Effect of Thiamine, Ascorbic acid and Gibberellic acid (GA3) on Growth Characteristics, Pigment Content and Reduced Sugars of Petunia

Bedding plants, especially petunia is important element for urban landscaping and attracted the attention of landscapers. This is due to some properties such as growth habit and color. The petunia (Petunia hybrida L.) belongs to Solanaceae family that has annual and perennial varieties. This plant is originally from Argentina, Brazil and Uruguay. Some plant growth regulators such as gibberellic acid (GA3) and vitamins including thiamine and ascorbic acid affect plant growth and development and may extend flowering period. Vitamin C affects cell division and cell growth in plants and is effective on the feeding cycle activity in higher plants and it has an important role in electron transport system. The concentrations of 50 and 100 ppm of vitamin C and thiamine can increase the plant height, leaf number, leaf area, fresh and dry weight, and chemical compounds of the Syngonium plant. The application of 100 mg/l of GA3 significantly increased plant height and the number of leaves of gladiolus.
Material and The experiment was arranged in a factorial based on a completely randomized design with five replications. In this research, growth characteristics (lateral branch number, flower number, flower diameter, stem diameter, root length, and lateral branch length) and biochemical characteristics (chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, and reducing sugar) were measured. After seeding and transplanting the seedling at 6 leaf stage, plants sprayed at 4 various growth stages with following treatments: 1- Control
2- Vitamin C(100 mg/l)
3- Thiamin (100 mg/l)
4- Gibberellic acid (100 mg/l)
5- Vitamin C and Thiamin (The concentration of both 100 mg/l)
6- Vitamin C and Gibberellic acid (The concentration of both 100 mg/l)
7- Thiamin and Gibberellic acid (The concentration of both 100 mg/l)
8- Vitamin C, Thiamin and Gibberellic acid (The concentration of three 100 mg/l)
Data obtained from the measured parameters analyzed using statistical package SAS and means were compared using LSD test at the level of statistical significance of P˂0.05.
The results indicated that GA3 affected all the measured characteristics except carotenoids in comparison with thiamine and ascorbic acid. Meanwhile, the combined application of GA3 and ascorbic acid affected stem growth, root growth and flower diameter. Simultaneous use of GA3 and thiamine was effective on pigments, reducing sugar, carotenoids and flower number. The simultaneous application of three chemicals resulted in a considerable increase in growth and development traits, such as stem and root growth, flower number and diameter, pigments and reducing sugar compared to control. Generally, gibberellic acid will increase vegetative growth with impress cellular processes, including stimulation cell division and cell elongation. It was reported that the uses of ascorbic acid and gibberellic acid in Thyme (Thymus vulgaris) increased plant height and root length. Ascorbic acid makes a set of functions such as cell division and enlargements, cell wall development and other developmental processes in plants. Ascorbic acid affects plasma membrane proton pump and according to the acidic theory stimulates weaking cell wall and consequently will increase cell wall development and cell enlargement. It was found that thiamine significantly increased flower number in chrysanthemum .
The results indicated that the synergistic effects of this material can be used to enhance the growth and development of petunia. On the other hand, in arid and semiarid areas of the country, that drought and salinity stresses somewhat inevitable, these materials, especially vitamins are effective in reducing stress and increase flowering period.