Effect Of Simulated N Deposition On Physiological And Biochemical Characteristics Of Different Gender Morus Alba L.Seedlings Exposed To Cadmium Pollution

Nowadays,soil cadmium pollution and nitrogen deposition are global environmental problems.Dioecious plants show sexually different responses to environmental stresses.However,little is known about the dimorphic morphological and physiological responses to soil pollution To investigate sex related adaptive responses of Morus alba L.seedlings when exposed to cadmium(Cd),nitrogen deposition(N)and their combination(N+Cd),we analyzed growth parameters,Cd accumulation and allocation,photosynthetic capacity,relative chlorophyll content,chlorophyll fluorescence and biochemical responses under different treatments,the results are as follows:(1).Both excess Cd and N+Cd have a negative effect on plant growth.Cadmium treatment significantly reduced the biomass accumulation of the organs of different genders mulberry seedlings,and monoecism decreased more.The nitrogen deposition treatment had little effect on the total biomass accumulation of mulberry seedlings,but significantly changed the biomass allocation.Compared with cadmium treatment,the addition of N increased the biomass of males,but decreased the biomass of monoecism,thus,the combined treatment increased the biomass accumulation difference between different genders mulberry seedlings.Besides,cadmium treatment significantly inhibited the elongation of roots of mulberry seedlings,and the root tips of monoecism decreased more than males.The combined treatment also significantly inhibited the growth of mulberry roots,the inhibitory effect on the males was less than that of cadmium treatment,but the inhibitory effect on the monoecism was greater than that of cadmium treatment.(2).The photosynthesis limitation could be attributable to a lower stomatal conductance,SPAD?Fv/Fm?Fv/F0 and Yield induced by Cd accumulation.Compared with cadmium treatment,the addition of nitrogen deposition promoted the recovery of Gs?Yield?ETR and qP of males,but had no obvious alleviation effect on monoecism(3).The degree of membrane lipid peroxidation was detected,and monoecism showed higher levels of MDA than males under excess Cd and N+Cd.Accumulation of free proline in vivo is another adaptive mechanism of mulberry seedlings of two genders to cope with cadmium stress,N deposition causes the male to produce a large amount of soluble protein to reduce the toxic effect of cadmium,however,monoecism accumulated a large amount of free proline to adapt to cadmium stress,this may be the reason for the widening of cadmium tolerance differences between the two genders.Meanwhile,males have a greater potential than monoecism to Cd,the cadmium content in leaves of male was lower than that of monoecism because the cadmium retention effect of root system of male was greater than that of monoecism,thus,the decrease in total root length may be due to the accumulation of large amounts of cadmium in the root system.Taking into account the Cd accumulation and the resulting injuries in plants,we suggest that Cd causes sex-related adaptive responses,and males possess a more effective self-protection mechanism,N deposition increased the gender differences in cadmium adaptation strategies of mulberry seedlings.