*2.1. Seed Material*

Matured capsules of black cardamom were collected at the end of December 2020 from the cardamom forest in Tam Duong district, Lai Chau province, Vietnam, around 22◦23 04.5 N latitude and 103◦32 44.0 E longitude. After harvesting, they were rinsed with water, preserved by vacuum packing, and transferred to the biotechnology laboratory of the Russian State Agrarian University—Moscow Timiryazev Agricultural Academy. At the laboratory, seeds were extracted from the capsules, rinsed thoroughly with tap water to remove the aril, and used immediately for experiments (Figure 1).

**Figure 1.** Black cardamom plants in Lai Chau province, Vietnam. (**a**) Black cardamom plants and their growing environment; (**b**) inflorescence shoots; (**c**) bloomed inflorescences; (**d**) fresh capsules; (**e**) fresh seeds; (**f**) dried ripe capsules (Photo by Ma A Chang, 2020).

A voucher specimen (No. QF 001) was deposited at the herbarium of Hanoi Pedagogical University N◦2, Vietnam. Botanical identification was achieved by Dr. Tam H. M.

#### *2.2. Morphological and Anatomical Characteristics of Black Cardamom Seeds*

The characteristics of the shape, color, and size of seeds were examined via stereomicroscope "Stemi" DV4 (Carl Zeiss, Oberkochen, Germany). Detailed morphology and anatomy of seeds were evaluated using a scanning electron microscope (SEM). Black cardamom seeds were fixed in 2.5% glutaraldehyde in a 0.1 M Sorenson buffer, pH 7.2. After that, they were washed with buffer and dehydrated through ethanol series (30%, 50%, 70%, 96%, and 2 × 100%). In the next step, carbon dioxide (CO2) for critical-point drying (Hitachi (Tokyo, Japan) HCP-2 critical point dryer) was applied. Dried seeds were mounted on an SEM stub with carbon-conductive tabs and coated with gold and palladium using an Eiko IB-3 ion coater (Eiko, Tokyo, Japan). Samples were observed and photographed under a JSM-6380LA SEM at 20 kV (JEOL, Tokyo, Japan).
