Effect of plant growth regulators and pinching on growth parameters in Gaillardia (Gaillardia pulchella)

Introduction

Gaillardia (Gaillardia pulchella) commonly known as blanket flower, is a widely grown annual flower crop in India. It is mainly cultivated for cut flowers, while its loose flowers are used for garlands and decorations in religious and social functions. The crop is easy to grow and is influenced by factors such as environment, genetics, and crop management. Plant growth regulators (PGRs) are used to control plant growth and development, including plant height, flowering, and yield. They affect hormonal and enzymatic activities, which in turn influence plant growth, flower yield, and quality. Pinching is a common practice in flower crops that encourages side branching, resulting in more flowers and improved quality. Both PGRs and pinching also affect plant and flower biomass. Therefore, the present study was conducted to evaluate the effect of PGRs and pinching on the vegetative parameters of plants in gaillardia.

Observations on plant height, branches, plant spread, leaf area, and internodal length were recorded and statistically analysed following the method of Panse and Sukhatme (1985) [10] .

Results and Discussion 1. Effect of plant growth regulators and pinching on plant height of gaillardia

The data on plant height of gaillardia as influenced by the plant growth regulator and pinching treatments are presented in Table 1.

Effect of plant growth regulators

Data revealed that the plant growth regulators had significant influence on the plant height at 60 DAT, 90 DAT and 120 DAT. However, at 30 DAT, the plant height was not significantly altered by PGR treatment as the plants showed almost uniform growth till 30 DAT. Maximum plant height (42.85 cm), (77.68cm) and (107.78 cm) at 60, 90 and 120 DAT, respectively observed in in T 5 (GA 3 @ 200 ppm). The lowest plant height at 60, 90 and 120 DAT, 20.37cm, 36.80cm and 53.98 cm was observed in the treatment T 7 (CCC @ 2000 ppm). The gibberellic acid is known for its effect on cell elongation in the plants. The increase in plant height with increase in GA 3 concentration was observed in current experiment. The rapid growth in GA 3 treatments might be due to a greater number of cells formed and increased elongation of the individual cell. These results are in closed confirmatory in Gaillardia reported by (Ghadage et al., 2010; Kadam et al., 2020) [2,7] .

Effect of pinching

It is revealed that the pinching had significant influence on the plant height at all growth stages except 30 DAT (Table 1) as pinching was done at 30 days after transplanting. At 60, 90 and 120 DAT, the significantly highest plant height (29.88 cm, (51.50 cm and 76.79 cm, respectively) was recorded in P 2 (No-pinching) treatment, while 28.88 cm, 50.65 cm and 74.29 cm plant height at 60, 90 and 120 DAT, respectively was found due to pinching at 30 DAT (P 1 ) treatment. The reduced plant height observed in pinched plant which might be due to fact that the vertical growth of a plant is arrested by removing top most part of the shoot i.e. apical growth. Certainly, the maximum plant height was produced by no-pinching treatment. Similar findings were also observed in marigold by (Sunita et al., 2007; Patade et al. 2020) [18,11] .

Interaction effect

The interaction effect between PGR and pinching treatment on plant height of gaillardia was non-significant at 30, 60 and 90 DAT. However, the plant height was significantly altered by plant growth regulators and pinching treatments at 120 DAT. maximum plant height (110.27cm) was recorded in T 5 P 2 (GA 3 @ 200 ppm + no pinching) treatment at 120 DAT and it was followed by T 5 P 1 (105.30), T 4 P 2 (101.37 cm), T 4 P 1 (98.80cm) treatment combinations. While the lowest plant height was recorded in T 7 P 1 (CCC @ 2000 ppm + pinching) (53.67cm) which was at par with T 7 P 2 . Growth might also be increased due to osmotic uptake of water and nutrients under the influence of GA 3 which maintain swelling force against the softening of cell wall and thereby increasing the plant height (Lockhart 1960) [9] .

Effect of plant growth regulators and pinching on plant spread (E-W and N-S) of Gaillardia Effect of plant growth regulators

The data on plant spread of gaillardia was influenced by the plant growth regulator and pinching are presented and in Table 2 and3. The data perused that the plant spread (E-W and N-S) at 60, 90 and 120 DAT growth stage was significantly influenced by the application of different plant growth regulators and the pinching treatments. At 30 DAT, the noteworthy difference was not observed at the treatments were imposed at 30 DAT. Their interaction showed the non-significant effect on plant spread (Table 2 and3). The spread was increased continuously in the growth phase and it was with faster rate up to 90 DAT and the rate was lowered down afterwards.

Effect of plant growth regulators

At 30 DAT, the plants showed nearly uniform spread and within the range of 13.93 cm to 15.97 cm (East-West) and 15.18 to 17.17 cm (North-South). At 60 DAT, treatment T 5 (GA 3 @ 200 ppm) recorded the significantly highest eastwest plant spread (33.93cm) which was at par with T 6 , T 7 , and T 1 treatments. The lowest east-west plant spread (26.47cm) was recorded in the treatment T 2 (Ethephon @ 500 ppm) which was at par with T 3 treatment. In case of north-south plant spread, the highest value (35.52 cm) was registered in T 5 (GA 3 @ 200 ppm) The minimum plant spread (North-South) was observed in T 2 treatment (28.84 cm) and it was at par with T 3 . At 90 DAT, the maximum plant spread (63.20 cm east-west and 64.73 cm north-west) was recorded in T 5 treatment (GA 3 @ 200 ppm) and it was at par with T 1 treatment (Control). Lowest plant spread (45.58cm and 47.32 cm, respectively) was observed in T 2 (Ethephon @ 500 ppm) treatment. The similar trend was consistently noticed in at 120 DAT and the significantly maximum east-west and north-south plant spread (69.22cm and 70.77 cm) was recorded in T 5 treatment (GA 3 @ 200 ppm). The lowest (E-W) plant spread (60.15 cm) and (N-S) plant spread (61.63 cm) was recorded in T 2 (Ethephon @ 500 ppm). GA 3 was found effective in increasing plant spread in gaillardia. According to (Verma, 1991) [19] it was due to the formation of new cells in meristematic region and an increase in size and mass of cells produced. The promotive effect of gibberellins on growth may be due to increasing auxin level of tissues which causes cell division and cell elongation which in terms induces the lateral growth and ultimately also increases the number of branches and thereby plant spread. The similar results were reported in chrysanthemum (Gohel 2001; Gupta and Dutta 2001) [3,4] .

Effect of Pinching

At 60 DAT, 90 DAT and 120 DAT the maximum plant spread (31.73cm, 56.48cm and 65.44 cm, respectively for east-west direction and 33.58cm, 57.85 cm and 66.70 cm, respectively for north-south direction) was in P 1 (pinching at 30 DAT) treatment which was significantly superior over P 2 (no pinching) treatment (30.50 cm, 54.55 cm and 63.37 cm, respectively for east-west direction and 32.18 cm, 56.11cm and 64.80 cm, respectively for north-south direction) .The higher plant spread in pinched plants was possibly due to the fact that by removal of the apical portion more energy might have been created to promote the number of side branches. (Moon et al., 2018) [9] also observed higher plant spread of plant at 50% flowering were recorded in pinching at 30 DAT and. The similar results were reported in marigold (Jyothi et al., 2018) [6] .

Interaction Effect

The interaction effect between PGR and pinching treatment on plant spread (east-west and north-south) of gaillardia was non-significant at all growth stages.

Effect of plant growth regulators and pinching on primary and secondary branches of Gaillardia

The data pertaining to the effect of number of primary and secondary branches at 30, 60, 90 and120 days interval are presented in Table 4 and5.

Effect of plant growth regulators

It is revealed that the plant growth regulators had significant influence on the number of primary and secondary branches at 60, 90 and 120 DAT. At 60 DAT, the treatment T 5 (GA 3 @ 200 ppm) registered the highest number of primary branches (22.70). The lowest number of primary branches per plant (17.30) was in T 6 (CCC @ 1000 ppm). At 90 DAT, the significantly highest number of primary branches (25.53) was recorded in treatment T 4 (GA 3 @ 100 ppm) which was closely followed by T 5 treatment. The least number of primary branches (22.52) was in T 3 i.e. Ethephon @ 100 ppm treatment which was at par with the rest of the treatments. At 120 DAT, the trend was changed and again the highest number of primary branches (30.33) was recorded in treatment T 5 (GA 3 @ 200 ppm) and it was at par with T 4 treatment. The lowest number of primary branches (25.38) was observed in T 1 (Control) treatment. At 60 DAT, 90 DAT and 120 DAT maximum number of secondary branches were observed in T 5 (GA 3 @ 200 ppm) i.e. 27.38, 39.72 and 44.43, respectively. Lowest number of secondary branches was recorded in the treatment T 6 (23.07) in control at 60 DAT. Minimum number of branches at 90 DAT was recorded in T 6 (CCC @ 1000 ppm) and at, 120 DAT treatment T 1 (Control) recorded minimum number of branches. Increase in the number of branches by GA 3 treatment might be due to hyper elongation of internodal length and result antincrease in internodal count of the main axis. The similar observations were also recorded gaillardia and marigold (Patil, 2002 [12, 5, 13] .

Effect of Pinching

It is revealed that the pinching had significant influence on the on the number of primary and secondary branches at 60 DAT, 90 DAT and 120 DAT. However at 30 DAT number of primary and secondary branches was not significantly altered by pinching treatment. At 60 DAT, 90 DAT and 120 DAT highest number of primary branches (20.48, 24.43 and 27.58 respectively) was recorded in P 1 (pinching at 30 DAT) treatment, which was significantly superior over P 2 (nopinching) treatment and 60 DAT, 90 DAT and 120 DAT highest number of secondary branches (25.67, 36.27 and 40.33 respectively) was recorded in P 1 (pinching at 30 DAT) treatment, Which was significantly superior over P 2 (nopinching) treatment. Number of branches per plant may have increased due to pinching of plant which might have forced the auxiliary buds to thrive well Increasing number of branches per plant which might due to effect of removing apical portion of plant. Similar results were observed in marigold (Sarkar et al., 2018; Singh et al., 2019) [16,17] .

Interaction Effect

The interaction effect between PGR and pinching treatment on number of primary branches per plant of Gaillardia showed significant variation at 90 DAT but did not varied significantly at 30 and 60 and 120 DAT. Maximum (26.17) number of primary branches in T 5 P 1 (GA 3 @ 200 ppm + pinching) which was followed by treatment T 4 P 1 ( GA 3 @ 100 ppm + pinching) at 90 DAT and minimum (21.60) number of primary branches recorded in T 3 P 2 (Ethephon @ 1000 ppm + no pinching) treatment. At 120 DAT, maximum (45.60) number of secondary branches observed in T 5 P 1 (GA 3 @ 200 ppm + pinching) treatment. It was followed by T 5 P 2 (43.27) (GA 3 @ 200 ppm + no pinching) treatment and minimum (37.53) number of primary branches recorded in T 1 P 2 (Control + no pinching) treatment.

The data on leaf area of gaillardia as influenced by the plant growth regulator and pinching are presented in Table 6.

Effect of plant growth regulators

The plant growth regulators had significant influence on the leaf area at 60 DAT, 90 DAT and 120 DAT. However at 30 DAT, leaf area was not significantly altered by PGR treatments where the average leaf area was 2.37cm 2 . At 60 DAT treatment T 5 (GA 3 @ 200 ppm) recorded the significantly maximum (14.70 cm 2 ) leaf area and it was at par with T 4 (14.57 cm 2 ). The minimum leaf area (7.58 cm 2 ) was found in T 1 (Control). At 90 DAT and 120 DAT the maximum leaf area (30.77 cm 2 and 29.47 cm 2 ) was recorded in T 4 (GA 3 @ 100 ppm) which was at par with T 5 (GA 3 @ 200 ppm). The least leaf area (22.83 cm 2 ) was observed in treatment T 3 (Ethephon @ 1000 ppm) at 90 DAT. The treatment T 1 (Control) recorded minimum leaf area (22.20 cm 2 ) at 120 DAT. Increase in leaf area in GA 3 might be due to cell division and cell elongation when favours the increased plant height and number of branches. Similar results were recorded in African marigold and Gaillardia. (Yadav et al., 2013; Kadam et al., 2020) [20,7] .

Effect of Pinching

Significantly maximum leaf area per plant at 60 DAT, 90 DAT and 120 DAT was observed in P 1 (Pinching at 30 DAT) i.e. 11.18 cm 2 , 26.92 cm 2 and 26.11 cm 2 respectively. While minimum leaf area 10.40 cm 2 , 25.74 cm 2 and 24.81 cm 2 , respectively was recorded in P 2 (no pinching). In pinching practice, apical dominance of plant, branch and leaf may get more sunlight which increased leaf area due to pinching. (Saleh and Yousif 2013) [15] found that leaf area was decreased in non-pinched plants compared with pinched once and pinched twice in Geranium plants.

Interaction Effect:

The interaction effect between PGR and pinching treatment on leaf area of Gaillardia was non-significant at all growth stages.

Effect of plant growth regulators and pinching on internodal length of Gaillardia

The data on internodal length of gaillardia as influenced by the plant growth regulator and pinching are presented Table 7.

Effect of Plant Growth Regulators

Plant growth regulator had significant influence on internodal length of gaillardia. The maximum internodal length (7.26 cm) was observed in treatment T 5 (GA 3 @ 200 ppm) which was followed by T 4 (6.43 cm), T 6 (4.56 cm), T 2 (4.18 cm), T 1 (3.61cm) T 2 (2.58 cm). The shortest internode (2.50 cm) was found in the treatment T 7 (CCC @ 2000 ppm). GA 3 is able to both cell division and cell elongation (Reddy and Sulladmath, 1983a) [14] . Owing to the fact increase GA 3 application, increased internodal length and cell enlargement that increases growth of plants and also increases auxin content which enhanced the apical dominance indirectly. Similar results were observed in Gaillardia. (Kadam et al., 2020) [7] .

Effect of Pinching

Pinching had significant influence on internodal length of gaillardia and the highest internodal length (4.69 cm) was observed in treatment P 1 (Pinching at 30 DAT) while least internodal length (4.20 cm) was observed in no pinching (P 2 ). The internodal length is highest in the pinched plant was observed than control which may be attributed to the forcing of plant for profuse sprouting by tip cutting. (Devi et al., 2019) [1] assessed the pinching effect on internodal length in carnation.

Interaction effect

The interaction effect between plant growth regulators and pinching treatment on internodal length of Gaillardia was non-significant. Pinching Treatments: 1) T1-Control 2) T2-Ethephon @ 500 ppm 1) P1-Pinching @ 30 DAT 3) T3-Ethephon @ 1000 ppm 4) T4-GA3 @ 100 ppm 2) P2-No pinching 5) T5-GA3 @ 200 ppm 6) T6-CCC @ 1000 ppm T7-CCC @ 2000 ppm 2) T2-Ethephon @ 500 ppm 1) P1-Pinching @ 30 DAT 3) T3-Ethephon @ 1000 ppm 4) T4-GA3 @ 100 ppm 2) P2-No pinching 5) T5-GA3 @ 200 ppm 6) T6-CCC @ 1000 ppm 7) T7-CCC @ 2000 ppm 2) T2-Ethephon @ 500 ppm 1) P1-Pinching @ 30 DAT 3) T3-Ethephon @ 1000 ppm 4) T4-GA3 @ 100 ppm 2) P2-No pinching 5) T5-GA3 @ 200 ppm 6) T6-CCC @ 1000 ppm 7) T7-CCC @ 2000 ppm 2) T2-Ethephon @ 500 ppm 1) P1-Pinching @ 30 DAT 3) T3-Ethephon @ 1000 ppm 4) T4-GA3 @ 100 ppm 2) P2-No pinching 5) T5-GA3 @ 200 ppm 6) T6-CCC @ 1000 ppm 7) T7-CCC @ 2000 ppm 2) T2-Ethephon @ 500 ppm 1) P1-Pinching @ 30 DAT 3) T3-Ethephon @ 1000 ppm 4) T4-GA3 @ 100 ppm 2) P2-No pinching 5) T5-GA3 @ 200 ppm 6) T6-CCC @ 1000 ppm 7) T7-CCC @ 2000 ppm 2) T2-Ethephon @ 500 ppm 1) P1-Pinching @ 30 DAT 3) T3-Ethephon @ 1000 ppm 4) T4-GA3 @ 100 ppm 2) P2-No pinching 5) T5-GA3 @ 200 ppm 6) T6-CCC @ 1000 ppm 7) T7-CCC @ 2000 ppm

PGRs Treatments

Pinching Treatments: 1) T1-Control 2) T2-Ethephon @ 500 ppm 1) P1-Pinching @ 30 DAT 3) T3-Ethephon @ 1000 ppm 4) T4-GA3 @ 100 ppm 2) P2-No pinching 5) T5-GA3 @ 200 ppm 6) T6-CCC @ 1000 ppm 7) T7-CCC @ 2000 ppm

Conclusion

The present investigation revealed that, plant growth regulators and pinching had significant effect on vegetative characters of gaillardia (Gaillardia pulchella L.). In PGR treatment GA 3 @ 200 ppm spray was found best with respect to vegetative attributes. In pinching treatment (Pinching at 30 DAT) found best with respect to maximum plant spread, higher number of primary and secondary branches, maximum leaf area, maximum internodal length.

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