Jong Hyang Bae

Effect of root zone aeration on the growth and bioactivity of cucumber plants cultured in perlite substrate

This study was aimed at investigating the growth and nutrient uptake of cucumber plants affected by forced aeration of supplying oxygen and stimulating gas exchange rate in root zone in a substrate. Five aeration levels during the growth (0, 0.5, 1.0, 1.5 and 2.0 L/min) were applied. Maximum leaf area and leaf fresh and dry weights were obtained at an aeration level of 0.5 L/min. Excessive aeration in root zone inhibited leaf area expansion, relative leaf growth rate and crop growth rate. An optimum leaf area index of 3.0 to 3.5 was estimated in range of 0 and 0.5 L/min. The highest fruit yield was measured of 1.13 kg/plant at 0.5 L/min, whereas at 2.0 L/min it was 0.62 kg/plant. Potassium concentration in petiole sap was lower at 63 days after transplanting than that at 32 days after transplanting. Ethylene concentrations increased with higher aeration values, however, CO2 concentration reduced with increased aeration. All bioactive compounds (polyphenols, flavonoids, flavanols, tannins and ascorbic acid) and the levels of antioxidant activities by ferric-reducing/antioxidant power and cupric reducing antioxidant capacity in ethanol extracts of cucumbers differed significantly in the investigated samples and were the highest at aeration level of 0.5 L/min in comparison with other samples (P <0.05). In conclusion, antioxidant status (bioactive compounds and antioxidant activities) improved with the appropriate aeration, which is effective for higher fruit yield and bioactivity. Excessive aeration inhibited root respiration, nutrients, bioactivity, and water uptake, and it resulted in the reduction of plant growth and fruit yield.

Detection of Bioactive Compounds in Organically and Conventionally Grown Asparagus Spears

In the recent reports, there are contradictory conclusions about the nutritional and health properties of organic and conventionally growing vegetables. We hypothesized that organic cultivation system results in higher quality of asparagus (Asparagus officinalis L.) because of organic manure and effective organisms. Therefore, new analytical methods were applied in order to find the differences in bioactive compounds between the plants growing under various cultivation systems. Total antioxidant capacities (TAC) of the conventional and organic greenhouse and conventional open-field farming of asparagus spears were determined by 2,2-azino-bis (3-ethyl-benzothiazoline-6-sulfonic acid) diammonium salt (ABTS), 1,1-diphenyl-2-picryl-hydrazyl (DPPH), and ferric-reducing antioxidant power (FRAP) assays, and UHPLC-PDA-MS was used for identification of some phenolic acids and flavonoids. Total phenolic compounds (TPC), total flavonoids, rutin, vitamin C, chlorophylls, carotenoids, and the values of TAC, determined in organic growing asparagus spears, were higher than in conventional, but not always significant. The applied for the first time FTIR spectroscopy as an estimation of the differences between the investigated samples showed more prominent bands in the region of polyphenols in organic asparagus spears than in conventional and provides a rapid and precise alternative to other methods. The binding properties of extracted polyphenols to HSA determined by 3D-fluorescence were relatively higher in organic asparagus spears than in other samples. Correlation between the amounts of total polyphenols and flavonoids and their quenching properties showed a linear relationship. All proposed analytical methods can be applied to a variety of studied plants.