What these translucent formations exactly on central veins of rainbow eucalyptus can be? Trees are 6 weeks old, growing in a greenhouse with +25..35°C temperature and 90-100% humidity. Burrs look and feel somewhat like inside of cucumber - springy and light. It's almost like leave's flesh is bulging out. I tried to cut them (they're small), but didn't see anything inside.
Other than that, plants look healthy and have no alarming symptoms.