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International Journal of Horticulture 2025, Vol.15, No.5 http://hortherbpublisher.com/index.php/ijh © 2025 HortHerb Publisher, registered at the publishing platform that is operated by Sophia Publishing Group, founded in British Columbia of Canada. All Rights Reserved. Publisher HortHerb Publisher Edited by Editorial Team of International Journal of Horticulture Email: edit@ijh.hortherbpublisher.com Website: http://hortherbpublisher.com/index.php/ijh Address: 11388 Stevenston Hwy, PO Box 96016, Richmond, V7A 5J5, British Columbia Canada International Journal of Horticulture (ISSN 1927-5803) is an open access, peer reviewed journal published online by HortHerb Publisher. The journal publishes all the latest and outstanding research articles, letters and reviews in all aspects of horticultural and its relative science, containing horticultural products, protection; agronomic, entomology, plant pathology, plant nutrition, breeding, post harvest physiology, and biotechnology, are also welcomed; as well as including the tropical fruits, vegetables, ornamentals and industrial crops grown in the open and under protection. HortHerb Publisher is an international Open Access publisher specializing in horticulture, herbal sciences, and tea-related research registered at the publishing platform that is operated by Sophia Publishing Group (SPG), founded in British Columbia of Canada. All the articles published in International Journal of Horticulture are Open Access, and are distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. HortHerb Publisher uses CrossCheck service to identify academic plagiarism through the world’s leading plagiarism prevention tool, iParadigms, and to protect the original authors’ copyrights.
International Journal of Horticulture (online), 2025, Vol. 15, No.5 ISSN 1927-5803 http://hortherbpublisher.com/index.php/ijh © 2025 HortHerb Publisher, registered at the publishing platform that is operated by Sophia Publishing Group, founded in British Columbia of Canada. All Rights Reserved. Latest Content Effect of Growing Media on Germination and Seedling Characteristics of Tomato (Solanum lycopersicum c.v. Srijana) in Kaski District Manjita Tiwari, Binayak Sigdel, Prapti Ghimire, Bishal Shrestha International Journal of Horticulture, 2025, Vol. 15, No. 5, 208-217 Formation Mechanisms of Stem Sweetness and Texture in Fresh-Eating Sugarcane: Sugar Metabolism, Cell Wall Modification, and Gene Expression Regulation Wenzhong Huang, Kaiwen Liang International Journal of Horticulture, 2025, Vol. 15, No. 5, 218-233 Physiological Mechanisms of Fruit Ripening in Yellow Pitaya Genetic Regulation of Softening, Sugar Accumulation, and Antioxidant Metabolism Hongpeng Wang, Dandan Huang International Journal of Horticulture, 2025, Vol. 15, No. 5, 234-241 Enhancing Abiotic Stress Resilience in Horticultural Crops Through Seed Priming: A Comprehensive Review JoséLuis Castañares International Journal of Horticulture, 2025, Vol. 15, No. 5, 242-256 Perceptions, Impacts, and Adaptation to Climate Change Among Farmers in Jumla District, Nepal: A Community Survey Prakash Dhungana, Nishchal Pokhrel, Kiran Puri, Bipin Kumar Neupane, Deependra Subedi, Nitesh Bhattarai, Palak Chhetri, Abhisek Shrestha International Journal of Horticulture, 2025, Vol. 15, No. 5, 257-266
International Journal of Horticulture, 2025, Vol.15, No.5, 208-217 http://hortherbpublisher.com/index.php/ijh 208 Research Article Open Access Effect of Growing Media on Germination and Seedling Characteristics of Tomato (Solanum lycopersicum c.v. Srijana) in Kaski District Manjita Tiwari 1 , Binayak Sigdel 1, Prapti Ghimire 1, Bishal Shrestha 2 1 Faculty of Agriculture, Agriculture and Forestry University, Rampur, Chitwan, 44200, Nepal 2 Department of Horticulture, Agriculture and Forestry University, Rampur, Chitwan, Nepal, 44200, Nepal Corresponding author: manjitatiwari033@gmail.com International Journal of Horticulture, 2025, Vol.15, No.5 doi: 10.5376/ijh.2025.15.0022 Received: 08 May, 2025 Accepted: 10 Sep., 2025 Published: 02 Oct., 2025 Copyright © 2025 Tiwari et al., This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Tiwari M., Sigdel B., Ghimire P., and Shrestha B., 2025, Effect of growing media on germination and seedling characteristics of tomato (Solanum lycopersicum c.v. Srijana) in Kaski district, International Journal of Horticulture, 15(5): 208-217 (doi: 10.5376/ijh.2025.15.0022) Abstract In Nepal, the quality of tomato seedlings is generally low, which often limits overall crop productivity. The use of suitable growing media is crucial for improving seedling performance. The objective of this study was to evaluate the effects of seven different growing media combinations on seed germination and seedling growth of tomato (Solanum lycopersicum) to identify the most suitable medium for producing quality seedlings. The experiment was conducted at the Agriculture Knowledge Centre, Kaski, using a Completely Randomized Design (CRD) with three replications. The seven treatments included: T1 - soil (control), T2 - cocopeat + vermicompost (1:1), T3 - cocopeat + perlite (1:1), T4 - soil + vermicompost (1:1), T5 - soil + FYM (1:1), T6 - soil + cocopeat (1:1), and T7 - conventional medium (soil + sand + FYM in 1:1:1). Among all treatments, T2 (cocopeat + vermicompost) consistently produced the most robust seedlings, with the highest seedling length (20.44 cm), number of leaves (13.8), fresh weight (1.56 g), and dry weight (0.192 g). Although some traits showed maximum values in other media, T2 outperformed overall in terms of seedling vigor and plant stand percentage (98.58%). Based on these findings, a combination of cocopeat and vermicompost (1:1) is recommended as an optimal growing medium for tomato seedling production under mid-hill conditions in Nepal, due to its effectiveness in enhancing seedling quality. Keywords Tomato; Growing media; Seedling vigor; Germination 1 Introduction Tomato (Solanum lycopersicum) is recognized as one of the most extensively cultivated vegetable crops worldwide, ranking second after potatoes in terms of consumption and leading among processed vegetable crops (Sharma et al., 2015; Atif et al., 2016). In addition to its culinary value, tomatoes serve important roles in medicine, cosmetics, and the food industry (Dahliani and Darmayanti, 2023). They are rich sources of potassium, fiber, and essential vitamins such as A, C, and K (Ramasami, 2023). In Nepal, tomatoes hold the position of the third most important vegetable crop; however, their productivity has slightly decreased from 19.14 tons per hectare in 2021 to 18.45 tons per hectare in 2023 (MoALD, 2023). One of the primary causes of the decline in output is the inferior seedling quality, which is a direct consequence of the selection of proper growing media during the nursery phase. Traditional soil-based media generally do not meet the optimal physical and chemical requirements needed for vigorous seedling growth (Ati et al., 2016). Even though various alternative substrates have been studied globally, research specific to Nepal's midhill conditions remains limited. Growing media, which provide structural support and nutrients, are generally classified into organic (e.g., vermicompost, cocopeat, farmyard manure) and inorganic (e.g., perlite, sand) types (TM et al., 2020). Cocopeat, a byproduct of coconut fiber processing, is favored for its excellent water retention and aeration properties (Krishnapillai et al., 2020). Vermicompost, which results from the decomposition of organic matter by earthworms, improves nutrient availability and soil structure (Adhikary, 2012), whereas farmyard manure enhances soil fertility and microbial balance (Gama et al., 2015). Besides that, perlite, a thermally expanded volcanic glass, improves aeration and drainage.
International Journal of Horticulture, 2025, Vol.15, No.5, 208-217 http://hortherbpublisher.com/index.php/ijh 209 An ideal growing medium should have an adequate water-air ratio, adequate drainage, good aeration, low soluble salt concentration, and stronger cation exchange capacity (Bagci et al., 2011; Hazarika et al., 2022). These properties greatly influence root development, germination rates, and overall seedling vigor (Abad et al., 2002; Bilderback et al., 2005; Periasamy and Duraisamy, 2017). Furthermore, the use of well-formulated growing media reduces the risk of soil-borne diseases, promoting healthier seedling emergence (Mathowa et al., 2016). Since this topic has minimal research in individual regions, particularly in Nepal’s midhill areas, such as Kaski District. This study aimed to identify the most effective growing media for tomato seedling production under the mid-hill conditions of Nepal by evaluating seed germination traits and seedling vigor across seven substrate combinations. By determining the optimal substrate formulation, the study seeks to enhance nursery management practices, promote the production of healthy and vigorous seedlings, and ultimately contribute to improved tomato yield and productivity in the region. 2 Materials and Methods 2.1 Experimental site and conditions The experiment was conducted at Birauta-17, Pokhara, Kaski, in a naturally ventilated plastic greenhouse. The site's geographical location was 28° 12' 47.693'' N latitude and 83° 58' 16.596'' E longitude with an elevation of 800 m above sea level (Figure 1). The average temperature and relative humidity inside the greenhouse during the study period were approximately 28 °C to 35 °C and 70% to 80%, respectively. Figure 1 Map of the study area 2.2 Experimental design and treatments The experiment was laid out in a Completely Randomized Design (CRD), with three replications. Seven treatments of growing media i.e., T1 - soil (control), T2 - cocopeat + vermicompost (1:1), T3 - cocopeat + perlite (1:1), T4 - soil
International Journal of Horticulture, 2025, Vol.15, No.5, 208-217 http://hortherbpublisher.com/index.php/ijh 210 + vermicompost (1:1), T5 - soil + FYM (1:1), T6 - soil + cocopeat (1:1), and T7 - conventional growing medium (soil, sand, and FYM in 1:1:1) were tested (Table 1). Srijana, a popular hybrid variety, was selected for the study due to its widespread adoption by farmers in Kaski District. The treated seeds of the Srijana variety were brought from a certified source. The required manures and other inputs were obtained from the local sources and agrovets. The N% was determined by Kjeldhal’s method, available P by Modified Olsen’s method, available K by Flame photometer, and pH by Digital pH meter. Table 1 Nutrient content and pH in different growing media used Treatment Description N% P2O5 (kg/ha) K2O (kg/ha) pH T1 Soil (control) 0.23 321.78 2 567.6 6.9 T2 Cocopeat + vermicompost (1:1) 0.84 510.90 32 259.6 7 T3 Cocopeat + perlite (1:1) 0.06 47.99 27 123.6 7.4 T4 Soil + vermicompost (1:1) 0.28 1 297.01 15 675.6 7 T5 Soil + FYM (1:1) 0.29 467.15 21 843.6 8.4 T6 Soil + cocopeat (1:1) 0.27 245.57 12 867.6 7.3 T7 Conventional growing medium (Soil, sand, and FYM in 1:1:1) 0.11 283.68 5 283.6 8.2 2.3 Nursery management practices Seeds were sown directly in a plastic seedling tray placed inside a greenhouse. For the first few days, the trays were covered by soaked newspaper to create a dark condition for germination. Seedlings were periodically and equally irrigated using a spray bottle with a nozzle, but no additional nutrient elements were supplied. 2.4 Data collection and measurements Data on germination and seedling growth parameters were recorded during the seedling stage. Germination percentage was calculated using the formula: (%) = ×100 This value indicated the proportion of seeds that successfully germinated in each replication. Germination speed was calculated according to the formula described by Mangure (1962), which considers the number of seeds germinated over time: = 1 1 + 2− 1 2 +⋯+ − ( − 1) Where X1, X2...Xn are the cumulative numbers of seeds germinated on days Y1, Y2...Yn after sowing. This parameter reflects the rapidity of germination. Seedling vigor I was determined using the formula given by (Abdul-Baki, 1973): = × ℎ This index provides insight into the early growth potential of seedlings under each treatment. For seedling growth parameters, ten seedlings per replication (30 per treatment) were randomly selected for measurement. Shoot length and root length (in cm) were measured after 24 days of sowing using a standard ruler. From these values, the shoot-to-root length ratio was calculated using the formula:
International Journal of Horticulture, 2025, Vol.15, No.5, 208-217 http://hortherbpublisher.com/index.php/ijh 211 ℎ − − ℎ = ℎ ℎ / ℎ Total seedling length was calculated by summing the shoot and root lengths for each seedling: ℎ = ℎ ℎ + ℎ The number of leaves per seedling was recorded by counting the true leaves (excluding cotyledons) on each of the selected seedlings, and the average was computed. Seedling fresh weight was determined by weighing seedlings using an electronic balance after removing surface moisture with butter paper. The mean fresh weight per seedling was then calculated. Seedling dry weight was measured after oven-drying the sampled seedlings (including roots) at 105 °C for approximately 17 hours. Dry weights were recorded using a digital weighing balance. The shoot-to-root fresh weight ratio was computed using the formula: ℎ − − ℎ ℎ = ℎ ℎ ℎ ℎ ℎ Likewise, the shoot-to-root dry weight ratio was determined using oven-dried values, calculated as: ℎ − − ℎ = ℎ ℎ ℎ Finally, the plant stand percentage was calculated by observing the number of seedlings that remained viable 24 days after sowing. The percentage was derived using the formula: Plant stand percentage = total plant stand total germinated seedlings ×100 2.5 Statistical analysis The observations were recorded on various seed germination and seedling growth parameters. Data were subjected to analysis of variance (ANOVA) to compare media effects. The differences between the means were compared using the least significant difference (LSD) test at a 5% significance level. All analyses were performed using R-studio version 4.4.1. 3 Results and Analysis 3.1 Germination performance Significant differences were observed in germination percentage, speed, and seedling vigor index among the seven tested growing media treatments (Table 2). The highest germination percentage (94.67%) was recorded in T3 (cocopeat + perlite), which was statistically at par with T2 (cocopeat + vermicompost, 90.00%), T6 (soil + cocopeat, 86.67%), T4 (soil + vermicompost, 86.00%), T5 (soil + FYM, 86.00%), and T7 (conventional medium, 84.00%). The lowest germination percentage was observed in the control (T1, 62.00%). Similarly, germination speed and seedling vigor index I followed the same trend, with T6 and T2 showing significantly higher values. The F-test showed highly significant effects (p < 0.001) for all three parameters. 3.2 Seedling morphological traits Different growing media treatments had a significant effect on seedling shoot length, root length, shoot-to-root length ratio, and total seedling length (Figure 2; Figure 3; Figure 4; Figure 5). The highest shoot length (12.99 cm) was observed in T2 (cocopeat + vermicompost), while the shortest (3.29 cm) was recorded in the control (T1). For root length, T6 (soil + cocopeat, 8.73 cm) and T2 (7.44 cm) performed best. The highest shoot-to-root ratio (1.40)
International Journal of Horticulture, 2025, Vol.15, No.5, 208-217 http://hortherbpublisher.com/index.php/ijh 212 was also recorded in T2, statistically at par with T4 (1.39). T2 exhibited the maximum seedling length (20.44 cm), whereas T3 (cocopeat + perlite) and T1 had the lowest values. Table 2 Germination parameters as influenced by different growing media on tomato in Kaski district, 2024 Treatment Germination percentage (%) Germination speed Seedling vigor index I T1 62.00 b 3.52e 566.18d T2 90.00 a 6.41ab 1 841.00a T3 94.67 a 6.16abc 823.29cd T4 86.00 a 4.77d 1058.12bc T5 86.00 a 5.29cd 980.33c T6 86.67 a 6.65a 1 351.60b T7 84.00 a 5.35bcd 923.85c Grand mean 84.19 5.45 1 677.77 CV(%) 7.44 11.33 15.57 SEm (±) 1.36 0.135 36.62 LSD (0.05) 10.97 1.08 293.90 F test *** *** *** Note: CV= Coefficient of variance, LSD= Least Significant Difference, SEm= Standard Error of Mean, Mean followed by different letter(s) within columns are significantly different based on LSD (5%) ***significant at 0.001 P level Figure 2 Shoot length as influenced by different growing media on tomato in Kaski district, 2024 Note: Error bars represent LSD (0.05); Letters indicate significant differences Figure 3 Root length as influenced by different growing media on tomato in Kaski district, 2024 Note: Error bars represent LSD (0.05); Letters indicate significant differences
International Journal of Horticulture, 2025, Vol.15, No.5, 208-217 http://hortherbpublisher.com/index.php/ijh 213 Figure 4 Seedling length as influenced by different growing media on tomato in Kaski district, 2024 Note: Error bars represent LSD (0.05); Letters indicate significant differences Figure 5 Shoot-to-root length ratio as influenced by different growing media on tomato in Kaski district, 2024 Note: Error bars represent LSD (0.05); Letters indicate significant differences 3.3 Biomass characteristics Fresh and dry weights of seedlings were significantly affected by the growing media (Table 3). The highest fresh weight (1.56 g) and dry weight (0.192 g) were observed in T2. Other notable treatments were T4 (soil + vermicompost) and T6 (soil + cocopeat), while T3 (cocopeat + perlite) showed the lowest biomass accumulation. Significant differences were also noted in shoot-to-root fresh weight and dry weight ratios. The control (T1) showed the highest shoot-to-root fresh weight ratio (5.86), followed closely by T2 and T4. T2 also recorded the highest shoot-to-root dry weight ratio (5.34). Table 3 Fresh weight, dry weight, shoot-to-root fresh weight ratio, and shoot-to-root dry weight ratio as influenced by different growing media on tomato seedlings in Kaski district, 2024 Treatment Fresh weight (g) Dry weight (g) Shoot-to-root fresh weight ratio Shoot-to-root dry weight ratio T1 0.37 cd 0.049c 5.86a 4.32ab T2 1.56 a 0.192a 5.80a 5.34a T3 0.17 d 0.019d 4.50ab 4.44ab T4 0.92 b 0.097b 5.72a 4.88a T5 0.32 cd 0.040cd 4.49ab 4.36ab T6 0.56 c 0.059c 3.08b 3.35b T7 0.26 cd 0.035cd 3.50b 3.32b Grand mean 0.59 0.07 4.71 4.29 CV(%) 29.47 20.77 22.14 17.52 SEm (±) 0.042 0.003 1 0.23 0.164 LSD (0.05) 0.307 0.025 5 1.85 1.316 F test *** *** * * Note: CV= Coefficient of variance, LSD= Least Significant Difference, SEm= Standard Error of Mean, Mean followed by different letter(s) within columns are significantly different based on LSD (5%) ***significant at 0.001P level *significant at 0.05P level
International Journal of Horticulture, 2025, Vol.15, No.5, 208-217 http://hortherbpublisher.com/index.php/ijh 214 3.4 Plant stand and leaf development The number of leaves per seedling and plant stand percentage varied significantly among the treatments (Table 4; Figure 6). T2 (cocopeat + vermicompost) produced the highest number of leaves (13.8), followed by T4 (soil + vermicompost, 10.4). The fewest leaves were observed in T3 (3.23). Regarding plant stand percentage, T2 again ranked highest (98.58%), while T1 (control) showed the lowest stand (84.49%). Table 4 Plant stand percentage as influenced by different growing media on tomato seedlings in Kaski district, 2024 Treatment Plant stand percentage (%) T1 84.49 c T2 98.58 a T3 90.16 b T4 89.94 b T5 90.69 b T6 89.28 b T7 92.09 b Grand mean 90.75 CV(%) 2.71 SEm (±) 0.54 LSD (0.05) 4.32 F test *** Note: CV= Coefficient of variance, LSD= Least Significant Difference, SEm= Standard Error of Mean, Mean followed by different letter(s) within columns are significantly different based on LSD (5%) ***significant at 0.001 P level Figure 6 Number of leaves as influenced by different growing media on tomato seedlings in Kaski district, 2024 Note: Error bars represent LSD (0.05); Letters indicate significant differences 4 Discussion The findings of this study demonstrate that the choice of growing media significantly affects seed germination and seedling growth characteristics in tomatoes. Among the treatments, T2 (cocopeat + vermicompost) consistently outperformed the others across various growth parameters. The enhanced performance of T2 can be attributed to physiological and substrate-related mechanisms. Seed germination requires adequate water, oxygen, and temperature. Water softens the seed coat (Kumar et al., 2016), oxygen supports aerobic respiration to fuel early growth, and warm temperatures accelerate enzymatic activity in seeds (Hazarika et al., 2022). Cocopeat and vermicompost possess favorable physical properties, such as high porosity and moisture retention, which ensure adequate oxygen diffusion and water availability for seedling emergence (Alam et al., 2014).
International Journal of Horticulture, 2025, Vol.15, No.5, 208-217 http://hortherbpublisher.com/index.php/ijh 215 Vermicompost further contributes to seedling development due to its balanced nutrient composition, particularly the availability of phosphorus and potassium, and bioactive substances that stimulate root and shoot growth (Mahala and Sharma, 2020; Ramasami, 2023). These characteristics result in vigorous germination and growth compared to inert media such as perlite. In the case of T3 (cocopeat + perlite), although high porosity supports aeration, the lack of nutrients limits shoot development, as perlite contains negligible amounts of essential macronutrients (Hazarika et al., 2022). The improved root and shoot lengths in cocopeat + vermicompost media may be due to the enhanced mobilization of nutrients and moisture, facilitating better root development and increased photosynthate accumulation. This supports greater biomass production, as indicated by the highest fresh and dry weight in T2 (Anjanawe et al., 2013). In contrast, the control and cocopeat + perlite media provided suboptimal nutrition, resulting in lower biomass. The compactness of the control medium likely hindered root elongation, while cocopeat + perlite lacked key nutrients despite sufficient moisture availability. Biomass partitioning, as shown by the shoot-to-root biomass ratio, also favored T2, indicating that nutrient-enriched organic media encouraged both below- and above-ground growth. Organic amendments like vermicompost enhance porosity and water retention, thereby improving nutrient uptake and translocation to shoots (Gogoi and Sarma, 2015). This is consistent with Zhang et al. (2011) and Anjanawe et al. (2013), who reported a similar trend in nutrient-enriched substrates. The number of leaves per seedling, another important indicator of seedling vigor, was also highest in T2, followed by T5 (soil + vermicompost). This trend is likely due to the contribution of vermicompost’s nutrients, which support vegetative growth. Adiloğlu et al. (2018) and Lohani (2023) observed that vermicompost application increases leaf number, area, and biomass. These results align with Mahala and Sharma (2022), Periasamy and Duraisamy (2017), and Panthi et al. (2023), who reported significant increases in leaf production with vermicompost-based growing media. The superior performance of the cocopeat + vermicompost mixture aligns with studies conducted in various crops. Periasamy and Duraisamy (2017) and Atif et al. (2016) observed better seedling emergence and growth in tomatoes under vermicompost-based media. Cocopeat’s beneficial pH and electrical conductivity also support early root development, as observed in nutmeg seedlings by Abirami et al. (2010). Kalaivani and Jawaharlal (2019) noted similar effects in tomato root development due to better nutrient and water retention in cocopeat. Hazarika et al. (2022), Mathowa et al. (2016), and Panthi et al. (2023) also found positive effects of cocopeat and vermicompost on seedling development. The nutrient-rich environment promotes cell division and elongation, thereby contributing to greater seedling mass and vigor. Mualchin and Verma (2022) and Mahala and Sharma (2022) also documented reduced disease incidence and improved potassium uptake in cocopeat + vermicompost media, supporting the current findings. 5 Conclusion The findings of this study support that the choice of growing medium has a significant influence on the germination and early growth of tomato (Solanum lycopersicum cv. Srijana) seedlings. Among the tested media, the combination of cocopeat and vermicompost (1:1) consistently outperformed others in promoting both germination efficiency and seedling vigor. Despite the fact that cocopeat mixed with perlite improved germination percentage, it did not support seedling development as effectively, likely due to its lower nutrient level. In conclusion, it is recommended that the cocopeat-vermicompost mix is the most suitable growing medium for tomato seedling production in Kaski district's environmental conditions. Its use can lead to the development of stronger, healthier seedlings, higher transplanting success rates, and ultimately increased tomato yields. Future studies should examine the economic practicality and potential application of this mix across different agro-ecological zones in Nepal.
International Journal of Horticulture, 2025, Vol.15, No.5, 208-217 http://hortherbpublisher.com/index.php/ijh 216 Authors’ contributions MT conceived and designed the study, performed the experiments, collected the data. Interpreted the results, and wrote the manuscript. BSi assisted with data analysis, statistical interpretation, and the preparation of figures and tables. PG contributed to the literature review and helped gather relevant resources for manuscript development. BS supervised the study, provided critical feedback, and helped enhance the manuscript through suggestions and revisions. All authors read and approved the final manuscript. Conflict of Interest Disclosure The authors affirm that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest. 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International Journal of Horticulture, 2025, Vol.15, No.5, 218-233 http://hortherbpublisher.com/index.php/ijh 218 Research Report Open Access Formation Mechanisms of Stem Sweetness and Texture in Fresh-Eating Sugarcane: Sugar Metabolism, Cell Wall Modification, and Gene Expression Regulation Wenzhong Huang 1, Kaiwen Liang 2 1 Biomass Research Center, Hainan Institute of Tropical Agricultural Resouces, Sanya, 572025, Hainan, China 2 Resource Utilization Center, Hainan Institute of Tropical Agricultural Resources, Sanya, 572025, Hainan, China Corresponding author: kaiwen.liang@hitar.org International Journal of Horticulture, 2025, Vol.15, No.5 doi: 10.5376/ijh.2025.15.0023 Received: 01 Jun., 2025 Accepted: 15 Sep., 2025 Published: 08 Oct., 2025 Copyright © 2025 Huang and Liang, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Huang W.Z., and Liang K.W., 2025, Formation mechanisms of stem sweetness and texture in fresh-eating sugarcane: sugar metabolism, cell wall modification, and gene expression regulation, International Journal of Horticulture, 15(5): 218-233 (doi: 10.5376/ijh.2025.15.0023) Abstract Fresh sugarcane is widely loved by consumers for its high sugar content and excellent texture. The sweetness and texture of the stems are the core indicators of its quality evaluation. This study systematically reviewed the main mechanisms of sweetness and texture formation of fresh sugarcane stems, focusing on the role of key enzymes such as SuSy, SPS and invertase in the sugar metabolism pathway, the regulation of sugar transporters such as SWEET and SUT, and the accumulation dynamics of sucrose, glucose and fructose at different developmental stages. At the same time, the functional mechanisms of cell wall polysaccharide structure, lignin synthesis, and cell wall modification enzymes such as swollenin and pectinase in texture formation were also systematically explained. At the gene expression level, this study explored the spatiotemporal expression patterns of sugar metabolism and cell wall-related genes and the synergistic effects of transcription factors such as NAC, MYB, and bZIP in regulating quality traits, analyzed the effects of hormones (auxin, gibberellin, ethylene) and environmental factors (light, temperature) on related pathways, and finally compared the molecular regulation differences of different varieties such as purple skin and green skin, tender and crisp and crude fiber, in order to provide theoretical support for the molecular breeding of fresh sugarcane and provide direction for the future of multi-omics and precision breeding. Keywords Fresh sugarcane; Sweetness; Texture; Sugar metabolism; Cell wall modification; Gene expression 1 Introduction As a high-sugar crop with both edible value and economic benefits, fresh sugarcane (Saccharum spp.) is widely cultivated in many provinces and regions in southern my country (Chen et al., 2022). Its main characteristics include high sucrose content, rich juice, crisp taste, and easy peeling. It is a special economic crop that combines fruit use and ornamental (Liu et al., 2024). With the improvement of residents' consumption level and the enhancement of health awareness, the demand for fresh sugarcane in the domestic and foreign markets continues to expand, and the added value of the industry has increased significantly, which has positive significance for optimizing the planting structure and promoting farmers' income. In the quality evaluation system of fresh sugarcane, sweetness and texture are the two most critical indicators. Sweetness directly determines the edible quality and consumer preference, and its level is mainly regulated by the content of sucrose, glucose and fructose in the stem; while texture is related to the chewing experience, which is jointly determined by factors such as cell wall structure, lignin content and cell wall enzyme activity (Liu et al., 2024). However, in actual breeding, high sweetness is often accompanied by an increase in the degree of tissue lignification, which reduces the palatability of texture. Therefore, in-depth analysis of the synergistic regulation mechanism of sweetness and texture is of great scientific and practical significance for breaking the negative correlation between quality traits and achieving the breeding goal of "sweet and crisp" high-quality sugarcane (Huang and Li, 2024). This study will systematically sort out the physiological and molecular mechanisms of sweetness and texture formation in fresh sugarcane stalks, and analyze the core contents such as sugar metabolism-related enzymes
International Journal of Horticulture, 2025, Vol.15, No.5, 218-233 http://hortherbpublisher.com/index.php/ijh 219 (such as SuSy, SPS, invertase), sugar transport systems (such as SWEET, SUT), cell wall polysaccharide structure and modification enzymes (such as expansin, XTH, pectinase), etc., focusing on the gene expression regulation mechanism affecting sweetness and texture formation, including the spatiotemporal expression pattern of key genes, the role of transcription factors such as NAC/MYB/bZIP, and the regulatory role of plant hormones and environmental factors (such as light and temperature). Finally, through comparative studies among typical varieties, attempts are made to reveal the molecular basis of the formation of different types of sugarcane quality traits from the perspective of transcriptome, in order to provide theoretical support for molecular breeding and precise improvement of high-quality fresh sugarcane. 2 Sugar Metabolism and Accumulation 2.1 Key enzymes: roles of SuSy, SPS, and invertases in sucrose synthesis and breakdown Sugarcane is famous for its rich sucrose content in its stems, and its sweetness essentially depends on the high concentration of sucrose accumulated in the pith cells of the stems. This process is strictly regulated by a series of enzymatic reactions, among which sucrose phosphate synthase (SPS), sucrose synthase (SuSy), and invertase are the key enzymes for sucrose synthesis and decomposition. SPS catalyzes the synthesis of uridine diphosphate glucose (UDP-Glc) and fructose-6-phosphate produced by photosynthesis into sucrose-6-phosphate, which is then dephosphorylated by sucrose-6-phosphate phosphatase to produce sucrose. It is the rate-limiting enzyme in the sucrose biosynthesis pathway (Khan et al., 2023). Studies have shown that the SPS enzyme activity level in different sugarcane varieties is significantly positively correlated with their final sucrose content, and high-sucrose varieties tend to show stronger SPS activity. SuSy can reversibly catalyze between sucrose and UDP-Glc. On the one hand, it works with SPS in the direction of sucrose synthesis, and on the other hand, it provides substrates for cellular respiration and the construction of polysaccharides such as cellulose in the direction of sucrose decomposition. There are usually multiple SuSy isoenzymes in crops such as sugarcane, with spatiotemporal expression patterns to adapt to the needs of sucrose synthesis or decomposition at different developmental stages. In contrast, invertases are responsible for irreversibly hydrolyzing sucrose into glucose and fructose, including acid invertases in the vacuole and neutral invertases in the cytoplasm. High invertase activity often means that sucrose is continuously broken down into reducing sugars, which provides energy and carbon skeletons in rapidly growing young tissues, but excessive invertase activity reduces the net accumulation rate of sucrose in the stem (Mehdi et al., 2024b). Comparative tests of high-sugar and low-sugar sugarcane varieties confirmed this difference in key enzyme activity: the SPS activity in the stems of high-sugar varieties (such as GT35) was significantly higher than that of low-sugar varieties, while the invertase activity was relatively low, so the sucrose content in the stem cells was significantly higher than that of low-sugar varieties. On the contrary, in low-sugar varieties, neutral and acid invertase activities were stronger, resulting in more sucrose being decomposed into glucose and fructose, and sucrose accumulation in the stems was limited. This shows that the efficient expression of synthases such as SuSy and SPS and the moderate decrease in invertase activity are conducive to the accumulation of sucrose in sugarcane stems (Niu et al., 2019). On the other hand, the sucrose decomposition enzyme system cannot be too low, otherwise the stem cells will lack sufficient respiratory substrates and metabolic regulation, which will inhibit plant growth. Therefore, sugarcane achieves a carbon distribution balance between the source (leaf photosynthetic products) and the sink (stem sugar storage) by finely regulating the expression of sucrose synthesis and decomposition enzymes, so as to meet growth needs and maximize sugar storage (Mehdi et al., 2024a). 2.2 Sugar transport and storage: function of SWEET, SUT, and tonoplast transporters The sucrose produced by photosynthesis needs to be transported through sieve tube assimilates to reach "sink" organs such as stems and stored in intracellular vacuoles, which is an important mechanism for the accumulation of high sugar content in sugarcane. In the long-distance transport of sucrose, SWEET and SUT family transporters play a key role. SWEET is a class of sucrose transmembrane export proteins that mediate the release of sucrose from source tissue cells into the intercellular space, and then is actively loaded by sucrose transporters (SUTs) in phloem companion cells and sieve tubes, thereby realizing the transport of sucrose from leaves to stems (Chen et
International Journal of Horticulture, 2025, Vol.15, No.5, 218-233 http://hortherbpublisher.com/index.php/ijh 220 al., 2022). A variety of SUT and SWEET genes have been identified in sugarcane, among which SWEET13c is mainly highly expressed in mature mesophyll cells, promoting the export of photosynthetic product sucrose to the phloem, while SWEET4a/4b is mainly expressed in stem tissues, participating in the unloading of sucrose from sieve tubes to surrounding storage cells. On the "sink" side, sugarcane proteins such as SUT1 and SUT4 are located on the sieve tube companion cells and parenchyma cell membranes of stem tissues, responsible for absorbing sucrose from the intercellular space into the cells. In addition to plasma membrane transport, stem medullary parenchyma cells also pump sucrose into the vacuole for storage through the sucrose/H+ antiporter on the vacuole membrane. For example, Arabidopsis vacuolar sugar transporter TMT1/2 can actively transport glucose and sucrose into the vacuole, and there is a highly homologous Tonoplast Sugar Transporter (TST) family in sugarcane that performs similar functions. These transport processes increase the sucrose concentration in the vacuole of sugarcane stem cells, which can be as high as more than 50% of the dry weight, which is the source of the high sweetness of sugarcane (Mehdi et al., 2024b). It should be pointed out that the accumulation of sucrose in the vacuole will increase the osmotic pressure of the cell. In order to maintain balance, sugarcane often increases the storage of reducing sugars such as glucose and fructose in the vacuole. Studies have found that transgenic sugarcane with increased sucrose synthase SPS activity also increases the acid invertase activity in its leaves, and the glucose and fructose content increases. This may be a compensatory mechanism: plants adjust excessive sucrose concentrations by moderately increasing sucrose decomposition to avoid feedback inhibition of photosynthesis and osmotic stress. Therefore, the long-distance transport and intracellular storage of sugars is a dynamic equilibrium process, and the sugar signal sensing and transporter expression of both the source and the sink are precisely regulated to achieve effective redistribution and efficient accumulation of sucrose in sugarcane. 2.3 Dynamic balance of sucrose, glucose, and fructose in different maturation stages The ratio of sucrose, glucose and fructose in sugarcane stalks changes significantly from the elongation stage to the maturity stage. In tender stems and elongation tissues, the invertase activity is high, and sucrose is quickly decomposed and utilized, so the content of reducing sugars (glucose, fructose) is relatively higher and the sucrose concentration is lower. As internodes mature, photosynthate input increases and stem tissue growth slows down, the activity of synthases such as SPS and SuSy reaches a peak at the mature stage, while the activity of acidic and neutral invertases decreases significantly, causing sucrose to accumulate in large quantities in mature stem cells. Especially in the late stage of sugarcane growth, the decrease in the activity of neutral invertase (NI) in the stem is considered to be one of the main reasons for the high accumulation of sucrose (Khan et al., 2021; Martins et al., 2024). The distribution pattern of neutral invertase activity in mature sugarcane internodes is closely related to the sugar gradient - in the mature zone at the base of the internode, lower NI activity is accompanied by higher sucrose concentration, while in the tender zone at the top of the internode, higher NI activity leads to an increase in the proportion of reducing sugar. Recent experimental data also support this dynamic: the high-sugar variety GT35 has a much higher sucrose content in mature stem segments than the low-sugar variety B8, while the glucose and fructose contents are lower. Correspondingly, the activities of SPS and cell wall invertase (CIN) in mature stem segments of GT35 are significantly higher than those of B8, while the activities of invertase and SuSy decomposition are lower. This indicates that in the late stage of sugarcane stalk development, the enzymes that synthesize sucrose maintain high activity, while the enzymes that decompose sucrose are feedback inhibited, allowing sucrose to accumulate continuously in the cells. In addition, the source-sink signal regulation of different varieties is also different: heat-resistant varieties can maintain high SPS and SuSy expression at high temperatures, so that sucrose can still accumulate in the late growth period, while sensitive varieties have a sharp drop in enzyme activity under heat stress, resulting in blocked sugar accumulation (Mehdi et al., 2023). It can be seen that the dynamic balance of sucrose, glucose and fructose in sugarcane stems depends on the coordinated changes of multiple enzymes under developmental stages and environmental conditions. The large accumulation of sucrose in the mature stage is the result of the combined effects of multiple metabolic regulations.
International Journal of Horticulture, 2025, Vol.15, No.5, 218-233 http://hortherbpublisher.com/index.php/ijh 221 3 Cell Wall Structure and Texture Formation 3.1 Composition of cell wall polysaccharides: cellulose, hemicellulose, pectin Cellulose, hemicellulose and pectin each play their own role in the sugarcane cell wall, and together determine the mechanical properties and degradability of the cell wall. The cellulose content directly affects the stiffness of the stalk - the more and denser the cellulose microfibrils, the greater the tensile and shear strength of the cell wall, and the tougher and harder the tissue is to chew (Liu et al., 2024). Hemicellulose (mainly arabinoxylan) fills the pores between cellulose microfibrils and cross-links with them. Its presence increases the rigidity of the cell wall, but also reduces the degradation efficiency of the fiber in chemical pretreatment and enzymatic hydrolysis. Lignin is deposited on the cellulose-hemicellulose network, making the cell wall hydrophobic and stronger, and plays a "gluing" and reinforcement role on the cell wall (Buckeridge et al., 2019). The degree of lignification of sugarcane stalks gradually increases during maturity, and the wall thickness increases. Although this improves the ability to resist lodging, it increases the chewing resistance of the stem meat fiber. Therefore, sugarcane is usually harvested at the right time of maturity when lignification is not too serious, so as to take into account both sugar content and texture (Chen et al., 2022). Pectin in the primary wall also affects the softness of the texture. Pectin is composed of polygalacturonic acid as the main chain, and its degree of esterification and cross-linking determines the hardness of the middle layer of the cell wall: highly methylated pectin chains are soft and sticky, which is conducive to intercellular adhesion; after demethylation by pectin methylesterase, pectin is easily cross-linked with calcium ions to form an "egg box" structure, making the middle layer hard and brittle. Some fresh sugarcane varieties may have a higher degree of pectin methylation, so the intercellular binding force is moderate, and it is neither too loose nor too hard and brittle when chewing. These hypotheses still need further experimental verification, but from the research on other fruit tissues, pectin modification does play an important role in the softness and hardness of the taste (Tipu and Sherif, 2024). 3.2 Lignin biosynthesis and its influence on chewing resistance Lignin content is considered to be one of the key factors affecting the chewing difficulty of sugarcane stalks. High-fiber and high-lignin stalks are often thick and hard, making them difficult to chew and break; while low-lignin tender stalks are easy to chew into dregs. Plants enhance mechanical strength to resist adverse environments by regulating the content of cellulose, hemicellulose and lignin in cell walls. Comparisons between sugarcane varieties show that fiber content (mainly representing the total amount of cellulose and lignin) is significantly positively correlated with stalk toughness, that is, varieties with high fiber content have harder stalks, more chewy and less likely to be chewed. Therefore, reducing lignin synthesis is a potential way to improve the texture of sugarcane. Genetic engineering intervention has proved this: using site-directed mutagenesis technology to knock out the key gene caffeic acid-O-methyltransferase (COMT) in sugarcane lignin synthesis can reduce the lignin content of transgenic sugarcane by about 20%, while increasing the sugar accumulation level, and even increasing the enzymatic saccharification rate of fiber raw materials by more than 40%. More importantly, this lignin-reduced sugarcane mutant did not show obvious growth defects or yield reduction in the field, indicating that moderate reduction of lignin can soften the stem without compromising the mechanical strength of the plant, providing a genetic target for improving the texture of sugarcane (Kannan et al., 2018). In addition to regulating lignin content through genetic means, agricultural measures can also affect the degree of stem lignification. For example, silicon can be deposited in the cell wall of sugarcane stems to form siliceous bodies, thereby improving the lodging resistance and insect resistance of the stems. Adding silicon fertilizer often makes the stem wall thicker and harder, which is beneficial for sugarcane but not for the texture of fresh sugarcane, and needs to be weighed in cultivation (Wang et al., 2020). Reducing the relative content of lignin and cellulose and optimizing the composition of cell walls are one of the important ideas for improving the chewability of sugarcane. In actual breeding, by screening materials with weaker lignin synthesis or using molecular means to inhibit the expression of some lignin pathway genes, new sugarcane varieties with softer fibers and easier chewing may be obtained.
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