Response Of Anatomical Structure Of Cinnamomum Camphora To Na₂SO₄ Stress And Natural Cooling

The introduction of Cinnamomum camphora（Linn.）Presl.is difficult to carry out smoothly in Xinxiang area.The root cause is soil salinization and low temperature in autumn and winter.The response of its anatomical structure to salt and low temperature is explored to provide cytological basis for the introduction of C.camphora.This experiment was divided into two parts.One part was salt stress.The seedlings of potted C.camphora seedlings in five introduction areas were treated with clear water control（CK）and different Na₂SO₄concentrations(25 mmol·L^-1、50 mmol·L^-1、100 mmol·L^-1、200 mmol·L^-1).The SPAD,chlorophyll fluorescence parameters and microscopic changes of seedlings after Na₂SO₄treatment were studied to evaluate salt tolerance.The leaves of seedlings in three places with strong salt tolerance were made into ultrathin sections and analyzed.The other part is to investigate the freezing damage of C.camphora under natural cooling,and the changes of microstructure and submicrostructure of branches and leaves.The following results are obtained through research:1.The site conditions of C.camphora are different,and the degree of freezing injury is also different.Most of the C.camphora in the three places surveyed are subject to different degrees of freezing injury,and 60%of the C.camphora leaves are almost all withered.The leaf freezing injury index from large to small is:Henan Institute of Science and Technology>Xinxiang Pipeline Bureau>Xindong Farm;the freezing injury index of branches from large to small is:Xindong Farm>Henan Institute of Science and Technology>Xinxiang Pipeline Bureau.2.From the SPAD and chlorophyll fluorescence parameters of C.camphora seedlings,it can be seen that with the increase of Na₂SO₄concentration,the SPAD,Fv/Fm andΦPSII of seedlings in various regions showed a downward trend.The q P of seedlings in Shanghai showed a trend of increasing first and then decreasing,and the other four places showed a downward trend.The non-photochemical quenching NPQ value gradually increased with the increase of concentration.3.It can be seen from the anatomical structure of C.camphora seedlings that with the increase of Na₂SO₄concentration and the extension of time.Except Nanjing,the thickness of root cortical cells in the other four places showed an upward trend.The thickness of root xylem in each place showed an overall upward trend.When the concentration was 200 mmol·L^-1,the phloem thickness of Nanjing,Shanghai and Wuhan seedlings reached the minimum.Except Fuzhou,the medullary diameter of the other four places showed a downward trend.The thickness of epidermal cells and xylem of stem segments in different places showed a downward trend as a whole.The cortical cell thickness and pith diameter of Fuzhou and Wuhan seedlings showed an upward trend.Except Shenzhen,the thickness of phloem cells in other places showed a downward trend.Only the leaf thickness of Shanghai seedlings showed an upward trend.The thickness of upper epidermal cells did not change much.The thickness of lower epidermal cells and palisade tissue decreased as a whole.The thickness of sponge tissue in Shenzhen and Wuhan showed a downward trend.The main vein thickness of Fuzhou and Nanjing increased first and then decreased,while the other three places showed a downward trend.4.From the ultrastructure of leaves,it can be seen that with the increase of Na₂SO₄concentration and the prolongation of stress time,the cell wall will be separated and the cell wall will be wrinkled.Chloroplasts swelled,thylakoids were disordered,cavities appeared,the volume of internal starch granules decreased,and the number of oil droplets increased.Mitochondria continued to swell to a spherical shape,tubular cristae arranged in disorder,gradually close to the chloroplast.The vacuole volume decreased or was separated into several small vacuoles,the number of internal proteins gradually decreased,occasional crystals appeared,the lysosomal structure became complex,and more organelles were accumulated.The ultrastructural changes at low temperature were basically consistent with salt stress,but osmiophilic bodies appeared in chloroplasts when the temperature decreased.5.According to the principal component analysis method,the salt tolerance of seedlings in different introduction areas was evaluated.The 24 indexes measured could be divided into three principal components to evaluate the salt tolerance of C.camphora seedlings.The salt tolerance of five introduction areas was as follows:Fuzhou provenance>Shanghai provenance>Nanjing provenance>Wuhan provenance>Shenzhen provenance.6.With the decrease of temperature,the thickness of epidermal cells,cortical cells,xylem and phloem of 1-year-old branches of C.camphora increased first and then decreased,and the diameter of pith reached the minimum at-5℃.The leaf thickness,palisade tissue thickness,sponge tissue thickness and main vein thickness gradually increased with the decrease of temperature.Low temperature increased the thickness of upper and lower epidermal cells and the ratio of palisade to sea.