what is coleoptiles?
The first visible signs of growth in plants is the emergence of the embryo root, the radicle. Subsequently, the embryo shoot and the plumule emerges. In the grasses, Which are monocotyledons, the plumule is protected by a sheath called coleoptile which is positively phototropic and negatively geotropic. The first leaf grows out through the coleoptile and unrolls in response to light.
@Siddhartha: Very good! Keep up the good work.
Coleoptile is the pointed protective sheath covering the emerging shoot in monocotyledons such as oats and grasses. Coleoptiles have two vascular bundles, one on either side. Unlike the flag leaves rolled up within, the pre-emergent coleoptile does not accumulate significant protochlorophyll or carotenoids, and so it is generally very pale. Some preemergent coleoptiles do, however, accumulate purple anthocyanin pigments.
Coleoptiles consist of very similar cells that are all specialised to fast stretch growth. They do not divide, but increase in size as they accumulate more water. Coleoptiles also have several (frequently two) water vessels along the axis to provide a water supply.
When a coleoptile reaches the surface, it stops growing and the flag leaves penetrate its top, continuing to grow along. The wheat coleoptile is most developed in the third day of the germination (if in the darkness)....!!
Schematic image of wheat coleoptile (above) and flag leaf (below)...!!
Hopes dis answer will help u...!! :)))))