Overall, plant growth regulators cause physiological and morphological changes that are controlled by their concentrations, tissue sensitivity and species involved
(Llanes et al., 2019). The main purpose of this study was to know whether phytohormones like indole butyric acid and gibberellins, would have any better response than untreated control on different agro-morphological parameters of chickpea.
The results of Petri dishes experiment denoted that the shoot length varied in different doses of exogenous GA3 (Table 2). The shoot length was significantly improved with all GA3 doses at 6 and 9 days after hormone application. Furthermore, the concentrations 0.1 g/l and 0.2 g/l increased significantly (P<0.05) the shoot length especially at 12 days after hormone treatment. The results in pots confirmed those found in Petri dishes conditions (Table 6). The different GA3 treatments increased significantly (P<0.05) the plant height compared with the control. Our results showed that the best GA3 treatment for highest plant height was 0.2 g/l. A previous study revealed that gibberelic acid treatment (0.2 mg/l) obtained the maximum shoot elongation of African violet (
Saintpaulia ionantha) with an average of 19.9 mm
(Ghasemi et al., 2012). It was also revealed that the treatment with GA3 at 20 mg/l concentration increased the cell size in higher plants of
Chlorella sorokiniana (Ozioko et al., 2015). Another study indicated that the GA3 may play a role in stimulating cell elongation and expansion but not in cell division of plant
(Romanenko et al., 2016). Studies of GA3 signal transduction, using genetic approaches, GA3-regulated transcriptional responses are controlled by the DELLA proteins, which function by repressing different types of transcription factors
(Lantzouni et al., 2020).
The results of Petri dishes experiment showed that IBA hormone increased significantly (P<0.05) the shoot length under 10
-4 and 10
-3 g/l compared to the untreated plant. In contrast, the shoot length decreased significantly (P<0.05) compared to the control after the IBA treatment with 10
-5 and 10
-2 g/l concentrations (Table 3). Overall, the findings of pots revealed that all IBA treatments improved the plant height. A significant (P< 0.05) differences between treated and control plants were only observed in IBA treatment (10
-4 g/l and 10
-3 g/l) at pre-flowering stage (Table 6). This is in agreement with the results of
Zayed et al., (2017) who reported that the plant height was significantly increased due to auxin treatments in two sunflower cultivars (Sakha 53 and China) grown under saline stress (120 mM NaCl). It has also been postulated that the application of Indole-3-acetic acid (auxin) improved the length and dry matter yield of shoot on wheat plant
(Youssef et al., 2020). In this context, auxins may enhance plant growth by stimulating the photosynthesis by raising the contents of chlorophylls and by activating cellular redox systems (
Piotrowska-Niczyporuk and Bajguz, 2014;
Dao et al., 2018).
Regarding the effect of phytohormone on the radicle length, the results of Petri dishes experiment showed that the IBA concentrations (10
-5 g/l and 10
-4 g/l) increased significantly (P< 0.05) the radicle length (Table 4). However, the treatment with IBA concentrations (10
-3 and 10
-2 g/l) reduced significantly (P< 0.05) the radicle growth compared to the control plants.
Wolters and Jürgens (2009) suggested that the auxin increased roots branching, which is important in enhancing drought tolerance. According to
Tilahun et al., (2019), the tip cutting with the 11 g/l IBA treatment increased the length and number of roots of
Araucaria heterophylla species.
Chauhan et al., (2015) also observed that the application of IAB (0.5 mg/l) promoted the root initiation and growth in “
Allium hookeri Thw. Enum.” plant.
The results of Petri dishes experiment showed that the concentration of GA3 at 0.2 g/l increased significantly (P<0.05) the radicle length compared to the control in the different dates of the hormonal treatments (Table 5). However, for the other concentrations, a decrease in radicle length was observed.
The exogenous application of IBA was found positive and suitable in the level of nodulation. As shown in Table 6, the average number of nodules was 18.2 for the control plant. After IBA treatment, the nodules number was significantly (P<0.05) increased compared to control plant for various hormone treatment doses and different plant development stages. The highest number of nodules was recorded for the IBA treatment (10
-3 g/l) on post-flowering. These data are in agreement with
Hirsch et al., (1989) who showed that auxin transport inhibitors (N-1-naphthyl) phthalamic acid (NPA) and 2, 3, 5-triiodobenzoic acid (TIBA) evolved the nodules formation
in Medicago sativa.
de Billy et al., (2001) indicated that auxin phytohormone is necessary through the development of nodule primordial and of the vasculature within the nodules of
Medicago truncatula.
The number of nodules varied according to the stage of contribution of the GA3 phytohormone (Table 6). The highest level of nodulation was found with the GA3 contribution (0.1 g/l) at post-flowering.
Ferguson et al., (2005) postulated that the application of an exogenous GA3 increased significantly the nodules number of the mutants of
Pisum sativum plants and also noted that the nodule formation of these mutants is strictly controlled by the GA3 concentration. According to
Rafique et al., (2021), the highest levels of nodules (16) and their dry biomass (0.22 g) were obtained by exogenous treatment of GA3 at 10
-5 M combined with
Rhizobium inoculation.
The analysis of results showed that only the 10
-4 g/l IAB concentration at germination then at pre-flowering stages induced significantly leaves number in comparison with the control sample (Table 6). All GA3 phytohormone treatments resulted in a significant increase in the number of leaves compared with the untreated plant.
For the number of branches, a significant increase between treated and control plants were only observed in IBA treatment (10
-4 g/l) at germination then at pre-flowering stages and at post-flowering stage (Table 6). All treatments of plants with GA3 phytohormone increased significantly (P<0.05) this parameter compared to the untreated plant. The highest number of branches was noted for the 0.1 g/l GA3 treatment on pre-flowering. At the cellular level, the auxin responses were dependent upon the presence of Auxin Response Factors (AFRs) transcription factors and Auxin/Indole-3-Acetic Acid (Aux/IAA). These proteins are determined on their capacity to bond to promoter elements that confer auxin responsive gene expression (
Emenecker and Strader, 2020).
No significant variation was observed in fresh weight of the aerial part of the plant between treated and non-treated plants among the different IBA phytohormone treatments (Table 6). The fresh weight of the aerial part of the plant was significantly raised under treatment with GA3 phytohormone at post-flowering stage (0.1 g/l and 0.2 g/l) and at pre-flowering stage (0.2 g/l). Dry weight of the aerial part of the plant was significantly improved with IBA phytohormone treatment (10
-4 g/l and 10
-3 g/l) at germination then at pre-flowering stages and at pre-flowering stage (Table 6). However, dry weight was significantly higher in the all GA3 hormone-treated plants as compared to the controls ones. Overall, the vegetative growth parameters of chickpea such as number of branches, fresh and dry weight of the aerial part and leaves number, were increased in plants treated with IBA and GA3 in certain treatment stages. According to
Mousavi et al., (2016), the β-carotene content and cell growth of
Dunaliella salina, were positively affected by indole-3-acetic acid at 1 μM.
Zayed et al., (2017) postulated that the growth parameters such as leaf area and shoot and root fresh and dry weight were increased in sunflower plant treated with indole-3-acetic acid (auxin).
No significant increase in flowers number between treated and control plants, was observed in different IBA phytohormone treatments (Table 6). The highest flowers number was found with 10
-4g/l IBA at germination then at pre-flowering stages. The seeds number was significantly raised at IBA phytohormone treatments compared with the control plants (Table 6). The treatment of chickpea plants with IBA phytohormone (10
-4 g/l and 10
-3g/l concentrations at different stages) increased significantly the weight of seeds (Table 6). Compared to the control, the seeds weight of plants treated by 10
-3g/l IAB at germination then at pre-flowering stages was 3-fold higher.
Hasami and Abdi (2010) reported that application with Naphthaleneacetic acid (synthetic auxin) at 100 ppm, caused appreciable and significant increases in physical properties (Fruit weight, height, diameter and size) of date palm.
We note that all treatments with GA3 raised significantly the flowers number compared to the untreated plant. In addition, the weight and the number of seeds were increased in GA3 hormone-treated plants at post-flowering.
Rady et al., (2021) revealed that foliar application of gibberellic acid at 20 mg/l in faba bean increased the growth, green pod yield and water use efficiency.
Perumal et al., (2021) suggested that the application of GA3 significantly improved the average fruit yield in plant of kinnow (
Citrus reticulate Blanco). Moreover,
Valleser (2023) working in pineapple plant found that the presence of auxin, gibberellin and cytokinin promoted fruit size and quality.