Effect of freezing stress on some physiological and enzymatic responses of Ornamental plant, viola (Viola × wittrockiana) and snapdragon (Antirrhinum majus)

Freezing is one of the abiotic stresses that has harmful effects on plant growth and productivity. This study was performed to investigate some physiological and biochemical responses of two ornamental and cold-resistant plants, including the viola (Viola × wittrockiana) and snapdragon (Antirrhinum majus) under freezing stress.

To apply different temperature treatments on 70-day-old plants, the minimum temperature in January was used in three different places, including the greenhouse, the city of Isfahan and Fereydunshahr (temperatures of 20, 3- and -11 ° C, respectively) for 15 days.

Changes in the chlorophyll a/b ratio were differences in the two plants with increasing freezing stress, but shoot length gradually decreased and at the lowest temperature in viola and snapdragon plants were 63 and 50% of their controls (20 °C), respectively. The content of phenolic compounds, soluble carbohydrates and hydrogen peroxide also increased. In addition, a significant increase in catalase activity was observed in both plants under freezing temperatures, while the increase in ascorbate peroxidase activity was significant only in snapdragon at -11 °C. However, no significant change in the activity of guaiacol peroxidase was found in two plants under freezing temperatures.

Therefore, it seems that snapdragon and violet plants can withstand freezing stress by using osmotic regulation mechanisms as well as different abilities of antioxidant enzymes, which indicate different resistance strategies depending on their genotype.