Effect of Antigonon leptopus Leaf Extract on Seed Germination and Seedling Growth of Trigonella foenum graecum (Part 2)

3. Results and Discussion

In agriculture, allelopathy is the subject of much research because both the plants primarily were screens for their capacity to suppress the weed growth and secondly the loss of biodiversity can be controlled to overcome the growth and spread of invasive weeds. Trigonella foenum-graecum grown under the extract of Antigonan leptopus leaf extracts and various parameters were studied. It was observed that there is marked seed germination and seedling growth inhibition occur in all different dilutions of extract. The growth of Trigonella plant was also observed under various leaf extracts like methanolic, ethanolic and water extract. It was observed that growth inhibition was severe under methanolic extract (Table 1).

Table 1. Growth inhibition assay in three different solvent extract of Antigonan leptopus.

Methanolic extract of A. leptopus leaves was further analyzed qualitatively by LCMS for the presence of various allelochemicals. The mass spectrum analyses mass of the compounds which is obtained in the form of peaks at different m/z ratios. These mass spectra were identified from the National Institute of Standards and Technology (NIST) Chemistry WebBook (U.S. Secretary of Commerce, 2018) . Various phytotoxins, phenolics coumarins, caeboxlic acid derivatives are presents in the leaf extract (Figure 1, Table 2).

Figure 1. Liquid Chromatography Mass Spectra of Antigonan leptopus methanolic leaf extract.

Inhibition of germination is one of the strategies of some allopathic invasive plants. Seeds of Trigonella in present studies showed (62%) germination which was appeared to be suppressed as compared to distilled water grown control (Figure 2). Suppression of the seed germination occur due to the imbalances on various growth regulators thats are active during seed germination and early seedling growth like gibberelic acid (GA) or IAA.

Figure 2. Germination percentage of the seed of Trigonella grown under the Antigonan leaves extracts.


 Growth of Trigonella seedlings was inhibited in almost all dilutions of Antigonan leaf extracts i.e. from 10 to 50%. Root growth was more severely inhibited as compare to the shoot growth (Figure 3A, B). Growth was significantly inhibited in higher dilutions (i.e., 50% extract) from 5 days to 15th days with the decrease of fresh and dry weight (Figure 3C).

Figure 3. A and B, Shoot and root length, C dry weight of Trigonella seedlings grown under the extract of Antigonan leaves extracts respectively.

Somewhat similar observations were also made with Marsilea minuta aqueous extract on rice and wheat by Tanveer et al. The decrease in plant moisture contents indicates the poor water absorption through the root and this decrease was accompanied by decrease in the density of tissue mass resulting in the decrease in fresh and dry weight . The root growth was severely affected due to the presence of extracts, the growth was completely inhibited after 15 days of radicle emergence and become dries (Figure 4).

Figure 4. Trigonella seedlings (10 days old) grown in different concentrations of Antigonan leaf extracts.

The seedlings growth is dependent on the minerals and waters that absorbed by the roots and the photosynthesis done by the green cotyledon and primary leaves nourished the seedlings . The presence of the extracts inhibits normal functioning of the seedling results in retarding of growth. The growth inhibition was due to the presence of many active phytochemical that is to be further investigated. Most of the workers analyzed phytochemicals of the Antigonan leptopus and observed that its methanol extract contains various active metabolites such as alkaloids, glycosides, flavonoids, volatile oils, tannins, anthraquinones, terpenes, saponins etc.. Alkaloids are plant growth inhibitors first reported by Waller and Burstrom isolated from common larkspur, Delphinium ajacis. The effects of phytochemicals on the inhibition of both seeds germination and seedling root length was also studied in radish seeds when crude extract of I. rugosus was applied that contains glycosides, alkaloids, tannins, terpenoids, flavonoids, saponins, anthraquinones and oils similar to the Antigonan leptopus. However, the percentage of these metabolites may vary from plant to plants.

The nitrogen is very essential for the plant growth and development throughout their life. Better nitrogen assimilation is required for attaining tolerance for biotic and abiotic stresses. Total nitrogen contents of Trigonella seedlings was declined from 5 to 15 days treatment indicates that seedlings under stress caused by Antigonan leaf extracts and their secondary metabolites. (Figure 5).

Figure 5. Total nitrogen contents in the seedlings of Trigonella grown under the Antigonan leaves extracts.

After 10th day under extract the total nitrogen is taken only for shoots because the roots are completely damage (Figure 1). The damaged root tips were turned brown and become somewhat swollen.

Qualitative phytochemical analysis of the methanolic leaf extracts of A. leptopus revealed that the plant contains phenolics, Ferulic acid derivatives, arachidonic acid, citronellic acid, and coumarins derivatives (Table 2).

Table 2. Compounds identified in LCMS of Antigonan leptopus.

The ferulic acid is well known cinnamic acid derivative and potent allelochemical that is secreted by various plant to suppress the growth of other plants by inhibiting various physiological process like water utilization efficiency, seed germinations and root growth . In our experiment root growth was severely inhibited as compared to shoot due to the presence of ferulic acid derivatives in leaf extract of A. leptopus. Ferulic acid are also inhibits the nitrate and chloride uptake and responsible for net potassium uptake in maize . Similar properties were also observed in coumarins and it also inhibits the plasma membrane H+-ATPase etc. These allelochemicals also affect the amino acid absorption and transport and ultimately inhibition of protein synthesis which affect the cell growth. These phytotoxins are not only interferes in mineral absorption and protein synthesis but also inhibits nucleic acid integrity.

In present investigation it is confirmed that the inhibition of root and shoot growth of the Trigonella seedling was due to the presence of these phenolic acids derivatives mentioned above because it was already noted that phenolic acids can depolarized root cell membranes and cause other perturbations of cellular functions that interfere with ion accumulation . The plant should be eradicated from the agricultural field by manual plucking. However, the plant showed many pharmacological properties and used as a medicine so It should be allowed to grow in restricted areas away from agricultural fields.

When there is leaf fall after summer season in A. leptopus the leaves residues are left, and these compounds released into the soil and are supposed to be accumulated in soil micelles or in humic acids, modulates the growth of other plants. The A. leptopus leaf extract turned dark brown when kept for 10 days in lab condition also indicates the presence of phonolics and other phytotoxins. So, it is advisable that the plant residues should be eradicated after the summer.

4. Conclusions

In the present investigation the effect of the Antigonan weed was studied on the germination and seedling growth. Both germination and seedling growth was inhibited and at 5th day there was more inhibition of root growth occurred. The growth inhibition was increases in accordance to the extract concentration. These results indicated that Antigonan plants are harmful and growth inhibitory activity for not only the wild plants but also for our crop plants like legumes. More experiments should be conducted to analyzed exact dose so that it can be used to inhibits the growth of unwanted weeds in the field. New practices should be conducted to use Antigonan leaves extract into natural and agricultural management systems that may reduce the use of herbicides, fungicides and insecticides.