Rapid Evaluation Of Salt Tolerance Of A.Donax.L Using Chlorophyll A Fluorescence Combined With Reflection Spectrum

Currently,saline-alkali soil covers 10%of our country,occupying an area of 9913×104 hm²,and poses a significant threat to our ecological and food safety.Compared to chemical or engineering solutions,vegetation presents clear cost advantages and is easier to implement.With their ability for rapid reproduction,large biomass,and developed roots,JUNCAO species have potential in the ecological improvement of saline-alkali land and can be applied in the ecological management of arsenic sand,slope collapse,sandy,and saline-alkali land.Breeding JUNCAO that can grow in saline-alkali land is an urgent task.The physiological and biochemical components of plants during the breeding process of dominant varieties are mainly measured through destructive sampling,which is laborious and time-consuming and can’t evaluate the resistance during the entire growth period.In this study,three typical JUNCAOs（A.donax.L No.1,A.donax.L No.5 and A.donax.L No.10）were used as the research object,and a fusion of rapid Chlorophyll a fluorescence（Chl F）and Visible-near infrared spectroscopy（Vis-NIR）was used to achieve non-destructive perception of internal biochemical components,physiological metabolism,and other plant growth characteristics related to internal and external phenotypic information.The method of salt tolerance evaluation based on optical technology was explored.The study’s main research contents and conclusions are as follows:（1）The optimal leaf position for salt tolerance evaluation was identified.The effects of salt stress on rapid chlorophyll a fluorescence induction transient（OJIP）and morphological physiology characteristics of A.donax.L.were investigated.Compared with the control group,leaf pigment decreased by 3.8%to 65.1%,malondialdehyde increased by 1.172to 2.101 times,stem relative growth decreased by 27.9%to 78.5%,water content decreased by 7.7%to 26.7%,and Fv/Fm decreased by 2.7%to 9.5%under 100 m M and 200 m M Na Cl.The Euclidean distance of the mean OJIP curve before and after salt stress was quantitatively analyzed to judge the similarity of the curve.Finally,it was determined the third leaf is fully unfolded（position 3）was the most suitable leaf position for salt tolerance evaluation when the salt stress duration reached 15 days.（2）The effects of salt stress on fast chlorophyll fluorescence and near-infrared reflectance spectra of A.donax.L.were analyzed.The salinity caused significant changes in chlorophyll a fluorescence kinetics,with L-,K-,and J-bands,indicating disruption of energy connectivity between photosystemⅡ（PSII）units,impaired oxygen evolutionary complex（OEC）,and inhibited primary plastoquinone electron acceptor（Q_A^-）reoxidation.Salt stress caused an increase in spectral reflectance in the visible region,the red edge position（REP）,and the blue edge position（BEP）towards the shortwave direction.Compared with near-infrared spectral reflectance,the reflectance in the visible range（400-700 nm）was more suitable to reflect the effect of salt stress on A.donax.L.（3）The study established a method for the rapid evaluation of salt tolerance in A.donax.L using chlorophyll a fluorescence and reflectance spectroscopy.The fusion of JIP-test parameters,including Fo,Fm,Fv/Fo,ABS/RC,TRo/RC,ETo/RC,DIo/RC,REo/RC,φPo,ΨEo,φEo,δRo,φRo,PIabs,and PItotal,with visible to near-infrared（Vis-NIR）reflectance spectral indices,namely TCI,TCARI,MCARI,CRI₅₅₀,CRI₇₀₀,R_BEP and R_REP were determined as the evaluation parameters for assessing the salt tolerance of A.donax.L.The study compared and analyzed the applicability of weighted principal component analysis and principal component analysis combined with membership function method to quantify salt tolerance in A.donax.L.The results showed that the principal component analysis combined with membership function method was the most suitable method for salt tolerance evaluation of A.donax.L.The evaluation results showed that A.donax.L No.10 had the highest salt tolerance followed by A.donax.L No.5 and A.donax.L No.1.The results were consistent with traditional physicochemical indexes such as pigment content,MDA content,stem relative growth,and water content.The study concludes that the rapid chlorophyll a fluorescence fusion reflectance spectroscopy technique could realize the rapid evaluation of salt tolerance in A.donax.L.