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Article

Elicitor-Mediated Response of Growth, Yield, and Quality of Kalmegh (Andrographis paniculata Wall. ex Nees, Family Acanthaceae)

by
Pavan Gowda M.
1,
Amit Baran Sharangi
1,*,
Tarun Kumar Upadhyay
2,*,
Nahaa M. Alotaibi
3,
Modhi O. Alotaibi
3,
Nawaf Alshammari
4 and
Mohd Saeed
4,*
1
Department of Plantation, Spices, Medicinal & Aromatic Crops, BCKV-Agricultural University, Mohanpur 741252, West Bengal, India
2
Department of Biotechnology, Parul Institute of Applied Sciences and Animal Cell Culture and Immunobiochemistry Lab, Centre of Research for Development, Parul University, Vadodara 391760, Gujarat, India
3
Department of Biology, College of Science, Princess Nourah Bint Abdulrahman University, P.O. Box 88828, Riyadh 11671, Saudi Arabia
4
Department of Biology, College of Sciences, University of Hail, Hail P.O. Box 2240, Saudi Arabia
*
Authors to whom correspondence should be addressed.
Agronomy 2023, 13(9), 2313; https://doi.org/10.3390/agronomy13092313
Submission received: 5 August 2023 / Revised: 23 August 2023 / Accepted: 28 August 2023 / Published: 2 September 2023
(This article belongs to the Special Issue Medicinal and Aromatic Plants: Cultivation, Chemistry and Promising Applications)
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Abstract

:
With the objective of studying the influence of elicitors on the growth, yield, and quality of kalmegh, we carried out an investigation for two consecutive years. Nine treatments with three replications were laid out in a completely randomized design (CRD). Chitosan (CHT), yeast extract (YE), jasmone acid (JA), and salicylic acid (SA)were evaluated at different concentrations. The CHT treatment at 1000 ppm exhibited the tallest plant height (73.91 cm) and the highest number of secondary branches (29.07) at the time of harvest. The primary branches and number of leaves per plant were highest with the CHT treatment at 1000 ppm (26.36; 88.32), and were not significantly different with the SA treatment at 200 ppm (26.28; 81.51). The plant spread was the highest with the SAtreatment at 200 ppm (35.46 cm2) and was not significantly different with the CHT treatment at 1000 ppm (35.11 cm2). The CHT and SA sprays did not result in significant changes in yield parameters, but the highest fresh (42.34 g) and dry (18.30) herbage yields per plant were exhibited with the SA treatment at 200 ppm. The highest total chlorophyll (4.459 mg g−1) and total andrographolide (3.494%) contents were recorded after treatment with the SA spray at 200 ppm. A significant and positive improvement in the growth, yield, and quality of kalmegh was noticed with the salicylic acid spray treatment at 200 ppm 30 and 60 days after sowing (DAS), signifying its benefits for the cultivation of kalmegh in terms of high productivity, quality, and better returns for farmers.

1. Introduction

Since the beginning of human civilization, plants have been one of the most important sources of medicine. Plants continue to be one of the primary sources of medicine used in both modern and traditional medical systems that are practiced by people globally. Among these medicinal plants, kalmegh, or Andrographis paniculata, is gaining more significance in present-day situations due to its medicinal and curative properties [1]. Andrographis is one of the most important genera of the family Acanthaceae. Kalmegh plays a significant role in 26 Indian Ayurvedic formulations and holds a vital position in the Indian Pharmacopoeia [2].It also has the potential to fight against COVID-19 due to its strong antipyretic and antiviral properties [3].
A wide variety of bioactive substances, including andrographolides and polyphenols, are produced by kalmegh. One of the pharmacologically significant compounds is andrographolides. A minimum of 26 Ayurvedic remedies used to treat liver problems contain a strongly bitter flavored andrographolide: a labdane diterpenoid produced from Andrographis paniculata [4]. Andrographolides are an important anticancer and immunomodulatory pharmacophore and have the potential to be developed as anticancer chemotherapeutic agents [5]. In India, China, and other Southeast Asian nations, kalmegh is used to treat throat infections, fevers, colds, and a number of infectious diseases like dysentery, diarrhea, and malaria. This plant also possesses antibacterial, antithrombotic, anti-inflammatory, and immunological properties [3].
Elicitation is the process of enhancing or inducing the production of metabolites by adding small amounts of elicitors. An elicitor may be defined as: “a substance for stress factors which, when applied in small quantity to a living system, induces or improves the biosynthesis of specific compound which do have an important role in the adaptations of plants to a stressful condition” [6]. In addition to its many applications for enhanced productivity, elicitation is recognized as the most practically possible method for enhancing the synthesis of desirable secondary metabolites from plants without compromising their quality [7,8,9].
Plant growth agents are now being used more frequently to improve crop quality and yield. Plants naturally produce some organic molecules under stress conditions, which helps to combat stress through the production of secondary metabolites [7]. Some of the organic substances, like chitosan, yeast extract, salicylic acid, and jasmonic acid, have recently been used by farmers as elicitors for the purpose of increasing the growth and yield of crops, along with their quality [9]. However, although the application of elicitors for enhancing secondary metabolites is well-established, a full knowledge of the effects of elicitors on the overall development of plants with respect to growth, yield, and quality at specific time points has rarely been studied. One of the most crucial ways to boost the yield and production of secondary metabolites in plants is through the application of elicitors. According to research by Poornananda and Jameel [7], elicitors increase the bioaccumulation of andrographolides in kalmegh.
For pharmaceutical industries, bulk herbs with a high quantity and quality of their principal components are important for ease and are worth full extraction. In recent years, studies on the use of elicitors, both biotic and abiotic, for improving the quality of medicinal plants have been more prevalent. However, these studies are confined to invitro levels, and only a smaller number of studies have been conducted on the ex vitro spraying of elicitors [7]. The use of elicitors fulfills the requirement for a high yield of quality herbs, supporting both farmers and buyers for the purpose of cost-effective production and high returns. However, there is a scarcity of research that proves yield increment through elicitation. Thus, there is a basic need to study the elicitor-mediated response of growth, yield, and quality in kalmegh. The biosynthesis of the bioactive chemicals in medicinal plants and the creation of biomass are both significantly impacted by nutrients and direct or indirect exposure of herbs to foreign molecules (biotic or abiotic),i.e., elicitors. Therefore, studies on the efficacy of organic nutrients and elicitors on the growth yield and quality of medicinal herbs is required. The emerging global scenario with respect to the demand for herbs in various ayurvedic preparations and pharmaceutical industries suggests that kalmegh may become a very important crop in the near future [10]. The purpose of the present research work was to acquire insight into the impacts of elicitors (both biotic (chitosan and yeast extract) and abiotic (jasmonate and salicylic acid)) on the enhancement of the growth, yield, and quality of kalmegh, while keeping in mind the significance of this crop.
Elicitation studies on quality production of kalmegh are meager, and only few studies have been performed at the laboratory scale. The exogenous spray of elicitors for enhancing secondary metabolites, growth, and yield in medicinal plants and other crops has been reviewed previously. To extend this application of elicitors in kalmegh crops to achieve quality production, as well as to check whether any variations are present in the growth and yield attributes, the present experiment was conducted. Extensive reviewing of earlier studies showed that different concentrations of biotic (0.2 to 2 g L−1 or 200 to 2000 ppm) [11,12,13,14] and abiotic elicitors (0.5 to 1 mM or 100 to 200 ppm) [15,16,17,18,19] influenced the crop response in a positive direction.

2. Materials and Methods

After applying an extrapolative and qualitative approach to our research, the following treatments were fixed and evaluated: T1: chitosan at 500 ppm; T2: chitosan at 1000 ppm; T3: yeast extract at 500 ppm; T4: yeast extract at 1000 ppm; T5: jasmonic acid at 100 ppm; T6: jasmonic acid at 200 ppm; T7: salicylic acid at 100 ppm; T8: salicylic acid at 200 ppm; T9: control (water spray). The details of the elicitors used for the experiment are presented in Table 1.Elicitors were sprayed 30 and 60 days after the kalmegh was sown. Approximately 100 mL of solution was sprayed onto each plant.
The investigation was carried out for two consecutive years during 2021 and 2022 at the herbal garden of Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Nadia, West Bengal, India, which is located at 23.5° N latitude and 89° E longitude and has an average altitude of 9.75 m above mean sea level. The area is classified as subtropical-humid. The average annual rainfall is 1500 mm, with the summer months having an average temperature range of 25 °C to 36.5 °C and the winter months having an average temperature range of 12 °C to 25 °C. Meteorological data during the period of experimentation is presented in supplementary material. The soil used in the experiment was organic Gangetic alluvial soil (Entisol), which had a sandy clay loam texture and good water-holding capacity, was well-drained, and had a moderate level of soil fertility. A pot culture experiment with nine treatments and three replications was established using a completely randomized approach; three plants per replication were maintained. Seeds of “CIM-Megha”, a variety of kalmegh released from the Council of Scientific and Industrial Research-Central Institute of Medicinal and Aromatic Plants, Lucknow, India, were used for this research.
Plastic containers measuring20 cm by 20 cm with a volume of 296 cubic inches were used to plant the seeds in January, and the crops were harvested in June of each year. At the 50% flowering stage, crop was harvested, since the andrographolides content reaches its peak only during the flowering season [20]. A basal dose of well-rotten farmyard manure (FYM) at 20 t ha−1 and 75:75:50 kg NPK ha−1 was incorporated into the soil. The ratio and proportion method was used to compute the amount of fertilizers and FYM needed for the pot experiment [21]. To determine the growth pattern, some growth parameters were measured at 70 and 100 days after sowing the seeds (DAS). The leaf areas of 20 randomly selected leaves from each plant were measured using the Systronics leaf area metre 211 model, and the average was calculated in order to obtain the leaf area of a single leaf. The leaf area per plant and leaf area index (LAI = specific leaf area per plant cm2/land area cm2 (i.e., 20 cm × 20 cm = 40 cm2) were calculated by adopting the specific leaf area method [22]. The air-dry matter content, as a percentage, was calculated by dividing the dry weight of the air-dried herb by its fresh weight [23].

2.1. Measurement of Quality Parameters

At harvest, the chlorophyll content of the leaves was measured in a randomly selected plant from each replication, and an average was determined as per theprocedure outlined by Sadasivam and Manickam [24]. The carotenoid content was calculated using the formula given by Bajracharya [25].

Extraction and Estimation of Andrographolides

The extraction and estimation of the andrographolides from the methanol extract of the dry powdered kalmegh sample were conducted through HPLC at the Floriculture and Medicinal Crops Division, ICAR-Indian Institute of Horticultural Research, Bengaluru, Karnataka, India. The Kalmegh samples were dried and powdered at 50 °C for 30 minutes, then allowed to come to room temperature. With accuracy, 1.5 g of each sample was weighed and placed into a 100 mL beaker; then, 40 mL of methanol (HPLC-grade) was added and kept in a water bath maintained at 90 °C with continuous stirring for 20 minutes. After 20 minutes, it was kept aside until it reached room temperature, and the supernatant was collected in a 50 mL volumetric flask. To the remainder, 30 mL methanol was added, and it was kept in a water bath for 10 minutes before the above procedure was repeated. Then, 20 mL of methanol was added, an extraction was performed for another 10 min, and the above procedure was repeated. Finally, methanol was added until the extract volume reached 50 mL, and it was shaken well and allowed to settle. Then, the supernatant was filtered (Nylon 0.2 um, 13 mm nylon membrane) and injected into HPLC.
The HPLC studies were completed using a Shimadzu Series LC-10A system (Shimadzu, Kyoto, Japan), which includes liquid chromatography linked to a UV-VIS detector (10 A) and a binary pump. The system was controlled using Shimadzu Class VP Workstation software (Shimadzu Nexara X2 HPLC). Gemini, 250 × 4.6 mm, 5 μmC18 (Phenomenex, Torrance, CA, USA) was the type of column which was used, and the security guard column was also made of the same material. A Shimadzu model SIL-20 A HT autosampler was used to inject the samples. The thermostat was set to 32 °C for the column and the guard column. The mobile phase contained phosphate buffer (solvent A) and acetonitrile (solvent B), and the flow rate was 1.5 mL min−1. A linear gradient mode was used to operate the equipment. The gradient conditions were 0 to 18 min, 5 to 60% B, and 18 to 25 min, 47 to 74% B. At 223 nm, the detection was monitored.

2.2. Statistical Analysis

Observations of all parameters were recorded during 2021 and 2022 in all plants foreach replication, and the averages were computed. The International Rice Research Institute’s Statistical Tool for Agricultural Research (STAR) software version 2.0.1 was used for the pooled analysis on the mean data over two years, i.e., 2021 and 2022.Each pair of means was compared using Duncan’s multiple range test (DMRT).Correlations were calculated by comparing correlation coefficients with table values, and the significance of the correlation coefficients was examined. The grouping of treatments was achieved using the UPGMA clustering method, as given by Michener and Sokal [26].

3. Results and Discussion

3.1. Growth Parameters

The growth parameters, according to the mean of the resulting data included the height (Figure 1) and spread of the plant, as well as the number of primary and secondary branches per plant (Table 2). These changed significantly when elicitors were used compared to the control treatment. Chitosan treatment at 1000 ppm spray led toa 25.95% higher plant height and 26.21% higher secondary branches per plant (29.07) at harvest. The next most effective treatment was salicylic acid at 200 ppm spray (22.78% and 15.99%) compared to the control treatment(56.93 cm and 23.35). Compared to the water spray, plant spread was the highest with the salicylic acid treatment at 200 ppm spray (22.42%), which was not significantly different from the results of the1000 ppm chitosan treatment (21.44%). The number of primary branches per plant was at its maximum with the chitosan treatment at 1000 ppm spray (23.59%), which was not significantly different from the200 ppm salicylic acid treatment (23.55%). The control treatment showed the minimum values for both the parameters.
The findings with the elicitor treatments made it clear that there is a substantial correlation between the plant height and the number of primary branches, which is then correlated with the number of secondary branches and the plant spread. The treatments were seen to lead to an acceptable number of branches and plant spread when the plants reached their maximum heights at maturity. This can be explained by the fact that taller plants were able to bear a greater number of branching nodes and to show a higher degree of plant spread. Increased availability and uptake of water and vital nutrients, achieved by adjusting cell osmotic pressure and reducing the accumulation of harmful free radicals by increasing antioxidant and enzyme activities, are likely the causes of chitosan’s stimulatory effect on plant growth [27]. Additionally, it might be credited with improving nitrogen transfer to functional leaves, photosynthesis, and enzymatic nitrogen metabolism activities (nitrate reductase, glutamine synthetase, and protease), all of which facilitate plant growth and development [28]. Additionally, chitosan boosted the tryptophan-independent pathways for auxin production, and this may have increased the plant height [29]. The results obtained from this study are in concurrence with those of Gornik et al. [30], Abdel-Mawgoud et al. [31], Yin et al. [32], Sulthana et al. [33], Ahmed et al. [34], and Malekpoor et al. [12].
The longer and more numerous branches that resulted in a tilt outward, which boosted the plant spread, may have been responsible for the increased plant spread with the chitosan spray treatment. Chitosan increases nitrogen transport in the functioning leaves of kalmegh plants by enhancing the enzyme activities of nitrogen metabolism (nitrate reductase, glutamine synthetase, and protease) [28]. The findings of Gorniket al. [30], Abdel-Mawgoud et al. [31], Pirbalouti et al. [35], and Kra et al. [36] are in agreement with these findings.
Salicylic acid also has a significant impact on the morphology and physiology of the kalmegh plant. The use of salicylic acid in the current investigation may have increased the photosynthetic activities of the kalmegh plant. These outcomes are consistent with the research of Hashemabadi and Zarchini [37], Farouk and Osman [38], Jadhav and Bhamburdekar [39], and Sharma [40]. Salicylic acid increased the chlorophyll content, which resulted in significant photosynthesis and increased plant growth [41].Also, due to the increased length of the internodes, the number of internodes increased, which directly increased the height of the plants and the number of branches [40]. Ali and Mahmoud [42], Rahimiet al. [15], and Mulgir et al. [43] also reported similar results. The increased plant spread with salicylic acid application may have been due to higher vegetative growth, chlorophyll content, number of branches, and root growth, which could have result in increased plant spread. The results also support earlier works by Asgari and Moghadam [44], Kaur et al. [45], Abd-Elkader [46], Koppad et al. [47], Nangare [48], and Sathiyamurthy et al. [49].
A pooled analysis of two years of data on single leaf parameters, such as length, width, and area (Table 3), showed that the control treatment achieved the highest values (4.53 cm, 1.35 cm, and 6.04 cm2), whereas the lowest length and width were recorded for the chitosan treatment 1000 ppm spray, which was not significantly different from the500 ppm chitosan and 200 ppm salicylic acid treatments. In the case of leaf area, all of the elicitor treatments showed non-significant results for both years. The leaf parameters of the plants showed significant differences with the elicitor treatments. Compared to the water spray, the number of leaves per plant was highest with the chitosan spray at 1000 ppm (42.87%), which was not significantly different from the chitosan treatment at 500 ppm (39.86%) or the salicylic acid treatment at 200 ppm (35.15%). The leaf area of the plants and the leaf area indices (Table 3) recorded maximum values for chitosan treatment at 1000 ppm (23.05% and 22.58%), which were not significantly different from chitosan treatment at 500 ppm (17.39% and 16.66%). The control treatment resulted in the lowest values for the above three parameters.
In this study, the numbers of leaves were higher for those treatments with a prime position in terms of branch number, and, in turn, the number of leaves appeared to have governed the total leaf area of the plant. The treatments with more leaves per plant produced more dry substances simultaneously. This may, perhaps, be due to their higher photo-assimilation capacity due to the maximum green area of individual plants actively synthesizing carbohydrates through photosynthesis. The increase in the number of leaves per plant is likely due to increased nutrient absorption. The foliar application of chitosan-stimulated molecular signals had a plant growth-promoting effect and induced a higher rate of cell division and cell elongation in the sub-apical meristems of kalmegh shoots, increasing the number of leaves that each plant produced [50]. Mondal et al. [28] and Abdel-Mawgoud et al. [31] also obtained similar results. The likely cause of the increase in leaf area per plant may have been the increase in epidermal parenchyma cells and in the number of functional leaves. Furthermore, foliar application of chitosan improved the cell osmotic pressure, which improved the water availability and nutrient uptake [51], and nitrogen transfer in functional leaves promoted photosynthesis, which in turn improved plant growth and development and increased the leaf area naturally [28]. These outcomes are consistent with the work of Gornik et al. [30], Abdel-Mawgoud et al. [31], Xu and Mou [52], Thengumpally [53], and Ashwini [54].
Salicylic acid administration enhanced the number of leaves, as the number of leaves was positively associated with the number of nodes and primary branches per plant [55]. Andrey et al. [56], Mona et al. [57], Ram et al. [58], Anwar et al. [59], Padmalatha et al. [60], and Manoj [61] obtained similar results. The increased number of leaves per plant in Kalmegh as a result of the spraying of salicylic acid at 200 ppm may be attributable to the peridined division and expansion of the central cell in the leaf axis, made possible by the salicylic acid’s morphactin-like properties; as a result, the number of leaves per plant in Kalmegh might also increase. Meena et al. [62], Koppad et al. [47], Sathiyamurthy et al. [49], and Vitthal [63] reported similar results.
In our pooled analysis, plants sprayed with salicylic acid at 200 ppm followed by chitosan at 1000 ppm showed early flowering and harvest (Figure 2).The maximum days were taken by plants under the control treatment for flower initiation and harvest, which was not significantly different from the yeast extract elicitation results. This might be due to the fact that salicylic acid promotes sexual development, which results in an enhancement in flower production [64]. It may also be due to the induction of early flowering through the transition from vegetative to reproductive growth. Maniramet al. [65] and Ramet al. [58] confirmed this. Salicylic acid’s florigenic activity, or, more likely, its effect on the ratio between flower-promoting and flower-inhibiting components, boosted the synthesis of floral stimuli in an inductive cycle [60]. Several researchers have reported that salicylic acid causes flower induction in annual crops [66,67]. Choudhary et al. [68] concluded that salicylic acid induced flowering by acting as a floral stimulus in the leaves, which may have regulated flowering. Salicylic acid serves as an internal growth regulator for flowering and the florigenic response [69].
In this study, it was noticed that the chitosan-treated plants began flowering earlier compared to the others, which indicates that chitosan stimulated nutrient absorption and regulated the plant signaling pathways that helped to induce early flowering in kalmegh. While a greater number of days were needed for the first flower bud to appear on water-sprayed plants because of hormonal imbalances that promoted vegetative growth instead of flowering, these outcomes were consistent with those of Farouk and Amany [70], Salachna and Zawadzinska [71], Mutka et al. [72], Dhakad [29], and Nithin [27]. The highest chlorophyll concentration was found in the plants sprayed with salicylic acid and chitosan, which led to a greater generation of photosynthates and their accumulation. Additionally, the stimulatory effects of salicylic acid and chitosan on the absorption of nutrients may aid in timely nutrient supply with simple uptake throughout the overall plant growth process, resulting in early maturity by flowering.

3.2. Yield Parameters

The application of elicitors resulted in an increasing trend for the yield parameters, including fresh and dry herbage yield and air-dry matter content per plant, as compared to the control (Table 4). For both years, as well as the pooled study, chitosan and salicylic acid sprays produced results that were similar in terms of yield characteristics. The yield data for the treatments with salicylic acid at 200 ppm, chitosan at 1000 ppm, salicylic acid at 100 ppm, and salicylic acid at 500 ppm were reported to show non-significant differences, but significantly better results than those of other elicitor treatments and the control. Any agricultural plant’s production is influenced by the assimilatory surface of the plant system. A reliable source with regard to plant height, LAI, number of branches, and leaves is logically capable of increasing the air-dry matter content, and its distribution in various regions is crucial for determining the crop’s overall output. In cases in which the treatments are able to perform similarly in terms of holding moisture and air-dry matter content, a more or less similar trend can be found for both the dry and fresh weight of the whole plant. Those treatments with the maximum leaf area could exhibit greater values of fresh as well as dry weight of the whole plants. Similarly, in the present study, the fresh weight and dry weight values among the treatments were ranked similarly.
Yield is a composite trait governed by polygenes and is associated with several other traits, which contribute in increments. In kalmegh, it is well established that yield is related to improvements in height, leaf area, and primary and secondary branches [39]. Salicylic acid and chitosan were found to considerably improve plant height, spread, number of leaves, branches, and leaf area per plant in the current study. Similarly to this, during harvest, treatments with salicylic acid and chitosan applications dramatically increased the generation of photosynthates, boosting biomass output and air-dry matter content accumulation. The treatments with salicylic acid and chitosan resulted in an overall increase in growth and yield qualities, which led to better fresh and dried herbage yields [61].
The abilities of the plants to regenerate were boosted by salicylic acid’s inhibition of ethylene synthesis, which might have contributed to the enhanced herbage yield [69]. It is generally known that SA promotes cell elongation and cell division [34]. According to reports, SA can boost yield in many plant species by improving plant growth factors, including height, number of branches, leaves, and leaf area per plant (Gharib [73], Sayyari et al. [74], Mohsen et al. [75], Karimian et al. [76], Pradhan et al. [77], Koppad et al. [47], and Sathiyamurthy et al. [49]. Furthermore, foliar sprays of SA and chitosan helped to activate the signaling pathways of growth-regulating substances like gibberellins and auxins, which might also have contributed to the increased biomass of the plants by increasing the numbers and sizes of cells [16,27,63,78,79,80]. The stimulation of physiological processes, improved vegetative growth, active translocation of photo-assimilates from source to sink tissues, increased number of leaves and branches per plant, and accumulation of dry matter may all have been contributing factors to the increase in yield per plant under the treatment with chitosan spray. While the frequent foliar application of water creates moisture stress, which affects the physiological processes of plants, including uptake and translocation of nutrients, it also results in a hormonal imbalance, which accounts for the reduction in yield per plant under the water-sprayed treatment. The current findings are consistent with those of Asghari-Zakaria et al. [81], Ghoname et al. [82], and Chookhongkha et al. [83].
The increased total dry weight of the plants was linked to the maximum vegetative growth characteristics, including a rise in plant height, leaf count, leaf area, and plant spread. This resulted in the production and accumulation of a greater amount of photosynthates in plants, leading to increased biomass accumulation, which in turn yielded a higher air-dry matter content. Our findings of increments in air-dry matter by chitosan application were in line with Ahmed et al. [84], Bistgani et al. [85], Thengumpally [53], and Ashwini [54]. Jayalakshmi et al. [86], Bekheta and Iman [87], Mahammad [88], Bhasker et al. [55], Mohammadi et al. [89], and Priya [90] compiled the results on dry matter and their interdependence on salicylic acid.

3.3. Quality Parameters

The chlorophyll pigments in the leaves varied significantly according to the application of elicitors in kalmegh (Table 4). The pooled analysis of two years of data showed the highest chlorophyll a, b, and total (38.81%, 38.84%, and38.76%) with the salicylic acid treatment at 200 ppm spray compared to water spray. The carotenoid pigment (Table 4) in the leaves was highest with the salicylic acid treatment at 200 ppm spray (44.60%, which was not significantly different from 100 ppm SA (41.97%), and the control recorded the minimum amount. The maximum chlorophyll content in leaves was found when 200 ppm of salicylic acid was sprayed over the leaves. These outcomes may be explained by regulating the plant water, which carries nutrient components, particularly nitrogen and phosphorus, which increase the overall chlorophyll concentration [91]. A similar finding was also reported by Divya et al. [92] and Choudhary et al. [68].
Chlorophyll and carotenoid levels rose after SA applications in plants, which was at-tributed to the hormone’s beneficial effects on nutrient uptake [93]. This was because higher levels of Fe, Mg, and Ca can stimulate the biosynthesis of chlorophyll [94]. Additionally, SA’s stimulatory influence on the activity of the Rubisco enzyme and photosynthesis may have been the cause of the rise in photosynthetic pigments [45]. A decrease in stomatal and non-stomatal transpiration, as well as an increase in chlorophyll concentration, can all be attributed to exogenous salicylic acid application on leaf surfaces, which reduced abiotic stressors and improved the water usage efficiency. Salicylic acid applied topically to leaves helped to stimulate the enzymes required for the production of chlorophyll in biological processes. These outcomes were in line with those of Mahammad [88], Pradhan et al. [77], Kirtikumar [95], and Gothwal [96].
The quantification of secondary metabolites exhibited varied trends in the andrographolide contents achieved by different treatments (Table 5) (Figure 3). Pooled analysis showed a 42.76% higher total andrographolide content in the herbs with salicylic acid treatment at 200 ppm spray; this was far more effective than any other treatment. The lowest value was recorded in the control (2.263%). The enhanced overall plant growth and metabolism identified in the present investigation may have been the cause of the beneficial effect of foliar sprays of elicitors on alkaloid synthesis. Through improved plant growth, photosynthesis, and general plant metabolism in the current study, it appears that the elicitor may have enhanced the intrinsic genetic ability of the kalmegh plants to produce an additional yield with improved alkaloid quality via biochemical pathways. The elicitors had the ability to increase metabolic activity, which in turn caused the accumulation of secondary metabolites in kalmegh plants by terpenoid synthesis. According to Rivas-San and Plasencia [97], metabolic alterations at the chloroplast level (Rubisco enzyme activity, photosystem II efficiency, and supply of ATP and NADPH for the carbon reduction cycle) can be attributed to the observed increase in the photosynthesis rate in plants sprayed with SA. The stimulatory effect of SA on gas exchange parameters and plant development, however, depends on a number of variables, including the application method, exposure duration, and ontogenetic stage [98].
Andrographolide is a diterpenoid compound. The terpenoid biosynthesis occurs through the mevalonate isoprenoid pathway in the glands present in the leaves. The improvements in leaf and herbage development increased the terpenoid yield. In fact, the trichomes in leaves are the major sites for the biosynthesis of andrographolide alkaloids. Terpenoid biosynthesis is an integration of several steps, including the continuous production of pre-cursors, their transport, and their translocation to active sites for alkaloid biosynthesis. The metabolic pathway for the biosynthesis of alkaloids improved in plants in response to the application of elicitors, especially with salicylic acid. Increased endogenous salicylic acid (SA) levels can activate cell-signaling pathways, which control the expression of genes encoding enzymes connected to the phenylpropanoid pathway (which produces flavonoids) and the mevalonate system (which produces terpinoids). IPP (isopentayl pyrophosphate) synthase and DMAPP (dimethylallyl pyrophosphate) synthase activity, enzymes that diverge from the MVA (mevalonate) and MEP (methylerythriol phosphate) pathway to generate terpinoids in plants, are two examples of enzymes whose activity is improved by SA. [99,100]. In Salvia miltiorhiza and Michelia chapensis, it has been demonstrated that SA transcriptionally upregulates the genes involved in isoprenoid production [101,102]. The expression of three prenyl transferases from the core terpenoid biosynthetic pathway has been shown to be upregulated by SA in different species as well (by Shabani et al. [103] in licorice and by Kai et al. [104] in Arabidopsis). Similarly, the levels of many isoprenoids have been shown to be upregulated during drought or salt stress, parallel to increases in SA levels. Despite the fact that the full mechanism of SA in plants is still not fully known, everyone agrees on the crucial role that SA plays in plants [105].

3.4. Character Association between Yield, Quality, and Its Component Traits in Elicitor Treatments and UPGMA Based Grouping of Treatments

Correlation analysis between different traits with the elicitor treatments (Table 6) revealed that fresh herbage yield of the plants had a highly significant positive association with plant height (0.80), spread (0.95), primary (0.91) and secondary branches (0.87), leaf number (0.88), leaf area (0.87), leaf area index (0.87), dry herb yield (0.99), and air-dry matter content (0.97), as well as positive significant associations with the total chlorophyll (0.81) and total andrographolide contents (0.82). A similar positive association was reported by Jadhav and Bhamburdekar [39], Sayyari et al. [74], Mohsen et al. [75], Karimian et al. [76], Pradhan et al. [77], Koppad et al. [47], Manoj [61], and Pawar et al., [69]. The dry herb yields exhibited a highly significant positive correlation with plant height (0.82), spread (0.96), primary (0.92) and secondary branches (0.89), leaf number (0.89), leaf area (0.88), leaf area index (0.88), fresh herb yield (0.99), air-dry matter content (0.97), total chlorophyll (0.81), and total andrographolide content (0.82). Similar results were also reported by Ghoname et al. [82], Chookhongkha et al. [83], Supriya [78], Gorni and Pacheco [16], Youssef et al. [79], Vitthal [63], Forouzandeh et al. [80], and Nithin [27].The total andrographolide content in kalmegh plants with the elicitor treatments showed a positive and significant association with the plants’ number of leaves (0.72), leaf area (0.69) and leaf area index (0.69). Positive and highly significant associations were found with the plants’ fresh (0.82) and dry herb yields (0.82), air-dry matter content (0.82), and total chlorophyll content (0.98). Manoj [61] recorded a similar positive relation between growth, yield, and quality components under elicitor treatment in turmeric; and Nithin [27] in strawberry.
According to a correlation study of elicitor treatment parameters, plant height, number of primary and secondary branches, number of leaves, leaf area per plant, LAI, air-dry matter content per plant, total chlorophyll content in leaves, and total andrographolide content in plants were all positively and significantly correlated with the fresh and dry yield of the herbs. With the exception of plant height and branch number, the total andrographolide content in kalmegh was, likewise, found to be related to the same factors, regardless of level of significance. Therefore, it can be inferred that elicitors achieved improvements in the herbage yield and the quality of kalmegh by improving the above characteristics of kalmegh production.
The clustering pattern of elicitor treatments based on the UPGMA clustering method, employing twelve important characteristics, showed five clusters (Figure 4). Cluster I consisted of chitosan at 500 ppm and yeast extract at 1000 ppm spray; cluster II contained chitosan at 1000 ppm and salicylic acid at 200 ppm spray. Cluster III included yeast extract at 500 ppm and jasmonic acid at 200 ppm spray. Treatments with 100 ppm jasmonic acid and 100 ppm salicylic acid spray belonged to cluster IV. The control (water spray) treatment fell into cluster V. Treatments belonging same cluster had relatively similar or non-significant effects on the yield and quality of kalmegh.

4. Conclusions

A significant and positive improvement in the growth, yield, and quality of kalmegh was noticed with chitosan and salicylic acid spraying. We found that 200 ppm salicylic acid spray at 30 and 60 DAS on kalmegh exhibited the best results in terms of the quantity and quality of the produced kalmegh, signifying its benefits in the cultivation of kalmegh, including high productivity, quality, and better returns for farmers and processors. The positive effect of elicitors as foliar sprays on the quality of kalmegh is being reported for the first time. This novel and useful finding requires further understanding of how, when, and exactly where these chemicals elicit the accumulation of andrographolides. As the concentration and frequency of elicitor application significantly affect various characteristics under study, different concentrations may yet be tried depending on the method of application, i.e., seed treatment, seedling dip, etc., on kalmegh.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/agronomy13092313/s1. Meteorological data during the period of experimentation.

Author Contributions

P.G.M.—designing, analysis, 1st draft, revising, final approval, accountability; A.B.S.—conceptualization, supervision, data interpretation, first draft, critical revising, approval, accountability; T.K.U.—analysis, first draft, critical revising, approval, accountability; N.M.A.—software, analysis, revising, approval, funding acquisition; M.O.A.—designing, analysis, first draft, revising, approval, accountability; N.A.—software, analysis, revising, approval, funding acquisition; M.S.—conceptualization, data interpretation, 1st draft, critical re-vising, approval, funding acquisition. All authors have read and agreed to the published version of the manuscript.

Funding

Indian Council of Agricultural Research (ICAR)—Senior Research Fellowship; Bidhan Chandra Krishi Vishwavidyalaya (BCKV) and Princess Nourah bint Abdulrahman University Researchers Supporting Project number (PNURSP2023R356), Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

All the authors obtained consent to publish the article.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Elicitors’ effects on the plant height of kalmegh. T1: chitosan spray at 500 ppm; T2: chitosan spray at 1000 ppm; T3: yeast extract spray at 500 ppm, T4: yeast extract spray at 1000 ppm, T5: jasmonic acid spray at 100 ppm, T6: jasmonic acid spray at 200 ppm, T7: salicylic acid spray at 100 ppm, T8: salicylic acid spray at 200 ppm, T9: control (water spray). The treatments with same superscripts within each parameter were not significantly different at p ≤ 0.05, according to Duncan’s multiple comparison procedure (DMRT). Values represent the means with error bars.
Figure 1. Elicitors’ effects on the plant height of kalmegh. T1: chitosan spray at 500 ppm; T2: chitosan spray at 1000 ppm; T3: yeast extract spray at 500 ppm, T4: yeast extract spray at 1000 ppm, T5: jasmonic acid spray at 100 ppm, T6: jasmonic acid spray at 200 ppm, T7: salicylic acid spray at 100 ppm, T8: salicylic acid spray at 200 ppm, T9: control (water spray). The treatments with same superscripts within each parameter were not significantly different at p ≤ 0.05, according to Duncan’s multiple comparison procedure (DMRT). Values represent the means with error bars.
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Agronomy 13 02313 g002
Figure 2. Elicitors’ effect on days to flower initiation and fifty percent flowering (harvesting stage) of kalmegh.T1: Chitosan spray at 500 ppm, T2: chitosan spray at 1000 ppm, T3: yeast extract spray at 500 ppm, T4: yeast extract spray at 1000 ppm, T5: jasmonic acid spray at 100 ppm, T6: jasmonic acid spray at 200 ppm, T7: salicylic acid spray at 100 ppm, T8: salicylic acid spray at 200 ppm, T9: control (water spray). The values with same superscripts within each parameter were not significantly different at p ≤ 0.05, according to Duncan’s multiple comparison procedure (DMRT). Values represent the means with error bars.
Figure 2. Elicitors’ effect on days to flower initiation and fifty percent flowering (harvesting stage) of kalmegh.T1: Chitosan spray at 500 ppm, T2: chitosan spray at 1000 ppm, T3: yeast extract spray at 500 ppm, T4: yeast extract spray at 1000 ppm, T5: jasmonic acid spray at 100 ppm, T6: jasmonic acid spray at 200 ppm, T7: salicylic acid spray at 100 ppm, T8: salicylic acid spray at 200 ppm, T9: control (water spray). The values with same superscripts within each parameter were not significantly different at p ≤ 0.05, according to Duncan’s multiple comparison procedure (DMRT). Values represent the means with error bars.
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Figure 3. Chromatograms showing the highest and lowest andrographolide contents among the elicitor treatments in kalmegh.
Figure 3. Chromatograms showing the highest and lowest andrographolide contents among the elicitor treatments in kalmegh.
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Figure 4. Grouping of nine elicitor treatments in clusters, presented in the form of a dendrogram.T1: Chitosan spray at 500 ppm, T2: chitosan spray at 1000 ppm, T3: yeast extract spray at 500 ppm, T4: yeast extract spray at 1000 ppm, T5: jasmonic acid spray at 100 ppm, T6: jasmonic acid spray at 200 ppm, T7: salicylic acid spray at 100 ppm, T8: salicylic acid spray at 200 ppm, T9: control (water spray).
Figure 4. Grouping of nine elicitor treatments in clusters, presented in the form of a dendrogram.T1: Chitosan spray at 500 ppm, T2: chitosan spray at 1000 ppm, T3: yeast extract spray at 500 ppm, T4: yeast extract spray at 1000 ppm, T5: jasmonic acid spray at 100 ppm, T6: jasmonic acid spray at 200 ppm, T7: salicylic acid spray at 100 ppm, T8: salicylic acid spray at 200 ppm, T9: control (water spray).
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Table 1. Details of elicitors used for the experiment.
Table 1. Details of elicitors used for the experiment.
S. No.Elicitors UsedSpecificationProcured from
1ChitosanChitosan (Low MW) extrapure, 90% DASisco Research Laboratories Pvt. Ltd., Kolkata, India
2Yeast extractBrownish yellow powder, Laboratory grade prepared from baker’s yeast
3Salicylic acidSalicylic Acid extrapure AR grade, 99.9%
4Jasmonic acidTechnical grade jasmonic acid powder 99% pure, for agriculture useAquatic Chemicals, Mumbai, India
Table 2. Plant spread and number of branches with the use of elicitors in kalmegh.
Table 2. Plant spread and number of branches with the use of elicitors in kalmegh.
TreatmentsPlant Spread (cm2)Primary Branches (no.)Secondary Branches (no.)
70 DAS100 DASAt Harvest70 DAS100 DASAt Harvest70 DAS100 DASAt Harvest
T115.57 ± 0.18 c23.89 ± 0.17 c33.21 ± 0.21 b18.00 ± 0.36 b21.66 ± 0.28 c25.27 ± 0.27 b12.14 ± 0.33 b22.95 ± 0.41 bc26.99 ± 0.70 b
T217.31 ± 0.20 a27.07 ± 0.24 a35.11 ± 0.56 a18.96 ± 0.40 a23.30 ± 0.09 a26.36 ± 0.19 a13.11 ± 0.29 a24.76 ± 0.39 a29.07 ± 0.50 a
T313.32 ± 0.14 g19.99 ± 0.16 f30.02 ± 0.31 c15.15 ± 0.42 e19.34 ± 0.37 f22.16 ± 0.27 d9.44 ± 0.37 de19.93 ± 0.65 ef24.37 ± 0.85 e
T415.13 ± 0.14 d23.04 ± 0.14 d32.88 ± 0.13 b17.24 ± 0.47 c20.58 ± 0.31 d23.91 ± 0.14 c11.60 ± 0.39 b22.32 ± 0.45 c26.17 ± 0.73 c
T513.79 ± 0.14 f20.48 ± 0.16 f30.50 ± 0.31 c15.51 ± 0.42 de19.77 ± 0.37 ef22.63 ± 0.27 d9.90 ± 0.37 d20.37 ± 0.65 de24.91 ± 0.85 de
T613.18 ± 0.20 g18.86 ± 0.21 g28.94 ± 0.29 d13.97 ± 0.27 f18.64 ± 0.54 g21.07 ± 0.35 e9.05 ± 0.40 ef22.41 ± 0.41 c23.65 ± 0.81 f
T714.29 ± 0.10 e22.41 ± 0.11 e32.16 ± 0.14 b15.76 ± 0.45 d20.11 ± 0.41 e22.81 ± 0.29 d10.57 ± 0.39 c21.11 ± 0.58 d25.13 ± 0.81 d
T816.34 ± 0.10 b24.67 ± 0.15 b35.46 ± 0.26 a18.37 ± 0.52 a22.68 ± 0.19 b26.28 ± 0.28 a13.20 ± 0.33 a23.53 ± 0.34 b27.41 ± 0.62 b
T912.93 ± 0.20 g18.62 ± 0.21 g28.31 ± 0.29 d13.62 ± 0.27 f17.67 ± 0.54 h20.82 ± 0.35 e8.46 ± 0.40 f18.95 ± 0.54 f23.35 ± 0.81 f
S Em±0.150.150.250.110.110.250.20.340.15
CD (0.05)0.430.430.720.330.310.730.590.990.43
CV (%)2.551.691.951.741.332.674.673.881.46
T1: chitosan spray at 500 ppm, T2: chitosan spray at 1000 ppm, T3: yeast extract spray at 500 ppm, T4: yeast extract spray at 1000 ppm, T5: jasmonic acid spray at 100 ppm, T6: jasmonic acid spray at 200 ppm, T7: salicylic acid spray at 100 ppm, T8: salicylic acid spray at 200 ppm, T9: control (water spray). The treatments with same superscripts within each parameter were not significantly different at p ≤ 0.05, according to Duncan’s multiple comparison procedure (DMRT). Values represent the means and ± the standard errors.
Table 3. Response of leaf parameters to elicitors in kalmegh.
Table 3. Response of leaf parameters to elicitors in kalmegh.
TreatmentsLeaf Parameters at Harvest
Leaf Length (cm)Leaf Width (cm)Leaf Area (cm2)Number of Leaves per Plant−1Leaf Area plant−1 (cm2)Leaf Area Index
T15.10 ± 0.21 a1.35 ± 0.01 de6.15 ± 0.29 c85.59 ± 3.20 a521.92 ± 11.80 ab1.30 ± 0.03 ab
T25.32 ± 0.26 a1.32 ± 0.01 e6.31 ± 0.32 bc88.32 ± 3.20 a552.59 ± 13.93 a1.38 ± 0.03 a
T35.50 ± 0.21 a1.52 ± 0.01 b7.56 ± 0.35 ab59.65 ± 1.28 f448.96 ± 12.30 e1.12 ± 0.03 e
T45.25 ± 0.17 a1.44 ± 0.01 c6.80 ± 0.35 ab73.00 ± 1.72 cd494.80 ± 11.06 bcd1.24 ± 0.03 bcd
T55.31 ± 0.20 a1.46 ± 0.01 c6.98 ± 0.30 ab67.81 ± 1.67 de470.77 ± 11.10 cde1.18 ± 0.03 cde
T65.37 ± 0.13 a1.50 ± 0.01 b7.24 ± 0.22 ab63.45 ± 0.32 ef459.18 ± 11.99 de1.15 ± 0.03 de
T75.23 ± 0.17 a1.43 ± 0.01 c6.71 ± 0.24 bc75.81 ± 1.82 bc507.10 ± 10.40 bc1.27 ± 0.03 bc
T85.14 ± 0.21 a1.37 ± 0.01 d6.33 ± 0.29 bc81.51 ± 2.86 ab511.97 ± 11.11 bc1.28 ± 0.03 bc
T95.28 ± 0.25 a1.63 ± 0.01 a7.71 ± 0.40 a57.14 ± 1.28 f438.38 ± 14.62 e1.10 ± 0.04 e
S Em±0.220.010.332.3513.420.03
CD (0.05)0.640.020.956.7538.490.09
CV (%)0.81.6918.147.966.726.7
T1: Chitosan spray at 500 ppm, T2: chitosan spray at 1000 ppm, T3: yeast extract spray at 500 ppm, T4: yeast extract spray at 1000 ppm, T5: jasmonic acid spray at 100 ppm, T6: jasmonic acid spray at 200 ppm, T7: salicylic acid spray at 100 ppm, T8: salicylic acid spray at 200 ppm, T9: control (water spray). The values with same superscripts within each parameter were not significantly different at p ≤ 0.05, according to Duncan’s multiple comparison procedure (DMRT). Values represent the means, and ± the standard errors.
Table 4. Response of fresh and dry herbage yield, air-dry matter, chlorophyll content, and carotenoid content to elicitors in kalmegh.
Table 4. Response of fresh and dry herbage yield, air-dry matter, chlorophyll content, and carotenoid content to elicitors in kalmegh.
TreatmentsYield Parameters at HarvestChlorophyll Contents (mg g−1)Carotenoid Content
(mg g−1)
Fresh Herbage Yield Plant−1 (g)Dry Herbage Yield Plant−1 (g)Air-Dry Matter Content Plant−1 (%)Chl. aChl. bTotal Chl.
T137.47 ± 1.47 abc15.00 ± 0.96 ab39.84 ± 0.91 ab2.14 ± 0.06 e1.60 ± 0.05 e3.75 ± 0.11 e2.97 ± 0.07 b
T240.41 ± 1.17 ab17.42 ± 0.83 a43.00 ± 0.77 a2.22 ± 0.07 d1.66 ± 0.05 d3.89 ± 0.13 d3.02 ± 0.07 b
T332.79 ± 1.44 cd12.36 ± 0.88 bc37.50 ± 0.94 b1.85 ± 0.06 h1.38 ± 0.04 h3.23 ± 0.10 g2.69 ± 0.08 c
T435.96 ± 1.54 bcd13.59 ± 0.92 bc37.62 ± 0.86 b1.99 ± 0.07 g1.40 ± 0.04 g3.41 ± 0.10 g2.72 ± 0.06 c
T534.89 ± 1.44 bcd13.24 ± 0.90 bc37.75 ± 0.95 b2.24 ± 0.07 c1.69 ± 0.05 c3.95 ± 0.13 c3.46 ± 0.07 a
T629.87 ± 2.05 de11.03 ± 1.04 cd36.64 ± 0.85 b2.09 ± 0.06 f1.54 ± 0.05 f3.65 ± 0.11 f2.82 ± 0.07 bc
T737.66 ± 1.41 abc15.05 ± 0.91 ab39.81 ± 0.87 ab2.37 ± 0.08 b1.78 ± 0.06 b4.17 ± 0.14 b3.57 ± 0.08 a
T842.34 ± 0.96 a18.30 ± 0.76 a43.13 ± 0.79 a2.53 ± 0.08 a1.91 ± 0.06 a4.46 ± 0.14 a3.67 ± 0.08 a
T925.29 ± 2.05 e8.34 ± 1.00 d32.52 ± 1.11 c1.71 ± 0.05 i1.29 ± 0.05 i3.01 ± 0.10 i2.33 ± 0.14 d
S Em±1.320.790.770.0010.0010.0030.046
CD (0.05)3.792.262.20.0030.0030.0080.131
CV (%)9.214.024.930.130.0950.1733.682
T1: Chitosan spray at 500 ppm, T2: chitosan spray at 1000 ppm, T3: yeast extract spray at 500 ppm, T4: yeast extract spray at 1000 ppm, T5: jasmonic acid spray at 100 ppm, T6: jasmonic acid spray at 200 ppm, T7: salicylic acid spray at 100 ppm, T8: salicylic acid spray at 200 ppm, T9: control (water spray).The treatments with same superscripts within each parameter were not significantly different at p ≤ 0.05, according to Duncan’s multiple comparison procedure (DMRT). Chl.: Chlorophyll. Values represent the means, and ± the standard errors.
Table 5. Response of andrographolide contents in kalmegh to elicitors.
Table 5. Response of andrographolide contents in kalmegh to elicitors.
TreatmentsAndrographolides Content% w/w on Dry Weight Basis
AndrographolideNeo-
Andrographolide		14-Deoxy-11,12-
Didehydroandrographolide		AndrograpaninTotal Andrographolide
T12.51 ± 0.02 d0.38 ± 0.01 c0.17 ± 0.01 b0.03 ± 0.01 c3.08 ± 0.04 d
T22.68 ± 0.02 c0.35 ± 0.01 c0.12 ± 0.01 c0.02 ± 0.01 cd3.17 ± 0.04 cd
T32.06 ± 0.02 g0.38 ± 0.01 c0.07 ± 0.01 d0.02 ± 0.01 cd2.53 ± 0.04 g
T42.30 ± 0.02 e0.36 ± 0.01 c0.06 ± 0.01 d0.02 ± 0.01 cd2.74 ± 0.04 f
T52.90 ± 0.02 b0.23 ± 0.01 d0.12 ± 0.01 c0.02 ± 0.01 cd3.26 ± 0.04 bc
T62.14 ± 0.02 f0.58 ± 0.01 a0.18 ± 0.01 b0.04 ± 0.01 b2.93 ± 0.04 e
T72.72 ± 0.02 c0.41 ± 0.01 b0.13 ± 0.01 c0.03 ± 0.01 c3.29 ± 0.04 b
T82.97 ± 0.02 a0.24 ± 0.01 d0.25 ± 0.01 a0.05 ± 0.01 a3.49 ± 0.04 a
T91.87 ± 0.01 h0.25 ± 0.01 d0.13 ± 0.01 c0.02 ± 0.01 d2.26 ± 0.04 h
S Em±0.0130.0070.0040.0020.026
CD (0.05)0.0370.0190.0120.0060.074
CV (%)1.3014.5167.85420.8062.141
T1: Chitosan spray at 500 ppm, T2: chitosan spray at 1000 ppm, T3: yeast extract spray at 500 ppm, T4: yeast extract spray at 1000 ppm, T5: jasmonic acid spray at 100 ppm, T6: jasmonic acid spray at 200 ppm, T7: salicylic acid spray at 100 ppm, T8: salicylic acid spray at 200 ppm, T9: control (water spray).The values with same superscripts, within each parameter, were not significantly different at p ≤ 0.05, according to Duncan’s multiple comparison procedure (DMRT). Values represent the means, and ± the standard errors. Total andrographolide content = andrographolides + neoandrographolides + 14-Deoxy-11,12-didehydro Andrographolide + Andrograpanin.
Table 6. Correlation matrix of important parameters of kalmegh (elicitor treatments).
Table 6. Correlation matrix of important parameters of kalmegh (elicitor treatments).
PHPSNPBNSBNLLAPLAIFRYDRYDMATCHLOANDR
PH
PS0.94 **
NPB0.97 **0.98 **
NSB0.96 **0.95 **0.98 **
NL0.91 **0.92 **0.93 **0.93 **
LAP0.89 **0.92 **0.90 **0.94 **0.98 **
LAI0.89 **0.91 **0.90 **0.94 **0.98 **0.99 **
FRY0.80 **0.95 **0.91 **0.87 **0.88 **0.87 **0.87 **
DRY0.82 **0.96 **0.92 **0.89 **0.89 **0.88 **0.88 **0.99 **
DMAT0.79 *0.92 **0.89 **0.87 **0.87 **0.87 **0.87 **0.97 **0.99 **
CHLO0.470.68 *0.610.540.67 *0.64 *0.65 *0.81 **0.82 **0.81 **
ANDR0.500.68 *0.630.590.72 *0.69 *0.69 *0.82 **0.82 **0.82 **0.98 **
PH: Plant heightNL: Number of leavesDRY: Dry herbage yield
PS: Plant spreadLAP: Leaf area per plantDMAT: Dry matter content
NPB: Number of primary branchesLAI: Leaf area indexCHLO: Total chlorophyll
NSB: Number of secondary branchesFRY: Fresh herbage yieldANDR: Total andrographolides
*: Significant at a 5% level of significance; **: Significant at a 1% level of significance.
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Gowda M., P.; Sharangi, A.B.; Upadhyay, T.K.; Alotaibi, N.M.; Alotaibi, M.O.; Alshammari, N.; Saeed, M. Elicitor-Mediated Response of Growth, Yield, and Quality of Kalmegh (Andrographis paniculata Wall. ex Nees, Family Acanthaceae). Agronomy 2023, 13, 2313. https://doi.org/10.3390/agronomy13092313

AMA Style

Gowda M. P, Sharangi AB, Upadhyay TK, Alotaibi NM, Alotaibi MO, Alshammari N, Saeed M. Elicitor-Mediated Response of Growth, Yield, and Quality of Kalmegh (Andrographis paniculata Wall. ex Nees, Family Acanthaceae). Agronomy. 2023; 13(9):2313. https://doi.org/10.3390/agronomy13092313

Chicago/Turabian Style

Gowda M., Pavan, Amit Baran Sharangi, Tarun Kumar Upadhyay, Nahaa M. Alotaibi, Modhi O. Alotaibi, Nawaf Alshammari, and Mohd Saeed. 2023. "Elicitor-Mediated Response of Growth, Yield, and Quality of Kalmegh (Andrographis paniculata Wall. ex Nees, Family Acanthaceae)" Agronomy 13, no. 9: 2313. https://doi.org/10.3390/agronomy13092313

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