UPRAWA / ROZMNAŻANIE / 3

Asymbiotic micropropagation of orchids from seeds (flasking)

12.
Seed Sterilization and Sowing. The first student activity on the day of the class lab is seed sterilization and sowing, as shown in the following diagram:

Although many commercial orchid flasking labs use immature seeds within green pods (mainly because intact pods are more easily sterilized), we prefer to use fully ripe seeds collected from dehisced capsules for 2 reasons:

fewer stock plants are necessary since each pod contains 50,000+ seed
mature seed stores better

13.
Here is a plate of freshly sown seeds on Knudson C medium (see lab manual) with 20 g/l sucrose, 7 g/l agar, pH 5.5. Commercially, undefined organic additions like bananna pulp, coconut milk, etc are added to the nutrient medium to stimulate seedling growth, but these additions are unnecessary for this excise.

Question: why would organic additions stimulate seedling growth?

14.
Several weeks after sowing, viable uncontaminated seed will have swollen and turned green.

15.
At this point (several weeks after sowing, and weekly thereafter for the remainder of the semester) students should observe their plates under a dissecting microscope, and record (notes and sketch) the stages of germination which you observe.

In ungerminated seed, observe the more or less transparent testa (seed coat) and the spherical rudimentary embryo within.
In seed just beginning to germinated, observe the swollen embryo, and ruptured seed coat.