Droplet-vitrification cryopreservation of shoot tips of the endangered plant Lilium tsingtauense.

This study established an efficient droplet-vitrification cryopreservation protocol for the endangered plant Lilium tsingtauense. Through optimization, the best conditions were determined as follows: shoot tips were precultured in 0.3 M sucrose at 4 °C for 7 days, treated with loading solution for 20 min, dehydrated with PVS2 solution at 0 °C for 90 min, and then rapidly plunged into liquid nitrogen using the aluminum foil strip droplet method. A mean regrowth rate of 67% was achieved. Histological observations showed that cells recovered normal morphology after protective dehydration, and ISSR marker analysis confirmed genetic stability in regenerated plantlets. This system provides a reliable method for the safe long-term ex situ conservation of this endangered species.