Effects Of Elevated Temperature And CO₂ Concentration On Sex Ratio And Reproductive Organs In Morus Alba Seedlings

Mulberry（Morus alba L.）is a dioecious species in Morus of Moraceae,but it has been observed in field that many individuals is monoecism in recent years.This sex differentiation may be related with global climate change represented by increasing temperature and CO₂.To test the hypothesis,one-year-old cuttings of mutant M.alba（monoecism）were grown in elevated temperature（+ 2℃）and CO₂（+380 ppm）in open top chamber,and the responses of flowers on sex ratio,morphology,biomass,nutrient and endogenous hormones with changes of temperature and CO₂ were investigated.The results reported here are beneficial to predict the sex-related adaptive strategy of M.alba in future.The main results as follows:1.The effects of elevated temperature and CO₂ concentration on inflorescence number,inflorescence biomass and sex ratio of male and female inflorescences in monoecious mulberryCompared with controls,elevated temperature significantly increased the number and biomass of female inflorescences and the sex ratio（female : male;thereafter）of inflorescences but decreased biomass of male inflorescences;elevated CO₂ concentration significantly increased the number and sex ratio of female inflorescences but decreased significantly male inflorescences biomasses and reproductive biomass;both of temperature and CO₂ increasing,a significant increase in female number of flower and biomass of inflorescences,sex ratio of inflorescences,reproductive biomass but decrease in number and biomass of male inflorescences found.These results demonstrated that it is more beneficial to female inflorescences than male when temperature and CO₂ concentration increase.2.The effects of elevated temperature and CO₂ concentration on florescence and floral organ morphogenesis in monoecious mulberryCompared with controls,elevated temperature significantly increased the florescence and another width of male inflorescences but decreased length and dry mass of female inflorescences and tepal size and the no.of flowers and length,dry mass and tepal length of male inflorescences;elevated CO₂ concentration significantly increased the florescence of male inflorescences but decreased length and dry mass of female inflorescences and also decreased ovarian length,femaleflower tepal size and male number of flower.Both of temperature and CO₂ increasing,a significant decrease in tepal size,ovarian size,dry mass and length of female inflorescences and length,dry mass,single flower biomass and flowers of male inflorescences.These results demonstrated that there is beneficial to increasing male florescence of inflorescences but is negative on female flower and inflorescence development when temperature and CO₂ concentration increase.3.The effects of elevated temperature and CO₂ concentration on element and endogenous hormones of florescence in monoecious mulberryCompared with controls,elevated temperature significantly decreased the contents of C,N,P,and K of male inflorescence and ABA concentrations of both sex inflorescence but increased significantly N,P and ZR of female inflorescence and IAA,GA3,BR and ABA concentrations of both sex inflorescences;elevated CO₂ concentration significantly decreased the contents of C,N,P、K,ABA and BR of male inflorescence and IAA,ABA,GA3,BR and ZR concentrations of female inflorescence but increased GA3 concentrations of male inflorescences and N concentrations of female inflorescences;both of temperature and CO₂ increasing,significantly decreased the contents of C,N,P,ABA and BR of male inflorescence and ABA,GA3 and ZR concentrations of female inflorescence but increased N,P concentrations of female inflorescences.These results demonstrated that there are different responses between female and male inflorescences under temperature and CO₂ concentration increase.4.Relationships of number or morphological traits and element concentrations in inflorescencesThe content of C was significantly positively related to length,numbers,and flowers of male inflorescences,while was negatively related to male inflorescence number.In addition,no relationships were observed between C concentration and anther size and tepal size.The content of N was significantly positively related to length,numbers,tepal length,flowers of male inflorescences,while was negatively related to female tepal length.In addition,no relationships were observed between N concentration and anther size and male tepal width.The contents of P and K was significantly positively related to anther size and,female inflorescence number,but no relationships were observed between P or K concentration and length,numbers,tepal size,flowers of male inflorescences.The C/N was significantly negatively related tolength,numbers,and flowers of male inflorescences,while was negatively related to female tepal length.In addition,no relationships were observed between C/N and anther size and male tepal size.These results demonstrated that inflorescence nutrients are related with their number and morphological traits and the relationships are sex-related.