Determination of orchid seed viability using fluorescein diacetate

Abstract Fluorescein diacetate (FDA) staining (0.25% FDA for 10 min) was found to be a suitable technique for the rapid determination of orchid seed viability. Penetration of the dye through the testa varies between species, thus the test is ideally performed on isolated embryos. Direct FDA application to isolated embryos of seeds taken from dry storage, but after the surface had been sterilized, elicits a poor staining reaction. Incubation of the surface sterilized seeds in distilled water for 16 h, either at 6°C or at room temperature, prior to applying the test was found to overcome this problem. In the range of species studied, FDA staining accurately indicates seed viability when compared with germination of seeds on sterile nutrient media. Storage of dry Dactylorhiza fuchsii (Druce) Soó seed at an elevated temperature of 62°C indicated that, under such conditions of accelerated ageing, the FDA test accurately describes the rate of seed viability loss.