| Tomato cultivation in facilities often be suffered by sub-optimal temperature,which cause retarded growth and the decline of yield and quality.The sub-high temperature(35℃) is very frequently occurs in the end of spring and the initial of summer in midday period,which brings troubles of tomato cultivation. Fo rmerly some researches already confirmed:The sub-high temperature(35℃) cause the decline of yield and quality of tomato is related to the changes of photosynthesis,but the reason that made the diverse effect of photosynthesis is not clear.This research is undertaken with "Lycopersicon esculentum Mill.",the change of photosynthesis and photosynthetic apparatus under sub-high temperature(35℃) are studied, definite the main reason that caused the decline of photosynthesis under sub-high temperature(35℃) and preliminary clear the longest standing duration of tomato under short-term sub-high temperature in order to provide theoretical basis of the mechanism that sub-high temperature effect photosynthetic production.On this basis,the whole plant under sub-high temperature stress(day time 35℃) are sprayed CaCl2(10 mmol'L-1) and salicylic(0.2 mmol.L-1) in order to seek the regulative function of CaCl2 and salicylic on photosynthetic production of tomato leaves under sub-high temperature,provide theoretical basis of chemical regulation the metabolize of plant to alleviate sub-high temperature obstacle.The main results are as follows:1.It is clear that tomato leaves treated with sub-high daytime temperature(35℃) for 3 days can improve net photosynthetic rate.When treated with sub-high temperature for 6 days,the net photosynthetic rate is decreased significantly,at the same time,the stomatal conductance(Gs)and intercellular CO2 concentration is higher than control,the stomatal limitation value(Ls) is lower than control,this shows that the decline of net photosynthetic rate is not caused by stomatal factors.After sub-high temperature treatment and recovery in optical temperature for some days,net photosynthetic rate is increased.When tomato leaves are treated with sub-high temperature for less than 12 days and then recover for some days, the net photosynthetic rate could come back to control,but when tomato leaves are treated with sub-high temperature for more than 15 days,the net photosynthetic rate could not come back to control.2.It is clear that short-term sub-high temperature(35℃) can make PSⅡinactivation.Treated with sub-high temperature(35℃) for more than 6 days,it is shown that the maximum photochemical efficiency(Fv/Fm),the actual photochemical efficiency of PSⅡreaction center(ΦPSⅡ),rate of electronic transmission of photosynthesis(ETR) of tomato leaves are decreased.Treated for more than 9 days,it is shown that intrisic fluorescenc(Fo) of tomato leaves is increased.This indicate that treated with sub-high temperature(35℃) for 6 days can cause the damage of PSⅡ,lead to reversible or irreversible inactivation of PSⅡreaction center and decrease rate of electronic transmission of photosynthesis.When tomato leaves are treated with sub-high temperature then recover for some days,chlorophyll fluorescence parameters Fv/Fm,ΦPSⅡand ETR are premoted and Fo is demoted,but when treated for more than 15 days these chlorophyll fluorescence parameters could not come back to CK.These results show that treated with sub-high temperature for more than 15 days can make irreversible inactivation of PSⅡ.3.It is clear that tomato leaves treated with sub-high temperature(35℃) for 6 days make photochemical quenching coefficient(qP) decreased.Non-photochemical quenching coefficient(qN) increase at first and then decrease in the treatment,when treated for less than 6 days,qN is higher than control,but when treated for more than 9 days,qN is significantly lower than control.The decline of qN can indicate that surplus light energy injury photosynthetic mechanism,this may be the reason that inactivation of PSⅡ.When treated with sub-high temperature then recovery in optical temperature for some days,qN can come back to control.4.When tomato treated with sub-high temperature(35℃) for 3 days,it shows that carboxylation efficiency(CE) is lower than control,when treated for 9 days,RuBP regeneration rate is decreased,with the treatment is processed,CE and RuBP regeneration rate are lower than control significantly.When treated with sub-high temperature then recovery in optical temperature for some days,CE and RuBP regeneration rate improve.When treated for less than 9 days,the effect of sub-high temperature on RuBPase activity is recovery,but treated for 15 days,the effect is not recovery.This indicate that photosynthetic enzyme RuBPase activity is influenced by sub-high temperature,and the effect is not recovery earily.5.It is clear that sub-high temperature(35℃) treatment for more than 9 days,the content of MDA in tomato leaves is increased.This indicate that sub-high temperature treatment could make the balance of reactive oxygen speices production and clearance breaking,induce membrance transfer peroxidation of tomato leaves,which make the cell physiological function decreaed.After the sub-high temperature treatment then recovered in optical temperature for some days,the content of MDA is reduced,but when treated for more than 15 days,it could not come to control.6.Short-term sub-high temperature treatment could effect the activities of antioxidant enzymes.At initial time,the activities of SOD and POD are higher than control,but when the treatment lasted for more than 6 days,the activities of SOD,POD and CAT are lower than control significantly.After the sub-high temperature treatment then recovered in optical temperature for some days,the activities of antioxidant enzymes are increased,when treated with sub-high temperature for less than 12 days,the activities of antioxidant enzymes could come back to control,When treated for more than 15 days,these could not come to control.7.It is clear that sub-high temperature(35℃) treatment could increase the amount of unit area stomata significantly.When tomato leaves treated with sub-high temperature(35℃) for less than 9 days,it is shown that stomatal open ratio is similar to control,but when treated for more than 9 days,stomatal open ratio increase significantly.8.It is clear that sub-high temperature(35℃) treatment could change the chloroplast ultrastructure of tomato leave.The amount of grana and osmiophilic globule are reduced,the amount of starch grain is reduced,but the length and width of starch grain are increased.Sub-high temperature(35℃) treatment make the length of chloroplast reduced,but width increased.At the same time due to the increasing of starch grain,the thickness of grana is reduced.These results show that sub-high temperature(35℃) treatment can change the chloroplast ultrastructure of tomato leaves,which lead to the damage of photosynthetic mechanism,then effect the photosynthesis of tomato leaves.9.When tomato treated with sub-high temperature(35℃),it is shown that amount of fructose,glucose and sucrose are reduced,amount of starch is increased of tomato leaves.At the same time,the activities of sucrose-metabolizing enzymes also changed:the activities of acid invertase and neutral invertase are reduced,the activities of sucrose synthase and sucrose phosphate are increased.When tomato leaves treated with sub-high temperature(35℃) then recovered in optical temperature,the conent of sugar is irreversible.when treated for more than 6 days,the content of sugar could not come back to control.When treated for less than 15 days,the activities of acid invertase and neutral invertase could come back to control,but the activities of sucrose synthase and sucrose phosphate could not come back to control.10.Under the sub-high temperature condition(35℃),spraying CaCl2(10mmol/l) treatment make the net photosynthetic rate is similar to control(spraying water) and sub-high temperature treatment(spraying water) at first of the treatment,when treated for more than 6 days,the net photosynthetic rate is higher than sub-high temperature treatment(spraying water),at the end of the treatment,the net photosynthetic rate meet the level of control.At the same time,the stomatal conductance(Gs) and intercellular CO2 concentration(Ci) are higher than control and sub-high temperature treatment,the stomatal limitation value (Ls) is decreased.These indicated that under the sub-high temperature condition(daytime 35℃),spraying CaCl2 can regulate open and close of stomata.11.Under the sub-high temperature condition(daytime 35℃),spraying SA(0.2mmol/l) treatment enhance net photosynthetic rate,at the end of the treatment,net photosynthetic rate could come to control level.At the same time,the stomatal conductance(Gs) and intercellular CO2 concentration(Ci) are similar to control(spraying water) and sub-high temperature treatment(spraying water),the stomatal limitation value(Ls) is changed acute and unregularly.These indicated that under the sub-high temperature condition (daytime 35℃),spraying SA can not regulate open and close of stomata.12.Under the sub-high temperature condition,spraying CaCl2 treatment could decrease the improvement of intrisic fluorescenc of(Fo),enhance maximum photochemical efficiency(Fv/Fm),the actual photochemical efficiency of PSⅡreaction center(ΦPSⅡ) and rate of electronic transmission of photosynthesis(ETR) under sub-high temperature condition,at the end of the treatment,these indicators meet the control level.These indicate that under the sub-high temperature condition(daytime 35℃), spraying CaCl2 can improve the activity of PSⅡ,improve the ability of the photosynthetic apparatus,so that avoid the decline of photosynthetic under sub-high temperature condition.13.Under the sub-high temperature condition(daytime 35℃),spraying SA treatment could increase maximum photochemical efficiency(Fv/Fm),the actual photochemical efficiency of PSⅡreaction center (ΦPSⅡ),rate of electronic transmission of photosynthesis(ETR),decrease intrisic fluorescenc of(Fo).At the same time,photochemical quenching coefficient(qP) and non-photochemical quenching coefficient (qN) are higher than sub-high temperature treatment.These indicate that under the sub-high temperature condition(daytime 35℃),spraying SA can alleviate the decline of PSⅡwhich due to the sub-high temperature treatment,prevent the inactive of PSⅡreaction center to make sure photosynthesis is in progress under sub-high temperature condition.14.Under the sub-high temperature condition(daytime 35℃),spraying CaCl2 and SA treatment decrease the content of MDA in tomato leaves,increase the activities of SOD,POD and CAT,at the end of the treatment,these indicators meet or exceed the control level.The premoted of activity of SOD by CaCl2 is larger than SA,but the premoted of activities of POD and CAT by SA are larger than CaCl2 These indicate that under the sub-high temperature condition(daytime 35℃),spraying CaCl2 and SA can enhance the activities of antioxidant enzymes,restrain membrance transfer peroxidation,maintain the nomal physiological structure of cell membrane,maintain the nomal function of photosynthetic system to alleviate the damage of sub-high temperature treatment. |
