Effect of inhibition of biosynthesis of phenylpropanoids on sessile oak somatic embryogenesis

The inhibition of phenylpropanoid biosynthesis by 2-aminoindan-2-phosphonic acid (AIP) in embryogenic culture of sessile oak (Quercus petraea (Matt.) Liebl.) was associated with a strong reduction of the amount of cinnamic acid derivatives, decline in lignin content and changes in the proportion of different types of somatic embryos. The decrease in the level of phenylpropanoid lignin precursors after AIP application decreased the amount of embryos with deep green cotyledons that are in control cultures characterized by high content of lignin. Their proportion in the total yield represented 30% and 10% in the control and AIP media, respectively. On the contrary, the reduced endogenous pool of cinnamic acids stimulated the cell division activity and the formation of early stages of somatic embryos. Globular, heart- and torpedo-shaped stages of somatic embryos represented in AIP-treated culture about 25% from the total yield of embryos, while only 10% in the control culture. Higher amounts of free putrescine (Put), spermidine and spermine and significantly lower levels of their conjugated forms were characteristic for embryos cultured for 7 weeks on AIP medium (related to controls). Significant increase in Put contents in cotyledonary embryos after 7-week culture with AIP might reflect the stress caused by lowered levels of phenylpropanoids in treated cells.