Allelopathic effect of apple hairy root exudates on the germination and seedlings growth of Arabidopsis thaliana in vitro

Abstract

In the previous study, phenolic acids and polyphenolic flavonoids were identified as putative allelochemicals in apple cv. Golden Delicious hairy roots growth medium. In order to examine their allelopathic potential, the effect of hairy root exudates on the germination and seedling growth of the test species Arabidopsis thaliana was elucidated. Arabidopsis seeds were cultivated in Erlenmeyer flasks containing 25 mL of liquid medium in which apple hairy roots were cultivated for 4 weeks. The effect of apple hairy root growth medium on Arabidopsis was evaluated after 5 and 10 days of seed cultivation. Apple hairy root exudates had no significant effect on Arabidopsis germination rate, while growth characteristics of seedlings were significantly affected both after 5 and 10 days of treatment. The roots of treated seedlings were significantly shorter (35.1%), with lower number (74% decrement) of lateral roots compared to control after10 days of treatment. The growth and morphology of Arabidopsis shoots and leaves have been affected too. Thus, the shoots of treated seedlings were almost twice shorter compared to control after 5 days of treatment. At the 10th day, this distinction became more pronounced, when two fully expanded leaves were visible in treated seedlings, while control had completely developed rosettes with six leaves. In addition, leaves of treated seedlings were smaller and pale in colour compared to control. qPCR expression analysis of genes involved in regulation of the cell cycle showed reduction of transcript levels in roots of treated seedlings, with the highest expression decrease detected for CDKA1 and CYCB2;4 cyclin.