| Zanthoxylum armatum is of ecological,social and economic importance,especially Zanthoxylum armatum(Zanthoxylum,Rutaceae),which is a variety of Chinese traditional trees for providing spice,oil and medicinal resources,and also for returning farmland to forests.In recent years,with people’s preference,the area of application and promotion of Zanthoxylum armatum has been expanding,Zanthoxylum armatum was introduced blindly in a lot of areas,and the cultivation region has been gradually expanded to high altitude and high latitude areas where have potential low-temperature disasters,which may lead to poor growth or freezing injury and affect the yield of Zanthoxylum armatum.Besides,the yield and quality may also be affected by the low photosynthetic efficiency resulting from insufficient light or strong light.Previous studies have been made on cold resistance and photosynthetic characteristics of some species of Zanthoxylum,but these studies are not systematic enough,besides,the specie which mainly studied was Zanthoxylum bungeanum,and there was no report about Zanthoxylum armatum.The cold-resistance and Photosynthetic characteristic of Zanthoxylum armatum was studied to provide references for its cultivation management and application promotion.A new cultivar of Zanthoxylum armatum ’hanyuan putao qingjiao’(HPQ)and its few thorn variation species(SHPQ)were studied,we investigated the diurnal variations and light response of photosynthesis of HPQ and SHPQ;we investigated the changes of cold resistance physiological indexes(relative conductivity,MDA content,SOD activity,POD activity,soluble sugar content,soluble protein content,proline content)of HPQ and SHPQ during overwintering period,and a pot experiment with the soil moisture(including 20%,40%,60%and 80%field water capacity(FWC)),nitrogen(including 0,75,150 and 300 kg N/hm2),phosphorous(including 0,30,60 and 120 kg P2O5/hm2)and potassium(including 0,75,150 and 300 kg K2O/hm2)fertilizer four factors and four levels orthogonal design was conducted to study the cold resistance physiological indexes of HPQ at different low temperature(25℃,10℃,5℃,0℃,-3℃,-6℃ and-9℃)for 5 h,meanwhile,the subordinate function was applied to evaluate the cold resistance of the plants under different water and fertilizer treatments comprehensively.The results are as follows:(1)The diurnal variations of net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance(Gs)and vapor pressure deficit on leaf surface(VpdL)presented a single-peak curve.with the peak appeared at 12:00 and 14:00 for Pn and other parameters,respectively;while intercellular CO2 concentration(Ci)presented a single-valley curve,with the valley at 12:00.Mean value of diurnal water use efficiency(WUE)of SHPQ was significantly higher than that of HPQ,but there was no significant difference for mean value of diurnal Pn,Gs,Tr,Ci and VpdL between them.The Pn of HPQ was higher than that of SHPQ from 12:00 to 14:00 under high temperature and strong illumination condition,while the Pn of HPQ was lower than that of SHPQ at the other time.The Pn,Tr and Gs were significantly and positively correlated with photosynthetic active radiation(PAR)(P<0.01),and the correlation coefficients were higher than those of three with other environmental factors;Pn was significantly and positively correlated with total chlorophyll content and yield(P<0.01).The light compensation point(LCP),maximum net photosynthetic rate(Amax),dark respiration rate(Rd)and apparent quantum efficiency(AQY)of HPQ were higher than that of SHPQ,while the light saturation point(LSP)of HPQ was lower than that of SHPQ,and there is no significant difference for those parameters except for LCP between HPQ and SHPQ.(2)The relative conductivity,SOD activity,soluble sugar and proline content of HPQ and SHPQ presented a single-peak curve during natural overwintering period,with the peak appeared when air temperature reached the lowest,which has a significant negative correlation with temperature;the MDA content presented a double-peak curve and the POD activity presented a "inverted N" curve during natural overwintering period;the comprehensive value of cold-resistance of HPQ and SHPQ decreased first,then increased,and finally decreased during natural overwintering period.The mean comprehensive value of cold-resistance of HPQ was lower than SHPQ,suggested that the cold-resistance of SHPQ was stronger than that of HPQ.(3)The SOD,POD and CAT activities,soluble sugar and soluble protein contents in leaves of Zanthoxylum armatum increased at first and then decreased with the decrease of temperature,all of them reached the peak at 0℃.The mean value of SOD,POD and CAT activities,soluble sugar and soluble protein contents and the comprehensive value of cold resistance were all highest in 60%WFC treatment,while the lowest in 20%WFC treatment.All those indexes were significantly correlated with comprehensive value of cold resistance.The comprehensive value of cold resistance increased first and then decreased with the increase of field water capacity(FWC)and the amount of nitrogen,phosphorus and potassium application,estimated that the plant could get higher comprehensive cold resistance under the optimal combination of water and fertilizer with 62%WFC,252 kg N/hm2,87 kg P2O5/hm2 and 237kg K2O/hm2.The SHPQ has a potential strong adaptability to low light environment and high water use efficiency,and it more adaptable to grow under less sunshine hours and drought conditions.SHPQ is more adaptable to plant in the low temperature condition and cold injury areas.Suitable soil water and nitrogen,phosphorus and potash fertilizer can significantly improve the protective enzyme activity,osmotic adjustment substance content and low temperature tolerance of Zanthoxylum armatum leaves,which is important for improving cold resistance of Zanthoxylum armatum;... |
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