Il-Seop Kim

Ehretia asperula’s physiological responses to growth performance following oak-wood biochar application under water stress conditions (WSC) and no water stress conditions (non-WSC) were investigated in a pot experiment. Biochar (WB) was incorporated into the soil at concentrations of 0, 5, 10, 15, and 20 tons ha⁻¹ before transplanting Ehretia asperula in the pots. One month after transplanting, Ehretia asperula plants were put under water stress by withholding water for ten days. Water stress significantly decreased the growth and physiology of Ehretia asperula. Under WSC, the application of WB at the concentrations of 15 and 20 tons ha⁻¹ to the soil increased the plant height; number of leaves; fresh and dry weight of the roots, shoots, and leaves; F_v/F_m; chlorophyll content; leaf relative water content; and soil moisture as well as decreased the relative ion leakage. The application of WB enhanced drought tolerance in Ehretia asperula plants by lowering the wilting point. The findings suggest that WB application at the concentration of 15 tons ha⁻¹ could be recommended for ensuring the best physiological responses and highest growth of Ehretia asperula plants.

This study was carried out to balance the production and consumption of assimilates according to crop conditions as a basis to reduce the waste of assimilation through leaf and fruit control. There were four treatments: one fruit and two leaves (F1L2); two fruits and two leaves (F2L2); two fruits and three leaves (F2L3); and two fruits and four leaves (F2L4). This study showed that, as the number of leaves increased in Periods 1 and 2, the stem diameter and average weight decreased, with F1L2 having the highest stem diameter and average weight, although its numbers of leaves and fruits were the fewest. In the summer, Period 3, F1L2 production was the lowest due to increased rates of flower drop and fruit drop. In Period 4, when ambient temperature and light levels were decreased, the number of fruits was increased. However, the production was decreased. F1L2 and F2L4 showed significant decreases in production. Although F1L2 showed the highest average weight, it had a low production due to a decrease in the number of fruits. F2L4 showed weak generative growth due to an imbalance in growth over the summer. After reaching the last stage of development, the number of leaves showed the highest average weight and production in F2L4.

The aim of this study was to investigate the effects of green light, added with red and blue LEDs, on the growth, leaf microstructure and quality of spinach plants. Plants were transplanted and grown hydroponically for 30 days under different combinations of red:blue with a 4:1 ratio (R4B1), red:blue:green with a 5:2:3 ratio (R5B2G3) and red:blue:green with a 1:1:1 ratio (R1B1G1), at a 190 µmoL m⁻²·s⁻¹ photosynthetic photon flux density (PPFD). The results showed that green light, added to red and blue LEDs at a reasonable ratio, could reduce the growth, leaf microstructure and quality of spinach plants, but not the organic acid content. The highest values for the growth parameters, photosynthetic pigments, leaf structure characteristics and quality of the spinach plant were observed for the R4B1 treatment, but not for the organic acid content. Therefore, our results suggest that green light added to red and blue LEDs at a reasonable ratio is not suitable for the growth of spinach.

Introduction

The objective of this study was to examine responses of vegetable seedlings grown on plug seedling system (Plug) or cylindrical paper pot (CPP) system to water stress. Cucumber 'Jo-eun' was grafted onto stock 'Huckjong'. Watermelon 'Jo-eunggul' was grafted onto stock 'Bulojangsaeng'. Growth factors of seedlings were investigated. Top-to-root ratio (TRR), compactness (CP), and Dickson Quality Index (DQI) as indicators of seedling quality were calculated based on time periods. Results revealed that the overall shoot of cucumber and watermelon grown in the CPP system was higher than the shoot grown in the Plug system. In both CPP and Plug systems, the total growth decreased as the irrigation water volume increased, while the seedling stem was thick and hard. The higher the irrigation water level, the greater was the inhibition of root zone development. When the degree of growth reduction was comparing between the two systems, the growth rate of cucumber was lower in the CPP system than that in the Plug system, whereas the growth rate of watermelon was decreased due to increased irrigation water content only in the Plug system. The degree of growth tended to decrease with increasing volume of irrigation water in both CPP and Plug systems. The degree of decreased growth was greater in the Plug system than in the CPP system. The decrease started to occur in the mid-growth phase. It intensified with further growth. In conclusion, extensive irrigation during early stages of growth can enhance the growth of seedlings in both CPP and plug systems. However, growth was suppressed after reaching a certain level. This effect was relatively lower in the CPP system than in the Plug system.