Effects of exogenous phenolic acids on roots of poplar hydroponic cuttings

Phenolic acids was a group of allelochemicals with relatively high activity which was reported to have significant accumulation in soil of continuous cropping poplar plantations. The impact of phenolic acids on growth and development of poplars was essential in researches on degradation mechanism of forestland productivity. The effect of phenolic acids on detailed roots morphologic changes of poplars was discussed in this paper. Five levels of phenolic acids respectively were set as 0X, 0.5X, 1X, 1.5X and 2X, in which, the level 1X was determined by actual phenolic acids content in soil of the 2
^nd
generation of continuous cropping poplar plantation, and other levels were determined by analogy from the value of 1X. Hydroponic cuttings were cultured for 40 days, and then harvested for observation and measuring of roots morphologic characteristics. Result showed that the number of roots, mean root length, mean root area, mean root forks, mean root fractal dimension and mean root dry weight were significantly inhibited by increasing concentrations of phenolic acids while mean root diameter and mean root water saturation deficit were promoted by increasing concentrations (P<0.05) Provided that certain morphologic characteristics tended to be promoted by phenolic acids of low level while most roots morphologic characteristics tended to be inhibited by phenolic acids of high level, it's suggested that the influence of phenolic acids on the roots growth of poplar hydroponic cuttings was significant, imbalanced and closely related to the concentration of phenolic acids.