Abstract: Background and Objective: Algae extract has a unique potential to participate in improving agricultural productivity and ecological situations. So, the objective of this study was to examine the possibility of using algae extract as a foliar spray on peanut plants as alternative environmental friend fertilizer. Materials and Methods: Two field experimental trials were implemented, during two successive summer seasons 2017/2018 and 2018/2019. To study the effect of the blue-green algae extract (algae extract) treatments (0, 1, 2 and 3%) and or water stress (skipping irrigation) treatments (40, 60 and 80% WHC) on peanut grown in sandy soil were applied. Results: Drought stress led to a lowering in vegetative growth, photosynthetic pigments, yield components and carbohydrate contents in comparison with 80% of WHC. At the same time, significant accumulation for a large amount of some compatible solute such as; (proline, free amino acids and total soluble sugar) under water stress was observed. Foliar treatments of 1, 2 and 3% of algae extract led to an increment in growth parameters, yield components, photosynthetic pigments and carbohydrate. Also, a significant increment of the organic solutes of leaves (total soluble sugar, proline and free amino acids), antioxidant compounds and some minerals (N, P and K) was observed due to algae extract the application. The nutritional value of yielded peanut seeds was also improved when sprayed with algae extract. Conclusion: Algae extract considered good foliar nutritional substances incremented peanut plants tolerance to water deficiency stress throughout its mineral elements and phytohormones which improved its yield quantitatively and qualitatively.
INTRODUCTION
Peanut (Arachis hypogaea L.) are considered as a source of protein and oil from leguminous crops. In addition to other vital components, its seeds considered high nutritive value1 due to their edible oil and protein. Pelto et al.2 reported that peanut as an energy source contains carbohydrates, lipids, proteins, vitamins, minerals, some organic acids and purines are growth supplementing constituents. Gersen et al.3 mentioned that the malnutrition suffering population from many countries by 30%. Peanuts as a rich source of protein, essential amino acids can support in preventing malnutrition problems. Also, energy rich compounds (lipids and carbohydrates) from peanut seeds are capable of offering the human body basic energy needs for sustaining its normal health. In Egypt, during the last 2 decades, with increasing population land reclamation is necessary for increasing the production of incremented demand on food.
Drought as abiotic stress creates the Reactive Oxygen Species (ROS) responsible for drastically hinder of the growth and productivity of plants via alternations in their physiological and biochemical processes4. Bakry et al.5 reported that drought affects plant growth and development throughout inducing changes in the hormonal balance of the main plant tissue that cause decreases in water potential, cell division, net photosynthesis and protein synthesis which cause the reduction in yield via reducing total biomass, relative water content and chlorophyll content. Therefore, attempts had been made to overcome such problems in newly reclaimed soils to improve the growth and yield of different crops. Rauf and Sadaqat6 followed different strategies to reduce the losses caused by drought, e.g., increasing water use efficiency and producing drought-resistant cultivars, use of growth regulators (GA3, IAA and CK3), seed treatments with osmoprotectants and the use of biofertilizer in such soils. Grzesik et al.7 stated that with the increasing interest of the environment plant scientists focused on the use of microorganisms, e.g., algae extract and green algae, as biofertilizers. From an economic and ecological point of view, these new sources can be used as an alternative to chemical fertilizers in sandy soils in crop production.
Haggag et al.8 indicated that algae extract induced an increment in the plant height, lateral shoot numbers, stem diameter, leaves number and root length on olive plant. Moreover, Sahu et al.9 concluded that bio fertilization reduced the use of chemical fertilizers and pesticides which threatens the environment and human health. Rodriguez et al.10 found that algae extract excreting growth-promoting substances, e.g., hormones (Auxin, Gibberellins), vitamins and amino acids. Proline accumulation considered a biochemical indicator for incremented stress tolerance in plant species under stress conditions. Flavonoids are the main and most complex subgroup of polyphenols proved to have a wide range of biological functions11. Moreover, phenolic compounds as structural components of cell walls play multiple roles in plants through participating in the regulation of growth and development processes. These compounds participate in the mechanisms of defense against biotic and abiotic stress12. The main objective of the present study was to alleviate the adverse effects of drought stress, on growth, some physiological aspects, yield and yield components of peanut plants through the foliar treatments of blue-green algae extract.
MATERIALS AND METHODS
Study area: Two field experiments were carried out at the Research and Production Station of the National Research Centre, Nubaria region (30 30.054'N-30 19.421'E), Behira Governorate, Egypt during 2017/2018 and 2018/2019.
Experimental procedures: Seeds of peanut (Arachis hypogaea L.) Giza 6 were sown in August in both seasons. The experimental design was a split-plot with 4 replications. The Water stress treatments (40, 60 and 80% water holding capacity, WHC) occupied the main plots and the blue-green algae extract treatments (0, 1, 2 and 3%) were allocated at random in the sub-plots. The plot area was 10.5 m2 (3.5×3.0 m). Some physical and chemical properties of a representative soil sample used of the experimental site were determined before sowing13 and presented in (Table 1).
Calcium super-phosphate (15.50% P2O5) was added pre-sowing at 150 kg fed–1 (ha = 2.4 fed, fed = feddan) to the soil; similarly, nitrogen in the form of ammonium nitrate (33.0% N) at the rate of 20 kg N/fed as starter dose was added before first irrigation, Potassium sulphate (48% K2O) was added at the rate of 50 kg fed–1 to the soil in two equal doses at 21 and 35 days after sowing. Peanut plants were irrigated and maintained during the whole growth season using a sprinkler irrigation system. In both seasons, a foliar spray of blue-green algae extract was applied twice to peanut plants during the elongation stage (at 45-60 days from sowing). The interaction of different concentrations of both compounds was also assessed in addition to untreated plants (control).
Plant samples were taken after 75 days from sowing to measure the growth parameters plant fresh and dry weight (g/plant), root fresh and dry weight (g) and root length.
| Table 1: Some physical and chemical properties of the experimental soil (Mean of two seasons) | |||||||
| Particle size distribution | Texture | ||||||
| pH (1:2.5) | Electeric conductivity (dSm–1) | Organic matter (%) | CaCO3 (%) | Sand (%) | Silt (%) | Clay (%) | Class |
| 8.06 | 1.29 | 0.86 | 3.48 | 76.2 | 4.9 | 18.32 | Sandy loam |
| Cation (mg/100 g soil) | Anion (mg/100 g soil) | ||||||
| Na+ | K+ | Ca++ | Mg++ | CO3-- | HCO3- | Cl- | SO4-- |
| 3.67 | 1.3 | 3.42 | 1.51 | 0.38 | 3.62 | 1.91 | 3.51 |
| Available macronutrients (mg/100 g soil) | Available micronutrients (mg kg–1) | ||||||
| N | P | K | Fe | Zn | Mn | Cu | |
| 15.26 | 4.65 | 17.23 | 12.8 | 0.11 | 6.97 | 0.013 | |
dSm-1: DeciSiemens per metre, mg: Milligram, g: Gram, kg: Kilogram |
|||||||
Biochemical aspects (total photosynthetic pigments, some biochemical analysis i.e., total soluble sugars, total phenol, proline, free amino acids, total indole and some element content (nitrogen, phosphorous and potassium) were measured. At harvest, the following characters were recorded a number of branches, number of pods/plant, pod yield and seed yield. Also, the nutritive value of yielded seeds (oil%, protein%, total carbohydrates%, nitrogen, phosphorus and potassium contents) was estimated. Phenol, flavonoids and the antioxidant activity (DPPH radical scavenging) were also determined.
Chemical analysis: Some biochemical aspects were determined including photosynthetic pigments in fresh leaves using the method of SPAD (Soil Plant Analysis Development; SPAD, Minolta Camera Co., Osaka, Japan) chlorophyll meter according to Minolta14. Indole acetic acid content was extracted and analyzed by the method of Larsen et al.15. Phenolic content was measured as described by Danil and George16. Free Amino Acids (FAA) were extracted according to Vartainan et al.17 and determined with the ninhydrin reagent method by Yemm and Cocking18.
Proline content was extracted and calculated according to Bates et al.19. Total Soluble Sugars (TSS) extracted by Homme et al.20 and assayed according to Yemm and Willis21. Macroelement ions content was extracted and estimated by the method described by Rebecca13.
The antioxidant activity (DPPH radical scavenging) was determined using the method of Liyana-Pathiranan and Shahidi22. Total flavonoids were determined by using the method reported by Chang et al.23. Dry samples of seeds were used to determine total carbohydrate using the colorimetric method described Dubois et al.24. Crude protein percentage was extracted and determined by Micro-Kjeldahl method and oil content as described by A.O.A.C25. The value of total crude protein was calculated by multiplying the total values of total-N by factor 6.25.
Statistical analysis: A combined analysis of data for the two seasons was statistically analyzed according to the technique of Analysis of Variance (ANOVA) for the split-plot design by using MSTAT26 computer software package. Least Significant Difference (LSD) method was used to test the differences among treatment means at 5% level of probability as described by Snedecor and Cochran27.
RESULTS AND DISCUSSION
Changes in growth parameters: Data in Table 2 showed the influence of the different concentrations of algae extract on some growth indicators of peanut plants grown under drought stress in forms of different Water Holding Capacity (WHC) levels. The two levels of WHC (60-40%) in the soil induced significant (p<0.05) reduction in some morphological parameters (plant fresh and dry weights of both shoot and root and root length) compared to plants grown under 80% WHC.
Treatment of peanut plants with different concentrations of cyanobacteria incremented the estimated growth criteria under different water levels compared with similar WHC. Maximum increments in the measured growth indicators were obtained by using a high concentration of algae extract (3%) under different WHC levels. The reduction in the growth parameters under 60-40% WHC levels may be attributed to the losses of tissue water which inhibited cell division and enlargement28. Moreover, such an effect could result from the decrease in the meristematic tissues (responsible for elongation) activity29. Moreover, total fresh and dry weights decreased due to the low levels of drought which might have resulted from a reduction in chlorophyll content and consequently, photosynthetic effectiveness30. Decreasing photosynthesis and consequently plant growth with drought stress accompanied by the promotion of ROS production which is responsible for the degradation of proteins and membranes31.
| Fig. 1: | Effect of algae extract on chlorophyll contents of peanut under water stress SPAD: Soil Plant Analysis Development chlorophyll meter WHC: Water holding capacity, BGA: Blue-green algae |
| Table 2: Effect of algae extract on some growth parameters of peanut under water stress | ||||||
| Treatments | Fresh weight (g plant–1) | Dry weight (g plant–1) | ||||
| WHC | BGA |
Root |
Shoot |
Root |
Shoot |
Root length (cm) |
| 80% | 0 |
7.66 |
128.99 |
2.25 |
38.02 |
11.23 |
1% |
8.52 |
136.20 |
2.43 |
40.2 |
12.32 |
|
2% |
9.21 |
138.83 |
2.75 |
42.81 |
12.67 |
|
3% |
9.43 |
163.98 |
2.87 |
46.65 |
13.33 |
|
| 60% | 0 |
6.86 |
116.76 |
2.04 |
34.46 |
9.27 |
1% |
7.29 |
122.76 |
2.18 |
38.15 |
9.67 |
|
2% |
8.28 |
134.43 |
2.33 |
41.12 |
11.32 |
|
3% |
8.36 |
143.70 |
2.41 |
42.68 |
11.58 |
|
| 40% | 0 |
3.84 |
71.38 |
1.68 |
26.35 |
8.67 |
1% |
4.16 |
80.02 |
1.76 |
27.45 |
9.05 |
|
2% |
4.57 |
89.26 |
1.86 |
27.90 |
10.12 |
|
3% |
4.93 |
91.48 |
1.95 |
31.60 |
10.67 |
|
| LSD (0.05) | WHC |
0.06 |
3.78 |
0.031 |
0.60 |
2.23 |
BGA |
0.07 |
4.37 |
0.035 |
0.69 |
2.58 |
|
WHC*BGA |
0.11 |
7.98 |
0.058 |
1.15 |
4.77 |
|
WHC: Water holding capacity, BGA: Blue-green algae, g: Gram |
||||||
Blue-green algae foliar spraying on peanut plants incremented significantly (p<0.05) growth of shoot and root compared with control plants grown under water stress or normal conditions. The obtained results are in agreement with those obtained by Khafagy et al.32 on the barley plant in terms of drought stress effect. The obtained results of the promotive effect of algae extract on growth criteria of peanut plants are similar to those obtained by Ismail and Abo-Hamad33 on barley and fenugreek. These increments in growth parameters could be attributed to nitrogen atmospheric fixation in addition to algae extract (biofertilizer) that containing some of the necessary macro and microelements (N, P, K, Ca, Mg, Zn, Fe, Mn, Cu, Mo, Co) and various bioactive materials and growth regulators (e.g., IAA) as well. Moreover, Stirk et al.34 concluded that algae extract found to release different active substances, e.g., phytohormones, proteins, vitamins, carbohydrates, amino acids and polysaccharides which function as signaling molecules enhances plant growth.
Photosynthetic pigments: The data in Fig. 1 illustrated the influence of different concentrations of algae extract on total chlorophyll in leaves of peanut plants under different levels of WHC. Decreasing the WHC of soil from 80, 60 and 40% induced significant (p<0.05) decrease of photosynthetic pigments (total chlorophyll). Peanut plants sprayed with different levels of concentrations of algae extract significantly (p<0.05) incremented total chlorophyll under different levels of water compared with similar WHC. Maximum improvement in total chlorophyll was obtained by using a high concentration of algae extract (3%) under different WHC levels.
| Table 3: Effect of algae extract on compatible solutes, phenol and indole acetic acidcontents of peanut under water stress | ||||||
| Treatments | Compatible solutes (mg g–1 dry wt.) | |||||
| WHC* | BGA* |
Total soluble sugars |
Proline |
Free amino acids |
Phenol (mg g–1 dry wt.) |
Indole acetic acid (mg g–1 dry wt.) |
| 80% | 0 |
10.86 |
3.85 |
22.47 |
13.48 |
7.62 |
1% |
12.73 |
3.49 |
22.86 |
14.55 |
9.07 |
|
2% |
14.68 |
2.82 |
24.14 |
15.45 |
10.42 |
|
3% |
18.95 |
2.06 |
26.77 |
18.65 |
13.98 |
|
| 60% | 0 |
11.52 |
4.15 |
23.84 |
13.42 |
7.37 |
1% |
12.03 |
3.53 |
24.64 |
14.44 |
8.00 |
|
2% |
14.13 |
3.06 |
24.78 |
15.36 |
10.25 |
|
3% |
17.50 |
2.34 |
25.65 |
17.48 |
12.19 |
|
| 40% | 0 |
12.40 |
4.90 |
24.89 |
11.19 |
6.30 |
1% |
12.92 |
4.55 |
25.51 |
14.39 |
7.72 |
|
2% |
13.73 |
3.10 |
26.05 |
14.90 |
9.73 |
|
3% |
16.53 |
2.65 |
26.17 |
16.96 |
10.48 |
|
| LSD (0.05) | WHC |
0.78 |
0.12 |
0.46 |
0.35 |
0.56 |
BGA |
0.90 |
0.14 |
0.53 |
0.40 |
0.64 |
|
WHC*BGA |
NS |
0.22 |
NS |
0.62 |
NS |
|
*WHC: Water holding capacity, BGA: Blue-green algae, (mg g–1 dry wt.): milligram/gram dry weight |
||||||
The data for the reduction effect on photosynthetic pigments obtained herein are in accordance with those recorded by Ezzo et al.35 on the moringa plant with drought. Rong-Hua et al.36 stated that the disorganization of thylakoid membranes accompanied by more degradation than the synthesis of chlorophyll through the formation of proteolytic enzymes (e.g., chlorophyllase) results in the reduction of chlorophyll content in most stressed plants. Such action is responsible for the degradation of chlorophyll and photosynthetic apparatus damage. Anjum et al.37 stated that disruption in the photosynthetic pigments causing permanent disadvantage in the photosynthetic apparatus, gas exchange reduction, accompanied by a decrease in growth parameters and productivity result from drought stress. Grzesik et al.7 explained the incremented levels of various photosynthetic pigments in response to algae extract by the availability of a high amount of atmospheric nitrogen assimilated by algae extract and transported to plant tissues.
Changes in some compatible solutes, phenol and auxin contents: Table 3 shows that levels of drought stress (60-40%) resulted in significant (p<0.05) increment in compatible solutes concentrations (total soluble sugars, proline and free amino acids) of peanut leaves comparison with their control plants. Moreover, spraying peanut plants with the tested concentrations of algae extract significantly (p<0.05) incremented concentrations of compatible solutes ascendingly in the unstressed plants as well as those of the drought-stressed plants (60-40% WHC) relative to the corresponding controls.
Foliar application of algae extracts to the cultivated peanut plants induced significantly (p<0.05) increment in TSS as compared with plants cultivated without algae extract. This treatment enhanced the accumulation of TSS in water deficit plants throughout the increase of endogenous levels of phytohormones or by acting as promotors of carbohydrates synthesis. Bakry et al.38 reported that total soluble sugars of two linseed varieties played a vital role in carbon storage and osmotic adjustment and radical scavenging were incremented under water stress conditions. Ezzo et al.35 and Hellal et al.39 on moringa and barley plants showed that free amino acids, proline and TSS incremented under water stress. They revealed that these osmoprotectants participated in the adaptation of cells to different environmental stress conditions. These substances raised osmotic pressure in the cytoplasm, stabilized proteins and membranes and maintained the relatively higher water content obligatory for plant growth and cellular functions.
Also, proline considered as nitrogen and carbon source for recovery from stress and acting as a stabilizer for membranes and some macromolecules and free radical scavenger as well37. A biotic stresses various caused the accumulation of proline in plant tissues could be attributed to the decrease in proline oxidase activity under drought conditions38 and might a vital role played against oxidative damages resulted from ROS (Reactive Oxygen Spices) resulting in increasing membrane stabilization and help in the stabilization of tertiary structures of proteins and enzymes40. Abbas et al.41 found that the total proline content of rice plants incremented significantly (p<0.05) with applying algae extract inoculation.
Table 3 illustrated that both drought stress levels (60-40%) caused significant (p<0.05) decreases in phenolic and IAA contents relative to control (unstressed) plants.
| Table 4: Effect of algae extract on some nutrient contents peanut of root and shoot under water stress | |||||||
| Treatments | Nitrogen (%) | Phosphorus (%) | Potassium (%) | ||||
| WHC* | BGA* |
Root |
Shoot |
Root |
Shoot |
Root |
Shoot |
| 80% | 0 |
1.20 |
1.77 |
0.86 |
1.05 |
0.41 |
0.85 |
1% |
1.30 |
1.85 |
0.94 |
1.21 |
0.48 |
0.87 |
|
2% |
1.35 |
2.03 |
0.97 |
1.28 |
0.51 |
0.96 |
|
3% |
1.41 |
2.12 |
1.03 |
1.31 |
0.53 |
0.99 |
|
| 60% | 0 |
1.15 |
1.66 |
0.76 |
0.95 |
0.37 |
0.86 |
1% |
1.25 |
1.82 |
0.84 |
1.06 |
0.39 |
0.88 |
|
2% |
1.33 |
2.02 |
0.92 |
1.13 |
0.42 |
0.94 |
|
3% |
1.38 |
1.96 |
0.96 |
1.21 |
0.48 |
0.98 |
|
| 40% | 0 |
1.07 |
1.52 |
0.73 |
0.83 |
0.34 |
0.82 |
1% |
1.21 |
1.81 |
0.82 |
0.92 |
0.38 |
0.86 |
|
2% |
1.30 |
1.96 |
0.91 |
0.98 |
0.41 |
0.95 |
|
3% |
1.34 |
1.89 |
0.94 |
1.02 |
0.43 |
0.98 |
|
| LSD (0.05) | WHC |
0.009 |
0.02 |
0.018 |
0.019 |
0.013 |
0.034 |
BGA |
0.017 |
0.028 |
0.039 |
0.013 |
0.013 |
0.044 |
|
WHC*BGA |
0.022 |
0.043 |
0.051 |
0.03 |
0.024 |
0.071 |
|
*WHC: Water holding capacity, BGA: Blue-green algae |
|||||||
| Table 5: Effect of algae extract on some yield parameters of peanutunder water stress | ||||||
| Treatments | ||||||
| WHC* | BGA* |
No. of pods/plant |
Pod yield (g plant–1) |
Pod yield (t fed–1) |
Seed yield (g plant–1) |
Seed yield (t fed–1) |
| 80% | 0 |
31.3 |
46.17 |
2.48 |
15.21 |
1.53 |
1% |
32.2 |
51.64 |
2.56 |
17.52 |
1.64 |
|
2% |
35.8 |
52.5 |
2.63 |
19.76 |
1.88 |
|
3% |
36.4 |
53.74 |
2.91 |
20.78 |
1.90 |
|
| 60% | 0 |
23.3 |
41.34 |
1.74 |
13.02 |
0.91 |
1% |
24.7 |
43.44 |
1.94 |
13.79 |
0.92 |
|
2% |
27.8 |
45.4 |
2.13 |
14.69 |
1.07 |
|
3% |
28.9 |
47.37 |
2.25 |
16.78 |
1.11 |
|
| 40% | 0 |
23.8 |
29.72 |
1.41 |
9.12 |
0.66 |
1% |
25.1 |
32.61 |
1.54 |
9.84 |
0.68 |
|
2% |
26.4 |
34.29 |
1.58 |
11.36 |
0.81 |
|
3% |
28.2 |
35.14 |
1.67 |
12.11 |
0.85 |
|
| LSD (0.05) | WHC |
0.86 |
1.93 |
0.026 |
2.46 |
0.012 |
BGA |
0.99 |
2.23 |
0.038 |
2.71 |
0.014 |
|
WHC*BGA |
1.78 |
3.89 |
0.057 |
5.01 |
NS |
|
*WHC: Water holding capacity, BGA: Blue-green algae, g: Gram, fed: Feddan = 0.42 hectares |
||||||
Regarding algae extract foliar application effect, it was noted that there was a gradual increment in both parameters with increasing algae extract concentration as compared with corresponding WHC control. Moreover, it was noticed that algae extract at 3% level treatment was more effective than 2-1%, respectively in enhancing phenol and IAA contents. The improvement in auxin content with algae extract treatments may explain the increment in tested peanut plant’s resistance to drought stress. These results are in agreement with Gheda and Ahmed42, who reported that auxins, gibberellins, cytokinins, proteins and lipids reported as bioactive algae extract substances are effective on promoting plant growth, development and its tolerance to drought stress.
Macro-elements in shoot and root of plants: Increasing water stress (WHC from 60-40%) in the soil induced significant (p<0.05)decrease in N, P and K percentages in comparison with their control (Table 4). Treating plant shoots with different levels of algae extract concentrations under various levels of WHC caused a significant (p<0.05) increment in the N, P and K percentage in comparison with the control ones. The most pronounced increment was observed in 3% blue-green algae foliar spraying.
Concerning the effect of water stress some research work (Abdallah et al.4 and Hellal et al.43) recorded decreases in the N, P, K content supported the obtained results of the present work. While El Sayed et al.44 found that the application of blue-green algae resulted in significantly (p<0.05) higher macronutrient of moringa compared with the untreated control. Also, Abbas et al.41 recorded significant (p<0.05) increment in the total contents of N, P and K rice plants subjected to algae extract inoculation treatments.
| Fig. 2: | Effect of algae extract on macronutrient contents of seeds (%) under water stress BGA: Blue-green algae, WHC: Water holding capacity |
| Table 6: Effect of algae extract on oil, carbohydrate and phenol contents of peanut under water stress | ||||||
| Treatments | ||||||
| WHC* | BGA* |
Oil (%) |
Carbohydrate (%) |
DPPH (%) |
Flavonoids (mg/100 g dry wt.) |
Phenol (mg/100 g dry wt.) |
| 80% | 0 |
38.72 |
14.65 |
48.28 |
12.38 |
294.14 |
1% |
40.45 |
15.95 |
52.05 |
13.11 |
317.17 |
|
2% |
41.6 |
17.75 |
59.04 |
14.67 |
336.45 |
|
3% |
46.38 |
18.05 |
61.97 |
15.90 |
351.86 |
|
| 60% | 0 |
38.03 |
14.24 |
42.95 |
11.35 |
216.29 |
1% |
39.92 |
15.95 |
46.14 |
12.06 |
249.30 |
|
2% |
41.13 |
16.67 |
51.76 |
13.18 |
259.09 |
|
3% |
42.85 |
17.29 |
52.04 |
14.39 |
268.37 |
|
| 40% | 0 |
37.70 |
13.64 |
41.36 |
10.12 |
208.87 |
1% |
39.23 |
14.33 |
50.67 |
11.98 |
234.25 |
|
2% |
40.46 |
16.34 |
51.92 |
12.60 |
245.92 |
|
3% |
41.78 |
16.62 |
52.31 |
12.87 |
255.15 |
|
| LSD (0.05) | WHC |
0.771 |
0.298 |
0.59 |
0.524 |
3.055 |
BGA |
0.891 |
0.344 |
0.682 |
0.605 |
3.528 |
|
WHC*BGA |
1.377 |
0.531 |
1.054 |
0.935 |
5.453 |
|
*WHC: Water holding capacity, BGA: Blue-green algae, DPPH: (1,1-Diphenyl-2-Picrylhydrazyl), (mg/100 g dry wt.): Milligram/100-gram dry weight |
||||||
Moreover, Godlewska et al.45 found that macro and microelement contents increment when soaking and foliar spraying with spirulina filter at applied on radish seedlings.
Changes in yield and yield components: The results in Table 5 showed the exposure of plants to 60-40% of WHC leads to a significant (p<0.05) decrease in all studied yield parameters in comparison with the control. While positive influence for different concentrations of algae extract on peanut plants yield parameters under various water holding capacity levels. Treatment of peanut plants with different levels of algae extract concentrations incremented all yield parameters with different levels of water in comparison with the control treatment. The maximum increments in pods number, pod weight and seed yield were obtained by using 3% blue-green algae as compared to the corresponding controls at the three tested WHC levels. The results of algae extract foliar spraying enhancing role are in agreement with those obtained previously41,46. These obtained positive effects may be attributed to that, algae extract could produce growth-promoting hormones that incremented seed germination, root and shoot growth and protein contents47. Pimratch et al.30 found that application of blue-green algae plainly incremented growth and yield of rice plants grown in greenhouse.
Nutritive value and antioxidant compounds of seeds: Water stress (from 60-40% WHC) in the soil induced significant (p<0.05) decreases in the percentages of oil, carbohydrate, antioxidant activity (DPPH radical scavenging), flavonoids and phenol content in the yielded seeds in comparison with their corresponding control. Foliar spraying of tested plants with different levels of algae extract concentrations under the different levels of WHC caused an increment in the nutritive value parameters (oil and carbohydrate) in comparison with the control plants (Table 6). The magnitude of increase in these tested chemical constituents in the yielded seeds was most pronounced with the highest concentration of algal extract (3%) in comparison with the corresponding WHC controls.
The obtained results came online with those of Shariatmadari et al.48, who found that algae extract had a positive effect on the essential oil content of Mentha piperita. In this domain, Hashtroudi et al.49 and Thangavelu et al.50 suggested that the positive effect of algae extract on essential oils composition in M. piperita and other plants is a result of special metabolites as auxins which are synthesized and released by the microorganisms. The increment in carbohydrate content helps to ameliorate oxidative losses and maintenance of protein structure during water shortage through reducing water potential. El-Bassiouny et al.51 stated that the algae extract usage in wheat cultivation resulted in incremented soluble sugars content compared to plants cultivated without algae extract. They added that algae extract enhancement of total soluble carbohydrates accumulation in salt-stressed wheat plants throughout either increasing levels of endogenous phytohormones or by acting as a motivator of carbohydrate synthesis. Rahul et al.52 concluded that algae extract contains many antioxidant activities that promote the content of phenolic compound, flavonoids and consequently DPPH radical scavenging activity in seeds which act as defense system of plants.
Macro-nutrient in yielded seeds: Water stress at 60-40% WHC of the soil induced significant (p<0.05) decreases in the percentage of nitrogen, phosphorous and potassium in the yielded seeds in comparison with controls of similar WHC (Fig. 2). On the other hand, peanut foliar spraying with different levels of algae extracts concentrations under the different levels of WHC caused an increment in all the above-mentioned macronutrients in comparison with the control at similar WHC levels. The treatment with 3% algae extracts surpassed the other two treatment levels (1-2%) in increasing NPK levels of seeds compared to their controls.
Pimratch et al.30 found that the application of blue-green algae resulted in significantly (p<0.05) higher macronutrient in seeds compared with the untreated control. Also, Hegazi et al.53 showed that algae extract of such types; Nostocmuscorum, Nostochumifusum, Anabaena oryzae, Wollea sp. Phormedium and Spirulinaplatensis can, reduce the use of N mineral fertilizer. They added that, NPK content showed significant (p<0.05) effects in seeds of the common bean when algae extract was used.
CONCLUSION
Conclusively, algae extract proved to be a good foliar nutritional substance alternative to mineral fertilizer and increased peanut plants tolerance to water deficiency stress throughout its mineral elements and phytohormones which reflected positively on its yielded seeds quantity and quality.
SIGNIFICANCE STATEMENT
From the environment and human health points of view, bio fertilization will be of a great impact compared to chemical fertilizers and pesticides which threatens globalization. The plant researchers should focus on the use of biological resources as alternatives to chemical fertilizers and pesticides without adverse effects on the quantity and quality of the produced plants. This study will help the researchers to uncover the critical areas of the positive impact of using similar techniques, e.g., soil amendment with biotreatments on plant health that many researchers were not able to explore. Thus, a new theory on well-prepared soils and natural material application for plant nutrition produce more healthy plants (resistant to environmental stresses, metabolic disorders and insects) may be arrived at.