What is a key feature of the Flag Stage in onion seedlings?

The key feature of the Flag Stage in onion seedlings is that the bent tip of the seed leaf resembles a flag. At this stage of development, the leaf has begun to unfurl, and its unique curled or bent appearance gives it a flag-like characteristic. This visual cue is important for identifying the growth stage of onion seedlings and indicates that the plant is transitioning from the initial development phase to a more advanced one. The flag leaf is critical for the plant's photosynthetic activity, which supports further growth and development as it continues to mature.

The other options pertain to different stages or characteristics that do not align with the Flag Stage specifically. For instance, the first node being above the soil surface relates to a different growth phase, while maturity and flowering occur much later in the plant's life cycle. Recognizing these specific stages is essential for proper management and cultivation practices in onion production.