Effect of auxins on the asymbiotic seed germination of Malaxis acuminata- A medicinally important orchid

Abstract: Malaxis acuminata D. Don (= Microstylis wallichii Lindl.), The Crimson Shield Orchid, is a widely distributed species found in Thailand, China, Burma and Indo-China. In India, it is available in temperate and subtropical Himalaya, Western Ghats, Nilgiri Hills and Andaman Islands. An important ingredient of ‘Ashtavarga’ drugs used in the preparation of an ayurvedic tonic ‘Chavyanprash,’ the species is marketed under the trade name ‘Rshbhak’. Immature seeds procured from green capsules (12 wap) of Malaxis acuminata were inoculated in Mitra medium for the assessment of their germination potential in media containing different concentrations of IAA, IBA and NAA. 55 and 64% seeds germinated in basal M medium in the absence and presence of AC, respectively. Healthy seedlings were obtained on basal M medium under light conditions in 33 weeks. When the medium was enriched with IAA, as many as 60% seeds germinated under light conditions only at lower concentration of 4.4 μM. However, IAA, in general, supported morphogenesis only till the protocorm stage. Pseudobulbs were formed only at 8.8 μM. IBA supported 45% seed germination at 8.8 μM concentration followed by leaf formation as well. NAA when supplied at 8.8 μM led to a marked increase in the percentage of seeds germinating 63.5%; eventually leading to the multiplication of pseudobulbs. AC was beneficial in rooting in basal M medium and enhancing the seed germination in basal M medium and IBA medium at 4.4 μM concentration.

Keywords: Activated charcoal, Indole-3-acetic acid (IAA), Indole-3-butyric acid (IBA), Malaxis acuminata, Mitra medium, 1-Naphthalene acetic acid (NAA).