The coleoptile, a protective sheath covering the emerging shoot in grasses, is typically how long in Mexican dwarf wheat varieties? (MCAER 2017)

✔Explanation: The coleoptile plays a crucial role in protecting the delicate shoot as it emerges from the seed. In Mexican dwarf wheat varieties, the coleoptile length is stated to be 5 cm. This relatively short length may be an adaptation related to their dwarf stature.
🔑Key Points
-Coleoptile is the protective sheath covering the emerging shoot in monocotyledons such as grasses. Coleoptiles have two vascular bundles, one on either side.
-Function:
-Protects the first leaf and the growing stem in seedlings.
-Allows the first leaf to emerge.
Structure
-Composition:
-Contains very similar cells specialized for fast stretch growth.
-Cells do not divide but increase in size by accumulating water.
-Vascular Bundles:
-Contains two vascular bundles, one on either side.
-Water vessels (frequently two) along the axis provide a water supply.
Characteristics
-Coloration:
-Generally pale due to low accumulation of protochlorophyll or carotenoids.
-Some preemergent coleoptiles may accumulate purple anthocyanin pigments.
-Growth Behavior:
-Grows until it reaches the soil surface.
-Stops growing upon emergence, allowing the flag leaves to penetrate its top and continue growing.