Growth and yield parameters
Days to 50% flowering
From the data shown in Table 2 we can observe that significantly least number of days to 50% flowering was observed in treatment T5 in seeds treated with gibberellic acid (125 PPM) with 93.67 DAT and T4 with 94.00 DAT is statistically at par with T5. Highest days to 50% flowering was observed in T0 with 97.33 DAT. Gibberellic acid influences the hormonal balance within the plant, promoting the transition from vegetative to reproductive stages. This can lead to earlier panicle initiation and flowering, critical steps toward early crop maturity (
Haifaa and Moses, 2022).
Days to maturity
As per the data pertained in Table 2 it can be observed that seeds primed with gibberellic acid (125 PPM) (T5) varied significantly and matured earlier over other treatments within 123.67 DAT and statistically at par values were observed in T4 with 124.33 DAT and higher days to maturity was recorded in T0 with 129.33 DAT. Gibberellic acid treated seeds generally exhibit quicker and more uniform germination. This early start allows seedlings to establish and develop faster than untreated counterparts. Gibberellic acid stimulates cell division and elongation, leading to rapid vegetative growth. This means that the plants reach the critical phases of their life cycle, such as tillering and heading, earlier
(Wang et al., 2019).
Plant height
A perusal of data on plant height was recorded during the experimental crop growth period at the time of harvest, revealing a significant difference in plant height from treatment to treatment, which was recorded and tabulated in Table 2. The higher plant height was observed in treatment (T5) in which seeds treated with gibberellic acid (125 PPM) with 213.53 cm and statistically at par values were observed in T4 (210.38 cm) and the lowest was recorded in T0-control (140.33 cm). Gibberellic acid promotes plant height primarily through the stimulation of cell elongation and division in the internodes of the stem. The hormone activates the synthesis of enzymes that loosen the cell wall, allowing cells to expand. Additionally, GA influences the expression of genes involved in cell division and elongation, further contributing to increased plant height
(Zhang et al., 2023).
Flag leaf length
Significantly higher flag leaf length was obtained in treatment (T5- gibberellic acid (125 PPM) with 37.83 cm and statistically at par values in flag leaf length were observed in T4 with 35.26 cm and lowest flag leaf length was observed in T0-control with 25.43 cm. The data pertaining to flag leaf length can be observed in Table 2. Gibberellic acid (GA) plays a crucial role in the redistribution of nutrients throughout the plant, effectively directing essential elements such as nitrogen, phosphorus and potassium to areas where they are most needed. In the case of the developing flag leaf in rice, Gibberellic acid facilitates the transport of these nutrients from storage tissues or older leaves to the growing flag leaf. This process ensures that the flag leaf, which is vital for photosynthesis during the grain filling stage, receives an ample supply of nutrients. As a result, the flag leaf can achieve optimal growth, contributing to higher photosynthetic efficiency and, ultimately, improved crop yield and quality
(Singh et al., 2018).
Flag leaf width (top)
From the data shown in Table 2 we can observe that significantly highest flag leaf width at the top was observed in treatment T5 in seeds treated with gibberellic acid (125 PPM) with 0.56 cm and T4 with 0.54 cm is statistically at par with T5. Lowest flag leaf width at the top was observed in T0 with 0.41 cm.
Flag leaf width (middle)
As per the data pertained in Table 2 it can be observed that seeds primed with gibberellic acid (125PPM) (T5) and treatment - T6 [gibberellic acid (150PPM)] varied significantly and realized highest flag leaf width in the middle over other treatments with 1.04 cm and statistically at par values were observed in T4 with 1.03 cm and least flag leaf width in the middle was recorded in T0 with 0.78 cm.
Flag leaf width (bottom)
Significantly higher flag leaf width at the bottom of the leaf was obtained in treatment [T5- gibberellic acid (125PPM)] with 1.02 cm and statistically at par values in flag leaf width were observed in T4 with 0.97 cm and lowest flag leaf width was observed in T0-control with 0.77 cm. The data pertaining to flag leaf width can be observed in Table 2.
Number of tillers
From the data shown in Table 2 we can observe that significantly highest number of tillers were observed in treatment T5 in seeds treated with gibberellic acid (125 PPM) with 22.63 and T4 with 21.87 is statistically at par with T5. Lowest number of tillers were observed in T0 with 18.39.
Number of productive tillers
As per the data pertained in Table 2 it can be observed that seeds primed with gibberellic acid (125 PPM) (T5) varied significantly and recorded higher number of productive tillers over other treatments with 18.29 and statistically at par values were observed in T4 with 17.71 and least number of productive tillers were recorded in T0-control with 11.71. Gibberellic acid primarily influences tillering by enhancing cell elongation and division within the meristematic tissues at the base of the stem. GA improves nutrient mobilization and assimilation within the plant. Enhanced nutrient uptake supports vigorous growth and development of new tillers. The hormone also interacts with other phytohormones like auxins and cytokinin’s, which are vital for bud initiation and outgrowth
(Pandey et al., 2017).
Panicle length
Significantly highest panicle length was obtained in treatment [T5- gibberellic acid (125 PPM)] with 32.76 cm alongside treatment [T4- gibberellic acid (150 PPM)] with 32.14 cm and statistically at par values were observed in T3 with 31.64 cm and lowest panicle length was observed in T0-control with 27.88 cm. The data pertaining to panicle length can be observed in Table 2. When rice seeds are treated with gibberellic acid, it penetrates the seed coat and initiates a cascade of biochemical events that culminate in germination. One of the primary mechanisms through which gibberellic acid functions is by stimulating the synthesis of hydrolytic enzymes such as α-amylase. This results in the increase of internodal length in panicles and increase in its length
(Dong et al., 2016).
Number of spikelets per panicle
Significantly highest spikelets per panicle were obtained in treatment [T5- gibberellic acid (125 PPM)] with 81.43 and statistically at par values were observed in T4 with 80.69 and lowest spikelets per panicle were observed in T0-control with 72.37. The data pertaining to spikelets per panicle can be observed in Table 2.
Seed yield per plot
From the data shown in Table 2 we can observe that significantly highest seed yield per plot was observed in treatment T5 in seeds treated with gibberellic acid (125 PPM) with 35.84 gm and T4 with 34.61 gm is statistically at par with T5. Lowest seed yield per plot was observed in T0 with 21.79 gm. There is a positive correlation between flag leaf length and grain yield. Longer flag leaves can improve light capture and photosynthetic efficiency, contributing to better grain filling and higher yield. A longer flag leaf provides a larger surface area for light absorption, increasing the photosynthetic capacity of the plant. This is particularly beneficial during the grain filling stage when the flag leaf is the primary source of photosynthates
(Chunthaburee et al., 2014).
Test weight
As per the data pertained in Table 2 it can be observed that seeds primed with gibberellic acid (125 PPM) (T5) varied significantly and recorded higher test weight with 25.87 gm and statistically at par values were observed in T4 with 25.43 gm and lowest test weight was recorded in T0-control with 22.71 gm.
Biological yield
Significantly highest biological yield was obtained in treatment [T5- gibberellic acid (125 PPM)] with 142.84 gm and statistically at par values were observed in T4 with 137.65gm and lowest biological yield was observed in T0-control with 91.46 gm. The data pertaining to biological yield can be observed in Table 2.
Harvest index
From the data shown in Table 2 it is clear that T5 @ gibberellic acid (125 PPM) with 25.09% and T4 @ gibberellic acid (150PPM) with 25.15% had performed better over all other treatments and at par values were obtained in T7 and T3 with 24.20%, 24.16% and the lowest harvest index was observed in T1 with 23.21%. During the leaf growth stage, the rice root system is also developing and beginning to shape. The primary and secondary root systems of water-seeded crops share the same ancestor. In rice sown directly into the soil, the primary root system begins its growth at or close to the seed and the secondary system appears above the seed, emerging from the coleoptile’s base. These variations in rice root systems may impact nutrient delivery and other crop management decisions throughout rice growth stages (
El-Ekhtyar et al., 2008).
Seedling analysis
As per the data pertained in Table 3 the treatment (T5) in which seeds treated with gibberellic acid (125PPM) was significantly higher in germination percentage, root length, shoot length, seedling length, fresh weight, dry weight, vigor index -I and vigor index-II.
