Influence of gibberellic acid on vegetative , floral and corms yield of gladiolus cultivars under the agro-climatic condition of Peshawar-Pakistan

Gladiolus is an important cut flower commercialized in Pakistan, and the use of gibberellic acid (GA3) to cultivate it in the Peshawar valley may promote the production of high quality flower spikes. Therefore, an experiment “Influence of Gibberellic acid on vegetative, floral and corm yield of gladiolus cultivars” was conducted under the climatic condition of Peshawar, during 2016. The experiment was laid out in two factors Randomized Complete Block Design there were five treatments replicated three times. Factor “A” was the gibberellic acid (GA3) concentrations i.e. 0, 50, 100, 150, 200 mgL Factor “B” was the two cultivars of gladiolus i.e., White Prosperity and Red Advance. It revealed from the results that most of the parameters were significantly influenced by gibberellic acid at 200 mgL. The maximum sprouting percentage (96.25), number of leaves plant (10.6), number of floret spike (14.4), number of shoots plant (3.17), number of daughter corm plant (3.54) and survival percentage (88.50), less days to corm sprouting (17.9), number of days to spike emergence (48.83), days to floret opening (72.73) were recorded in plants treated with 200 mgL of gibberellic acid (GA3) concentration. Whereas, the maximum plant height (75.62 cm), length of spike plant (57.15 cm), corm diameter (3.37 cm) corm weight (14.90 g) were recorded in plants treated with 150 mgLGibberellic acid. Red advance produced more number of leaves plant (9.89), number of shoots plant, (2.69) corm diameter (3.04 cm), corm weight (13.03 g), survival percentage (70.9), less number of days to spike emergence (53.8) and days to floret opening (74.5). It can be concluded from the present findings that the treatment of corms with 200 mgL gibberellic acid can improve the growth and yield of Red Advance cultivar of gladiolus under the agroclimatic conditions of Peshawar valley.


Introduction
Gladiolus (Gladiolus grandiflorus), is an ornamental flowering plant.It's another name is "Sword Lily" and its origin is South Africa.It is a monocot plant and belongs to family Irideaceae.Upto now its one hundred and fifty species are known [1].Gladiolus has herbaceous stem and narrowly linear leaves, sheathing at the base and side are flattened.Its flowers are bisexual [2].Gladiolus bears unparallel elegance, aesthetic an economic value for its beauty.It is frequently used in landscape, bedding and gardens is an excellent cut flower.These are also widely used in bouquets, in flower arrangements, artistic garland, etc.The gladiolus has captured a major share in the local and world floriculture markets, for its attractiveness and assortment of cultivar of colors [3].The high ranker countriesof gladiolus production are America, Italy, Australia, Poland, Holland, India, Iran, Singapore and Malaysia.However gladiolus cut flower spikes quality and its mass production is still trouble in numerous countries.Due to low production of cormels and corms, its commercial cultivation is still limited [4].A lot of factors i.e. corm size, sowing depth, planting time, management of fertilizer and use of growing hormones like GA3, Indole Acetic acid (IAA) etc., can influence the quality and production of gladiolus flowers and its corm and cormel size are increases.Bulbous crops are greatly influenced by the bulbs or corms size.Gladiolus corm is the propagule and food-storing underground stem.The corm size highly influences thedevelopment and vegetative growth, ultimately thecorms production, flowers and spike [5].Gibberellic acid increases height of theplants, number of leaves, number of flowers, induce early flowering and also increase the yield of gladiolus at different concentrations [6].Being a potential cut flower gladiolus grown worldwide due to its huge demand.The gladiolus spikes and florets have good looking stunning color, Long vase life and different sizes [7].The objectives of this study were to investigate the response of two gladiolus cultivars to gibberellic acid treatments and to determine the effects of these treatment on growth and corms yield of two gladiolus cultivars.Considering the above facts, the present experiment was designed, to study "The Influence of Gibberellic acid on vegetative floral and corms yield of gladiolus Cultivars", with the following objectives.To explore the suitable cultivar for growth and production of gladiolus.To find out the optimum concentration of Gibberellic acid for growth, flower and corms production of gladiolus.To determine the interactive effect of Gibberellic acid concentration and gladiolus cultivars on the growth and production of gladiolus.

Materials and methods
The experiment entitled "Influence of gibberellic acid on vegetative, floral and corms yield of gladiolus cultivars" was conducted during the year 2016 at Horticulture field in Agriculture Research Institute Tarnab, Peshawar.The experiment was laid out in Randomized Complete Block Design with two factors.During the experiment the corms of Gladiolus cultivars (White Prosperity and Red Advance) were treated with five different concentration of Gibberellic acid (0, 50, 100, 150 and 200 mgL -1 ) and was replicated three times.A total of 24 corms were used per treatment.As Gibberellic acid is not easily dissolved in water for this purpose, Ethanol was added for dissolving Gibberellic acid into water.Corm soaking was done in Gibberellic acid solutions for about 24 hours before corm sowing.

Parameters studied
Data were recorded on the following parameters: Days to corms sprouting Number of days for corms sprouting was counted from the date of corms sowing to the date of corms sprouting and the average was calculated.

Corms sprouting percentage
The sprouted corms were counted from the first sprouting to the last sprouting and the percentage was calculated by the following formula.

Number of leaves plant -1
Number of leaves plant -1 was recorded by counting the number of leaves in each treatment in every replication and then average was calculated.Days to spike emergence Number of days for Spike emergence was counted from the date of corm sowing to the first spike emergence and average was calculated.

Plant height (cm)
Plant height was measured with the help of measuring tap in each treatment in every replication from the ground level to top of flowering spike then average was calculated.

Number of floret spike -1
Number of floret spike -1 was counted in of each treatment in every replication and then average was calculated.

Number of shoots plant -1
The average number of shoots plant -1 was recorded by counting the number of shoots in each treatment in every replication and then average was calculated.

Length of spike (cm)
The spike length was measured from the base of the flower spike with the help of measuring tap from each treatment in every replication and then average was calculated.Days to flower opening Data regarding days to flowering emergence was recorded from the date ofcorms planted to flower emergence and then average was calculated.

Number of daughter corms plant -1
Data pertaining number of daughter corms was counted in each treatment in every replication and their mean was computed.

Diameter of daughter corms (cm)
Diameter of corms was recorded with the help of Vernier caliper for all treatments in every replication and then average was calculated.

Corms weight (g)
The weight of the harvested daughter corms was recorded in each treatment in every replication by using electronic balance and average was calculated.

Survival percentage
Number of survived plants were recorded and the averages were then calculated with the following formula.

Statistical procedure
The data was collected on various parameters and was applied analysis of variance (ANOVA) to view the difference between treatments as well as interaction.In case when the difference was significant, it was assess for difference through least significant difference (LSD) test.Statistical computer software "Statistix 8.1" was applied for computing both ANOVA and LSD at 5 % level of probability [8].

Results and discussion
The results pertaining to different growth and flowering parameters are described as under.

Days to corms sprouting
Data regarding days to corms sprouting of gladiolus are mentioned in (Table 1) which showed that the various Gibberellic acid concentration had significant effect on days to corm sprouting of gladiolus.While cultivars and their interaction showed nonsignificant results.The mean values pertainingthat less number (17.9) of days were observed in plants with the application of 200 mgL -1 gibberellic acid (GA3) treatment, followed by (18.8) days with the application of 150 mgL -1 gibberellic acid (GA3) treatments, while more number (22.8) of dayswere taken by plants in control treatment.The highest days to corm sprouting was observed in control treatment, while minimum number days to corms sprouting observed in plants treated with 200 mgL - 1 gibberellic acid (GA3).It might be due to the high nutrients preserved and gibberellic acid which can enhanced the cell expansion and promotes synthesis of DNA in cells.These findings are in line with [9,10]

Number of leaves plant -1
Data related to number of leaves plant -1 of gladiolus is given in (Table 3) revealed that numbers of leaves plant -1 was significantly affected by cultivars and Gibberellic acid concentrations, while the interaction between cultivars and gibberellic acid concentrations showed non-significant results.The mean value of different cultivars of gladiolus showed that more number (9.8) of leaves plant -1 were produced by Red Advance and minimum number (8.4) of leaves plant -1 were noticed in White Prosperity.Data recorded for gibberellic acid treatment is mentioned in Table-3, which shows that maximum number (10.6) of leaves plant -1 were produced in plants treated with 200 mgL -1 gibberellic acid, followed by (10.2) in plants that were treated with 150 mgL -1 gibberellic acid while, the minimum numbers (7.6) of leaves plant -1 were recorded in plants in control treatment.There are different factors which can enhance the growth of gladiolus cultivars that can be the genetic makeup of cultivars or may be the favorable environmental conditions.Hence more number of leaves plant -1 in Red Advance may be due to the genetic makeup or availability of suitable environmental conditions [12].An increase in growth parameter i.e., number of leaves, with the application of GA3 mightbe the enhanced cell division accured in shoot tip with cell elongation and growth promotory action of gibberellic acid.These findings are in lined with [13,14].Moreover increased in growth parameters may be due to the function of GA3 in plant tissues.Hence GA3 is known to be actively involved in various plant development process [15].In various studies, gibberellin application exogenously found as a promoter of shoot elongation and vegetative growth [16-18].

Number of floret spike -1
The data pertaining to number of floret spike -1 of gladiolus as described in (Table 6) which showed that Gibberellic acid concentrations had significant effected the number of floret spike -1 of gladiolus cultivars.While cultivars and their interaction showed non-significant results.
The mean values demonstrated that more number (14.4) of floret spike -1 was observed in plants treated with200 mgL -1 gibberellic acid, followed by (14.1) with 150 mgL - 1 gibberellic acid treatment, while less number (10.4) of floret spike -1 were noted in plants in control treatment.
The increase in number of floret spike -1 was due to increase in no. of leaves and ultimately the leaf area which increase photosynthates needed to improve reproductive growth in plants

Length of spike plant -1 (cm)
The data related to flower spike length (cm) is presented in (Table 8) which described that Gibberellic acid concentrations had significant effected on the length of spike plant -1 (cm) of gladiolus.While the cultivars and theirinteraction showednon-significant results.The mean value of different Gibberellic acid concentrations demonstrated that maximum (57.15 cm) length of spike plant -1 was gained by plants treated with150 mgL -1 Gibberellic acid concentration, followed by (55.45 cm) with the application of 200 mgL -1 Gibberellic acid concentration, whereas minimum spike length plant -1 (45.73 cm) was found in control treatment.Gibberellic acid promotes vegetative growth and increases the photosynthetic and metabolic activities causing more transport and utilization of photosynthetic products [12] in gladiolus due to which spike length and rachis length increased thereby allowing florets to grow larger [24].These findings are supported by [29] in tuberose flower and [14] in gladiolus.Days to flower opening Data pertaining days to flower opening is mentioned in (Table 9) show that cultivars and gibberellic level are highly significantly effected days to flowering emergence and their interaction are non-significant.The mean table data showed that less number of days (74.5) to flower opening were noted in Red Advance cultivar, while more number of days (76.1) were obtained by White Prosperity.Different concentrations of Gibberellic acid had significant response for days to floret opening.Less number of days (72.7) to flower opening were found in 200 mgL -1 gibberellic acid (GA3), followed by (73.9) days to floret opening observed in plant treated with150 mgL -1 Gibberellic acid, while the more number of days (79.2) to floret opening was resulted from plant in control treatment.
Early flower opening in Red Advance cultivar might be due to the early vegetative growth.As more photosynthates production was found in the plants of Red Advance which enhance the vegetative growth parameters and resulted in the earlier completion of life cycle, hence promoted the reproductive growth as well [12,19,30].Different concentrations of GA3 and cultivars significantly influenced on days to flowering of gladiolus (Table 9).This is might be regulating effect of increased vegetative growth in early phase due to increased photosynthesis and Co2 fixation.Further exogenous application of GA3 influences early floral initiation.It was also reported by [14, 31-33] that gibberellic acid promoted vegetative growth and increased the photosynthetic and metabolic activities caused more transport and utilization of photosynthetic products resulted early flowering in gladiolus.

Number of daughter corms plant -1
Data related to Number of daughter corms plant -1 is given in (Table 10) which showed that cultivars and Gibberellic acid were significant, while their interaction showed non-significant results.Gladiolus cultivars significantly affected number of daughter corms produced plant -1 and their mean values shows that maximum number of daughter corms (3.0) plant -1 were gained by Red Advance, while minimum number of daughter corms (2.7) plant -1 was noticed in White Prosperity cultivar.A significant response was observed regarding gibberellic acid for number of daughter corms plant -1 of gladiolus.More number of daughter corms (3.5) plant -1 were obtained in plants with the application of 200 mgL -1 Gibberellic acid concentration, followed by (3.3)number of daughter corms plant -1 treated with 150 mgL -1 Gibberellic acid concentration and less number (2.4) of daughter corms produced plant -1 were recorded in control treatment.
Higher number of corms plant

Diameter of corms (cm)
The observation about diameter of corms (cm) is tabulated in (Table 11) which described that cultivars and different gibberellic acid levels significantly affected corms diameter, where their interaction were not showed significant effect.The mean value identify that maximum corm diameter was observed (3.04 cm) in Red Advance and minimum corm diameter was noticed (2.87 cm) in White Prosperity.The mean value of different Gibberellic acid concentrations revealed that maximum corm diameter (3.37 cm) was obtained by plants treated with 150 mgL -1 Gibberellic acid concentration, followed by (3.25) with 200 mgL - 1 Gibberellic acid concentration while the lowest diameter of corm (2.47) were gained by plants in control treatment.There are different factors, which can enhance the diameter of corms.It might be due to the genetic makeup of cultivar or may be the favorable environmental conditions.Maximum corm diameter was observed in Red Advance cultivar, might be due to the application of gibberellic acid due to which the plants produced more photosynthates and carbohydrates accumulation, as a result cause large corm size.Gibberellins lead to increased cell division and cell growth apparently which lead to increased elongation of root [37] and it enhances corm diameter.

Survival percentage
The mean data for survival percentage is showed in (Table 13) which showed that cultivars, Gibberellic acid concentrations and their interaction had a significant effect on survival percentage of gladiolus.There was significant variation in survival percentage among the gladiolus cultivars.The mean data showed that maximum survival percentage (70.9)was recorded in Red Advance cultivar, while the less survival percentage (62.7)was noticed in White Prosperity cultivar.The Gibberellic acid had significant effect on survival percentage of gladiolus cultivars.However the maximum survival percentage (88.5)was recorded in plants applied with 200 mgL -1 gibberellic acid concentration, followed by (80.1) treated with 150 mgL - 1 gibberellic acid, while less survival % (42.5) were observed in control treatment.The interaction was found significant between gladiolus cultivars and gibberellic acid concentrations on survival percentage.However, more survival % (89.5) was observed in Red Advance cultivar treated with 200 mgL -1 gibberellic acid while, less survival % (39.3) was observed in White Prosperity cultivar in control treatment.From the results it was found that, more survival percentage was noted in plants of Red Advance cultivar that were treated with 200 mgL -1 gibberellic acid (GA3).It might be due to the genetic makeup or favorable environmental conditions that were available for the plants of Red Advance cultivar [19].Moreover, the presence of high of photosynthates resulted in the enhancement of vegetative and reproductive growth of plants, hence it can be the reason of high rate of survival percentage [12].GA3 application can also trigger the rapid cell division, cell elongation and nutrient availability, which leads to the more survival percentage of plants [41].

Conclusion
It is concluded from the above results that Gibberellic acid concentrations and cultivars significantly influenced vegetative, floral and corm yield of Gladiolus.Gladioulus cultivar Red Advance had significantly higher number of leaves plant -1 , number of shoots plant -1 , number of daughters corm plant -1 , length of spike plant -1 , corms diameter, corm weight, survival percentage, days to spike emergence and days to floret opening.Gibberellic acid concentration at the rate of 200 mgL -1 showed significant effect on sprouting percentage, number of leaves plant -1 , number of shoots plant -1 , number of daughter's corm plant -1 , survival percentage, number of days to corm sprouting, days to spike emergence and days to floret opening.Gibberellic acid at 150 mgL -1 exhibited significant effect on plant height (cm), length of spike plan t-1 , corms diameter and corm weight.
[25].More number of leaves can increase the amount of food required for number of floret spike -1 .Thepresent results are in close conformity with [1].

. Table 1. Influence of gibberellic acid concentrations and cultivars on the days to corm sprouting of gladiolus
[11]s sprouting percentageData pertaining days to corms sprouting percentage of gladiolus are shown in (Table2) which revealed that gibberellic acid concentrations having significant effect on sprouting percentage of gladiolus.While cultivars and interaction showed nonsignificant results.The mean values of Table-2, presented that more sprouting percentage (96.3)wasrecorded in plants treated with 200 mgL -1 gibberellic acid, followed by (91.71) with 150 mgL - 1 gibberellic acid treatment, while less sprouting (71.1) percentage were noted in control treatment.The balance between growth promoters hormones and growth retardant hormones can play an important role in plant growth and development.As Abscisic acid is dominant and hence responsible for the dormancy in gladiolus corms.The freshly harvested corms of gladiolus having dormancy for the period of three months.Reduction in the level of ABA is the major factor causing endogenous hormonal balance, which promotes the sprouting percentage in gladiolus corms.Gladiolus corms treated with 150 mgL -1 and 200 mgL - 1 gibberellic acid concentrations resulted in highest sprouting percentage 91.7,and96.3as mentioned in table-4.2.Which shows that, 150 mgL -1 and 200 mgL -1 gibberellic acid application was actively involved in the breaking of reserved food material with the help of hydrolytic enzymes present in GA3 which might have result in highest sprouting percentage[11].