Growth parameters
The pooled results of the present studies revealed (Table 1) that the growth parameters of tomato like plant height, leaf area and number of trusses per plant were significantly influenced by graded doses of SA and KNO
3 application. In this study, plant height of tomato were significantly varied from 87.18 cm in T
9 (stress check) to 115.77 cm in T
10 (irrigated control) with a mean value of 101.23 cm (SEm (±)= 4.18, CD (0.05)= 8.47) 7(Table 1). Under drought stress (stress check) plant height reduced to 24.70% as compared to irrigated control. Among the different doses of foliar application of SA and KNO
3, 100 ppm S.A (T
5) showed minimum reduction (4.52 %) followed by 5% KNO
3 (T
8) with 6.71%, however maximum reduction was observed in 10 ppm S.A (T
1)
i.e. 20.01% in plant height from the irrigated control. Similarly, number of trusses per plant varied from 9.48 in T
9 (stress check) to 11.63 in T
10 (irrigated control) with a mean value of 10.62 (SEm (±)= 0.4 , CD (0.05)= 0.82) (Table 1 ). As compared to irrigated control, in stress check treatment trusses per plant was reduced to 18.49%. Under drought, among different doses of foliar applications of SA and KNO
3, 5% KNO
3 (T
8) showed minimum reduction (3.44%) followed by 100 ppm S.A (T
5) and 10 ppm S.A (T
1) showed maximum reduction (12.21 %) in trusses per plant as compared to irrigated control. The leaf area significantly varied from 84.79 cm
2 in T
9 (stress check) to 98.72 cm
2 in stress free check (T
10) with a mean value of 91.97 cm
2 (SEm (±)=3.03, CD (0.05)= 6.14) (Table 1). As compared to irrigated control, under drought condition minimum reduction in leaf area (0.02%) was observed in 100 ppm S.A (T
5) followed by 0.08 % reduction in 5% KNO
3 (T
8) and maximum reduction (11.64%) was observed in 10 ppm S.A (T
1). All these parameters were found minimum in the stress check control plots T
9 (Drought stress). These similar findings were in accordance with the results obtained by
Qadir et al., (2019) in cherry tomato.
Alam et al., (2020) also reported similar result in Okra where in case of exogenous application of salicylic acid at 240 mgl
-1 had maximum plant height (130.75 cm), maximum number of leaves (30.39) and maximum number of pods (24.24) per plant.
Salicylic acid treatments effectively ameliorated the negative effects of drought stress by improving the leaf chlorophyll content, photosynthetic rate, stomatal conductance, carboxylation efficiency, transpiration rate and stability in membrane permeability, induction of stress proteinsand enhancing the activity of antioxidant enzymes
(Khalvandi et al., 2021 and
Amiri Adel et al., 2023). SA functions as a cofactor in enzyme systems and acts as an electron carrier, playing a crucial role in the oxidation and reduction mechanisms within plants
(Zulfiqar et al., 2021 and
Hasan et al., 2018). Auxin is synthesized in the meristem of the plant which is responsible for plant height, while their function is regulated by salicylic acid
(Li et al., 2022). The effect of salicylic acid on plant and flower yield could be due to increased vegetative growth, photosynthetic pigments, minerals and some bio constituents that affect plant growth. Similar findings were documented
(Qadir et al., 2019) who reported that plant height was found to be ameliorated by application of salicylic acid in tomato.
Umebese et al., (2009) and
Gerszberg and Hnatuszko-Konka (2017) found that water stress reduced tomato and amaranth stem height significantly at the vegetative stages and 3 mM application of salicylic acid was effective in keeping plant height similar to the control which was related to the ability of Salicylic acid to induce antioxidant responses that protect them from damage. Similar findings were reported (
Baltacýer et al., 2023) in tomato where Salicylic acid applications increase leaf area more effectively.
Abdelaziz and Taha (2018) indicated that supplementary spraying of K caused significant increase in terms of plant height, leaf area, number of leaves and dry weight of water-stressed tomato. These positive effects may be explained by the fact that foliar spraying increases available potassium uptake by plants, which is essential for enzyme utilization, IAA formation, regulating plant water status and optimizing plant growth performance. Likewise, plants treated with graded doses of potassium nitrate exhibited a higher number of flower clusters per plant compared to the stress control. These results could be attributed to potassium’s role in promoting shoot elongation, enhancing enzyme activity, facilitating protein synthesis, supporting photosynthetic transport and influencing chlorophyll content (
Abdelhameed and El-Hady, 2018).
Yield and yield attributing characters
The results of the pooled studies (Table 1) revealed that the maximum fruit yield per hectare (44.28 t/ha), number of fruits per plant (23.87), seed yield per hectare(266.39 kg/ha), seed germination % (88.17%), seedling length(14.93 cm), seed vigour index I(1315.49) and seed vigour index II(1201.82) noticed by T
10(Irrigated up to field capacity), which was significantly superior than all other treatments and at par with T
5 (100 ppm SA) along with T
8 (5% KNO
3).
Fruit yield per hectare varied from 26.64 tonnes in T
9 (stress check) to 44.28 tonnes in T
10 (Irrigated control) with a mean value of 35.80 tonnes (Table 1). As compared to irrigated control 39.84% reduction in stress check was observed in fruit yield. Under drought, among different doses of foliar application of SA and KNO
3, 100 ppm S.A (T
5) showed minimum reduction (1.22%) followed by 5% KNO
3 (T
8) and 10 ppm S.A (T
1) showed maximum reduction (30.80%) in fruit yield as compared to irrigated control. Number of fruits per plant varied from 18 in T
9 (Stress check) to 23.87 in T
10 (Irrigated control) with a mean value of 21.34 and in stress check, it is reduced to 24.59% as compared to irrigated control in number of fruits per plant. Under drought, among different doses of foliar application of SA and KNO
3, 5% KNO
3 (T
8) showed minimum reduction (2.76%) followed by 75 ppm SA (T
4) with 3.81% reduction and 10 ppm S.A (T
1) showed maximum reduction (22.29%) in number of fruits per plant as compared to irrigated control. Seed yield per hectare varied from 181.94 kg in T
9 (Stress check) to 266.39 kg in T
10 (Irrigated control) with a mean value of 229.09 kg (Table 1). In stress check, it is reduced to 31.70% as compared to irrigated control in seed yield per hectare. Under drought, among different doses of foliar application of SA and KNO
3, 5% KNO
3 (T
8) showed minimum reduction (0.73%) followed by 75 ppm SA (T
4) with 8.24% reduction in seed yield. However, maximum reduction was observed in 10 ppm SA (T
1) with 23.57% in seed yield per hectare as compared to irrigated control. Seed germination % varied from 67.33% in T
9 (stress check) to 88.17% in T
10 (irrigated control) with a mean value of 80.47 (Table 1). In stress check, it is reduced to 23.64% as compared to irrigated control in seed germination %. Under drought, among different doses of foliar application of SA and KNO
3, 100 ppm SA (T
5) showed minimum reduction (3.79%) and 10 ppm SA (T
1) showed maximum reduction (14.00%) in seed germination % as compared to irrigated control. Seedling length varied from 10.74 cm in T
9 (stress check) to 14.93 cm in T
10 (irrigated control) with a mean value of 12.82 cm (Table 1). In stress check, it is reduced to 28.06% as compared to irrigated control in seedling length. Under drought, among different doses of foliar application of SA and KNO
3, 5% KNO
3 (T
8) showed minimum reduction (7.10%) followed by 100 ppm SA with 7.97% reduction and 10 ppm SA (T
1) showed maximum reduction (23.64%) in seedling length as compared to irrigated control. Similarly, S.V I (seed vigour index I ) and S.V II (seed vigour index II) varied from 725.99 in T
9 to 1315.49 in T
10 and 506.90 in T
9 to 1201.82 in T
10 respectively. In stress check, S.V I and S.V II reduced to 44.81% and 57.82% as compared to irrigated control respectively. Under drought, among different doses of foliar application of SA and KNO
3, 5% KNO
3 (T
8) showed minimum reduction with 11.05% and 75 ppm S.A (T
4) with 5.90%, however maximum reduction in S.V I and S.V II as were observed in10 ppm S.A ( T
1) with 34.32% and 10 ppm S.A ( T
1) with 27.10% respectively as compared to irrigated control. Similar results were reported by
Soni et al., (2021) in garden pea where, exogenous application of SA resulted in an increase of yield components. Exogenous application of SA at 150 mg L
-1 as a foliar spray enhanced fruit yield by 41% compared with the control
(Chakma et al., 2021).
Application of KNO
3 also significantly increased yield parameters of tomato in accordance to control plots in water stress condition. Similar results were obtained in Tomato (
Abdelaziz and Taha, 2018) where single foliar K application recorded the highest number of fruits with control under water stress treatment, that justifying the crucial role of K in fruit bearing in tomato.
Under water stress conditions, plants treated with KNO
3 showed higher relative chlorophyll content, leaf area, photosynthetic rate, stomatal conductance, transpiration, carboxylation efficiency and higher levels of P, K, Mg, S, Cu and Fe than those not treated with KNO
3 (
Avila et al., 2022).
These findings are in close conformity with earlier findings
(Ali et al., 2021) where they found that KNO
3, SiO
2 and SA priming substantially improved emergence percentage, emergence index, seedling growth, seedling biomass and vigour of FARO44 rice under drought. Application of SA in drought–stressed plants resulted in growth recovery, increased photosynthesis and reduced oxidative stress
(Zulfiqar et al., 2021 and
Poór, 2020). The highest desirability index is found in case of T
8 (1.0), T
10 (1.0) and T
5 (1.0 ) followed by T
4 (0.75). This result reveals that T
8 and T
5 was similar to stress free check followed by T
4 with respect to yield and quality parameters.
Selection of best treatment
For the selection of best treatment(s) two criteria were taken into consideration
i.e. fruit yield and desirability index. The treatment having higher value in respect of these two parameters is considered as the best treatment. It was observed that T
5 (100 ppm S.A), T
8 (5% KNO
3), T
10 (Stress Free Check) and T
4 (75 PPM S.A) present in quadrant I and belongs to one cluster. T
10, T
8 and T
5 have highest rank for fruit yield and desirability index (Fig 1). T
4 is present in quadrant I and have above average rank for fruit yield and desirability index. The treatments T
6 (1% KNO
3), T
3(50 ppm S.A), T
2(25 ppm S.A), T
1 (10 ppm S.A) and T
9 (stress check) are present in quadrant IV and have below average rank for fruit yield and desirability index. Therefore T
8 (5% KNO
3) and T
5 (100 ppm of salicylic acid) is selected as the best treatment and among T
8 and T
5, T
8 (5% KNO
3) is considered as the optimum dose to be sprayed under water stress condition to improve yield and quality parameters of tomato seeds.
The scatter plot quadrant analysis was done through MS-excel 2010. In this analysis four clusters have been formed based on X- axis and Y-axis from where we identify the best suited treatments for drought tolerant tomato cultivation.