In Vitro Effect of Purple Amomum (Amomum longiligulare T.L. Wu) Extracts on Seed Germination and Seedling Growth of Different Crop Species

Abstract

The ginger family member purple amomum (Amomum longiligulare T.L. Wu) is an important medicinal plant in Vietnam. Although there have been studies on the chemical composition of essential oils and extracts of purple amomum, as well as their antibacterial, antifungal, activating macrophages, and immune enhancement effects, there is still a lack of evaluation of the phytotoxicity of this plant. In this study, the total content of phenolic (TPC) and flavonoid (TFC) in extracts of leaf, seed, pseudo-stem, rhizome, and root from purple amomum and the phytotoxic effect of these extracts against five test plant species, including four dicotyledonous: camelina (Camelina sativa Crantz), quinoa (Chenopodium quinoa Willd.), cabbage (Brassica oleracea var. capitata L.), tomato (Solanum lycopersicum L. cv. Dubrava), and one monocotyledonous: onion (Allium cepa L. cv. Stuttgarter risen), were investigated. Results showed that the seed and leaf extracts had higher total phenolic and flavonoid contents than the other two extracts (highest TPC value: 4.30 ± 0.03 mg GAE/mg dry weight of seed powder; highest TFC value: 1.32 ± 0.07 mg QE/mg dry weight of leaf powder). Furthermore, it was observed that the extracts of purple amomum inhibited seed germination and the growth of seedlings of all test plant species with different inhibition values. The general trend in all treatments showed that, when increasing the concentration of extracts from 0.10–0.20 mg/mL, the ability to inhibit seed germination, hypocotyl length, radicle length, fresh weight, and dry weight increased. Seed extract at a concentration of 0.20 mg/mL in most treatments showed the highest percentage inhibition of seed germination and growth of seedlings of the tested species. Onion was the most sensitive to purple amomum extracts among the five species tested. Based on these results, we conclude that extracts of different parts of the purple amomum exhibited phytotoxicity for the tested species. Further evaluation of the phytotoxic potential of the extracts on weed species and under field conditions is also recommended for the purpose of developing bio-herbicides for future weed management that are less toxic to the environment and human health.