What to do if I find no or just little white roots when repotting
 

Will be repotting cattleya seedlings in next few days. Just bought them this past week at Lowes discount rack. When I soaked them in water (for about 30 seconds) I could see some of them have the silvery roots that turned green, but on one I couldn't see anything. If when I go to repot the plants and see no roots at all on this plant (which has wrinkled leaves) what do I do with it?

cattleya seedlings
 

Besides roots, look for root tips. This is where the root grows. If the tip is lost, the root stops growing. Sometimes a new tip might form. The tip will be a darker color, usually reddish in color. Tips are fragile and can break off easily so be careful when repotting. The plant without roots is dying of dehydration. You might want to soak it in a solution of rooting hormone. Solutions of vitamin B6 can also be used with badly underwatered plants. If the plant begins to take up water it can be potted in fine fir bark and perhaps placing a plastic bag over the top will keep the humidity high. Cattleyas form most of their roots just after a new leaf begins to grow. This is usually the best time to repot them.

Actually, depending on the species or hybrid parents of the plant, the roots can start growing at different times. Some grow as the plant grows. Some grow roots when the plant is half grown. And some even growq roots after the plant has flowered. They're all different. For plants with no roots, you can get good results from hanging the plant in a jar with water in the bottom just below where the roots would be. Laid on a bed of sphagnum moss dampened. Placed in an open ziplock bag with some damp moss. Lots of ways. I take the plant and dip it in water every day to help give the leaves some moisture. But usually if the plant grew roots and then lost them, chances are it won't grow more roots.