Studies On Mechanism Of SO₂ Tolerance Of Colored-leaf Tree Species In Prunus

Using two-year-old ported seedlings of Prunus cerasifera Var atropurpurea, Prunus×cistenena 'pissardii',Prunus wrasifers 'nigra' and Prunus×bliriana 'Meirenmei' as materials which cultivated in closed chamber after treated with sulfur dioxide stress,the effects of different conditions on the morphological and Physiological features of seedings were analyzed,which include the sulfur dioxide stress of different concentration,17.1 mg.m^-3sulfur dioxide stress of different time and the sulfur dioxide stress of exogenous NO conditions.The mechanism of colored-leaf species in Prunus adapting to sulfur dioxide stress was clarified preliminarily to provide scientific evaluation of SO₂ resistance and scientific references for selecting proper species as ornamental trees in landscape.The results were as follows.1.The indices including membrane permeability,MDA,proline,soluble proteins,POD, SOD,CAT,pH value and sulfur absorbed content were analyzed with formula of fuzzy mathematics.Synthetical evaluation result of subordinate function analysis suggested that the resistance of four colored-leaf species to sulfur dioxide stress ranked from P.cerasifera var atropupurea,P.wrasifers 'nigra',P.×bliriana 'Meirenmei,P.×cistenena 'pissardii'.2.The visible injury of P.cerasifera var atropupurea and P.×cistenena 'pissardii' varied with different SO₂ concentrations.For an instance,under 17.1 mg.m^-3SO₂ treatment, lightly faded spots appeared on abaxial leaf surface edges of P.cerasifera var atropupurea. while obvious faded spots appeared on adaxial and abaxial leaf surface edges of P.×cistenena 'pissardii',and the abaxial leaf surface were damaged severely.3.The thickness of leaves,palisade tissue and spongy tissue was affected with different concentration of SO₂ treatment,CTR of P.cerasifera var atropupurea and P.×cistenena 'pissardii' increased first and then dropped with the increment of SO₂ concentration,SR was in an inverse trend,but the changes degree between two species were different.Under SO₂ treatment of 11.4mg.m^-3,CTR of P.cerasifera var atropupurea were increased by 4.9%,and its SR were decreased by 6.5%,while CTR of P.×cistenena 'pissardii'were decreased by 0.9%,and SR were increased by 7.6%compared with the control.SO₂ treatment of 22.8mg.m^-3decreased the CTR of P.cerasifera var atropupurea and P.×cistenena 'pissardii'by 1.3%and 7.4%respectively,and increased the SR of P. cerasifera var atropupurea and P.×cistenena 'pissardii'by 2.5%and 11.0%respectively compared to their controls.Under the SO₂ treatment of 22.8mg.m^-3,the abaxial foliar epidermis in leaves of P.×cistenena 'pissardii' were almost disintegrated,the outline of spongy cells were not distinct,while the abaxial foliar epidermis in leaves of P.cerasifera vat atropupurea were disintegrated a little.4.Active oxygen scavenging system and organic osmolytes contents were affected under the sulfur dioxide stress of different concentrations and different times:According to correlation analysis,the production rate of superoxide anion radical,MDA and H₂O₂ contents had significant or most significant positive correlation with the relative conductivity,Correlation analysis of P.cerasifera var atropupurea.was 0.531^*,0.784^**,0.572^* and Correlation analysis of P.×cistenena 'pissardii' was 0.663^**,0.912^**,0.600^*respectively. With the increment of concentration and duration of SO₂ treatment,the membrane permeability and MDA contents of two species increased steadily,while the rising extents in P.×cistenena 'pissardii' was larger than that in P.cerasifera var atropupurea. O₂^- production rate and H₂O₂ contents in leaves of P.cerasifera var atropupurea increased, and then decreased,while in P.×cistenena 'pissardii',they all increased with SO₂ treatment concentration and time enhancing.As SO₂ concentration and duration increased,activities of protective enzyme, including SOD,CAT,APX,DHAR,GR,GST,GPX,antioxidant such as GSH,DHASA, Car,and Pro contents of P.cerasifera var atropupurea and P.×cistenena 'pissardii' increased,and then decreased,while activities of POD,contents of soluble protein and soluble sugar were in an steadily increasing trend.GSSG contents of two species were reduced first and then increased.The deoxidize AsA contents of P.cerasifera var atropupurea increased at first then decreased,while those of P.×cistenena 'pissardii' decreased gradually.The relative conductivity of P.cerasifera var atropupurea had significant or most significant correlation with the indexes POD,APX,GST and had most significant positive correlation with GSSG,Pro,soluble protein,while the relative conductivity of P.×cistenena 'pissardii' had significant or most significant correlation with the indexes including protective enzymes POD,APX,DHAR,GPX,GST and antioxidants ASA,DHASA,GSH,GSSG,Car and Pro contents,correlation analysis showed that the damage of cellmebrance of P.×cistenena 'pissardii'was still serious through together function of protective enzymes,antioxidants and organic osmolytes.5.SO₂ treatment affected the contents and kinds of endogenesis hormone.With the increasing of concentration and prolonging of SO₂ treatment,contents of the endogenesis ABA,IAA,GA,ZT and DHZR increased,and then decreased.At the concentration of 17.1 mg.m^-3or higher than that,and the duration longer than 8 d,ZR was induced in P. cerasifera var atropupurea,but no ZR was examined in P.×cistenena 'pissardii'6.The contents of total chlorophyll,carotenoid,flavonoid,anthocyanin and total phenolic were affected in different degree,chroma values of leaf of two species were changed.With the increasing of SO₂ concentration,L^*,b^*,C of leaf of two species increased,and then decreased,a^* of P.cerasifera vat atropupurea Prunus×cistenena 'pissardii' increased first and decreased later,but a^* of P.×cistenena 'pissardii'decreased gradually.According to the correlation analysis of pigments contents and chroma value,the leaf color of P.cerasifera var atropupurea lied on anthocyanin,while for P.×cistenena 'pissardii',the leaf color was determined by anthocyanin and carotenoid.UFGT activity in leaves of P.cerasifera var atropupurea and P.×cistenena 'pissardii'increased and then decreased as SO₂ concentration increased and duration prolonged.PAL,CHI,PPO enzyme activities of Prunus cerasifera var atropupurea showed a trend of increasing first and then decreasing,differently,their activities of P.×cistenena 'pissardii' decreased gradually.According to correlation analysis,activities of PAL,UFGT, the contents of endogenesis and soluble sugar influenced leaf color directly or indirectly.7.With the increasing of concentration and prolonging of SO₂ treatment,the photosynthetic parameters Pn,Tr,Gs,WUE increased first and then decreased,but Ls were in opposition to them.Pn and Ci showed inverse variation trends compared with Ls,SO₂ treatment reduced photosynthetic rates were mainly caused by the decreasing of stomatal conductance(Gs).Under low concentration and short duration of SO₂ treatment,the values of Fv/Fm and F_v/F_o increased,while their values significantly decreased at thick concentration of SO₂.With the increasing of concentration and duration,for P.cerasifera var atropupurea,q_p decreased and q_N increased,but q_p and q_N of P.×cistenena 'pissardii'decreased.P.cerasifera var atropupurea maintained the definite ability of photorespiration and heat dissipation at the same time holding higher net photosynthetic and PSâ…¡electron transport rate,so P.eerasifera var atropupurea had the initiative adaptive mode which resisted damage of stress factors effectively and had self growth simultaneity.8.Exogenous NO could improve the ability of resistance of two species to SO₂ treatment.Exogenous NO could eliminate superoxide anion radical and abirritate of SO₂ damage through improving the activities of protective enzyme,contents of antioxidant, organic osmolytes and endogenesis hormone at different degree,the color and structure of leaf was maintain completely,the systems of photosynthesis and fluorescence was protected,the growth of twigs and leaves of two species was accelerated,the ability of SO₂ tolerance of species was improved.Compared with two species,exogenous NO had more effective resistance of SO₂ damage to P.×cistenena 'pissardii' because the injury of SO₂ was serious.