Abstract
During seedling production, growth control of seedlings is an important problem because the overgrowth of seedlings causes a decrease of seedling quality and has disadvantages after transplanting. In this study, we aim to evaluate the possibility of replacing chemical plant growth regulators using light quality in a closed-type plant production system (CPPS) for cucumber seedling production. We used various light treatments, such as monochromatic or combined red (R) and blue (B), and combined R and B with UV-A or Far-red (Fr) light, to compare with a chemical plant growth regulator conventionally using in nursery farms. The combined R and B treatment decreased stem elongation and increased dry matter and compactness. UV-A treatment increased compactness but did not significantly affect the stem elongation or dry matter. Fr increased stem elongation and stem diameter and decreased compactness and dry matter. In leaf growth, combined R and B treatments and UV-A treatments increased leaf area, specific leaf weight, and SPAD value, and decreased leaf shape index. Fr treatments increased leaf area and leaf shape index and decreased specific leaf weight (SLW) and SPAD values. Cucumber seedlings have many different morphological changes, and R5B5 light quality was more effective in growth control due to higher compactness than chemical plant growth regulators. Also, R5B5 light quality has increased seedling quality, such as dry matter and SLW compared with fluorescent lamps. Thus, the use of light quality is a possible alternative to a chemical plant growth regulator.
Highlights
Crop growth controls are an important aspect during the culture period; controlling the growth of seedling requires delicate management
Excessive mechanical stimulation may lead to plant wounding, and this method is not appropriate for horticultural crops
Using differences between day and night temperatures (DIF) is another method for plant growth control [5]. This method cannot be realistically applied to nursery farms, which mainly use unenclosed greenhouses
Summary
Crop growth controls are an important aspect during the culture period; controlling the growth of seedling requires delicate management. The excessive elongation of seedlings creates many problems, such as raising the position of the flower cluster, overgrowth after transplanting, poor fruiting, and fruit abscission during the fruiting season This excessive elongation generally occurs with the low light intensity and short photoperiod in winter seasons and rainy periods in the summer season. To solve this problem, many commercial nursery farms use plant growth regulators. Given regulatory restrictions on plant growth regulators, the increasing cost of chemicals, and the possibility of environmental pollution, alternative growth control methods are needed [1] Many different alternatives, such as mechanical stimulation, temperature control, and irrigation control, are available to replace chemical plant growth regulators [2,3]. This method cannot be realistically applied to nursery farms, which mainly use unenclosed greenhouses
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