What is indicated by a bent tip of the seed leaf in onions?

The bent tip of the seed leaf, or cotyledon, in onions is characteristic of the flag stage. During the flag stage, the plant develops its first true leaf, which often exhibits a distinctive bent tip. This phase is vital for the plant's growth as it transitions from the initial germination and seedling development stages towards further vegetative growth and eventual bulb formation.

In contrast, other stages like the rosette stage, tillering stage, and jointing stage have different morphological features. The rosette stage is marked by the formation of multiple leaves close to the ground, the tillering stage involves the development of additional shoots or tillers, and the jointing stage concerns the elongation of the stem internodes. Each of these stages presents unique growth characteristics that are distinct from the flag stage, making the recognition of the bent tip a key identifier for this particular phase of onion development.