Accumulation of L-DOPA in various organs of faba bean and influence of drought, nitrogen stress, and processing methods on L-DOPA yield

Faba bean(Vicia faba L.)has been identified as a rich source of L-DOPA,which is used in treating Parkinson's disease.Biosynthesis and accumulation of active substances such as L-DOPA in plant tissues may interact with growing conditions and processing methods.Accumulation trends of L-DOPA in various faba bean organs and the effect of drought stress and N fertilization on L-DOPA content were studied in a field and two greenhouse experiments.The influence of various processing methods on L-DOPA content of faba bean tissues was evaluated.The highest L-DOPA content was detected in fresh leaves(22.4 mg g^(-1))followed by flowers,young pods,mature seeds,and roots.Regardless of processing method,L-DOPA concentration in faba bean tissues was significantly reduced when tissues were boiled or dried.Among various methods of processing,freezing had the lowest detrimental effect,reducing L-DOPA concentrations by 24.1%and 21.1%in leaves and seeds,respectively.Drought stress elevated L-DOPA concentration,and maximum L-DOPA(23.3 mg g^(-1)of biomass)was extracted from plants grown under severe drought stress.However,L-DOPA yield(L-DOPA concentration×biomass)was compromised,owing to the adverse influence of drought stress on dry matter production.No significant difference in L-DOPA concentration was detected among various N application rates.

Quantifying cardinal temperatures and thermal time required for germination of Silybum marianum seed

The response of seed germination to environmental factors can be estimated by nonlinear regression. The present study was performed to compare four nonlinear regression models(segmented, beta, beta modified, and dent-like) to describe the germination rate–temperature relationships of milk thistle(Silybum marianum L.) at six constant temperatures, with the aim of identifying the cardinal temperatures and thermal times required to reach different germination percentiles. Models and statistical indices were calibrated using an iterative optimization method and their performance was compared by root mean square error(RMSE), coefficient of determination(R2) and Akaike information criterion correction(AICc). The beta model was found to be the best model for predicting the required time to reach 50% germination(D50),(R2= 0.99;RMSE = 0.004; AICc =-276.97). Based on the model outputs, the base, optimum, and maximum temperatures of seed germination were 5.19 ± 0.79, 24.01 ± 0.11, and 34.32 ± 0.36 °C,respectively. The thermal times required for 50% and 90% germination were 4.99 and7.38 degree-days, respectively.