Here is a time-lapse of a runner bean germinating underground. This is an example of Epigeal germination where the cotyledons expand, throw off the seed shell and become photosynthetic above the ground.
Beans like other seeds need temperature and moisture to stimulate germination.
Stage 1:
Radicle expands and pushes against the testa at the micropyle
Testa spilts open and radicle emerges
Lateral roots develop
Root hairs form behind tip of radicle which helps absorb water and mineral salts in the soil
Stage 2
Stem below cotyledons elongates
Pulling cotyledon through soil and above the ground
Sometimes the is testa remains underground or discarded above ground
Cotyledons are closed together to protect the delicate pumule within
Stage 3
Cotyledons open up above ground
Cotyledons turn green
First foliage leaves start to develop
Foliage expands and turns green carrying out photosynthesis
Runner bean seedling is now a self-supporting plant
This and other of my time-lapses can be found on You tube http://www.youtube.com/user/neilbromhall
Time-lapse copyright Neil Bromhall. filmed for my plant identification website. www.rightplants4me.co.uk
