Effect of Exogenous SA on Photosynthesis and Al Tolerance of Trichosanthes kirilowii Maxim Under Aluminum Stress

A solution culture experiment was conducted to study the effects of different SA concentration on growth characteristics,photosynthesis,oxidation resistance,UV-B absorbing compounds and MDA content of two Trichosanthes kirilowii cultivars,Anguo(Al-tolerant genotype) and Pujiang(Al-sensitive genotype),under 800 μmol/L aluminum stress.The results showed that 800 μmol/L Al treated for 15 days,the relative root length,plant height and fresh shoot weight,chlorophyll content,the maximum energy conversion efficiency(Fv/Fm),maximum fluorescence yield(Fm) and electron transport rate(ETR) were significantly lower of the two T.kirilowii cultivars.SOD,CAT activity changed in the opposite trend,indicating the differences of the two T.kirilowii cultivars in aluminum tolerance,POD activity and UV-B absorbing compounds decreased,MDA content and initial fluorescence(F0) increased.Adding 10,30,50 μmol/L exogenous SA could reduce aluminum accumulation in the apical cell wall,MDA content and initial fluorescence(F0),also increased the relative root length,plant height,fresh shoot weight,chlorophyll content,chlorophyll fluorescence of the relevant indicators and antioxidant enzyme activity to a certain extent.By increasing antioxidant enzyme activities and photosynthesis-related indicators,SA enhanced the ability of T.kirilowii to resistance to aluminum toxicity.Comprehensive analyzing evaluation by the method of subjection function,the results showed that the external source of SA could alleviate aluminum toxicity to some extent,but it did not eliminate the inhibition of T.kirilowii growth caused by aluminum.