About This Journal
About This Journal
Horticultural Science and Technology (abbr. Hortic. Sci. Technol., herein ‘HST’; ISSN, 1226-8763), one of the two official journals of the Korean Society for Horticultural Science (KSHS), was launched in 1998 to provide scientific and professional publication on technology and sciences of horticultural area. As an international journal, HST is published in English and Korean, bimonthly on the last day of even number months, and indexed in ‘SCIE’, ‘SCOPUS’ and ‘CABI’. The HST is devoted for the publication of technical and academic papers and review articles on such arears as cultivation physiology, protected horticulture, postharvest technology, genetics and breeding, tissue culture and biotechnology, and other related to vegetables, fruit, ornamental, and herbal plants.
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Research Article
- Cyanamide Releases Buds Dormancy of ‘Shuijing’ Grapevine via DNA Methylation Reduction
- Zuqin Qiao, Yongfu Zhang, Xiaoqin Li, Zhao Liu, Kai Wang, Xingmei Tao, Xuan Yi
- ‘Shuijing’ grape is a deciduous vine fruit tree, and the low-temperature period during winter is required for its sprouting. Global warming has …
- ‘Shuijing’ grape is a deciduous vine fruit tree, and the low-temperature period during winter is required for its sprouting. Global warming has been associated with substantially decreased grape yields and lower grape quality because it reduces the low temperatures needed for grape dormancy. Treatment with cyanamide can efficiently cause the grape hibernacle’s dormant release. However, the underlying epigenetic mechanisms remain unknown. This study collected mature branches of the annual ‘Shuijing’ grape and treated them with 2.5% cyanamide (on sprouts and joints). The treatment-induced sprouting and the physiological indices (e.g., soluble sugar, starch, and protein content) were measured. Whole-genome bisulfite sequencing (WGBS) was used for whole-genome differential methylation. The results demonstrated that following cyanamide treatment, sprouting and appearance of primordia occurred earlier, starch content decreased, and protein content and the bud axis increased during grape sprouting, facilitating flower-bud differentiation and inflorescence integrity. Cyanamide application resulted in a drop in DNA methylation levels in grapevine buds, particularly in the CHH methylation. This led to an increase in hypo-DMRs (regions with reduced methylation) and a decrease in hyper-DMRs (regions with higher methylation), ultimately resulting in the up-regulation of genes associated with sprouting. Biological processes (e.g., regulation of transcription, DNA-templated), cellular components (e.g., nucleus, plasma membrane, cytoplasm), and molecular functions (e.g., protein binding, ATP binding) involved in the dormancy release of grape were significantly enriched. Cyanamide treatment facilitated latent release since it damages the cell membrane and lipid structures of grapevine buds. Additionally, cyanamide treatment reduced DNA methylation levels of latent buds of the ‘Shuijing’ grapevine. The methylation traits associated with the ‘Shuijing’ grapevine aid in comprehending the molecular pathways involved in easing dormancy and encouraging bud differentiation. This work offers epigenetic references to understand the fundamental mechanisms involved in escaping dormancy in fruit trees. - COLLAPSE
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Research Article
- Macro-Elements in Liquid Fertilization Influence Differently in Occurrence and Growth of Runner Plants in Strawberry Propagation
- Saleha Farjana, In Sook Park, Jong Myung Choi
- Seedlings were transplanted to a commercial root medium in Autumn that had 83.9, 74.2, and 9.7% of total porosity, container capacity and …
- Seedlings were transplanted to a commercial root medium in Autumn that had 83.9, 74.2, and 9.7% of total porosity, container capacity and air-filled porosity, respectively. Then, 6 treatment solutions were formulated containing all the essential nutrients with only N, P, K, Ca, Mg, or S and applied until the cold treatment of the mother plants. The cold treated (low temperature treatment at 1°C) mother plants were transplanted in late March, and the growth of the mother plants and the occurrence of runner plants were investigated 90 days later. Data on the root medium chemical properties and tissue contents of the mother plants were analyzed in the Spring season. A significant statistical difference was absent in the root medium pH among the treatments (5.23–5.82). The greatest growth of mother plants in terms of dry weight and the occurrence of runner plants in ‘Altaking’ and ‘Vitaberry’ were found in the P- and K- controlled treatments respectively, but in ‘Kuemsil’, the growth of the mother plant was highest in the Mg- controlled treatment and maximum occurrence of a runner plant was observed in the S- controlled treatments. In contrast, the lowest growth was observed in the N- controlled treatment for all the cultivars of strawberries tested. In addition, the N content of the tissues of ‘Altaking’, ‘Kuemsil’, and ‘Vitaberry’ when their growth was highest was 3.59, 3.81, and 4.00%, respectively, based on the dry weight of the aboveground tissues. Furthermore, the root medium nutrient concentrations in the same treatments were as follows: 44.9, 48.0, and 47.8 mg L-1 NO3-; 138.5, 187.3, and 181.4 mg L-1 PO43-; 232.4, 174.6, and 147.1 mg L-1 K+; 14.7, 15.5, and 31.6 mg L-1 Ca2+; 11.0, 15.5, and 27.6 mg L-1 Mg2+, and 50.0, 47.5, and 39.9 mg L-1 SO42-, respectively. However, there was no significant statistical difference in the dry weights of the mother plants among the treatments of the strawberry cultivars; however, the lowest was with the N- controlled treatment. The above results indicate that the occurrence and growth of runner plants via vegetative propagation in the Spring season was influenced by N fertilization to the mother plants in the Fall season. - COLLAPSE
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Research Article
- Antifungal Activity and Phytochemical Analysis of Myrtaceae Leaf Extracts including the Induction of Defense Enzymes in Lettuce against Alternaria Leaf Spot
- Suriyasit Somnuek, Kamronwit Thipmanee, Tanimnun Jaenaksorn
- To avoid the risk of harmful effects from synthetic fungicides on human and natural environments, our study aimed to evaluate the potential …
- To avoid the risk of harmful effects from synthetic fungicides on human and natural environments, our study aimed to evaluate the potential use of the indigenous Thai Myrtaceae plants as a harmless means for controlling the plant diseases. Four Myrtaceae extracts showed no phytotoxicity towards lettuce cultivated in hydroponic conditions, with notable plant-growth-promoting potential observed in lettuce treated with Callistemon viminalis (EECV). With regard to a direct effect, Melaleuca cajuputi (95% EEMC) showed the strongest inhibition of mycelial growth of A. brassicicola (85–100%), followed by 95% EECV (40–63%), while both extracts significantly inhibited spore germination (80–100%). A GC/MS and LC/MS analysis revealed terpenoids as the predominant compounds at approximately 55% and 37% in EEMC and EECV, respectively, with high concentrations of phytol (14%) and 1,8-cineole (14%) being particularly notable. As an inducer of an indirect effect of the plant extracts, the results from the experiment with 95% EEMC (15,000 and 50,000 ppm) as well as 50 and 95% EECV (15,000 and 50,000 ppm) applications was in good agreement, demonstrating significant reductions in disease severity in hydroponically grown lettuce ranging from 50 to 70% together with the induction of defense enzymes (specifically β-1,3-glucanase, chitinase, and peroxidase) compared to those in the inoculated control and fungicide treatment groups. Furthermore, a correlation analysis revealed a negative correlation between disease severity and the three defense enzymes. Our findings underscore the considerable efficacy of the three botanical fungicides tested here (i.e., 95% EEMC as well as 95% and 50% EECV) for the management of Alternaria leaf spot in lettuce. - COLLAPSE
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Research Article
- Establishing a Quadratic Regression Model of the Growth Characteristics and Isoorientin Contents of Wheatgrass Seedlings in Response to Different Temperature Conditions
- Dae Ho Jung, Joonwoo Lee
- In this study, we aimed to optimize the growth conditions of wheatgrass (Triticum aestivum L. cv. ‘Keumkang’), a sprout vegetable known …
- In this study, we aimed to optimize the growth conditions of wheatgrass (Triticum aestivum L. cv. ‘Keumkang’), a sprout vegetable known for its enhanced nutritional and bioactive properties, including significant increases in antioxidants and amino acids. Using a quadratic regression model, we investigated the effects of different temperatures on wheatgrass growth characteristics and on the content of isoorientin, a potent flavonoid that contributes to health benefits. Wheat seeds were germinated and cultivated under controlled temperatures between 18–32°C, with growth parameters (plant height, leaf area, shoot fresh weight, and root fresh weight) and isoorientin contents analyzed post-harvest. We observed that a temperature of approximately 25°C was most suitable and significantly enhanced the plant height, shoot fresh and dry weights, and the isoorientin content, underscoring the critical role of the temperature in maximizing the nutritional value of wheatgrass. Root growth showed minimal responses to the temperature variations, suggesting a complex interaction between growth parameters and environmental conditions. This analysis advances our understanding of wheatgrass cultivation, providing actionable insights for maximizing its nutritional and medicinal properties through proper temperature management. The findings here are pivotal for agricultural practices aiming to enhance the quality of sprout vegetables, significantly contributing to the field of functional foods and nutraceuticals. - COLLAPSE
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Research Article
- Defoliation Timing of Fruit Cluster Leaves Influences Fruit Quality Attributes, Skin Coloration and Anthocyanin Contents in ‘Hongro’ Apples
- Nay Myo Win, Sangjin Yang, Soon-Il Kwon, Seonae Kim, Youngsuk Lee, Van Giap Do, Jingi Yoo, In-Kyu Kang, Juhyeon Park
- Apple skin color is an important quality trait affecting marketability. The anthocyanin accumulation in ‘Hongro’ apple skins was analyzed by evaluating different …
- Apple skin color is an important quality trait affecting marketability. The anthocyanin accumulation in ‘Hongro’ apple skins was analyzed by evaluating different defoliation timing treatments of fruit cluster leaves applied two, three, and four weeks before harvest (WBH). Non-defoliated plants served as controls. Defoliation did not affect the fruit weight, size, flesh firmness, soluble solid content, titratable acidity, or the starch pattern index at harvest. However, the fruit sunburn rate was higher for defoliation at 3 and 4 WBH compared to defoliation at 2 WBH and non-defoliation treatments. The red-colored area and a* value for both the sun-exposed and sun-shaded sides of apple skin were highest in the defoliation treatments at 3 and 4 WBH, intermediate at 2 WBH, and lowest in the non-defoliation treatment case. On the sun-exposed side, the L* value was lower after the defoliation treatments compared to the non-defoliation treatment, but the b* value was not affected by any of the defoliation treatments. On the sun-shaded side, the L* and b* values were lower under defoliation at 4 WBH compared to the other treatments. The anthocyanin content on the sun-exposed side was highest after defoliation at 4 WBH, followed by 3 and 2 WBH, and was lowest in the non-defoliation treatment. Similarly, the anthocyanin content on the sun-shaded side was highest in defoliated plants at 4 and 3 WBH, intermediate at 2 WBH, and lowest in the non-defoliated plants. Additionally, the expression levels of major anthocyanin biosynthetic genes (MdPAL, MdCHS, MdCHI, MdF3H, MdDFR, MdANS, MdUFGT, and MdMYB10) were upregulated in all defoliation treatments on both the sun-exposed and sun-shaded sides, particularly during early defoliation at 4 and 3 WBH. Therefore, this study showed that the defoliation timing influences the development of red skin coloration in ‘Hongro’ apples and that defoliation at 4 and 3 WBH achieves the optimum coloration for this cultivar. - COLLAPSE
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Research Article
- Effect of Nutrition Supplement on Water Quality and Growth of Geranium in Aquaponic System
- Ki Young Choi, Kyeong Ho Kim, Md Rayhan Ahmed Shawon, Hyoun-Jin Lee, Yeo Joong Yoon
- An aquaponic system combines growing plants and fish, where optimal water quality is essential to a balanced and productive system. This research …
- An aquaponic system combines growing plants and fish, where optimal water quality is essential to a balanced and productive system. This research evaluated effects of nutrition supplements and their combinations of T1 (KHCO3), T2 (KHCO3 + Fe-EDTA) and T3 (KHCO3 + Fe-EDTA + KH2PO4) on aquaponic water and plant growth. Geranium (Pelargonium zonale L.) plants and goldfish (Carassius auratus auratus) were kept together in a small tank for 60 days and a recycling deep flow system was installed for planterior purposes. Electrical conductivity (EC), pH, and nutrient concentration of water and plant growth parameters were measured. Results showed that EC and pH fluctuated during the treatment period, they were higher in T3 but lower in the control than in others. At 60 days after treatment, potassium, phosphate, and sulfate were significantly higher in T3-treated water than in other treatments. Magnesium, calcium, and nitrate were significantly higher in the control than in others. At 60 days after treatment, plant height and the number of leaves were the highest for T2-treated plants. Leaf length, leaf width, NDVI, and SPAD values were significantly higher for T2 and T3-treated plants than for others. However, leaf discoloration of plants was significantly lower in T2 and T3 treated groups. Leaf discoloration showed negative correlations with SPAD and NDVI values. These results suggest that T2 treatment is preferable for sustainable water quality and the growth of geranium plants in an aquaponic system as a planterior. - COLLAPSE
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Research Article
- A Field Application of Fermented Eucalyptus Bark Improves Dragon Fruit Yields by Altering the Soil Environment during the Current Growing Season
- Zhechao Dou, Zhiguang Chi, Chang Pan, Zhuchi He, Kunguang Wang, Qiaofang Lu, Jing MA, Dongming Cui, Yuanmei Zuo
- Proper field coverings can improve the plant growth environment and regulate plant growth. In Guangxi Autonomous Region, one of the main dragon …
- Proper field coverings can improve the plant growth environment and regulate plant growth. In Guangxi Autonomous Region, one of the main dragon fruit and eucalyptus production areas of China, local fruit farmers often use fermented eucalyptus bark as dragon fruit orchard field covering to reduce the need for orchard weeding. However, its impacts on the yield and quality of dragon fruit and the mechanisms of these impacts remain unclear. In this study, we investigated the effects of the application of fermented eucalyptus bark mulch as a field covering in a dragon fruit orchard in Long’an County, Guangxi. We utilized three treatment levels in winter: clear tillage (CK1), clover planting (CK2), and mulching fermented eucalyptus bark (MFEB). We measured factors including the soil nutrient contents, humidity, and dragon fruit yield outcomes and quality levels during different growth periods to evaluate the impact of the MFEB application on dragon fruit production. The results showed that MFEB had the greatest effect on dragon fruit production. It enhanced the soil nutrient environment, increased the soil nutrient contents, and improved the dragon fruit yield compared to control treatments. Soil organic matter and soil trace element contents (particularly available copper) were crucial factors influencing the dragon fruit yield. These findings provide a scientific basis for improving dragon fruit yields in Guangxi orchards as well as a new strategy for improving resource utilization through the use of eucalyptus bark during the production of dragon fruit. - COLLAPSE
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Research Article
- Effects of Controlled Irrigation Frequencies Using Load Cells on Growth and Abscission of Apical Meristems in Different Strawberry Varieties
- Saleha Farjana, In Sook Park, Jong Myung Choi
- Seedlings were planted in trays of 24 cells filled with a commercial root medium (total porosity, container capacity, and air-filled porosity were …
- Seedlings were planted in trays of 24 cells filled with a commercial root medium (total porosity, container capacity, and air-filled porosity were 83.9, 74.2, and 9.7%, respectively). The load cells were calibrated to 4 different irrigation frequencies (55, 48, 41, and 34%). Fertigation was started at 10 days after seedling transplantation, and the solutions contained N-P2O5-K2O (18-18-18, Haifa Chemicals Ltd.) in all the treatments with different frequencies until transplanting to plastic boxes. Sixty days old seedlings were then transplanted to rectangular sized plastic boxes filled with the same root medium and allowed to grow for another 60 days with equal fertigation levels in all the treatments. The emergence of inflorescence and abscission of apical meristems was investigated visually while the plants were growing. Data on growth and tissue nutrient contents of the mother plants and the root medium chemical properties were analyzed. The premature deterioration of shoot apical meristems was highly significant, and the maximum was found in plants with an irrigation frequency of 34% in each cultivar. Data on the root medium pH among the treatments (5.41–6.07) were statistically significant. The greatest growth of seedlings in terms of dry weight was observed in plants with an irrigation frequency of 55%; on the other hand, the lowest growth was in those with an irrigation frequency of 34%. Furthermore, the tissue nutrient content of ‘Altaking’, ‘Keumsil’ and ‘Vitaberry’ strawberries was statistically significant, and the highest was in 55% group; in contrast, the lowest was in the 34% group. In addition, the tissue N content of the ‘Altaking’, ‘Keumsil’ and ‘Vitaberry’ strawberries at their highest growth was 3.76, 3.65, and 3.68%, respectively, and the maximum abscission of the apical meristems was 2.60, 2.54, and 2.58%, respectively, based on the dry weight of the aboveground tissue. However, significant differences were observed in the dry weights of the seedlings and the abscission of the apical meristems among the treatments of the irrigation set points in all strawberry cultivars tested. The above results indicate that the flower bud differentiation, abscission of apical meristems, and growth of strawberry seedlings were influenced by the irrigation frequencies, and the set-point of 55% in irrigation showed the best results. - COLLAPSE
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Research Article
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Photophysiological Characteristics of Tomato Grown under a Greenhouse According to Seasonal Changes
계절 변화에 따른 온실 재배 토마토의 광생리적 특성
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Jae Myun Lee, Jae Yeon Jeong, Hyo Gil Choi
이재면, 정재연, 최효길
- This study aimed to identify the characteristics of the photophysiological responses at the leaf level of tomatoes depending on changes in the …
2021년 9월부터 2022년 1월까지 여름, 가을, 겨울의 계절적 특성을 갖는 온실 환경 변화에 따른 토마토 엽위별 광생리학적 특성을 규명하고자 하였다. 토마토 엽위는 …
- This study aimed to identify the characteristics of the photophysiological responses at the leaf level of tomatoes depending on changes in the greenhouse environment during the seasonal transition from September of 2021 to January of 2022, encompassing the summer, autumn and winter seasons. Tomato leaves were classified as upper, middle, and lower sections based on the locations of the stem nodes. Subsequently, the photosynthetic characteristics, chlorophyll fluorescence parameters, and chlorophyll components were investigated within the classified leaf sections. Correlations between each parameter were determined and a principal component analysis (PCA) was conducted. The photosynthetic rate, stomatal conductance, and transpiration rate of tomatoes measured in September, November, and January decreased in the order of the upper, middle, and lower leaves. In particular, the stomatal conductance and transpiration rate of the lower leaves decreased significantly in January, which affected the photosynthetic efficiency. The FV/FM values of the upper section measured in September and November were 0.71 and 0.80, respectively, which were lower than those of the middle and lower sections. However, the ABS/RC and TRO/RC values were significantly higher in the upper section compared to the middle and lower sections. Conversely, at the I−P level of the OJIP curve measured in September, the upper section exhibited lower values than the middle section. The chlorophyll a content did not show any variation in value across leaf positions with the changing seasons. However, the contents of chlorophyll b and chlorophyll a+b were reduced in winter, whereas the carotenoid content increased. In the correlation analysis of each parameter, the photosynthetic rate showed a strong positive correlation with the transpiration rate and stomatal conductance. In the PCA analysis of the photosynthetic parameters, the FV/FM value was one of the main contributing factors to PC1, showing a positive correlation, while the photosynthetic rate, transpiration rate, and stomatal conductance exhibited negative correlations.
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2021년 9월부터 2022년 1월까지 여름, 가을, 겨울의 계절적 특성을 갖는 온실 환경 변화에 따른 토마토 엽위별 광생리학적 특성을 규명하고자 하였다. 토마토 엽위는 위치에 따라 상, 중, 하위엽으로 구분하였다. 9월, 11월, 1월에 광합성률, 기공전도도, 증산율은 상, 중, 하위엽의 순으로 감소하였다. 특히 1월의 하위엽은 기공전도도, 증산율이 큰 폭으로 감소하여 광합성 효율에 영향을 미쳤다. 9월과 11월에 측정된 상위엽의 FV/FM 값은 각각 0.71과 0.80으로 중위엽과 하위엽보다 유의하게 낮았다. 그러나 ABS/RC 및 TRO/RC 값은 중위엽과 하위엽에 비해 상위엽에서 유의하게 높았다. 9월에 측정된 OJIP 곡선의 I−P 수준에서는 상위엽이 중위엽보다 낮은 값을 보였다. 엽록소 a 함량은 계절에 따라 변화를 나타내지 않았지만, 엽록소 b, 엽록소 a+b 함량은 겨울에 더 감소한 반면, 카로티노이드 함량은 증가하였다. 각 매개변수의 상관관계 분석에서 광합성률은 증산율, 기공전도도와 양의 상관관계를 보였고, 광합성 매개변수 PCA 분석에서 PC1의 주요한 변동 요인 중 하나로, FV/FM 값은 양의 상관관계를 나타내며, 광합성률, 증산율, 기공전도도는 음의 상관관계를 보였다.
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Photophysiological Characteristics of Tomato Grown under a Greenhouse According to Seasonal Changes
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Research Article
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Estimation of the Relationship between the Natural Frequency and Fruit Drop during the Fruit Enlargement Stage of Apple
사과 과실 비대기 고유진동과 과실 낙과간 관계 추정
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Young Min Choi, Ki-Pyo You, Dong Geun Choi
최영민, 유기표, 최동근
- This study was conducted to investigate changes in the adhesivity of ‘Fuji’ apple (Malus domestica Borkh) fruits during the period when …
본 연구는 태풍이 주로 도래하는 시기에 사과 ‘후지’(Malus domestica Borkh) 과실의 부착력 변화를 조사하고, 풍동 및 진동대를 이용한 시뮬레이션을 통해 낙과와 …
- This study was conducted to investigate changes in the adhesivity of ‘Fuji’ apple (Malus domestica Borkh) fruits during the period when typhoons mainly occur and to obtain agricultural engineering information related to fruit drop through a simulation using a wind tunnel and shaking table. Fruit adhesivity was assessed by measuring the tensile force at the time of fruit drop when pulling the fruit from the tree. Fruit adhesivity during the growing season (July to September) tended to decrease as maturity approached, but this was not statistically significant. On the other hand, fruit adhesivity when measured at artificial drop angles of 0°, 30°, and 60° based on the fruit stalk decreased significantly as the angle increased. Using an acceleration sensor, the natural frequencies of the inner, middle, and outer parts of the scaffold branch (in the direction of the main stem) were found to be 52.0 cycles·min-1, 332.2 cycles·min-1, and 346.5 cycles·min-1, respectively. The natural frequency according to the movement direction of the scaffold branch was higher for horizontal displacement (874.2 cycles·min-1) than for vertical displacement (443 cycles·min-1). The natural frequency of the fruit was measured and found to be 420.5 cycles·min-1. Additionally, as a result of measuring the natural frequency after binding 60 cm parts (from the main stem) of the scaffold branches, the natural frequency was found to be lower than the control (no binding), and the vertical displacement was lower than the horizontal displacement. Using a wind tunnel, fruits did not fall at wind velocity of 0 to 9 m·s-1, and the average displacement (up to 17 mm) tended to increase as the wind velocity was increased. In an experiment using a shaking table, displacement values in the range of 5 to 30 mm were applied based on the displacement coefficient calculated in the wind tunnel experiment, and the bearing branch of the apple tree was shaken using a ‘pendulum’ type of vibration method. The fruit drop began with a displacement coefficient of 10 mm, and the time required for fruit drop shortened as the displacement coefficient was increased. In the relationship between the displacement coefficient and the wind velocity, a displacement coefficient of 10 mm indicated a wind velocity of 6 to 9 m·s-1, but this result may lead to fruit drop even at lower wind velocities because certain cultivation characteristics (e.g., tree form, number of leaves, fruit yield, abscission layer maturity of fruit) and natural wind characteristics (e.g., gusts, eddies, wind direction) were not taken into account. Wind can cause primary displacement in apple trees containing fruits and can then induce secondary displacement due to the weight of the fruit and the elasticity of the branches, and it is presumed that these primary and secondary displacements cause fruit drop.
- COLLAPSE
본 연구는 태풍이 주로 도래하는 시기에 사과 ‘후지’(Malus domestica Borkh) 과실의 부착력 변화를 조사하고, 풍동 및 진동대를 이용한 시뮬레이션을 통해 낙과와 관련된 정보를 획득하고자 수행하였다. 과실 부착력은 과실을 잡아당겼을 때 낙과하는 시점의 인장력을 조사하였다. 생육기(7–9월) 과실 부착력은 성숙기에 가까워질수록 감소하는 경향이었으나 통계적인 유의성은 없었다. 반면 과경축을 기준으로 당기는 각도를 0, 30, 60도로 측정했을 때의 부착력은 각도가 커질수록 유의하게 감소하였다. 가속도센서를 활용한 주지의 기부, 중간과 바깥쪽의 고유진동수는 각각 52.0cycles·min-1, 332.2cycles·min-1, 346.5cycles·min-1로 측정되었으며, 주지의 운동 방향은 수직(443cycles·min-1)보다 수평(874.2cycles·min-1)적인 변위에서 더 높았다. 과실의 고유진동수는 496.9cycles·min-1로 측정되었다. 추가적으로 주지의 60cm 부위(원줄기로부터)를 결속하여 고유진동을 측정한 결과, 무결속보다 고유진동수가 낮았으며, 상대적으로 수직변위가 수평변위보다 낮았다. 풍동을 활용한 실험에서 0–9m·s-1의 풍속에서 과실은 낙과하지 않았으며, 풍속별 평균 변위는 풍속이 강해질수록 증가(최대 17mm)하는 경향을 보였다. 진동대를 이용한 실험은 풍동 실험에서 산출된 변위계수를 근거로 5–30mm까지 변위값을 적용하였으며, 진동방식은 ‘흔들림(pendulum)’ 형태로 과실이 착과된 결과지에 진동을 주었다. 과실 낙과는 변위계수 10mm(고유진동수 57.0–72.6cycles·min-1)부터 낙과가 시작되었고, 변위계수가 증가할수록 낙과까지의 소요시간은 단축되었다. 변위계수와 풍속과의 관계식에서 10mm의 변위계수는 풍속 6–9m·s-1를 의미하지만, 이와 같은 결과는 재배 특성(수형, 잎, 과중, 착과량, 과실 이층부의 성숙도 등)과 자연적 바람의 특성(돌풍, 와류, 풍향 등)이 적용되지 않아 보다 낮은 풍속에서도 낙과가 발생할 수 있다. 따라서 바람은 과실을 포함한 수체에 1차 변위를 발생시킨 후 과중과 가지의 탄력성에 의해 2차 변위를 유도할 수 있으며, 이러한 1, 2차 변위에 의해 낙과하는 것으로 추정된다.
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Estimation of the Relationship between the Natural Frequency and Fruit Drop during the Fruit Enlargement Stage of Apple
Horticultural Science and Technology
