Germination requirements: substrate

Many seeds will germinate on paper or sand. Water is essential, whichever of these is used. As you learned in module 4, water is required for imbibition and many of the chemical reactions necessary for growth can only take place in solution. There should be enough water on the substrate to allow the seeds to imbibe prior to germination, usually by taking water in through the seed coat.

Once germination starts, the substrate must support the seeds and the emerging radical and cotyledons. It should be easy for you to separate out the germinated seeds when you need to inspect them. It is a good idea to seal the container, which could be a Petri dish, sandwich box or other container. If the container is not sealed well enough to maintain moisture levels for the duration of the germination test, it is important to add water to the substrate at regular intervals.

Some crops, such pearl millet, chicory and rye grass, are likely to germinate best when placed on top of a paper substrate, like the rye grass in Figure 2 (below):

Other seeds, such as oats, chickpea, black gram or rice, will germinate best if rolled up in moist paper, so the seeds are surrounded by substrate. Figure 3 shows some paper toweling rolls containing oat seeds, stacked vertically in a basket within a germinator. Opening up one of the rolled papers reveals the germinated seedlings as shown below:

  

Some crops such as onion or cabbage are commonly germinated on pleated paper. Folding the paper towel separates the seeds into rows; the pleated paper is then placed in a sealable box and kept moist while the seedlings germinate, like the Brassica seedlings in Figure 4 (below):