Response of different potato cultivar seedlings to NaHCO3 stress and the screening of indicators for anti-NaHCO3 stress
[Objectives]We studied the responses of different potato cultivars to NaHCO3 stress from the growth,photosynthetic efficiency,and physiological indices,to screen out the high NaHCO3 tolerant cultivars,and the indicators to assess cultivars alkaline tolerance.[Methods]The potato cultivars used in the hypotonic experiment included cultivars"V7","Houqihong","Kexin 1","Xingjia 2","Holland 15"and"Kangnibeike".The 7-day-old potato seedlings were grown in normal 1/2 Hoagland nutrient solution for 3 days,and then subjected to six alkali stress solutions containing NaHCO3 0,10,20,30,40 and 50 mmol/L for 7 days.The seedlings were harvested for determination of 11 physiological indexes.Principle analysis was used to screen the alkali resistant indicators.[Results]With the increase of alkali stress intensity,the growth of potato seedlings was inhibited to different degrees.Compared with NaHCO3 0 mmol/L,the root length of V7 increased by 54.37%,46.04%and 25.58%under 30,40,and 50 mmol/L stress,respectively,while the root lengths of the other five cultivars significantly decreased.Under NaHCO3 50 mmol/L stress,the plant height and stem diameter of all cultivars were significantly lower than under NaHCO30 mmol/L control.The leaf N and relatvie chlorophyll content of all cultivars varied differently with the increase of stress intensities,the leaf N contents of V7,Houqihong and Kexin 1 reached the peaks under NaHCO3 40 mmol/L treatment,and the relative chlorophyll content of Xingjia 2 reached the peak under 50 mmol/L treatment,while the N and relative chlorophyll contents of Helan 15 and Kangnibeike reached the minimum under 50 mmol/l treatment.The root activities of all cultivar seedlings increased at first and then decreased.Under NaHCO3 40 mmol/L stress,the root activities of V7 and Houqihong were significantly higher,while that of Helan 15 decreased by more than 80%under 0 mmol/L control.The content of malondialdehyde in root of all seedlings increased with the increase of stress degree,nevertheles V7 was always recorded the lowest content among the 6 cultivars.The catalase(CAT)and superoxide dismutase(SOD)activities of all seedling roots increased first and then decreased.Cultivar V7,Houqihong,Kexin 1 and Xingjia 2 had similar but higher CAT and SOD activities than Kangnibeike and Holland 15.After calculation of the principal component analysis,based on the 11 indicators,5 prinsiple components were obtained with individual eigenvalue>1,and the cumulative contribution rate to alkali stress reaching 80.07%.Thereby the 11 individual indicators were screened out as seven commom physiological indexes for all the potato cultivars,including plant height,stem diameter,leaf N content,relative chlorophyll content,proline content,peroxidase(POD)activity and CAT activity.[Conclusions]The indicators for the alkaline resistance assessment are plant height,stem diameter,leaf nitrogen content,relavent chlorophyll content,proline content,POD activity and CAT activity.Among the tested 6 cultivars,V7 shows the strongest alkali resistance,Houqihong,Kexin 1 and Xingjia 2 show second strong alkali resistance,while Kangnibeike and Helan 15 are weak in alkali resistance.
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