Introduction
Agave americana cv. marginata from Agavaceae family is one of the important plants have many uses in various medicinal and food industrial. Among environmental stresses, water deficit stress plays an important role in the biosynthesis of secondary metabolites in medicinal plants in arid and semi-arid regions like Iran. Drought stress has detrimental effects on growth and yield and can upset the balance between the antioxidant defense system and free radicals by stimulating a series of biochemical reactions, where free radicals cause cell damage. In sustainable production systems of medicinal and aromatic plants, stable quantitative and qualitative functions can be achieved under conditions of environmental stress and it is possible to improve the production of secondary metabolites in these plants under adverse environmental conditions. Therefore, this study was done to evaluate some of important macro-micro nutrients on the morpho-physiological and phytochemical properties of Agave americana cv. marginata to determine and introduce the best combinations of fertilizers with use of superabsorbent nano-polymer under water stress conditions.
Materials and Methods
This research was performed in randomized complete block design (RCBD) in a split-split plot layout with three replications. Irrigation regimes (D1-D3: Field Capacity, 50% and 75% evaporation from basin class A) in main plots, superabsorbent nano-polymer application (S1-S2: use and not use) in sub plots and treatments of fertilizers [F1-F15: grow-more 1 (F1), grow-more 2 (F2), grow-more 3 (F3), iron chelate (F4), zinc chelate (F5), grow-more 1+iron chelate (F6), grow-more 1+zinc chelate (F7), grow-more 2+iron chelate (F8), grow-more 2+zinc chelate (F9), grow-more 3+iron chelate (F10), grow-more 3+zinc chelate (F11), grow-more 1+iron chelate+zinc chelate (F12), grow-more 2+iron chelate+zinc chelate (F13), grow-more 3+iron chelate+zinc chelate (F14) and control (F15)] in sub-sub plots were done. This research was performed in greenhouse condition of Islamic Azad University Branch of Shahrekord (latitude. 32°20′ N, longitude. 50°51′ E, altitude. 2061 m) in 2023-2024. In each year, fertilizer treatments were applied in foliar application after stage of V8 (plants had 8 leaf) in 6 stage by 14 days interval and harvesting was done after one month after the final application of fertilizers. The fertilizers of grow-more (NPK), iron and zinc in 4 gr.l-1 concentration by production company certification were used in V8 stage in plants and the effects were compared by control plants. Weed control was done manually during the entire experiment. During the experiment no systemic pesticide and herbicide were used. The harvested shoots transferred to the laboratory for measure of characters. Morphological characters such as leaf length, leaf diameter and dry/fresh root/leaf weight; physiological characters such as chlorophyll a, b, total chlorophyll and zinc, iron and nitrogen content in root/leaf and phytochemical characters such as contents of hecogenin, saponin, protein of leaf and root were measured. For assessment of the total chlorophyll content of A.americana, the leaves were extracted with 80% acetone. The absorbance of the extraction was read at 470, 648, and 664 nm, and the content of total chlorophyll was calculated as mg per g leaf fresh weight. For measure of hecogenin, saponin, total protein in leaf and root and nitrogen content in leaf and root use the protocols of Hackman et al., 2006, Sidana et al., 2016, Bradford, 1976 and Álvarez-Chávez et al., 2021; respectively.
Results and Discussion
In two sequential years, the obtained results showed that the use of treatments increased the characters and made the significant effectiveness. The most of means of leaf dry weight (30.11 g.plant-1), leaf fresh weight (207.33 g.plant-1), root dry weight (3.82 g.plant-1), root fresh weight (18.79 g.plant-1), length of leaf (64.55 cm), leaf diameter (0.41 centimeter), chlorophyll a (2.27 mg.g-1 fresh weight), chlorophyll b (0.53 mg.g-1 fresh weight), total chlorophyll (2.81 mg.g-1 fresh weight), hecogenin (35.48 mg.kg-1 fresh weight), saponin (66164.8 mg.kg-1 fresh weight), nitrogen of leaf (1.39 mg.g-1 dry weight), nitrogen of root (1.23 mg.g-1 dry weight), protein of leaf (25.34 mg.g-1 dry weight), protein of root (16.99 mg.g-1 dry weight), zinc of leaf (68.99 microg-1 dry weight), zinc of root (44.84 microg-1 dry weight), iron of leaf (81.01 microg-1 dry weight) and iron of root (49.84 microg-1 dry weight) made in grow-more fertilizers specially grow-more 1 (20-20-20) in combination with Fe/Zn Libfer. However the superabsorbent nano-polymer application had the aggressive effectiveness on amounts of characters especially in hardness of water stress. The least morpho-physiological and phytochemical characters such as leaf dry weight (12.81 g.plant-1), leaf fresh weight (89.54 g.plant-1), root dry weight (1.62 g.plant-1), root fresh weight (8.18 g.plant-1), length of leaf (41.12 cm), leaf diameter (0.24 centimeter), chlorophyll a (1.69 mg.g-1 fresh weight), chlorophyll b (0.26 mg.g-1 fresh weight), total chlorophyll (1.95 mg.g-1 fresh weight), hecogenin (21.88 mg.kg-1 fresh weight), saponin (22134.3 mg.kg-1 fresh weight), nitrogen of leaf (0.29 mg.g-1 dry weight), nitrogen of root (0.77 mg.g-1 dry weight), protein of leaf (10.11 mg.g-1 dry weight), protein of root (6.47 mg.g-1 dry weight), zinc of leaf (34.34 microg-1 dry weight), zinc of root (20.36 microg-1 dry weight), iron of leaf (43.77 microg-1 dry weight) and iron of root (27.73 microg-1 dry weight) made in control plants. In most of measured characters the treatments of D1S1F12, D3S1F14 and D2S1F14 were the best and control plants had the least of characters.
Conclusion
Generally the application of grow-more fertilizer 1 (20-20-20) with consumption of zinc and iron fertilizers can be a good strategy to improve the morpho-physiological and phytochemical characters of Agave americana cv. marginata specially the hecogenin and saponin amounts in the water stress conditions. However the use of superabsorbent nano-polymer in strenuous drought stress (75 %) is more effectivnes than other water stress levels. |
