UV-B辐射和干旱对丹参生长和叶片中酚酸类成分的影响

Abstract

Ultraviolet B and drought stress are common environmental stresses in arid and semi-arid regions of northwestern China. A pot experiment was conducted to investigate the separate and combined effects of UV-B radiation and drought stress on physiological characteristics of Salvia miltiorrhiza Bunge in this region,and on the accumulation of phenolic compounds in its leaves. In this experiment,the UV-B radiation was performed with two intensities,2.60 k J / m2( T1) and4.10 k J / m2( T2),meanwhile,three gradual drought stress treatments were carried out with field water capacity ranging from40% to 75%. The involved physiological characteristics included plant height,leaf area index,shoot biomass,root biomass,total biomass,root: shoot ratio,and those photosynthetic indices,such as net photosynthetic rate( Pn),transpiration rate( Tr),stomatal conductance( Gs) and intercellular CO2concentration( Ci). The phenolic compounds detected in leaves contained salvianolic acid B( SAB), rosmarinic acid( RA), caffeic acid( CA) and 3,4-trihydroxybenzenepropanoic acid( DSS). The results showed that both UV-B radiation and drought stress had cross-talk on the growth of S. miltiorrhiza,and the least plant height was found in the combined treatment( 40% T2),which significantly decreased 47.82%. Drought stress and UV-B radiation reduced leaf area 40.22% and 71.51%,respectively,and the leastvalue occurred in the combined treatment 75% T2. Similarly,the least root: shoot ratio also happened in combined treatment75% T1 and the least total plant biomass did in 40% T2. In terms of the effects of UV-B and drought stress on photosynthetic indices,similar tendency was observed among Pn,Tr and Gs,but Ci had reverse trend with these three indices. The three indices were found reaching the largest at growth season,but decreased to the lowest at harvest period in the combined 40%T2 treatment. Both UV-B and drought stress could promote the accumulation of four phenolic compounds,in which the former had more prominent influence. Both contents of SAB and RA increased 4.28 and 8 folds,respectively,under UV-B radiation,which were significantly higher than 1. 12 and 1. 51 folds in drought stress treatment. The SAB and RA accumulation reached the highest level( 4.75 and 3.15 μg / g,respectively) in the combined treatment 75% T2. Statistical data also exhibited that there was a cross-talk in accumulation of phenolic compounds between UV-B and drought stress. The SAB content increased 4.28 folds in T2 radiation intensity,while only 2.18 folds were observed in T1. The content increased1.12 and 0.52 folds in drought stress treatment with 40% and 55% field water capacity,respectively. If combined UV-B radiation and drought stress,the SAB content would increased 2. 69 and 1. 67 folds in 40% T2 and 55% T2 treatments,respectively. In conclusion,there was a cross-talk between UV-B radiation and drought stress,which had combined effects on the growth of S. miltiorrhiza and accumulation of phenolic compounds in leaves. Relatively,UV-B radiation had stronger influence than drought stress. Either UV-B radiation or drought stress had negative effect on plant growth. The higher UV-B radiation intensity( T2,4. 10 k J / m2) was helpful to accumulation of SAB,but the amount of accumulation would be decreased with the increase of drought stress intensity.