Abstract: Background and Objective: Brinjal is a perennial vegetable-fruit crop and produce fruits all the year-round and have a very short period of harvesting time. The plant possesses delay flowering with less number of flowers and fruit due to a low C: N ratio. The study was conducted to evaluate the effect of paclobutrazol on growth, flowering and fruit development of white eggplant variety. Materials and Methods: The eggplant plant was grown in potted condition using growth media (2 clay: 1 organic matter). The eggplants were treated with paclobutrazol (PBZ). The treatment was applied using a soil injection method for a single time only. This experiment was carried out with Completely Randomized Design (CRD) with six treatments each with five replications. Results: The results showed that the brinjal plant treated with 150-200 mg L–1 PBZ increased the plant height, number of leaves, number of branches, number of buds, and required less time for first and 50% flowering. In addition, leaf chlorophyll content, the total soluble solids content in fruits, yield, the number of harvested fruit, fruit length and diameter were also increased with paclobutrazol treatment. The increased fresh and dry biomass and reduced root length were also recorded in PBZ treatment. Conclusion: It was concluded that eggplants should be treated with paclobutrazol during early vegetative growth to increase flowering, fruit development and quality.
INTRODUCTION
Today, consumers are more aware of the health status that makes them be conscious of taking only what is healthy to their wellbeing1-2. The following phenomenon is in relation to the belief of the populace that intake of the vegetable plants minimizes the risk of degenerative disease; such as cancer, diabetes, heart attack and many more2. In relation to the above reasons, demand in vegetable plants has significantly increased. It has reported as at today trading in vegetables all over the world has superseded that of cereal plants3-4. Presently, the production of world eggplant is 35.3 million tonnes5. Out of the world total production of eggplants, more than 90% take place in Asia while the remaining is produced by America, Europe and Africa5-6. The plant is widely cultivated in temperate and tropical regions. Vegetable crops provide the nutrient requirements of the body at a very cheap rate. To meet the demand of vegetables growing request, it becomes imperative to improve their productivity with friendly environmental chemical, cost-effective and simple techniques for reproducibility. Increased eggplants demand all over the world. Eggplant is one of the most popular vegetable crops originated from India6. Eggplants belong to the family Solanaceae. Different type of eggplant cultivar was reported7. But, their fruit color, shape and size was used to differentiate them morphologically8. Anthocyanin was responsible for the coloration in eggplants. The color of the cultivars ranges from yellow, white, purple and black9.
The most popular cultivar among the eggplant is purple cultivar8. The plant is considered perennial but annually cultivated. The eggplants develop with undifferentiated leaves, to about 50 to 120 height in centimeters. The plants are well-branched, compact, upright and turn to bushy10. Eggplants have alternate leaves, lobed designed leaves and large in nature. The eggplant root system is lignified or fibrous. Flowers are violet color, large, inter-cluster or solitary in nature11. They have a hermaphrodite and actinomorphic flower system. The following vegetable crop was described to contain high nutritional content with low calories. The crop has the advantage of growing throughout the year, especially in Malaysia. Eggplant is used in the treatment of hypertension, diabetes, cholera, asthma and bronchitis; it is also used in diet control and reduction of cholesterol in the human blood12. Consumption of eggplant fruits reduced the risk of cardiovascular diseases and stroke13. They also stated that the plants have proved to have high antioxidants potential of scavenging free radicals in the human body. The leaves and root of the plants reported containing compounds from alkaloid group solanine14. Fruits of the plants contains (1.3%) protein, (0.3%) fat, (0.02%) phosphorus, (6.4%) carbohydrates, (0.0013%) iron and (0.02%) calcium15. It also contains a considerable amount of thiamine, vitamin B6, K and C. Eggplant is also very rich in magnesium and potassium contents which contribute greatly to human health.
Altering the plant's growth parameters will improve the yield of the fruits, nutritional contents and even resistance to diseases. Decreased in eggplant production was noticed recently. The decrease was attributed to soil fertility reduction and the contents of organic matter in the soil. Therefore, nutrients absorption is greatly affected. Plants growth regulators are taken into consideration for their ability to trigger developmental growth, increases the quality and yield of a plants16. Paclobutrazol,1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl) pentan-3-ol commercially known as PBZ is a plant growth regulators10. Owing to the nutritional contents, the medicinal value of eggplant, the large populace of Asia presumed to demand more of eggplant. Therefore, there is needed attention to increasing its production. As a result of the above reasons, the study was conducted to determine the influence paclobutrazol on the developmental growth, yield and quality of brinjal (Solanum melongena).
MATERIALS AND METHODS
Study area: The experiment was conducted from September 2018 to May 2019 at the research farm of Universiti Sultan Zainal Abidin (UniSZA), Besut Campus, 22200 Besut, Terengganu, Malaysia.
Planting materials: Brinjal seeds were obtained from Green World Genetic (GWG) seed company, Terengganu, Malaysia. The grow mate media with a mixture of clay and organic in ratio 2:1 was used as growing media. Inorganic fertilizers (NPK Green and Blue) were used. 16×16" polybag and sowing tray were used. Paclobutrazol powder, soil injector, Scott bottle, measuring cylinder and balance were used to treatment application.
Seeds sowing: Eggplants seeds were sowed in a germination tray that contains sowing media. Each hole was sowed with one Brinjal seed. After germination, thirty seedlings were transplanted into polybag containing the growing media. The plant watered twice daily. Fertilizer application was carried out one week after transplanting (to let the crop stabilize) and it was given one-week interval and about 10 g for each given (NPK green during vegetation and NPK blue during the reproductive stage. The fruit was collected on week 12 after transplanting.
Preparation of paclobutrazol solution: The paclobutrazol (PBZ) was dissolved in ethanol first. The solution was top up with distilled water to one liter. The solution was kept in Scott bottle and labeled according to the concentrations. The solution kept in the chiller and only the desire amount taken to the experimental site.
Experimental design and treatment application: Completely Randomized Design (CRD) design was used to set up the experiment. This experiment consists 6 treatments each treatment with 5 replicates was employed (T1 = 0, T2 = 25, T3 = 50, T4 = 100, T5 = 150, and T6 = 200 mg L–1 of paclobutrazol). Paclobutrazol applied for each treatment except for 0 mg L–1 (control) and all the treatments were applied one time only (during the vegetative stage and given one month after transplanting to let them settle down with new condition) during this experimental period. The treatment was applied by using a soil injector to the root zone of the transplanted seedlings.
Morphology parameters: The height of each was measured by a scale from ground level to the tip of the main stem plant at week 3, week 5 and week 7 DAT. The mean calculated for each replicate17. Daily observation made on each plant for first flower and 50% flowering. The number of days taken from the data of transplanting to flowering recorded and expressed in the number of days taken for each 50% flowering. The number of leaves for each plant calculated and recorded at week 3, week 5 and week 7 DAT. The mean calculated and expressed in a number. The number of branches for each plant calculated and recorded at week 3, week 5 and week 7 DAT. The number of buds for each plant calculated and recorded at week 3, week 5 and week 7 DAT. The area of 5th leaf for each plant calculated and recorded at week 3, week 5 and week 7 DAT by measuring the length of the leaf and 3 spots of width for each leaf. The area calculated with the formula:
Growth and developmental parameters: The numbers of mature fruits harvested on each in each treatment were determined, and the average calculated and expressed as several fruits per plant. The length of five randomly selected fruits from each treatment measured from the base of pedicel to the tip of the fruit and average counted and expressed in centimeters18. The diameter of five randomly selected fruits from each treatment measured using a vernier caliper. The average counted and expressed in centimeters11.
Eggplant harvested after two months of transplanting and the weight was calculated. The weight was recorded; average calculated and expressed in grams. The root length of the plant for each treatment was measured using meter tape from the base until the end. The mean of length was calculated and expressed in centimeter. The shoot of the plant for each treatment was measured using an electronic balance. The mean of weight was calculated and expressed in gram. The shoot of the plant for each treatment was dried using oven drying at (65°C for a day). Then, the weight was measured using an electronic balance.
Physiological parameters: Leaf chlorophyll content was measured with SPAD meter. Brinjal fruit TSS content was evaluated by using a hand refractometer. The root weight of the plant for each treatment was weighed by using an electronic balance. The mean of weight was calculated and expressed in gram. The root from two randomly selected plants for each treatment was dried using oven drying at (65°C for a day). Then, the weight was measured using an electronic balance. The mean of weight was calculated and expressed in gram.
Statistical analysis: The data obtained from the experiment were analyzed by using SAS (University version) software. Analysis of Variance (ANOVA) using one way was employed to measure the significant differences in different treatments of the studied parameters. Means comparisons were performed with Tukey’s test, significance at p<0.05.
RESULTS
Plant height and number of leaves: The result shows that plant height at weeks 3, 5 and 7 Days after Transplant (DAT) was influenced significantly due to the application of different concentrations of PBZ. T6 treatment produced the highest plant height (25.40 cm) at week 3 after transplanting. Whereas, the control plant height was only 15.10 cm. The plant height of eggplant in general increased up to the harvesting stage (Table 1).
Results from the study show number of leaves were influenced by different concentration of PBZ at different growth intervals and were analyzed statistically (Table 2). Generally, increase in the number of leaves was noticed from week 3 DAT and up to the harvesting stage. The study show T4 produced the highest number of leaves both at week 3, 5 and 7, respectively (Table 2).
Number of branch and leaf area: The number of branches was influenced by different concentrations of PBZ used in the study. The data was statistically analyzed (Table 3). The number branch was observed to be increasing 3 weeks after the application of the treatment. T1 was found to produce the highest number of branch in week 5 while T5 produced the highest number of branches in week 7, respectively (Table 3).The data pertaining to the progressive leaf area of 5th leaf influenced by different concentrations of PBZ (Table 3 and Fig. 1).The leaf area increased by multifold between week 3 DAT and up to the harvesting stage. At week 3 DAT it ranged from 49.64 to 101.40 cm2, at week 5 DAT it ranged 90.87 to 147.24 cm2 and at week 7 DAT it ranged from 106.81 to 144.63 cm2 (Table 3).
Number of bud and the emergence of flower: Application of PBZ at different concentration was statistically found to have significance difference (Table 4). Changes were first noticed 3 weeks after the application of the treatment until the harvesting stage. The highest number of budding was recorded at week 7 after treatment ranged from 5.80 to 9.60 (Table 4). Results in Table 4 revealed T5 and T6 produced the shortest day for first and 50% flowering 0.95 times faster compared to the control (Fig. 2). Generally decrease was observed with increasing concentration of PBZ (Table 4).
Number of harvested fruit: Table 5 showing the number of mature fruit that harvested, influenced by different concentrations of PBZ after 2 months of transplanting. The number of harvested fruit generally increases with the increasing concentration of PBZ (T3-T6). T6 produced the highest number of harvested fruit 2.80 times higher compared to the control (Table 5).
| Table 1: Effect of different concentration of paclobutrazol on plant height of eggplants | |||
| Plant height (cm) | |||
| Treatment | Week 3 DAT | Week 5 DAT |
Week 7 DAT |
| T1 | 15.10±0.95b | 37.66±1.71a |
42.06±5.12a |
| T2 | 19.82±2.31b | 33.52±1.70ab |
50.00±3.64a |
| T3 | 16.98±2.01b | 35.80±1.58ab |
45.90±2.55a |
| T4 | 15.72±0.62b | 33.92±2.91ab |
46.16±4.07a |
| T5 | 18.84±1.21b | 29.70±2.17b |
41.50±1.96a |
| T6 | 25.40±1.07a | 38.18±1.21b |
43.04±2.07a |
*Means±S.E within the same column followed by the same letter, do not differ significantly according to LSD test at α = 0.05 |
|||
| Table 2: Effect of different concentration of paclobutrazol on number of leaves of Eggplant | |||
| Number of leaves | |||
| Treatment | Week 3 DAT | Week 5 DAT |
Week 7 DAT |
| T1 | 25.00±0.33a | 42.00±1.00c |
56.00±3.51a |
| T2 | 23.00±1.73a | 46.67±2.65bc |
61.33±1.86a |
| T3 | 24.33±1.15a | 49.67±4.67ab |
60.33±4.37a |
| T4 | 29.33±0.88a | 54.33±5.36ab |
72.67±2.60a |
| T5 | 28.00±4.70a | 56.67±2.73a |
66.33±9.49a |
| T6 | 25.06±4.16a | 47.39±0.88a |
68.67±5.17a |
*Means±SE within the same column followed by the same letter, do not differ significantly according to LSD test at α = 0.05 |
|||
| Table 3: Effect of different concentration of paclobutrazol on number of branch of eggplant | ||||||
| Number of branch | Leaf area (cm2) | |||||
| Treatment | Week 3 DAT | Week 5 DAT |
Week 7 DAT |
Week 3 DAT | Week 5 DAT |
Week 7 DAT |
| T1 | 0 | 12.00±0.32a |
13.80±0.49a |
60.38±20.39ab | 122.77±19.14ab |
115.82±13.81a |
| T2 | 0 | 11.40±1.08a |
13.60±1.12a |
73.45±14.73ab | 147.24±9.90ab |
126.41±10.10a |
| T3 | 0 | 11.40±0.51a |
15.00±0.45a |
49.84±20.05ab | 108.06±14.00a |
123.11±12.04a |
| T4 | 0 | 11.20±0.37a |
15.20±0.73a |
57.69±15.34b | 90.87±3.43ab |
144.63±17.86a |
| T5 | 0 | 10.60±0.60a |
16.00±1.10a |
101.40±10.84ab | 121.08±16.82b |
121.13±15.24a |
| T6 | 0 | 11.00±0.32a |
15.20±0.20a |
68.33±9.51a | 120.98±16.24ab |
106.81±13.74a |
*Means±SE within the same column followed by the same letter do not differ significantly according to LSD test at α = 0.05 |
||||||
| Table 4: Effect of different concentration of paclobutrazol on number of bud of eggplant | ||||
| Number of bud | Emergence of flower | |||
| Treatment | Week 3 DAT | Week 5 DAT |
Week 7 DAT |
Day took for 1st and 50% flowering |
| T1 | 0 | 5.20±0.58b |
7.40±1.03ab |
68.25±0.75a |
| T2 | 0 | 5.00±1.10b |
5.80±0.58b |
66.25±0.75ab |
| T3 | 0 | 4.60±0.81b |
9.60±1.47a |
66.50±0.50ab |
| T4 | 0 | 5.20±1.02b |
7.60±0.87ab |
67.25±0.25a |
| T5 | 0 | 4.80±0.73b |
9.00±1.00ab |
64.50±0.87b |
| T6 | 0 | 9.40±1.08a |
6.80±1.28ab |
64.50±0.50b |
*Mean±S.E within the same column followed by the same letter, do not differ significantly according to LSD test at α = 0.05, DAT: Days after Transplant |
||||
| Fig. 1(a-f): | Effect of different concentration paclobutrazol on plant growth and development (leaf area) pf eggplant under polybag condition, Fruit, (a) 0 mg L–1, (b) 25 mg L–1, (c) 50 mg L–1, (d) 100 mg L–1, (e) 150 mg L–1 and (f) 200 mg L–1 |
| Fig. 2(a-c): | Effect of different concentration paclobutrazol on flower and fruit formation on 64th day of growth, (a) 0 mg L–1, (b) 25 mg L–1, (c) 50 mg L–1, (d) 100 mg L–1, (e) 150 mg L–1 and (f) 200 mg L–1 |
| Fig. 3(a-f): | Effect pf different concentration of paclobutrazol on number of eggplant fruit, (a) 0 mg L–1, (b) 25 mg L–1, (c) 50 mg L–1, (d) 100 mg L–1, (e) 150 mg L–1 and (f) 200 mg L–1 |
The data is showing yield in terms of weight of eggplants influenced significantly by different concentrations of PBZ after 2 months of transplanting. Table 5 shows that T2 produced the highest yield compared to the control (Fig. 3). The application of PBZ has a significant effect on the length of the fruits 2 months after transplanting. Table 5 shows the highest fruit length was produced by T1 (17.80±0.20 cm) and the least was produced by T2 compared to the control (Fig. 4). Means were subjected to statistical analysis. The highest fruit diameter was produced by T3 (4.03±0.13 cm) followed by T1 (3.94±0.24 cm), T5 (3.84±0.30 cm) (Table 5 and Fig. 3).
Root length, chlorophyll and TSS contents: Results showed that the longest root length obtained on T3 at (80.10±23.80 cm) and the lowest is obtained by T5 at (53.70±2.55 cm). In general the length of the root decrease with increasing PBZ concentration (Table 6 and Fig. 5). Chlorophyll content influenced by the application of different concentrations of PBZ. Chlorophyll content was found to be increasing 3 weeks after the application of the treatment (Table 6). The total soluble solid was influenced by the application of different concentrations of PBZ. The highest TSS content was obtained from treatment 2 and 5 (Table 6). Increased TSS contents were observed from treatment 2 up to treatment 5 but decreased was recorded at treatment 6 (Table 6).
Fresh and dry weight: The fresh weight of the shoot was influenced by the application of different concentrations of PBZ. The study revealed as shown in Table 7 T3 exhibited the highest fresh weight of shoot at 238.03±59.77 g. Increased in the weight of a fresh shoot was observed from T3 upward. Means differences were statistically analyzed (Table 7). Treatment 5 produced the highest dry weight of shoot at 91.30±50.10 g and the least was produced from treatment 2 at 28.00±1.90 g even as compared to control at 30.70±8.40 (Table 7). The data regarding to the fresh weight of the root was influenced by the application of different concentrations of PBZ.
| Fig. 4(a-f): | Effect of different concentration paclobutrazol on length and diameter of eggplant, Fruit, (a) 0 mg L–1, (b) 25 mg L–1, (c) 50 mg L–1, (d) 100 mg L–1, (e) 150 mg L–1 and (f) 200 mg L–1 |
| Table 5: Effect of different concentration of paclobutrazol on number of harvested fruit, yield, fruit length and fruits diameter of eggplant | ||||
| Treatment | Number of harvested fruit |
Yield (g) |
Fruit length (cm) |
Fruit diameter (cm) |
| T1 | 1.00±0.00b |
127.33±11.41b |
17.80±0.20a |
3.94±0.24a |
| T2 | 2.60±0.51a |
190.33±14.75a |
14.61±0.33b |
3.64±0.12a |
| T3 | 1.60±0.40ab |
154.67±9.17ab |
16.79±1.19a |
4.03±0.13a |
| T4 | 1.80±0.37ab |
119.33±6.06b |
14.27±0.51bc |
3.73±0.22a |
| T5 | 2.00±0.63ab |
117.33±24.55b |
12.23±0.63c |
3.84±0.30a |
| T6 | 2.80±0.20a |
187.00±14.73a |
13.22±0.69bc |
3.76±0.17a |
*Mean±S.E within the same column followed by the same letter, do not differ significantly according to LSD test at α = 0.05 |
||||
| Table 6: Effect of different concentration of paclobutrazol on root length, chlorophyll and TSS Contents of eggplant | |||||
| Chlorophyll content | |||||
| Treatment | Root Length (cm) |
Week 3 DAT | Week 5 DAT |
Week 7 DAT |
TSS contents (%) |
| T1 | 68.25±7.85a |
39.44±0.76a | 39.07±0.86c |
41.80±0.19c |
5.35±0.15a |
| T2 | 53.70±4.10a |
41.96±1.10a | 42.23±1.33bc |
43.27±0.71bc |
6.25±0.05b |
| T3 | 80.10±23.80a |
41.62±0.29a | 41.84±2.08abc |
47.92±2.36abc |
6.10±0.20b |
| T4 | 56.25±5.45a |
40.36±0.72a | 42.61±0.67abc |
47.69±2.67abc |
6.10±0.10b |
| T5 | 60.95±2.55a |
41.89±0.31a | 46.39±1.99ab |
48.69±1.16ab |
6.25±0.05b |
| T6 | 67.95±1.65a |
40.87±0.88a | 41.66±0.50a |
51.29±2.82a |
5.85±0.15b |
*Mean±S.E within the same column followed by the same letter, do not differ significantly according to LSD test at α = 0.05 |
|||||
| Fig. 5(a-f): | Effect of different concentration of paclobutrazol on root length of eggplant (a) 0 mg L–1, (b) 25 mg L–1, (c) 50 mg L–1, (d) 100 mg L–1, (e) 150 mg L–1 and (f) 200 mg L–1 |
| Table 7: Effect of different concentration of paclobutrazol on the fresh and dry weight of eggplant shoot | ||||
| Treatment | Fresh weight of shoot (g) |
Dry weight of shoot (g) |
Fresh weight of root (g) |
Dry weight of root (g) |
| T1 | 148.67±26.24a |
30.70±8.40a |
81.24±6.52a |
10.75±1.35a |
| T2 | 144.86±31.30a |
28.00±1.90a |
91.24±13.32a |
15.33±2.03a |
| T3 | 238.03±59.77b |
45.10±12.40b |
103.68±40.87a |
22.76±11.38a |
| T4 | 206.23±75.34b |
37.20±13.90a |
86.11±7.33a |
14.40±2.80a |
| T5 | 209.39±67.46b |
91.30±50.10b |
82.18±15.37a |
19.35±6.25a |
| T6 | 176.41±23.21b |
76.60±14.30b |
76.72±24.20a |
15.00±5.60a |
*Mean±S.E within the same column followed by the same letter, do not differ significantly according to LSD test at α = 0.05 |
||||
The fresh weight of the root was generally increasing with increasing of PBZ from T2 to T3 ranged 81.24 g to 103.68 g (Table 7).
The heaviest fresh root is obtained by T3 (103.68±40.87 g) and the smallest obtained by T6 (76.72±24.20 g). Table 6 shows that treatment 3 produced the highest dry weight at (22.76±11.38 g) and the smallest obtained by T1 (10.75±1.35 g). Generally, the dry weight of root is high when applying PBZ compared to control. However, there is an insignificant difference (p>0.05) on dry root weight under different PBZ concentrations.
DISCUSSION
Food agricultural organization has ranked Eggplant as 4th most consumed vegetables in the world and equally important vegetable crops in countries of Asia, Mediterranean and Africa also with medicinal potentials19. Brinjal is season warm crops that develop fruits in a ranging temperature during the 25 to 35°C and at night 20 to 27°C, respectively19. Ralmi et al.20 stated that the temperature affects the plant growth development as well as the resistance capacity of the plant. In Asia consumption of eggplants is increasing every day21. The growing interest of Asians on eggplants is as a result of the preference on their native vegetables14. People now are days are very conscious of their health status22. The Discovery of the natural and synthetic regulators for plant growth development is widely adopted15. Therefore, chemicals are applied to improve the quality, development and yield of vegetable crops.
PGRs (Plant growth regulators) that inhibit plant growth development are been effectively utilized for the wellbeing of the plant. Quite a number of growth chemical promoters are in used for the plant treatments for quality enhancement, yield and development23. Khandaker et al.18 reported usage of plant growth regulators for the modification of vegetative growth, quality and yield in horticultural crops. One of these essential natural chemicals is paclobutrazol that is an endogenous hormone responsible for the regulation of the physiological process taken place in plant development24. To increase productivity in potato in tropical climate paclobutrazol was applied17.
Six different treatments of paclobutrazol were examined at week 3, week 5, and week 7 days after the application of the treatment (DAT) in the present study respectively. The present study found increased in the application paclobutrazol of on eggplants has significantly increased the plant's height, number of leaves, leaves the area, number of branches and number of buds. In a similar vein, previously Khandaker et al.12 reported that plant growth regulators are significantly playing a role in the physiological development of horticultural crops. Miceli et al.22 reported on the effect of Gibberellic Acid on yield, growth, and Quality of Rocket and Lettuce and found the growth regulators significantly contribute to the morphological development of the said plants. Foliar application PBZ increased the number of leaves of Lagerstroemia indica plants10. Paclobutrazol were effectively reported as effective plant growth regulators in enhancing morphological features of ornamental plants.
Chlorophyll content has been described as a crucial parameter in agronomy18. Chlorophyll is the green pigment common to all photosynthetic cells that absorbs light to be used in the phosphorylation process25. PBZ used was found to increase chlorophyll content among the treatments with an increase in the concentrations. Chlorophyll levels in plants is in correlation with the nitrogen content of the leaves in plants, in a similar way with photosynthetic capacity and productivity of the plants. PBZ increased chlorophyll contents due to the increased number of chloroplast and their sizes also PBZ increased the synthesis of cytokinin which is responsible for the differentiation of chloroplast and prevent degradation of the chlorophyll. A total soluble solid (TSS) of fruit is one of the parameters that strongly affect consumer acceptability of a variety26. Total soluble solid was found to be significant as compared to the control. The relocation of carbohydrates was responsible for the increased TSS in plants27. TSS increased was also due to the assimilation under directional leading to the developments of fruits18.
Application of 150 and 200 mg L–1 of paclobutrazol as treatments 5 and 6, respectively, were found to produce early flowering as compared to the control that subsequently results in the harvesting higher number of fruits from the eggplant. Early flowing in plants is an indication of good developments in plants. The diameter of the harvested fruits was found to significantly higher than the control. Bottle gourd was observed to produce an early flower with the application of PBZ18. The superior effect of PBZ increased the number of fruit and fruit weight. Increased in fruits number and weight observed with the application of PBZ in vegetables is a result of the building of carbohydrates before leaf abscission28. Weight of fruits experience with the application is a result of carbohydrate accumulations which speed up rapid growth and increase crop yields. Dry matter is what remains after all of the water was evaporated out and was an indicator of the number of nutrients that are available to the plant. Fresh weight shoot, dry weight shoot, fresh weight root, dry weight root were found to have a significant difference among the treatments used for the study. Dry matter content was also an important attribute in plant ecology because they are associated with many critical aspects of plant growth and survival29.
PBZ application did not produce any significant effect on the root length of the brinjal plant. Mahmoud and Mohamed30 reported that the root length of the brinjal plant decrease by applying PBZ compared to control. However, Nivedithadevi et al.31 reported that root length of brinjal and soybean respectively increasing by applying PBZ compared to control. Basra32 reported that PBZ can stimulate or inhibit the root growth depending on plant species and concentration of PBZ. This study indicated that the fresh and dry weight of brinjal shoot increased with PBZ application. Similar findings are reported by Bundit et al.33 who stated that paclobutrazol application increased the fresh and dry shoot weight of rice plants under salt stress conditions. Paclobutrazol did not produce any significant effect on the root fresh and dry weight of brinjal plants. Besides, Hedayatullah et al.34 that reported the application of PBZ increases the dry weight of the root of the olive plant. Martinez et al.35 also stated that PBZ treatment increase the carbohydrate content in the seedlings that help to enhance the flowering and fruiting in plants. It was found that the higher concentration of PBZ decreases the length of the Brinjal plant. The root length of the soybean plant increased with PBZ applications36. It has been also reported that PBZ can stimulate or inhibit the root growth depending on plant species and concentration of PBZ32-37.
CONCLUSION
The growth parameters of Solanum melongena were significantly improved by the application of PBZ with an increase in concentration. It can be concluded that the tested concentration of paclobutrazol 200 mg L–1 increases the growth, yield and quality of brinjal under potted condition. Paclobutrazol reduces the vegetative growth specifically that related to gibberellin hormone and induce the early flowering and promotion of flower bud which increases yield and quality of brinjal fruit. The study recommends the use of PBZ on Solanum melongena for better yields and quality production.
SIGNIFICANCE STATEMENT
This study discovered that the potential application of paclobutrazol (TBZ) to enhance the growth, flowering, and fruit development of eggplant/brinjal crop. TBZ also significantly improved the fruit quality of eggplant. This study has a great significance on the improvement of vegetable as well as fruit industry under tropical field conditions.
ACKNOWLEDGMENT
The authors wish to acknowledge the support of the Center for Research Excellence and Incubation Management (CREIM), Universiti Sultan Zainal Abidin Malaysia, Terengganu, Malaysia.