Seasonal Variation Of Chemical Composition Of Bamboo Leaf Phytoliths

Phytolith morphology has made great breakthroughs in many fields such as plant taxonomy,archaeology and reconstruction of paleoenvironment,but its chemical composition is rarely studied.The study on seasonal variation of phytolith morphology and chemical composition of a single species is helpful to understand the relationship between phytolith and growth stages,and environmental factors.Studies have shown that modern plant phytoliths morphology assemblage have obvious seasonal changes,which is related to the growth stage and growth environment of leaves.It is not explicit whether there are changes in the chemical composition of phytoliths in modern plant leaves,and what factors influence them.Due to the cumulative effect of phytoliths formation,it is necessary to study the differentiation between old and new leaves.Taking one year as a growth cycle,we collected the new and old leaves of Dendrocalamus Ronganensis(Bamboo subfamily)month by month,and analyzed the morphology assemblage changes of phytoliths.Electron probe microanalysis was used to understand the difference of element content between old and new leaves phytolith,and to find out the formation mechanism of phytolith and the relationship between the changes of chemical elements and environmental factors.The main understanding is as follows:(1)The phytoliths morphology assemblage of 2019-2020 new leaves was dominated by short-cell phytoliths,while the proportion of cuneiform and elongate phytoliths increased in 2018 and 2019 old leaves.The size of oblong concave saddle and saddle-bilobate shape varies with leaf age.The longer the leaf age is,the smaller the size of long saddle and saddle-bilobate shape is.Under drought conditions,the proportion of cuneiform and stoma phytoliths in phytoliths morphology assemblage decreased,while the length and width of oblong concave saddle and saddle-bilobate shape phytolith increased.(2)The average phytosilicate content of new leaves,old leaves and old leaves from 2019 to 2020 was 4.9%,7.9% and 10.5%,respectively.The average phytolith-occluded carbon is 2.2%,3.2% and 1.5%,respectively.The phytolith-occluded carbon of 2018 old leaves was lower than that of 2019-2020 new leaves and 2019 old leaves.The phytolith-occluded carbon of 2019-2020 new leaves i decreased during the drought period(September to December 2019).The decrease of the percentage of cuneiform,elongate and stoma phytoliths will reduce the phytolith-occluded carbon.(3)The contents of Si,Na,Al,Mg,Ca,K and other elements in old leaves were higher than those in new leaves.The contents of P,Cr and Mn in 2019-2020 new leaves were higher than those in old leaves.With the increase of leaf age,the Si content in short-cell,cuneiform and elongate phytoliths increased.Influenced by phytolith formation mechanism,short-cell phytoliths have a preferential accumulation of silicon,so the Si content of short-cell phytoliths in 2019-2020 new leaves is the highest.Cuneiform phytoliths are influenced by the environment,short-cell phytoliths are controlled by genes.Thus,during the drought period(September to November2019),the Si content of both cuneiform and elongate phytoliths showed low values,while the Si content of short-cell phytoliths had a slight reduction.The results showed that the morphology assemblage,size and chemical elements of phytoliths of subfamily bamboos varied significantly in a single growth season,which was mainly related to the growth stage,environment of plants,and also related to the plant gene.Therefore,this study can provide a new approach for the identification of plant species,reconstruction of plant growth environment and archaeology,and has a certain value for the study of palaeo-ecology and palaeo-environment.