The Characteristics Of Calcium Oxalate In Different Groups Of Plants In Northern China

Calcium oxalate is an important and common biological mineral in plants,which has functions such as calcium regulation,improving plant stress resistance,enhancing mechanical support of plant tissues,and reducing palatability of plants.Previous studies have shown that the content of calcium oxalate in plants from different distribution areas varies significantly due to different environments,and that calcium oxalate is sensitive to drought and salinization habitats.However,if exposed to high temperature,whether the calcium oxalate is sensitive to high temperature changes or not;if they were located in natural close distribution,whether there be differences in the calcium oxalate content between different plant communities or not.In order to solve these problems,on the one hand,I selected three kinds of trees in the campus of Nankai University as the research objects,determined the content of calcium oxalate in leaves,analyzed the changes of calcium oxalate content in different months and time periods,and discussed the correlation between calcium oxalate and Ca²⁺;On the other hand,I chose a total of 12 species of plants within 30 m intervals in the transitional zone of arid and semi-arid areas of Ningxia Hongsipu District and the Habahu National Nature Reserve,determined and compared characteristics and differences of calcium oxalate content in leaves.In previous experiments,the study of calcium oxalate was mostly observed by optical microscope,which limited a large number of observations and comparisons;this paper used an improved chemical method to determine the content of calcium oxalate in plants,which improved the feasibility of such experiments.The main results are as follows:1.The calcium oxalate content in leaves of Fraxinus velutina Torr.,Sophora japonica and Salix babylonica in Nankai University showed clear monthly and daily variations.In July,during the intra-day high temperature period(12:00-15:00)when the temperature was higher,the contents of calcium oxalate in leaves of three tree species all decreased to the lowest value,and there was no significant correlation between the Ca²⁺and calcium oxalate contents;however,in August and September,during the intra-day high temperature period(12:00-15:00)when the temperature was relatively low,the leaf calcium oxalate content of the three tree species did not decrease to the lowest value(except for Sophora japonica in August),and existing an obvious positive correlation between the Ca²⁺and calcium oxalate contents(P<0.05).In conclusion,during the intra-day high temperature period of the higher temperature month,the calcium oxalate of the three tree species exercised the function of calcium reservoir,and the calcium oxalate was converted into Ca²⁺to support the physiological metabolic activities of the trees;in the non-high temperature months,more Ca²⁺were converted to calcium oxalate.This reversible conversion of Ca²⁺and calcium oxalate enabled plants to adapt to the uncomfortable growth conditions.2.For the plants with close distribution(within 30 m),including constructing species of plant community in different ecosystems and different successional stages,and different canopy heights of three leguminous bushes as well as different growth stages of Artemisia ordosica in Ningxia Hongsipu District and the Habahu National Nature Reserve,there were significant differences in calcium oxalate content between Artemisia sphaerocephala and A.ordosica,Stipa tianschanica var.gobica and S.bungeana,Ceratoides latens,Cleistogenes squarrosa and A.frigida;however,there was no significant difference in calcium oxalate content between Reaumuria songarica and Oxytropis aciphylla,S.bungeana and Cleistogenes squarrosa.The content of calcium oxalate in leaves of Caragana microphylla,Ammopiptanthus mongolicus and Amorpha fruticose with different canopy heights was significantly different,and the bottom was significantly higher than the top.There were significant differences in calcium oxalate content in leaves of A.ordosica at different growth stages.The content of calcium oxalate was the highest in young stage and the lowest in adult stage.As shown,the calcium oxalate content of the constructive species in desert were significantly higher than the constructive species in typical steppe,and there was no significant difference in the calcium oxalate content between the late successional stage and the middle-late successional stage.The calcium oxalate content was different in different canopy heights of bushes and different growth stages of plants.Thus,plant calcium oxalate content is the result of long-term adaptation to the environment,and is also related to the canopy height and growth stage of plants.In conclusion,plant calcium oxalate content is the result of long-term adaptation to the environment.When the constructing species of plant community in different ecosystems are distributed in close distance,the calcium oxalate content in their bodies still differs due to long-term adaptation to the environment.However,the calcium oxalate content in plants is variable and reversible,as well as sensitive.As a stress condition,high temperature environment induces calcium reservoir function of calcium oxalate in plants,and calcium oxalate is decomposed into Ca²⁺to meet the needs of normal physiological function of plants under high temperature.There were significant differences in calcium oxalate content between the same plants at different canopy heights and different growth stages,indicating that plants could enhance their ability to cope with stress by adjusting their calcium oxalate content.The purpose of this study is to provide a theoretical basis for improving the calcium reservoir function of calcium oxalate and further understanding the adaptation mechanism of typical steppe and desert plants.This paper contains 6 figures,2 tables and 160 references.