Morphological Characteristics Of Bulliform Phytoliths In Dongxiang Wild Rice And Cultivated Rice

Rice（Oryza sativa L.）is closely linked to human survival and the development of civilisation.While when,where,and under what environmental conditions cultivated rice became domesticated is of significant academic interest both locally and globally.The analysis of wild rice cell structures,tissues,organs,and other morphological characteristics and the development of identification markers for wild rice are the basis for identifying the origins and evolution of prehistorical rice agriculture.In this parer,Dongxiang common wild rice growing in the middle of the Yangtze River was used as the reference species for this study.Through analyzing the morphology of bulliform phytoliths between wild rice and cultivated rice,then analyzing the morphological characteristics of phytoliths of wild rice in original habitat and cultivated rice at different growth stages and leaf positions,comparing the morphological differences of phytoliths of wild rice in different ecotypes（original habitat and homozygous line）,and studying the effects of artificial fertilization on the morphological characteristics of bulliform phytoliths in paddy rice under the same climate background.Thus,this paper clarified the change rules of the shape and size of bulliform phytoliths in common wild rice and cultivated rice,revealed the effect of gene infiltration of domesticated rice and other plants on the phytoliths of wild rice,and explored the indicative role of phytoliths in the study of rice domestication,so provides a discriminant basis for phytolith analysis of the origin of rice agriculture.（1）Through the investigation and statistical analysis based on the large sample data,the author found that the size of the bulliform phytoliths of the common wild rice was larger than that of the cultivated rice,and that the size of phytoliths of the japonica rice was larger than indica rice;the B/A ratio（the ratio of the base portion length（B）to the non-base portion length（A）of bulliform phytoliths）of common wild rice was significantly higher than that of cultivated rice while the japonica rice was significantly lower than that of indica rice.The phytoliths of dongxiang wild rice and indica rice were mainly short-stalked phenotype,while those of japonica rice were mainly intermediate and long-stalked phenotype.From the perspective of phytolith,Dongxiang wild rice was indica type and occurred gene infiltration of cultivated rice.（2）Comparing the morphological characteristics of bulliform phytoliths in rice with different leaf positions,it was found that from flag leaf,the second leaf to the third leaf,the shape size of bulliform phytoliths in common wild rice and japonica rice showed a decreasing trend,and that of indica rice showed an increasing trend,but there was no difference in B/A ratio between wild rice and cultivated rice at different leaf positions.The distribution frequency of medium and large phytoliths（VL≥40μm&HL≥35μm）showed a decreasing trend in wild rice and japonica rice,and an increasing trend in indica rice from flag leaf,the second leaf to the third leaf.（3）Comparing and analyzing the phytolith morphologies of three common wild rice species from various habitats and one species of ectopically preserved homozygous common wild rice after six consecutive generations of self-crossing,it was found that the morphology of the bulliform phytolith in the homozygous wild rice with reduced domestication gene introgression had three significant differences compared with native wild rice:1)an overall reduction in size(body length decreased from 41.9?m in VL_nativeto 38.6?m in VL_homozygous);2)an increase in the proportion of the long-stalked phenotype,with the ratio of B/A decreasing from 1.22±0.47 in B/A_nativeto 0.92±0.30 in B/A_homozygous;and 3)a decrease in the number of fish-scale decorations,with the proportion of bulliform phytoliths with≥9 fish-scale decorations reduced from 53.4%in native wild rice to 37.2%in homozygous wild rice.From the perspective of bulliform phytolith,homozygous wild rice was japonica type.（4）By comparing and analyszing the rice bulliform phytolith morphologies of artificial fertilization（NF）and no fertilization（CK）at different growth stages,it was founded that:1)the morphology of bulliform phytoliths（fan width HL33.4-41.5μm,fan length VL36.9-49.4μm）under artificial fertilization（NF）was significantly larger than that of phytoliths（HL20.0-29.3μm,VL22.9-32.5μm）without fertilization（CK）,and the morphology of those phytoliths showed an increasing trend in the growth period（from tillering stage,filling stage to maturity）;2)there was no significant change in B/A ratio（the ratio of the base portion length（B）to the non-base portion length（A）of bulliform phytoliths）between NF treatment（0.74 tillering stage-0.93 mature stage）and CK treatment（0.58 tillering stage-0.94 mature stage）,and those of phytoliths had an increase in the proportion of the short-stalked phenotype and an decrease in the proportion of the long-stalked phenotype during the growth period（from tillering stage to maturity stage）;3)the proportion of bulliform phytoliths with≥9 fish-scale decorations median 44.5%,average about 60%in NF treatment was larger than that of the proportion median 27.8%,average about 54%in CK treatment,and the proportion of≥9 fish-scale decorations those treatments showed an increasing trend in the growth period（from tillering stage to maturity stage）.（5）By comparing the morphological characteristics of fan phytoliths in different populations and growth periods of Dongxiang wild rice,it was found that the fan width HL（32.4～41.4μm）and fan length VL（33.3～44.8μm）of Dongxiang wild rice showed an increasing trend during the growth period.Compared with seedling stage,the increase of larger phytoliths in mature stage was mainly in the range of B/A>1.2&40≤HL≤50μm.The phytolith B/A ratio（0.68～1.26）of Dongxiang wild rice increased during the growth period,and the phytoliths of wild rice had an increase in the proportion of the short-stalked phenotype and an decrease in the proportion of the long-stalked phenotype during the growth period,but there were no significant difference in B/a of wild rice among different populations at the maturity stage.In this study,the author clarified the morphological characteristics of bulliform phytoliths in Dongxiang wild rice;for the first time investigated the effects of gene infiltration from domesticated rice on wild rice bulliform phytoliths,also first time revealed the effect of fertilizer application on the morphology of phytoliths in rice motor cell,and clarified the morphological development process of phytolith in common wild rice and cultivated rice and the potential indication of the morphological characteristics of bulliform phytoliths on the study of rice domestication.Thus,this study provides a quantitative method and theoretical framework for evaluating the evolutionary processes in future rice origin studies.