Acta agriculturae Slovenica, 117/3, 1–11, Ljubljana 2021 doi:10.14720/aas.2021.117.3.1938 Original research article / izvirni znanstveni članek Style length and flower morphology of three eggplant (Solanum melon - gena L.) cultivars from Iran affected by fruit load Sedighehsadat KHALEGHI 1, 2 , Bahram BANINASAB 1 , Mostafa MOBLI 1 Received October 20, 2020; accepted August 15, 2021. Delo je prispelo 20. oktobra 2020, sprejeto 15. avgusta 2021 1 Department of Horticulture, College of Agriculture, Isfahan University of Technology, Isfahan, Iran 8415683111 2 Corresponding author, e-mail: khaleghi1360@yahoo.com Style length and flower morphology of three eggplant (Sola- num melongena L.) cultivars from Iran affected by fruit load Abstract: A common feature of eggplant is its hetero- styly. Long-style flowers bear fruits whereas short style ones fail to do so. Heterostyly is influenced by some factors such as genotype, climatic conditions and fruit load. In this study three eggplant cultivars from Iran were cultivated under greenhouse condition. The influence of presence of fruit (two fruits and four fruits) or absence of that on style length and some other flower morphological was studied in three po- sitions of single, basal and additional. The presence of fruit, specially four fruits reduced style length, stigma width as well as mass of flower, pistil and stigma compared to the control in all times during fruit growth, and after fruit harvest they increased again. Fruit load didn’t affect the number of sta- men and stamen length. These effects were observed in all three positons of single, basal and additional flowers of all three cultivars. Generally this study showed that fruit load has decreasing effect on style length and size of flowers forming after fruit setting, which reversed after fruit harvesting. Key words: eggplant; floral morphology; heterostyly; presence of fruit; style length Vpliv števila plodov na dolžino vrata pestiča in morfologijo cveta pri treh sortah jajčevca (Solanum melongena L.) v Iranu Izvleček: Splošno poznana lastnost jajčevca je heteros- tilija. Cvetovi z dolgim vratom cvetiča imajo plodove, tisti s kratkim vratom pa ne. Na heterostilijo vplivajo nekateri dejavniki kot so genotip, podnebne razmere in obloženost s plodovi. V raziskavi so bile gojene tri sorte jajčevca v ras- tlinjaku. Preučevan je bil vpliv števila plodov (dva in štirje plodovi) in njihova odsotnost na dolžino vrata pestiča in nekatere druge morfološke lastnosti cvetov v odvisnosti od njihovega položaja in sicer posamezni, prvi v socvetju in naslednji. Prisotnost plodov, še posebej štirih, je zmanjšala dolžino vrata pestiča, širino brazde kot tudi maso cveta, vratu in brazde pestiča v primerjavi s kontrolo v celot- nem obdobju rasti. Po obiranju plodov se je vrednost teh parametrov spet povečala. Obloženost s plodovi ni vplivala na število prašnikov in njihovo dolžino. Ti učinki so bili opaženi pri vseh treh položajih plodov (posamezni, prvi in naslednji), pri vseh treh sortah. Na splošno je raziskava pokazala, da je obloženost s plodovi vplivala na zmanjšanje dolžine vratov pestiča in velikosti cvetov, ki so nastali po zasnovi plodov, po njihovem obiranju pa so se vrednosti teh parametrov spet povečale. Ključne besede: jajčevec; morfologija cvetov; heteros- tilija; prisotnost plodov; dolžina vratu pestiča Acta agriculturae Slovenica, 117/3 – 2021 2 S. KHALEGHI et al. 1 INTRODUCTION Eggplant (Solanum melongena L.) from the Sola- naceae family, is belonging to tropical and subtropical regions (San José et al., 2016). India is primary centre of origin (Meyer et al., 2012); China and Japan are sec- ondary centres of origin, and today this crop is culti- vated worldwide from Mediterranean to Africa, Europe and America (Frary et al., 2007; Daunay, 2008). Its total world annual production reached over 55 million tons in 2019, which with an annual production of 670158 tons, Iran is the fifth leading eggplant producer after China, India, Egypt and Turkey (Faostat, 2019). Flowering and fruit setting are the most impor - tant factors in determining the yield of eggplant that is influenced by the genotype, the environmental condi- tions, the flower’s position on the plant and fruit load (Mohideen et al., 1977; Nothmann et al., 1983; Sun et al., 1990; Kowalska, 2003, 2006; Banik et al., 2018). Egg- plant flowers are large and usually violet-colored. They consist of five united and persistent sepals, five united and cup-shaped petals, usually five stamens alternating with the corolla, united carpels, and superior ovaries arranged either singly or in inflorescence. The number of flower bud is different in inflorescences and it is be- tween 2-7 flower buds (Rashid & Singh, 2000; Hazra et al., 2003; Jagatheeswari, 2014). Eggplant flowers report- edly exhibit a form of heterostyly. Based on this proper - ty, eggplant flowers are classified into the three groups of long style, medium style, and short style flowers based on the style length relative to that of the stamen (Prakash, 1968; Rylski et al., 1984; Handique & Sarma, 1995; Prasad & Sękara & Bieniasz, 2008). Style length plays an important role in the fruit set of eggplant since pollen liberated from pores at the apex of the anther cone thereby promoting the fertilization of long-styled pistils (Rylski et al., 1984; Passam & Bolmatis, 1997). Though short style flowers are not totally infertile, their fruit setting rate is much less than those of long and medium style flowers (Srinivas et al., 2016; Pohl et al., 2019). Since a considerable portion of eggplant flowers are short style ones, their failure to set fruit decreases their fruit-yielding potential significantly (Chadha & Saimbhi, 1977). Although heterostyly in eggplant flow- ers is a varietal characteristic (Rylski et al., 1984; Kow- alska, 2006; Sękara & Bieniasz, 2008), it is affected by such factors as plant age, fruiting dynamics, and en- vironmental conditions (Lenz, 1970; Sun et al., 1990). For instance, Nothmann et al. (1983) showed that low temperatures may have an adverse effect on fruit set- ting by reducing the length of style. Some researchers have also shown that treatment of seeds with gamma rays caused a change in heterostyly by increasing the long style flowers and decreasing the short style ones (Handique & Sarma, 1995). Moreover, exogenous ap- plication of some plant growth regulators such as auxin and kinetin was effective on changing heterostyly by changing the proportion of long and short style flow- ers (Lenz, 1970; Handique & Sarma, 1995; Passam et al., 2001). Moniruzzaman et al. (2015) and Hoque et al. (2018) also reported that using IAA, significantly in- creased the percentages of long and medium style flow- ers in eggplant. Although the effect of fruit load on style length of some cultivars has previously been studied by some researchers (Khah et al., 2000; Passam et al., 2001), in the present paper we studied this effect on style length and some other flower morphological traits in all three positions of single, basal and additional flowers of three eggplant cultivars from Iran. 2 MATERIALS AND METHODS 2.1 PLANT MATERIALS Three eggplant cultivars (TN74128, TN74243 and TN74239) obtained from the Gene Bank of the Agri- cultural Research Institute of Iran were used in this study. From each cultivar, 60 seeds were sown in the middle of March into boxes with a peat and perlite sub- strate at a ratio of 4:1; v/v. Six weeks after sowing, 18 uniform seedlings were selected from each genotype, and transplanted into an experimental field at spaces of 60 × 60 cm at Isfahan University of Technology, Is- fahan, Iran (latitude 32̊ 42ʹ N; longitude 51̊ 28ʹ E; al- titude 1624 m). The soil of the experimental site was sandy loam with neutral pH suitable for cultivation. Field was ploughed 2-3 times and organic manure 25 t ha -1 was applied. The fertilizer 20-20-20 including NPK 20-20-20+B+Cu+Fe+Mn+Mo+Zn was also applied once a month at a concentration of 1 mg l -1 . Plants were irrigated using the drip irrigation method, and weed- ing of the field was carried out several times manually. Pest management were conducted according to recom- mended standards during the growing season. 2.2 TREATMENTS AND OBSERV ATIONS In this trial three treatments applied including: 1) all flowers collected at anthesis (NF), 2) two fruits al- lowed setting, but all subsequent flowers collected at anthesis (2F), 3) four fruits allowed setting and all sub- sequent flowers collected at anthesis (4F). Each treat- ment comprises 9 plants that all of them were samples Acta agriculturae Slovenica, 117/3 – 2021 3 Style length and flower morphology of three eggplant (Solanum melongena L.) cultivars from Iran affected by fruit load through the trial. In all three cultivars, single flower that were formed in the third week were kept on plants for turning into fruit (for treatments of 2 fruits and 4 fruits), and from the fifth week, studies relevant to the flowers forming after fruit setting were carried out. For this purpose, flowers were excised twice a week. They were classified according to whether they were single, basal (first flower in inflorescence) or additional (sec- ond flower in inflorescence) flower. Then they imme- diately transferred to the laboratory. It was assessed the number of stamen, the length of style and stamen, the width of stigma, and the mass of flower, pistil and stig- ma. The length of style and stamen, as well as the width of stigma were measured using a caliper on the mil- limeter scale (style and stamen length measurements were made from the point of attachment of the style to the ovary). Flower, pistil, and stigma mass were also measured using a sensitive digital scale and reported in milligram (flower and pistil), and microgram (stigma). The ninth week, fruits were harvested, and the observa- tions lasted two weeks later, until the eleventh week. 2.3 DATA ANALYSIS The results were statistically analysed by analysis of variance (ANOVA) using the SAS software, and in order to compare differences, least significant differ - ences (LSD) test (p < 0.05) was applied for traits with significant F in ANOVA. Due to the lack of coordina- tion of different treatments at the time of measuring the factors, the resulting data obtained from the first four weeks of the experiment (before fruit setting) was carried out with Split-plot according to randomized complete block design, included the position of flow- ers on the plant (single, basal or additional). For plants without any fruits, and in order to analyse the data from the fifth to eleventh week was used the split-plot facto- rial based on randomized complete block design. Treat- ments included the number of fruits per plant (0, 2 and 4 fruits) and flower position on the plant (single, basal or additional) in 3 replications and each replicate con- tains 3 plants. 3 RESULTS 3.1 STYLE LENGTH AND OTHER FLOWER MORPHOLOGICAL TRAITS AFFECTED BY FRUIT LOAD As can be seen in Table 1, the presence of two and especially four fruits reduced the style length of the flowers that were later formed. The presence of fruit also significantly affected the size of the other female parts including width of stigma and mass of pistil and stigma, which reduced them in all three cultivars. The presence of four fruits per plant reduced the mass of the next flowers significantly in all three cultivars. The number and the length of stamen in any of the cultivars were not influenced by the number of fruits (data not shown). 3.2 STYLE LENGTH AND OTHER FLOWER MORPHOLOGICAL TRAITS BASED ON FLOWER POSITION As expected, in Table 2, all traits measured includ- ed style length, number of stamens, stamen length, stig- ma width and the mass of flower, pistil and stigma were significantly less in additional flowers in all three cul- tivars compared to the basal and single flowers. Some of these traits are not significant between the basal and single flowers, and some of them in the basal flowers are a little more than single ones. 3.3 FLOWER MORPHOLOGICAL TRAITS AT DIFFERENT STAGES OF FRUIT GROWTH AF- FECTED BY FRUIT LOAD 3.3.1 Style lenght As shown in Fig. 1, in cultivar TN74128, the mini- mum and maximum (min and max) of style length in the basal flower were 13.41 and 14.31 mm, up to the 9 th week in NF, while were 12.88 and 13.45 mm in 2F, and 12.03 and 12.33 mm in 4F, which increased to 13.30 mm in the 10 th and 11 th weeks after harvesting of fruits in 4F. This factor in the additional flower was 8.35 and 12.56 mm in control, 5.73 and 9.93 mm in 2F, and 4.1 and 9.36 mm in 4F, which increased after fruit harvest compared to the 9 th week. In single flowers, this value was 13.06 and 13.58 mm in control, which did not differ significantly with 2F. While in 4F were 11.31 and 12.10 mm, which increased to 13.01 mm after harvest. The min and max style length of basal flower in cultivar TN74243 were 11.40 and 12.59 mm until the 11 th week. There was no significant difference in 2F with control. But in 4F it was 10.65 and 11.68 mm, which increased to 12.27 mm after the 9 th week. In the addi- tional flower, a significant decrease in the style length of all three treatments was observed from the 5 th week to the 7 th that began to increase after the 9 th week. For single flower, this was 11.71 and 13.07 mm in control. In Acta agriculturae Slovenica, 117/3 – 2021 4 S. KHALEGHI et al. 2F were 11.21 and 12.25 mm, which increased to 12.46 mm after harvest, and in 4F were 10.78 and 11.93 mm, which no difference was created after the 9 th week. The min and max style length of the basal flower in cultivar TN74239 was 11.19 and 11.84 mm until the 11 th week. 2F did not show any significant difference with control, while in 4F, were 10.71 and 11.01 mm, which increased to 11.6 mm in the 11 th week. In the additional Fruit load Style length (mm) Stigma width (mm) Flower mass (mg) Pistil mass (mg) Stigma mass (µg) Cultivar TN74128 No fruit 12.72a 1.84a 0.88a 0.17a 2.70a 2 fruit 11.53b 1.67b 0.87a 0.16a 2.15b 4 fruit 10.34c 1.56c 0.73b 0.13b 1.80c Cultivar TN74243 No fruit 10.66a 1.74a 0.86a 0.15a 2.36a 2 fruit 9.88b 1.65ab 0.83a 0.14b 1.97b 4 fruit 8.94c 1.58b 0.78b 0.11c 1.80c Cultivar TN74239 No fruit 9.76a 1.52a 0.76a 0.12a 2.0a 2 fruit 9.20b 1.45b 0.71b 0.11b 1.67b 4 fruit 8.41c 1.35c 0.66c 0.10c 1.48c Table 1: Effect of fruit load on style length and some flower morphological traits in three eggplant cultivars The values with similar letters in each column for each cultivar have no significant difference using LSD test at 5 % probability. Flower position Style length (mm) Number of stamen Stamen length (mm) Stigma width (mm) Flower mass (mg) Pistil mass (mg) Stigma mass (µg) Cultivar TN74128 Basal 13.29a 6.67a 14.14a 1.98a 1.03a 0.21a 3.08a Additional 8.38c 6.33c 13.78b 1.21b 0.46b 0.04b 0.71c Single flower 12.92b 6.55b 14.04a 1.89a 0.99a 0.21a 2.86b Cultivar TN74243 Basal 11.93a 6.32a 14.24a 1.89a 1.01a 0.19a 2.98a Additional 5.63b 6.10b 13.81c 1.14b 0.46b 0.032b 0.35c Single flower 11.92a 6.34a 14.00b 1.94a 1.01a 0.18a 2.80b Cultivar TN74239 Basal 11.51a 6.40a 14.18a 1.66a 0.88a 0.16a 2.53a Additional 4.30b 5.92b 13.68b 1.08c 0.38b 0.02c 0.25c Single flower 11.56a 6.33a 14.09a 1.58b 0.86a 0.15b 2.36b Table 2: Differences between position of flower in the style length and other flower morphological traits of three eggplant cultivars The values with similar letters in each column for each cultivar have no significant difference using LSD test at 5 % probability flower, from the 5 th week to the 8 th and 9 th weeks, there was a significant decrease in the style length of all three treatments that increased from the 10 th to 11 th weeks. The min and max style length of single flower was 11.10 and 12.49 mm in NF, and no significant difference was observed between 2F with control, while this amount in 4F was 10.15 and 11.0 mm, which increased to 12.45 mm after harvest. Acta agriculturae Slovenica, 117/3 – 2021 5 Style length and flower morphology of three eggplant (Solanum melongena L.) cultivars from Iran affected by fruit load 3.3.2 Stigma width According to Fig. 2 in cultivar TN74128, the min and max width of stigma in basal flower in control was 1.97 and 2.31 mm up to the 9 th week, 1.75 and 2.35 mm in 2F, and 1.49 and 2.18 mm in 4F, which increased in two last treatments in the 10 th week compared to the 9 th week. There was also the similar trend in the addi- tional flowers. In single flower, this factor was 1.95 and 2.14 mm in control, 1.71 and 2.02 mm in 2F, and 1.55 and 2.07 mm in 4F, which increased at the 10 th and 11 th weeks in both last treatments. There was no significant difference between con- trol and 2F in stigma width of basal flower in cultivar TN74243, while in 4F at all times, especially on the 9 th week, the width of the stigma was less than the control and 2F, which increased after fruit harvest. The stigma width of the additional flowers had a sharp decrease in all three treatments from the 5 th week to the 8 th and 9 th weeks, and then increased at the 10 th and 11 th weeks. In single flower, these were 1.89 and 2.26 mm in control, while was lower in 2F and 4F, which increased at the 10 th and 11 th weeks. In cultivar TN74239, at all times, the stigma width of the basal flower was lower in 2F and 4F with a slight difference compared to the control, and after harvest in- creased. The additional flower showed a decrease trend from 5 th week to 8 th week in all three treatments and then began to increase. Min and max of stigma width in single flower were 1.52 and 1.68 mm in control until the 9 th week. There was no significant difference in 2F, and in 4F were 1.18 and 1.7 mm, which increased after fruit harvest in both treatments. Figure 1: Style length of basal, additional and single flower in millimeter in three eggplant cultivars along the growing period affected by fruit load. Vertical bars represent standard deviation of the means Acta agriculturae Slovenica, 117/3 – 2021 6 S. KHALEGHI et al. Figure 2: Stigma width of basal, additional and single flower in millimeter in three cultivars of eggplant along the growing period affected by fruit load. Vertical bars represent standard deviation of the means 3.3.3 Flower mass No significant differences were found between 2F and 4F with control in basal and additional flowers of all cultivars. But in single flower the min and max flower mass of control in cultivars TN74128, TN74243 and TN74239 was 1.03 and 1.46, 0.96 and 1.33, and 0.88 and 1.20 mg, respectively, while in 4F, this factor was significantly lower (0.74 and 1.09, 0.80 and 1.20, and 0.71 and 0.89 mg, respectively), which increased slightly after harvest (Fig. 3). 3.3.4 Pistil mass The min andmax pistil mass of basal flower in cul- tivar TN74128 until the 9 th week was 0.16 and 0.33 mg in control. 2F did not show any significant difference with control, while in 4F was 0.13 and 0.22 mg, which showed a significant increase after harvesting com- pared to the last weeks. This factor in additional flower was 0.027 and 0.074 mg in control, 0.026 and 0.058 mg in 2F, and 0.012 and 0.044 mg in 4F, which after the harvest increased. In single flower, this amount was 0.22 and 0.34 in control, 0.15 and 0.28 in 2F and 0.15 and 0.2 mg in 4F, which after harvest increased compared to the 9 th week. The min and max pistil mass of basal flower in cultivar TN74243 in control was 0.15 and 0.26 mg. 2F didn’t have significant difference with control, and in 4F, it was 0.14 and 0.22 mg. The pistil mass of additional flower was significantly reduced in all three treatments from the 5 th week to the 8 th week, and after the 10 th week it increased slightly. In single flower, there was no sig- Acta agriculturae Slovenica, 117/3 – 2021 7 Style length and flower morphology of three eggplant (Solanum melongena L.) cultivars from Iran affected by fruit load nificant difference between 2F with control, but in 4F was lower than the control at all times, which increased after the 9 th week. In cultivar TN74239, the pistil mass of basal flower was not significantly different in 2F and 4F with con- trol, although this factor was less than the control at all times. In the additional flower, the pistil mass decreased significantly from the 5 th to 7 th weeks in all three treat- ments and increased slightly after the 10 th week. In the single flower, 2F did not show any difference with the control, but in 4F at all times, the mass of the pistil was less than that of the control and after harvest increased compared to the previous one (Fig. 4). 3.3.5 Stigma mass In cultivar TN74128, the min and max stigma mass of basal flower until the 9 th week in control was 3.16 and 3.91 µg, in 2F, 2.53 and 3.73 µg, and in 4F, 1.99 and 3.04 µg, which increased after fruit harvest. Min and max of this factor in additional flower of control, 2F and 4F was 0.78 and 1.28, 0.58 and 0.75, and 0.37 and 0.46 µg, respectively, which increased slightly after the 9 th week. In single flower, this factor was 2.22 and 4.22 µg in control, 2.36 and 2.85 µg in 2F, and 1.73 and 2.67 µg in 4F, which at the 10 th and 11 th weeks was more than to the previous weeks. In cultivar TN74243, the min and max stigma mass of basal flower in control was 2.44 and 3.66 µg. This amount in 2F was 2.20 and 3.05 µg and in 4F was 2.10 and 2.75 µg, which increased in all three treat- ments after the 9 th week. The stigma mass of the ad- ditional flower was 0.25 and 0.62 μg in the control. In 2F, 0.10 and 0.35 µg, and in 4F, without significant dif- Figure 3: Flower mass of basal, additional and single flower in milligram in three cultivars of eggplant along the growing period affected by fruit load. Vertical bars represent standard deviation of the means Acta agriculturae Slovenica, 117/3 – 2021 8 S. KHALEGHI et al. ferences with 2F was 0.10 and 0.32 µg, which increased after harvest. In single flower, this factor was 2.20 and 3.45 µg in control, in 2F, 2.06 and 2.90 µg, and in 4F, 1.66 and 2.85 µg that at the 9 th and 10 th week reached to their maximum. In cultivar TN74239, the min and max stigma mass of basal flower in control was 2.12 and 3.57 µg, in 2F, 1.80 and 2.94 µg, and in 4F, 1.98 and 2.52 μg that increased after harvest than previous weeks. This factor showed a significant reduction in additional flowers in all three treatments from 5 th to 8 th and 9 th weeks, while the graph of 2F and 4F were lower than the control, and then increased at the 11 th week. The min and max stigma mass of single flower in control was 1.98 and 2.60 µg. This amount in 2F was 1.72 and 2.55 µg, and in 4F, 1.15 and 2.20 µg, which reached to the maximum value in all three treatments in the 10 th and 11 th weeks (Fig. 5). Figure 4: Pistil mass of basal, additional and single flower in milligram in three cultivars of eggplant along the growing period affected by fruit load. Vertical bars represent standard deviation of the means 4 DISCUSSION The presence of two or four fruits in all three cul- tivars reduced the length of style, as well as the width of stigma in all three positions of the next basal, additional and single flowers. This difference was especially sig- nificant and remarkable in 4F. This process continued from the beginning until the time of fruit harvesting, and after harvesting began to increase again. The mass of basal and additional flower in three cultivars was not significantly affected by 2F and 4F, while mass of sin- gle flower was especially decreased in 4F as compared to the control, which increased again after harvesting. This factor generally decreased from the beginning of flowering to the end of the fruit growth period in all three cultivars. The mass of pistil also showed a simi- lar trend to the mass of the flower during the growth Acta agriculturae Slovenica, 117/3 – 2021 9 Style length and flower morphology of three eggplant (Solanum melongena L.) cultivars from Iran affected by fruit load period. In most cases, 2F did not affect the mass of pis- til so much, while in 4F, this factor was more affected, so that it decreased until the fruit harvesting, and after that increased again. The mass of stigma was influenced by two and four fruits during the growth period, so that the presence of fruit per plant in all three cultivars re- duced the mass of stigmata of flowers that formed after fruit setting, and after fruit harvest increased again. The treatment of two fruits and four fruits did not affect the number and the length of stamen in any of the cultivars during the growth period. These results are in agreement with the study of Khah et al. (2000) on four eggplant varieties in the greenhouse conditions. They showed not only the length of style, but also the mass of flower, the mass of pistil and the number of flowers decreased by the number of fruits, and increased again after fruit harvest. Lenz (1970) also examined this issue in Hoagland’s culture and expressed that the formation of the fruit affected style length of the next flowers. Moreover, Passam et al. (2001) reported similar results. Their experiments were conducted under favorable climatic conditions for fruit formation. According to them, the presence of fruit caused length of style was smaller during the period of fruit growth, which increased after the maturity of the fruit. The mass of the flower was also affected by the presence of fruits, and this factor also similar to our results showed a downward trend in the trial period. Pistil mass also had a pattern similar to flower mass, and no significant difference was observed in cultivars in stamen length between treatments. Developing fruits reduce the growth of roots, stems and leaves in eggplants (Mochizuki, 1959), as oc- curs in other plant species (Leonard, 1962). Lenz (1970) Figure 5: Stigma mass of basal, additional and single flower in microgram in three eggplant cultivars along the growing period affected by fruit load. Vertical bars represent standard deviation of the means Acta agriculturae Slovenica, 117/3 – 2021 10 S. KHALEGHI et al. also showed this growth inhibition for flower style. This inhibitory growth is due to the competition of nutrients and assimilates, and may also result in hormones pro- duced in the fruit. According to the Lenz (1970), both the length of style and stamen are influenced by auxin. Therefore, auxin existing in developing fruits can inhibit the growth of the style, which suggests that developing fruits control the sex expression of the eggplant. Claus- sen (1986) also states that since fruits are strong sink, the use of leaf carbohydrates reduces vegetative growth and decreases flower size. The issue of the dominance of the first fruit in plants from Cucurbitaceae family has also been proven. In these plants, the developing fruit can prevent the formation of the next fruit and the growth of new and young fruits. This inhibition can be due to competition for available assimilates, or due to the dominance of growth regulators created by the developing fruit. The pollen-dependent seed content seems to play a role in the dominance of the first fruit (Stephenson et al., 1988; Bangerth, 1989). However, Pas- sam et al. (2001) demonstrated in a trial that the use of auxin in the absence of fruit did not affect the length of the style. Therefore, they stated that although the seeds of developing fruits through the synthesis of natural auxins or other growth regulators may have some effect on the length of the style, it seems that the main factor is the presence of fruit and the stage of fruit growth. 5 CONCLUSION In summary, although fruit load did not affect the number and length of stamen of flowers which form later, reduced style length, stigma width, mass of flower, pistil and stigma of those flowers, which increase again after fruit harvesting. Therefore, the presence of fruit on plant reduces the chance of fruit formation from subsequent flowers that shows timely harvest of fruit can be effective in the formation of more long style flowers during plant growth period and so, more fruit setting. 6 REFERENCES Bangerth, F. (1989). Dominance among fruits/sinks and the search for a correlative signal. Physiologia Plantarum , 76(4), 608–614. https://doi.org/10.1111/j.1399-3054.1989. tb05487.x Banik, S. C., Islam, S., Sarker, B., Chowdhury, D. D., & Uddin, M. N. (2018). Influence of flower types on fruit setting and yield dynamics of summer brinjal (Solanum melon - gena L.). Asian Journal of Agricultural and Horticultural Re- search, 1–9. https://doi.org/10.9734/AJAHR/2018/41185 Chadha, M. L., & Saimbhi, M. S. (1977). Varietal variation in flower types in brinjal (Solanum melongena L.). Indian Journal of Horticulture, 34(4), 426–429. Claussen, W. (1986). Influence of fruit load and environmen- tal factors on nitrate reductase activity and on concen- tration of nitrate and carbohydrates in leaves of eggplant (Solanum melongena). Physiologia Plantarum, 67(1), 73–80. https://doi.org/10.1111/j.1399-3054.1986.tb01265.x Daunay, M.C. (2008). Eggplant. In J. Prohens-Tomas & F. Neuz (Eds.), Vegetables II (pp. 163–220). Springer. https://doi. org/10.1007/978-0-387-74110-9_5 Faostat, F. (2019). Agriculture Organization of the United Nations statistics division. Production Available in http:// Faostat3. FAO. Org/Browse/Q/QC/S. Accessed December 22, 2020. Frary, A., Doganlar, S., & Daunay, M. C. (2007). Eggplant. In C. Kole (Ed.), Vegetables. Genome Mapping and Molecu- lar Breeding in Plants (pp. 287–313). Springer. https://doi. org/10.1007/978-3-540-34536-7_9 Handique, A. K., & Sarma, A. (1995). Alteration of heterostyly in Solanum melongena L. through gamma-radiation and hormonal treatment. Journal of Nuclear Agriculture and Bi- ology, 24(2), 121–126. Hazra, P ., Manda, J., & Mukhopadhyay, T. P . (2003). Pollination behaviour and natural hybridization in Solanum melon - gena L., and utilization of the functional male sterile line in hybrid seed production. Capsicum and Eggplant News- letter, 22, 143–146. Hoque, A. A., Ahmed, Q. M., Rahman, M. M., & Islam, M. A. (2018). Effect of application frequency of naphthalene acetic acid on physiomorphological characters and yield of brinjal. Research in Agriculture, Livestock and Fisheries, 5(2), 151-155. https://doi.org/10.3329/ralf.v5i2.38051 Jagatheeswari, D. (2014). Morphological studies on flowering plants (Solanaceae). International Letters of Natural Sci- ences, 15, 36-43. https://doi.org/10.18052/www.scipress. com/ILNS.15.36 Khah, E. M., Antonopoulos, A., & Passam, H. C. (2000). Floral behaviour and fruit set in four cultivars of aubergine. Acta Horticulturae, 579, 259–264. https://doi.org/10.17660/Ac- taHortic.2002.579.43 Kowalska, G. (2003). The influence of heterostyly, pollina- tion method and hormonization on eggplant’s (Solanum melongena L.) flowering and fruiting. Acta Agrobotanica , 56(1–2), 61–76. DOI: https://doi.org/10.5586/aa.2003.007 Kowalska, G. (2006). Eggplant ( Solanum melongena L .) flow- ering and fruiting dynamics depending on pistil type as well as way of pollination and flower hormonization. Folia Horticulturae, 18(1), 17–29. Lenz, F. (1970). Effect of fruit on sex expression in eggplant (Solanum melongena L.). Horticultural Research, 10, 81–82. Leonard, E. R. (1962). Inter-relations of vegetative and repro- ductive growth, with special reference to indeterminate plants. The Botanical Review, 28(3), 353–410. https://doi. org/10.1007/BF02868688 Meyer, R. S., Karol, K. G., Little, D. P., Nee, M. H., & Litt, A. (2012). Phylogeographic relationships among Asian eggplants and new perspectives on eggplant domestica- Acta agriculturae Slovenica, 117/3 – 2021 11 Style length and flower morphology of three eggplant (Solanum melongena L.) cultivars from Iran affected by fruit load tion. Molecular Phylogenetics and Evolution, 63, 685–701. https://doi.org/10.1016/j.ympev.2012.02.006 Mochizuki, T. (1959). The carbon metabolism of eggplants as affected by bearing fruits. Bulletin of the Faculty of Agricul- ture and Life Science, Hirosaki University, 5, 28–31. Mohideen, M. K., Muthukrishnan, C. R., Rajagopal, A., & Me- tha, V. A. (1977). Studies on the rate of flowering, flower types and fruit set in relation to yielding potential of cer - tain eggplant (Solanum melongena L.) varieties with refer - ence to weather conditions. South Indian Horticulture , 25, 56–61. Moniruzzaman, M., Khatoon, R., Hossain, M. F. B., Jamil, M. K., & Islam, M. N. (2015). Effect of GA and NAA on physio-morphological characters, yield and yield com- ponents of Brinjal (Solanum melongena L.). Bangladesh Journal of Agricultural Research, 39, 397–405. https://doi. org/10.3329/bjar.v39i3.21983 Nothmann, J., Rylski, I., & Spigelman, M. (1983). Interac- tions between floral morphology, position in cluster and 2,4-D treatments in three eggplant cultivars. Scientia Horticulturae, 20(1), 35–44. https://doi.org/10.1016/0304- 4238(83)90109-7 Passam, H. C., Baltas, C., Boyiatzoglou, A., & Khah, E. M. (2001). Flower morphology and number of aubergine (Solanum melongena L.) in relation to fruit load and auxin application. Scientia Horticulturae, 89(4), 309–316. https:// doi.org/10.1016/S0304-4238(00)00242-9 Passam, H. C., & Bolmatis, A. (1997). The influence of style length on the fruit set, fruit size and seed content of au- bergines cultivated under high ambient temperature. Tropical Science, 37, 221–227. Pohl, A., Grabowska, A., Kalisz, A., & Sękara, A. (2019). Bi- ostimulant application enhances fruit setting in egg- plant—An insight into the biology of flowering. Agrono - my, 9, 482. https://doi.org/10.3390/agronomy9090482 Prasad, D. N., & Prakash, R. (1968). Floral biology of brinjal (Solanum melongena L). Indian Journal of Agricultural Sci- ences, 38(6), 1053. Rashid, M. A., & Singh, D. P . (2000). A manual on vegetable seed production in Bangladesh. AVRDC-USAID-Bangladesh Project, Horticulture Research Centre, Bangladesh Agri- cultural Research Institute. Rylski, I., Nothmann, J., & Arcan, L. (1984). Differential fer - tility in short-styled eggplant flowers. Scientia Horti- culturae, 22(1–2), 39–46. https://doi.org/10.1016/0304- 4238(84)90081-5 San José, R., Plazas, M., Sánchez-Mata, M. C., Cámara, M., & Prohens, J. (2016). Diversity in composition of scarlet (S. aethiopicum) and gboma (S. macrocarpon) eggplants and of interspecific hybrids between S. aethiopicum and com- mon eggplant (S. melongena). Journal of Food Composition and Analysis, 45, 130–140. DOI: 10.1016/j.jfca.2015.10.009 Sękara, A., & Bieniasz, M. (2008). Pollination, fertilization and fruit formation in eggplant (Solanum melongena L.). Acta Agrobotanica, 61(1), 107. DOI: 10.5586/aa.2008.014 Srinivas, G., Jayappa, A. H., & Patel, A. I. (2016). Heterostyly: A threat to potential fruit yield in brinjal (Solanum melon - gena L.). Advancements in Life Sciences, 5, 1211–1215. Stephenson, A. G., Devlin, B., & Horton, J. B. (1988). The effects of seed number and prior fruit dominance on the pattern of fruit production in Cucurbita pepo (zucchini squash). Annals of Botany, 62(6), 653–661. https://doi.org/10.1093/ oxfordjournals.aob.a087705 Sun, W ., Wang, D., Wu, Z., & Zhi, J. (1990). Seasonal change of fruit setting in eggplants (Solanum melongena L.) caused by different climatic conditions. Scientia Horticulturae, 44(1–2), 55–59. DOI : 10.1016/0304-4238(90)90016-8