Time-Resolved Phenotyping Reveals Heterogeneous Rice Seed Germination Dynamics in Shallow-Water Culture

Germination percentage alone fails to reveal the timing and speed of individual seed growth, necessitating a more detailed approach. Researchers established a time-resolved phenotyping method to observe rice seed germination in shallow-water conditions. This system employed a camera mounted on a rail that captured images every hour for up to 80 hours, resulting in over 6,000 observations of individual seeds. A physical grid assigned unique identification to each seed, enabling precise tracking of their development.

Using an advanced image analysis tool, the system autonomously identified and separated the emerging plant tissue from the seed's outer shell. This allowed researchers to measure the size of the growing tissue and calculate the rate at which it expanded. Of the three normally germinating seeds examined, each followed a unique growth pattern.

The first signs of noticeable tissue appeared at the 48-hour mark, but the subsequent growth rates varied significantly. The final projected area of the seeds ranged from 2,605 to 4,700 pixels, while their peak interval growth rates varied from 106.88 to 287.92 pixels per hour. Notably, seed B-1 accumulated 63.71% of its maximum visible area in the last three days of observation, while seed B-3 reached the same milestone in the earlier half of the observation period.

This study demonstrates that even seeds with the same initial emergence interval can display substantial differences in the timing and extent of their post-emergence expansion. The proposed time-resolved phenotyping workflow provides a powerful tool for non-destructive research into rice seed vigor and germination heterogeneity.