Effects of Nitrogen Concentration in Fertilizer Solution on Vegetative Growth, Flowering, and Fruit Quality in Passion Fruit

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(1)Trop. Agr. Develop. 64 （4）：161 － 164，2020. Effects of Nitrogen Concentration in Fertilizer Solution on Vegetative Growth, Flowering, and Fruit Quality in Passion Fruit Tomohiro KONDO1, 2, *, Kakeru KOGA1, and Daiki SATO1 1. Faculty of Regional Innovation, University of Miyazaki, 1-1 Gakuen Kibanadainishi, Miyazaki 889-2192, Japan. 2. Present affiliation: Graduate School of Agriculture, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-8502, Japan. Abstract Demand for low acid passion fruit has been increasing, and cultivation methods, such as fertilizer management to produce low acid fruit is required. And so, the effects of N concentration in fertilizer solution on fruit quality were determined in this study. Fertilizer solutions, containing 6, 13, 25, 50, and 100 mM N, were applied to two-year-old passion fruit plants in sand culture. Artificial pollination was conducted and the number of fruits per plant was regulated to be six. Length of the fruit-bearing vine and leaf, SPAD value, stomatal conductance, and leaf mineral contents were measured. Just after harvest, fruit weight, and dimensions were measured and the days after pollination to harvest (DAP) was recorded. After a 10-day-storage at 25 ° C, titratable acidity (TA), total soluble solid (TSS), and juice content were measured. Vegetative growth and stomatal conductance increased as N concentration increased up to 50 mM. The number of flowers increased as N increased. Leaf N content increased as N concentration increased. Leaf Ca contents at 25 and 50 mM were higher than those in other treatments, while P, K, and Mg contents were not affected. TA decreased as N increased, while TSS was not affected. Fruit weight and dimensions were not affected, while juice content increased as N increased. DAP increased as N increased. Then, fruit quality was the highest at 100 mM, when leaf N content was 6.7 %. At 100 mM N treatment, DAP elongation might decrease acidity. Key words: Citric acid, Leaf nitrogen content, Nitrogen fertilizer, SPAD value, Stomatal conductance. Introduction. though its influence on vegetative growth and yield were determined (Menzel et al., 1991; 1993). Shibuya (1997). Passion fruit is a sub-tropical fruit which is native. reported that fruit acidity decreased as N fertilizer. to Latin America. The fruit has high sugar and citric. increased up to 500 kg/ha/year, while the plant N. acid content and unique scent. The main production. status, such as leaf N content, was not measured and so,. countries are located in Latin America, such as Brazil,. it is difficult to apply the results to other places where. Peru, Colombia, and Ecuador. Passion fruit was mainly. soil and climate conditions are totally different.. used for processing, such as juice materials, but fresh. In this study, the relationship between leaf N. consumption has been increasing recently. In Brazil,. content and fruit acid content was determined. The. before the 1990’s about 70 % of fruit was used for. findings should be available to produce low acid passion. processing, mainly for juice (Meletti, 2011), but recently. fruit, regardless of soil or climate condition.. 60 % of it has been for fresh consumption (Ferraz and Lot, 2007). Low acid content is demanded for fresh. Materials and Methods. consumption, and the price of such fruit is extremely. Two-year-old hybrid passion fruit (Passiflora edulis. high. Hence, cultivation methods for producing high. Sims × P. edulis f. flavicarpa Deg. cv. ‘Summer Queen’). quality fruit with low acid content is now demanded.. plants were grown in a greenhouse at the University of. Recently, effects of mineral nutrients, fertilizer. Miyazaki (131.4 ° E, 31.8 ° N). Twenty-eight plants were. management, and soil pH on fruit quality including. propagated by cutting in September 2016 and transplant-. acid content have been determined; NH4-N dominant. ed to 1/2000-a Wagner pots with river sand in December.. fertilizer (Kondo and Higuchi, 2013a), decreased P and. The pots were spaced in row at 90 cm between pots and. K fertilizer (Kondo and Higuchi, 2013b; 2013c), and. 60 cm between rows. CaCO3 and MgCO3 were applied,. acidic soil (Niwayama and Higuchi, 2019) are effective. 2.5 g each, to prevent a pH decline and to provide Ca. for producing low acid fruit. However, the amount of N. and Mg nutrients on the transplanting day and two more. fertilizer effect on fruit quality is not fully determined,. times in April 2017 and 2018. A fertilizer solution of 1000 mL containing 12.5 mM NH4-N, 12.5 mM NO3-N, 7.3 mM. Communicated by M. Yamamoto Received Feb. 7, 2020 Accepted May 8, 2020 * Corresponding author kondo.tomohiro.0z@kyoto-u.ac.jp. K, 1.0 mM P, 57 µM Fe, 0.6 µM Cu, 0.9 µM Zn, 9.9 µM Mn, 47.2 µM B and 0.08 µM Mo was applied appropriately until May 29, 2018, and the plants were irrigated daily. In the greenhouse, the minimum temperature was kept at.

(2) 162. Trop. Agr. Develop. 64 （4）2020. 10 ° C during the winter and the maximum temperature. maximum quantum efficiency of photosystem II (Fv/. was not regulated. The plants were trained hedge as. Fm) was also measured, using a portable chlorophyll. described by Kondo and Higuchi (2011). Fruit-bearing. fluorometer (OS-30P, Opti-science Inc., NH, USA) at. vines were thinned to three per plant. The fruit-bearing. 2000-2100 h.. vines, used in 2017, were then cut back on May 27, 2018,. Just after harvest, fruit weight and the dimensions. and newly emerged vines were used as fruit-bearing. were measured, and peel color was estimated visually on. vines in that year. From August, the fruit-bearing vines. 5 levels (1: pale green to 5: dark purple), and the number. that had reached ground level were cut near the ground.. of days after pollination to harvest (DAP) was recorded.. Treatment was carried out using fertilizer solutions,. After a 10-day-storage at 25 ° C, peel color was estimated. containing five different N concentrations as 6, 13, 25, 50,. again and wrinkle degree was estimated visually on 5. and 100 mM, from May 29 to September 17. Ammonium. levels (1: no wrinkle to 5: severe wrinkle). Total soluble. nitrate was used as the source of N. Concentrations of. solid (TSS), titratable acidity (TA) and percentage. other nutrients were the same as in the solution before. of juice content per fruit were measured by the same. the treatment. These fertilizer solutions of 1000 mL per. methods as described by Kondo and Higuchi (2011).. plant were applied twice a week. Replications of plants. The data were analyzed by analysis of variance,. applied 6, 25, and 100 mM N were six and others were. and the statistical differences among treatments were. five.. subjected to further analysis using Tukey’s test. The Flowering occurred from June 18 to July 10, and ar-. significance level was p < 0.05. The data of fruit quality. tificial pollination was conducted. On the flowering day,. at 6 and 13 mM treatment were little, so only the data at. the number of flowers per plant was counted, and just. 25, 50, and 100 mM was analyzed.. after the flowering period, the number of fruits per plant was counted. Then, the number of fruits per plant was. Results and Discussion. regulated to be six. Fruit thinning was not conducted. Length of the fruit-bearing vine increased as N. for plants which had fewer than six fruits. To retain the. concentration of the fertilizer solution increased up to. fruit on the vines to prevent them from dropping on the. 50 mM (Fig. 1). SPAD value and length of leaf on the. ground, each fruit peduncle was tied to the vine with. fruit-bearing vine also increased as N concentration. thread works. Mature fruits that were abscised from. increased up to 50 mM (Fig. 2; Table 1). Stomatal con-. vine were harvested.. ductance also increased as N concentration increased. Relative chlorophyll content (SPAD value) of the. up to 50 mM. Photosynthetic rate should increase as N. leaf on the fruit-bearing vine was measured monthly,. concentration increases up to 50 mM, because SPAD. using a chlorophyll-meter (SPAD-502, Konica Minolta. value and stomatal conductance increased. Menzel et al.. Sensing, Inc., Osaka, Japan). Length of the fruit-bearing. (1991) and Kondo and Higuchi (2012) also reported that. vine was measured June 26, and July 27. After July 27, the. vegetative growth and photosynthetic rate increased as. measuring was discontinued because the fruit-bearing. N concentration in fertilizer solution increased. Fv/Fm. vine that had reached ground level was cut. On July 27,. increased as N concentration increased up to 25 mM.. the leaf on the fruit-bearing vine was sampled for analy-. Fv/Fm values of undamaged leaves have been reported. sis of leaf N, P, K, Ca, and Mg contents. The sampled. to range from 0.8 to 0.83, regardless of plant species. leaf was oven-dried at 70 ° C for 3 days and grounded.. (Bjorkman and Demmig, 1987). In this study, at 6 and. After wet-ashing with nitric acid, leaf K, Ca, and Mg. 13 mM treatments, Fv/Fm values were below the range,. contents were determined using an atomic absorption. suggesting the plants had suffered slight damage,. spectrophotometer (AA-6200, Shimadzu, Kyoto, Japan),. though not critical for survival. N deficiency caused. and P content was determined by molybdenum blue. photoinhibition and Fv/Fm was also decreased in maize. method (Murphy and Riley, 1962). The ground leaf was. (Lu and Zhang, 2000).. also analyzed for N content with an NC analyzer (Vario. The number of flowers per plant increased as N. Max CHN, Elementar Analysensysteme GmbH, Ost,. concentration increased (Table 1). Menzel et al. (1991). Germany).. and Kondo and Higuchi (2012) also reported that the. On August 13, length of leaf on the fruit-bearing vine. flower number increased as N increased. Although the. was measured. On the same day, stomatal conductance. increase of flowers was partly due to the increase of. was measured, using a leaf porometer (SC-1, Decagon. nodes on the fruit-bearing vine, the increase of flowers. Devices Inc., Pullman, WA, USA) at 1000-1130 h, and. was more than that of the nodes. At 6 and 13 mM treat-.

(3) 163. Kondo et al.: Effects of nitrogen on passion fruit quality 200. 80 6 13 25 50 100. 150. 100. SPAD value. Vine length (cm). N concentration in fertilizer solution (mM). 50. 60. 40 N concentration in fertilizer solution (mM). 6 13 25 50 100. 20. 0. 0 6/26 7/26 8/27 5/29 6/26 7/26 Month/Day Month/Day Fig. 1. Effects of nitrogen concentration in fertilizer solution on length of Effectsofofnitrogen nitrogen concentration solution on Fig. 1. the Effects of nitrogen in fertilizer Fig.Fig. 2. 2.Effects concentrationininfertilizer fertilizer solution fruit-bearing vines concentration in 'Summer Queen' passionsolution fruit. SPAD value in 'Summer Queen' passion fruit. fruit. on length of the fruit-bearing vines in ‘Summer on SPAD value in ‘Summer Queen’ passion. 5/29. Queen’ passion fruit. Table 1. Effects of nitrogen concentration in fertilizer solution on leaf length, stomatal conductance, maximum quantum efficiency of photosystem II (Fv/Fm), and flower and fruit number in ‘Summer Queen’ passion fruit. N concentration in nutrient solution (mM). Stomatal conductance 2 -1 (mmol・m-・ s ). Leaf length (mm). 6 13 25 50 100. 148 170 181 191 188. c b ab a a. 245 301 474 947 893. c bc bc a a. Fv/Fm 0.78 0.77 0.80 0.82 0.81. bc c abc a ab. Flower number per plant. Fruit number per plant. 0.8 0.0 7.5 9.6 10.3. 0.5 0.0 7.2 8.4 8.0. b b a a a. b b a a a. Leaf length, stomatal conductance and Fv/Fm were measured on August 13. Different letters with columns indicate statistical differences by Tukey’ s test at p<0.05.. Table 2. Effects of nitrogen concentration in fertilizer solution on titratable acidity (TA), total soluble solid content (TSS), sugar/ acid ratio, juice content, fruit weight, dimensions, peel color, the wrinkle degree, and the number of days after pollination to harvest (DAP) in ‘Summer Queen’ passion fruit. N concentration in nutrient solution (mM). TA (%). TSS (%). 25 50 100. 2.30 a 1.92 b 1.67 c. 17.6 a 17.9 a 18.0 a. Juice Sugar/acid content ratio (%) 7.7 c 9.4 b 11.0 a. 37.8 b 42.7 a 43.2 a. Peel color 1 Weight Length Diameter (g) (mm) (mm) 85.3 a 84.1 a 79.8 a. 63.0 a 62.4 a 62.8 a. 58.4 a 59.2 a 58.4 a. At harvest. After 10-daystorage. Wrinkle degree 2. DAP. 3.2 a 3.5 a 3.6 a. 5.0 a 5.0 a 5.0 a. 1.4 b 2.6 a 2.9 a. 50.9 c 56.3 b 62.4 a. Different letters within columns indicate statistical differences by Tukey’s-test at p < 0.05. TA, TSS, sugar/acid ratio, and juice content were measured after 10-day storage at 25 ° C. 1 : Peel color was estimated visually on five levels (1: pale green to 5: dark purple), at harvest and after 10-day storage at 25 ° C. 2 : Wrinkle degree was estimated visually on five levels (1: no wrinkle to 5: severe wrinkles), after 10-day storage at 25 ° C.. ments, the number of fruits were lower than those at. during after-ripening. Peel color was not affected by. other 3 treatments.. N concentration. DAP increased as N concentration. Fruit quality was analyzed except for 6 and 13 mM. increased. TA decreased as matter production per fruit. treatments, because the fruit number at these treatments. increased (Kondo and Higuchi, 2011). At 25 mM treat-. were only three and one respectively. TA decreased. ment, SPAD value and stomatal conductance were lower. and sugar acid ratio and juice content increased as N. than those at other treatments and so, photosynthesis. concentration increased, while TSS was not affected. rate should be lower, and hence TA might increase.. (Table 2) and so, with high N fertilizer, expensive fruit. On the other hand, though the differences of SPAD. for fresh consumption can be produced. Fruit weight. value and stomatal conductance between 50 and 100. and dimensions were not affected by N concentration.. mM treatments were not detected, TA at 100 mM treat-. As N concentration increased, the fruit tended to winkle. ment was lower than that at 50 mM treatment. Lower.

(4) 164. Trop. Agr. Develop. 64 （4）2020. Table 3. Effects of nitrogen concentration in fertilizer solution on leaf mineral contents in ‘Summer Queen’ passion fruit. N concentration in nutrient solutions (mM) 6 13 25 50 100. Leaf mineral contents N (%) 1.50 1.70 3.09 4.89 6.66. d d c b a. P (%) 0.22 0.18 0.20 0.17 0.18. a a a a a. K (%) 1.76 1.83 1.35 1.49 1.63. a a a a a. Ca (%) 0.82 0.65 1.33 1.46 0.71. b b a a b. Mg (%) 0.32 0.27 0.38 0.37 0.27. a a a a a. Different letters with columns indicate statistical differences by Tukey’s test at p<0.05.. TA at 100 mM might be due to the elongation of DAP.. increased as leaf N content increased up to 3.1 %, and TA. In general, TA decreased as DAP increased in passion. decreased and fruit quality increased as leaf N content. fruit (Macha et al., 2006; Kondo and Higuchi 2011). In. increased up to 6.7 %.. this study, because of the elongation of DAP at 100 mM treatment, TA might be lower than that at 50 mM. DAP increased with low water potential irrigation water, including sodium chloride solution in passion fruit (Kondo and Higuchi, 2018). DAP elongation was also observed in our present experiment with the highest N solution, 100 mM treatment. Leaf N content increased as N concentration of fertilizer solution increased; at 50 and 100 mM treatments leaf N content was 4.9 % and 6.7 % respectively (Table 3). Leaf Ca content was higher at 13 and 25 mM treatments than those at others. Leaf P, K, and Mg contents were not affected by N concentration. Menzel et al. (1991; 1993) recommended 4.25-5.5 % leaf N content, because the vegetative growth and yield were the highest with that N range. In this study, vegetative growth increased as leaf N content increased up to 4.9 %. On the other hand, fruit quality was the highest when leaf N content was 6.7 %, which was much higher than recommendation range by Menzel et al. (1991; 1993). In general, plant with high N fertilizer had low tolerance against disease (Huber and Watson, 1974), and fruits with high N content had low tolerance against physiological disorder (Marcelle, 1995). In this study, at 100 mM treatment, 5 of 29 fruits partly rotted during after-ripening, while at 25 mM treatment, no fruit did, though there was no significant difference (date was not shown). High Ca content in fruit increased resistance of fruit to all disorder, the physiological and fungal ones (Marcelle, 1995) and so, low Ca content at 100 mM treatment might cause fruit rot in this study. Therefore, with 6.7 % leaf N content, careful pest management using chemicals could be necessary, especially at open field where damage of disease is generally more serious than that in a greenhouse. In conclusion, vegetative growth was enhanced as leaf N content increased up to 4.9 %, flower number. References Bjorkman, O. and B. Demmig 1987. 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