Seung Jae Hwang

Light Intensity and Photoperiod Influence the Growth and Development of Hydroponically Grown Leaf Lettuce in a Closed-type Plant Factory System

Effect of light provided by various light intensities combined with different photoperiods on the growth and morphogenesis of lettuce (Lactuca sativa L.) ‘Hongyeom Jeockchukmyeon’ in a closed-type plant factory system were evaluated in this study. Four light intensity treatments, i.e., 200, 230, 260, and 290 μmol·m−2·s−1 PPFD, provided from light-emitting diodes (LEDs), with a combination of three different photoperiods 18/6 (1 cycle), 9/3 (2 cycles) or 6/2 (3 cycles) (light/dark) were used. The combination of 290-9/3 (light intensity-photoperiod) showed the highest plant height and fresh shoot weight, while plants grown at 290-18/6 exhibited the greatest root fresh weight, leaf dry weight, and longest root length. The greatest leaf width, maximum number of leaves, and greatest root dry weight were observed in the treatment combination of 290-6/2. Anthocyanin content was found to be highest in the 290-6/2 and lowest in the 200-6/2 treatment, whereas chlorophyll fluorescence was observed to be highest in the 260-6/2 and the lowest in the 290-9/3 treatment. Our data showed that providing a high light intensity of 290 μmol·m−2·s−1 PPFD with a shorter photoperiod of 6/2 (light/dark) resulted in good plant growth and development of lettuce, whereas growth at light intensities of 230 or 260 μmol·m−2·s−1 PPFD with longer photoperiods of 18/6 and 9/3 (light/dark) resulted in good growth as well as higher photosynthetic capacity.

Light source and CO2 concentration affect growth and anthocyanin content of lettuce under controlled environment

The effect of light source and CO2 concentration on the growth and anthocyanin content of lettuce (Lactuca sativa L. ‘Seonhong Jeokchukmyeon’) grown in growth chambers was examined. The plant was grown under 140 μmol· m−2·s−1 PPF provided by either cool white fluorescent lamps (F, the control), white (W) light emitting diodes (LEDs), or a 8:1:1 mixture of red, blue and white (RBW) LEDs. Carbon dioxide concentration of the atmosphere was maintained at either 350, 700, or 1,000 μmol·mol−1. The RBW treatment promoted vegetative growth of the shoot and root. Chlorophyll fluorescence (Fv/Fm) was not significantly affected by the light source and CO2 concentration. Total anthocyanin content of the plant supplied with 1,000 mol·mol−1 CO2 was the greatest in the F treatment. Photosynthetic rate significantly increased with the increasing CO2 concentration. These results suggested that the RBW which provided a wider spectrum of PAR and the highest CO2 concentration provided the most the suitable environment condition for vegetative growth of lettuce among the tested light sources. To obtain plants with even higher quality, especially having greater content of anthocyanin, however, more considerations on supplemental light source including white LED are necessary in terms of optimum intensity, photoperiod, and optimum ratios of mixing with other LEDs.

Enhancing salt tolerance in eggplant by introduction of foreign halotolerance gene, HAL1 isolated from yeast

Agrobacterium-mediated gene transfer method for production of transgenic eggplants (Solanum melongena L. var. PKM1) has been optimized. Polymerase chain reaction of transgenic plants confirmed the presence of the expected HAL1 fragment. Different tests were carried out to evaluate the level of salt tolerance for the transgenic and control plants with culture media in vitro (0, 50, 100, 150, or 200 mM NaCl) and with soil in greenhouse (0, 25, 50, 75, or 100 mM NaCl). Differences in callus growth between transgenic and control lines were observed. At 150 mM NaCl, the weight of calli from the transgenic population did not differ significantly from that in non salt condition, while the growth of wild-type control calli was strongly inhibited. A preliminary evaluation in vivo under controlled greenhouse conditions showed that at moderate salt concentrations (25 mM NaCl), a similar response to salinity in the original line and in the transgenic progeny was found. However, at higher salt concentration (50 mM NaCl), total dry weight (relative growth) was not significantly decreased by salinity in the transgenic population, while a growth reduction was observed in the wild-type control. Our results indicated that a higher level of salt tolerance was found in the transgenic lines than in the wild-type control. Thus, in this present study we have demonstrated the possibility of increasing salt tolerance in eggplant by introducing the foreign gene, HAL1 derived from yeast.

Short-Term Ion Uptake by Phalaenopsis as Affected by Concentration of the Solution

ABSTRACT Nutrient uptake over a 72 h culture period by clonal micropropagules of Phalaenopsis Tanigawa × Yukimai Dream ‘KS 370’ and ‘KS 352’ were surveyed by Ichihashis (1997) nutrient solution at the original ion strength and its half and quarter. Uptake of major anions [nitrate (NO3 −), phosphate (H2PO4 −), and sulfate (SO4 2−)] and cations [ammonium (NH4 +), potassium (K+), calcium (Ca2+), and magnesium (Mg2+)] measured with an ion chromatograph increased as the ionic strength of the solution increased in both cultivars. The final uptake rates of nutrients were 0.8, 2.0, 2.1, 1.2, 3.0, 2.0, and 1.6 me L−1, respectively in the order of ions mentioned above. The ratios of the uptake rates between cations (mono or bivalent) were almost in proportion to the ratio of their initial ion strength. Therefore, no antagonistical absorption of cations was found in that ion strength. Leaf content of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and copper (Cu) increased as the ionic strength of the solution increased, but concentrations of iron (Fe), manganese (Mn), and zinc (Zn) were not affected significantly. Nitrogen (N) content of leaves in ‘KS 370’ after 72 h culture increased significantly by increasing the ionic strength of the solution. Root concentrations of P, K, Ca, Mg, and Fe increased as the ionic strength of the solution increased in both cultivars. The N concentrations of roots in either ‘KS 370’ or ‘KS 352’ had positive correlations with an increasing ionic strength of the solution, although they were constantly greater in ‘KS 370’ than in ‘KS 352’. The greatest fresh weight was obtained when the plants were cultured in a half strength solution. Whereas dry weight decreased in all treatments as the ionic strength of the solution decreased. These findings show that increased ion absorption affected plant dry weight. The obtained findings provide fundamental information for the closed hydroponic system of phalaenopsis cultivation.