Abstract: The effect of GA3 on germination and growth of two chickpea varieties i.e. C44 and Paidar 91 under different levels of NaCI salinity was studied. A gradual reduction in germination percentage plumule and radicle length and fresh and dry weights of plumule and radicle was observed under salt stress. GA3 treatment increased germination percentage under salt stress. It also improved fresh and dry weights of plumule and radicle along with an increase in their lengths. Significant results were obtained for all growth parameters except number of branches. Plant height and fresh and dry weight of shoot decreased under salinity stress. Application of 20 mg l–1 gibberellic acid compensated this adverse effect of salinity. The efficiency of gibberellic acid to mitigate the effect of salinity reduced with rise in salinity level.
Introduction
Salinity is a global problem that largely limits crop production, especially in irrigated areas of the world. It is also one of the major soil problems in Pakistan. Salt affected soils mostly occur in the arid and semi-arid regions of Pakistan. In Pakistan, total salinity affected area is 6173.5 thousand hectares. Soil salinity greatly hampers germination and related processes. It either completely inhibits germination at higher levels or induces a state of dormancy at low levels (Khan and Ungar, 1997).
Efforts have been made to ameliorate the adverse effect of salinity by employing certain chemical and biochemical agents. Gibberellic acid (GA3) and a mixture of GA4 and GA7 are used most frequently for the improvement of plant growth.
Radi et al. (1989) observed that increasing NaCI concentrations delayed germination and reduced germination percentage. Higher levels of salinity reduced seedling shoot length and root length. Pre-soaking in GA3 increased seedling growth. As salinity increased, growth regulator application had no effect on germination. However, growth regulators, have slightly counteracted the effects of salinity in cowpeas, pigeonpea and Phaseolus vulgaris (Khafagi et al., 1986).
Chickpea is a cash crop and cultivated on about 70 percent of total area in Pakistan. It is the cheapest and rich source ,of vegetable protein (20-24%), fats (4.3%) fiber (8.5%) and mineral matter (2.9%) that make up the deficiency of cereal diets. Because of diverse uses and its ability to thrive where inputs are inadequate and the environment is harsh, chickpea plays a vital role in the cropping system of subsistence farmers.
Keeping in view the importance and salt sensitivity of chickpea this project was initiated.
Materials and Methods
Lab. Experiment: The experiment to study the germination of chickpea varieties i.e. C441V1 ( and Paidar 91(V2) under different levels of salinity (NaCI) and salinity + GA3 solution was carried out in the laboratory of the Department of Botany, University of Agriculture, Faisalabad. It was designed as Completely Randomized with two factor factorial arrangement and three replications. A total of 42 petri dishes (21 for each variety) were used. Fifteen seeds of each variety were placed on a filter paper in each petri dish. 10 ml of water (control) or the specific solution of different treatments were added to the petri dishes.
Treatments were as follows:| T0 | = | Control (no salt added) |
| T1 | = | EC 4.00 dS m–1 |
| T2 | = | EC 8.00 dS m–1 |
| T3 | = | EC 12.00 dS m–1 |
| T4 | = | EC 4.00 dS m–1+20 mg l–1 GA3 solution |
| T5 | = | EC 8.00 dS m–1+20 mg l–1 GA3 solution |
| T6 | = | EC 12.00 dS m–1+20 mg l–1 GA3 solution |
The requisite amount of water, saline solution and saline+GA3 solution were applied regularly and carefully so as keep saturation of the filter papers. Data for seed germination were recorded, daily upto seven days. The data for the following parameters were also recorded.
Germination Percentage (%): Total number of seeds that germinated upto seven days was used to obtain germination percentage, which was calculated as under:
| DAP | = | Days after planting |
| 2. | = | Plumuie and Radicle length (cm) |
| 3. | = | Fresh weight of plumule and Radicle (g) |
| 4. | = | Dry weight of plumule and Radicle (g) |
Pot Experiment: The experiment was designed to study the effect of foliar application of gibberellic acid on growth of chickpea under different levels of NaCI salinity. The experiment was designed as completely randomized with two factor factorial arrangement and three replications. The soil used was analyzed and had the following properties.
| pH | = | 7.85 |
| Saturation percentage (%) | = | 28 |
| Electrical conductivity (Ece) | = | 2.0 dS m–1 |
The seeds were sown in earthen parts lined with polytene bags. Different treatments were given 21 days after germination. The following treatment schedule was followed.
| T0 | = | ECe 2.00 dS m–1 (control) |
| T1 | = | ECe 4 dS m–1 |
| T2 | = | ECe 8 dS m–1 |
| T3 | = | ECe 12 dS m–1 |
| T4 | = | ECe 4 dS m–1+20 mg l–1 GA3 |
| T5 | = | ECe 8 dS m–1+20 mg I–1 GA3 |
| T6 | = | ECe 12 dS m–1+20 mg 1–1 GA3 |
Data of various parameters were recorded at pod filling stage and analyzed statistically.
Results and Discussion
Germination (%): Application of different levels of salinity reduced germination percentage highly significantly (p<0.01) as show in Table 1.
| Table 1: | Gibberellin alleviation of NaCI salinity in chickpea (Cicer arietinum L.) |
| *,** = Significant at 5 and 1 %; NS = Non significant | |
| Table 2: | Gibberellin alleviation of NaCI salinity in chickpea (Cicer arietinum L.) |
| *,** = Significant at 5 and 1 %; NS = Non significant | |
Minimum germination (45.65%) was noted at 16 dS m–1 salinity in Paider 91, while maximum germination (100%) was observed in 4 dS m–1 salinity + 20 Mg 1-1 GA3 in C44. As the salinity levels increased the germination percentage decreased. Salinity induces numerous disorders in seed during germination. It reduces imbibition, causes toxicity, hampers protein metabolism and upsets plant growth regulator balance (Khan and Rizvi, 1994; Yupsanis et al., 1994).
Gibberellins under salt stress release the seed from physiological seed dormancy, enhance water uptake, mobilizes starch and improve the rate and percentage of germination. GA3 application has significantly alleviated the adverse effects of salinity on germination percentage. These results support the finding of Basalah and Mohammad (1999).
Plumule and Radicle Length (cm): Plumule and radicle length decreased under different levels of salinity. Table 1 shows that reduction in radicle length was counteracted by 20 mg l–1 GA3 application. Maximum compensation was observed at 4 dS m–1 salinity, while minimum was noted at highest level (16 dS m–1) of salinity. All the treatments resulted in substantial reduction in radicle length than control. Both varieties showed similar response to all treatments. A trend of reduction in plumule length was apparent with increasing levels of salinity, but GA3 was helpful in giving greater length of plumule under salt stress. These findings support the findings of Boubaker (1996) and Basalah and Mohammad (1999).
Fresh weight of plumule and radicle (g): Statistically a significant (p<0.05) reduction in fresh weight of plumule and radicle was recorded under salt stress. However, this reduction was ameliorated by GA3 treatment (Table 1). Minimum fresh weight of plumule (0.02 g) was noted at 16 dSm–1 in both varieties. At this salinity level GA3 failed to promote the fresh weight of plumule. GA3 counteracted the adverse effect of salinity at 4.00 dS rn-1 salinity level. Radicle fresh weight also decreased under salt stress. But GA3 compensated this reduction. However, the ability of GA3 to increase the fresh weight of plumule and radicale decreased with increasing levels of salinity. Dhingra and Sharma (1992) Radi et al. (1989) and Khafagi et al. (1986) have also reported similar results.
Dry weight of pumule and Radicle (mg): Data pertaining to dry weight of plumule (Table 1) showed highly significant (PC0.01) differences among varieties, treatments and variety x treatments interaction. A trend of gradual reduction in dry weight of plumule was observed with increasing levels of salinity.
Gibberellic acid application increased dry weight of plumule under salinity. Maximum dry weight of plumule (17.00 mg) was noted in variety C44 under control condition, while minimum (3.33 mg) was in Paidar 91 at 12 dS m–1 alone or in combination with 20 mg l–1 gibberellic acid. Increasing salinity levels gradually decreased dry weight of radicle. Maximum reduction was observed at 12 dS m–1 salinity as compared to control. Application of GA3 increased the dry weight under salt stress. However, the efficiency of GA3 to increase dry weight of plumule and radicle reduced as the salinity levels increased. Similar results were observed by Ashraf et al. (1989), Macharia et al. (1995) and Khafagi et al. (1986).
Plant height (cm): Different treatments applied affected the plant height highly significantly in both varieties (Table 2). Salinity caused reduction in plant height. Minimum plant height as compared to control was noted at 12 dS m–1 salinity in both varieties. Exogenous application of gibberellic acid to salinity treated plants showed an increase in plant height under different levels of salinity. At 4 dS m–1 salinity level, GA3 increased the plant height than control, while at 8 and 12 dS m–1 plant height remained lower than control. C44 was more premising with regard to plant height under salinity alone or with GA3. Similar results were also arrived at by Khafagi et al. (1986) and Zaidi and Singh (1993).
Number of branches: Statistical analysis for number of branches revealed non-significant differences among varieties, treatments and variety×treatment interaction (Table 2). The number of branches remained unchanged under all treatments. Both varieties showed similar response to different treatments applied. These results negate the finding of Goel and Varshney (1987) who found that number of branches decreased by increasing salinity. These results are also contrary to the finding of Khan and Rashid (1983) and Lee (1990), who observed that gibberellic acid treated plants showed more branches as compared to untreated plants.
Fresh weight of shoot (g): Table 2 exhibited reduction in fresh weight of shoot with rise in salinity. At highest levels of salinity (12 dS m–1), fresh weight of shoot was minimum as compared to all other treatments. Application of gibberellic acid under saline condition increased the fresh weight of shoot, and compensated adverse effects of different levels of salinity at different levels. Its minimum compensatory effect was noted at 12 dS m–1. However, at 4 dS m–1 it increased the fresh weight than control. All the treatments indicted reduction in fresh weight of shoot as compared to control, except T4 (4 dS m–1 + 20 mg 1-1 GA3). C44 gave more fresh weight of shoot as compared to Paidar 91. Similar results have also been reported by Eid et al. (1992) and Baz et al. (1984).
Dry weight of shoot (g): Analysis of variance exhibited highly significant (p<0.01) differences among treatments, while varieties and variety×treatment interactions were nonsignificant. Table 2 revealed that salinity decreased the dry weight of shoot. Minimum dry weight (5.90 g) was noted at 12 dS m–1 salinity in Paidar-91. Application of gibberellic acid increased the dry weight of shoot under different levels of salinity. As the salinity levels increased the efficiency of gibberellic acid to ameliorate the adverse effect of salinity decreased. Maximum alleviation of salinity was noted at 4 dS m–1.
Among varieties C44 proved better with regard to fresh weight of shoot. These findings are in line with those of Maliwal and Paliwal (1982) and Mahmoud and Abdel-Aziz (1985).