on the number of leaves is direct, the indirect influence is insignificant. This indicates that the larger the root volume, the smaller the number of leaves.
Figure 4 shows the changes in the linear regression of root volume and reducing sugars. According to the regression coefficient, each unit change in root length and soluble carbohydrates means that root volume and reducing sugars change by 0.6019 and 0.311 units.
The Pearson correlation coefficient of growth traits is shown in Figure 5. The results showed that number of leaves and plant height (0.379*) had the highest positive correlation and significance.
Heat map of relationships between variables in growth rate correlation coefficients. # Y Axis: 1-Index Ch., 2-Internode, 3-LAI, 4-N of leaves, 5-Height of legs, 6-Stem diameter. # Along the X axis: A – index H., B – distance between nodes, C – LAY, D – N. of the leaf, E – height of the trouser leg, F – diameter of the stem.
The Pearson correlation coefficient for wet weight-related attributes is shown in Figure 6. The results show the relationship between leaf wet weight and aboveground dry weight (0.834**), total dry weight (0.913**) and root dry weight (0.562*). . Total dry mass has the highest and most significant positive correlation with shoot dry mass (0.790**) and root dry mass (0.741**).
Heat map of relationships between fresh weight correlation coefficient variables. # Y axis: 1 – weight of fresh leaves, 2 – weight of fresh buds, 3 – weight of fresh roots, 4 – total weight of fresh leaves. # The X-axis represents: A – fresh leaf weight, B – fresh bud weight, CW – fresh root weight, D – total fresh weight.
The Pearson correlation coefficients for dry weight-related attributes are shown in Figure 7. The results show that leaf dry weight, bud dry weight (0.848**) and total dry weight (0.947**), bud dry weight (0.854**) and total dry mass (0.781**) have the highest values. positive correlation and significant correlation.
Heat map of relationships between dry weight correlation coefficient variables. # Y axis represents: 1-leaf dry weight, 2-bud dry weight, 3-root dry weight, 4-total dry weight. # X Axis: A-leaf dry weight, B-bud dry weight, CW root dry weight, D-total dry weight.
The Pearson correlation coefficient of pigment properties is shown in Figure 8. The results show that chlorophyll a and chlorophyll b (0.716**), total chlorophyll (0.968**) and total pigments (0.954**); chlorophyll b and total chlorophyll (0.868**) and total pigments (0.851**); total chlorophyll has the highest positive and significant correlation with total pigments (0.984**).
Heat map of relationships between chlorophyll correlation coefficient variables. # Y axes: 1- Channel a, 2- Channel. b,3 – a/b ratio, 4 channels. Total, 5-carotenoids, 6-yield pigments. # X-Axes: A-Ch. a.B-Ch. b,C- a/b ratio, D-Ch. Total content, E-carotenoids, F-yield of pigments.
Dwarf Schefflera is a popular houseplant all over the world, and its growth and development is currently receiving much attention. The use of plant growth regulators resulted in significant differences, with all treatments increasing plant height compared to the control. Although plant height is usually controlled genetically, research shows that application of plant growth regulators can increase or decrease plant height. Plant height and number of leaves treated with gibberellic acid + benzyladenine 200 mg/L were the highest, reaching 109 cm and 38.25, respectively. Consistent with previous studies (SalehiSardoei et al.52) and Spathiphyllum23, similar increases in plant height due to gibberellic acid treatment were observed in potted marigolds, albus alba21, daylilies22, daylilies, agarwood and peace lilies.
Gibberellic acid (GA) plays an important role in various physiological processes of plants. They stimulate cell division, cell elongation, stem elongation and size increase24. GA induces cell division and elongation in shoot apices and meristems25. Leaf changes also include decreased stem thickness, smaller leaf size, and a brighter green color26. Studies using inhibitory or stimulatory factors have shown that calcium ions from internal sources act as second messengers in the gibberellin signaling pathway in sorghum corolla27. HA increases plant length by stimulating the synthesis of enzymes that cause cell wall relaxation, such as XET or XTH, expansins and PME28. This causes the cells to enlarge as the cell wall relaxes and water enters the cell29. Application of GA7, GA3 and GA4 can increase stem elongation30,31. Gibberellic acid causes stem elongation in dwarf plants, and in rosette plants it retards leaf growth and internode elongation32. However, before the reproductive stage, the stem length increases to 4–5 times its original height33. The process of GA biosynthesis in plants is summarized in Figure 9.
GA biosynthesis in plants and levels of endogenous bioactive GA, schematic representation of plants (right) and GA biosynthesis (left). The arrows are color coded to correspond to the form of HA indicated along the biosynthetic pathway; red arrows indicate decreased GC levels due to localization in plant organs, and black arrows indicate increased GC levels. In many plants, such as rice and watermelon, GA content is higher at the base or lower part of the leaf30. Moreover, some reports indicate that bioactive GA content decreases as leaves elongate from the base34. The exact levels of gibberellins in these cases are unknown.
Plant growth regulators also significantly influence the number and area of leaves. The results showed that increasing the concentration of plant growth regulator resulted in a significant increase in leaf area and number. Benzyladenine has been reported to increase calla leaf production15. According to the results of this study, all treatments improved leaf area and number. Gibberellic acid + benzyladenine was the most effective treatment and resulted in the greatest number and area of leaves. When growing dwarf schefflera indoors, there may be a noticeable increase in the number of leaves.
GA3 treatment increased internode length compared with benzyladenine (BA) or no hormonal treatment. This result is logical given the role of GA in promoting growth7. Stem growth also showed similar results. Gibberellic acid increased the length of the stem but decreased its diameter. However, combined application of BA and GA3 significantly increased stem length. This increase was higher compared to plants treated with BA or without the hormone. Although gibberellic acid and cytokinins (CK) generally promote plant growth, in some cases they have opposite effects on different processes35. For example, a negative interaction was observed in the increase in hypocotyl length in plants treated with GA and BA36. On the other hand, BA significantly increased root volume (Table 1). Increased root volume due to exogenous BA has been reported in many plants (e.g. Dendrobium and Orchid species)37,38.
All hormonal treatments increased the number of new leaves. Natural increase in leaf area and stem length through combination treatments is commercially desirable. The number of new leaves is an important indicator of vegetative growth. The use of exogenous hormones has not been used in the commercial production of Liriodendron tulipifera. However, the growth-promoting effects of GA and CK, applied in balance, may provide new insights into improving the cultivation of this plant. Notably, the synergistic effect of BA + GA3 treatment was higher than that of GA or BA administered alone. Gibberellic acid increases the number of new leaves. As new leaves develop, increasing the number of new leaves can limit leaf growth39. GA has been reported to improve the transport of sucrose from sinks to source organs40,41. In addition, exogenous application of GA to perennial plants can promote the growth of vegetative organs such as leaves and roots, thereby preventing the transition from vegetative growth to reproductive growth42.
The effect of GA on increasing plant dry matter can be explained by an increase in photosynthesis due to an increase in leaf area43. GA was reported to cause an increase in leaf area of Maize34. The results showed that increasing the BA concentration to 200 mg/L could increase the length and number of secondary branches and root volume. Gibberellic acid influences cellular processes such as stimulating cell division and elongation, thereby improving vegetative growth43. In addition, HA expands the cell wall by hydrolyzing starch into sugar, thereby reducing the cell’s water potential, causing water to enter the cell and ultimately leading to cell elongation44.
Post time: Jun-11-2024