Morphological Characteristics and Significance of Bulliform Phytoliths in Haploid Rice

The morphology of bulliform phytoliths serves as a key proxy for tracing the origin and evolution of ancient rice cultivation in archaeobotanical research; however, the correlation between these morphological traits and the genetic background of rice is unclear. To the best of our knowledge, for the first time, this study demonstrates that chromosome ploidy level is a key genetic factor influencing rice phytolith morphology, based on a comparative analysis of fan-shaped bulliform phytoliths from haploid and diploid rice. Compared with diploid rice, we found that the bulliform phytoliths in haploid rice exhibited two significant differences: (1) an overall reduction in morphological dimensions (fan width HL = 34.8 μm, fan length VL = 37.6 μm), with dimensions reduced by ~ 18%, a decrease in the number of fish-scale facets (~ 6.7), and an extremely low proportion of bulliform phytoliths with ≥ 9 fish-scale facets (~ 7.0%); and (2) a 46.8% decrease in the ratio of fan face length to stalk length (B/A) of phytoliths (~ 0.58), with very few short-stalk types (accounting for 0.0%-1.5%) and a predominance of long-stalk types (accounting for ~ 86.6%). These results revealed the regulatory mechanism governing chromosome ploidy on plant cell silicification patterns, manifesting as both quantitative (reduced size and fewer facets) and qualitative (possible absence of certain morphotypes) changes. This study provides important empirical evidence and a theoretical foundation to bridge modern rice genetics and archaeobotany.