CHANGES IN ABSCISIC ACID, STOMATAL CONDUCTANCE, AND ANTIOXIDANTS DURING LOW TEMPERATURE PRECONDITIONING AGAINST SO_2 INJURY IN CONTRASTING CULTIVARS OF COLEUS

The influence of 5 days of low temperature preconditioning (13℃) on SO_2 sensitivity in relationship to abscisic acid (ABA) concentration, stomatal conductance, transpiration rate, and SO_2 injury was examined in two cultivars of coleus found previously to differ in stress tolerance: SO_2-sensitive 'Buckley Supreme' ('BS') and SO_2-insensitive 'Marty' ('M'). 'BS' plants grown at 20℃ for 5 days and then fumigated with SO_2 for 2hr had 75% overall injury; those grown at 13℃ for 5 days had only 13% SO_2 injury. Corresponding 'M' plants given 20 and 13℃ pretreatment had 17 and 0% injury, respectively. This decrease in SO_2 sensitivity following preconditioning at 13℃ was associated with an increase in ABA concentration and a decrease in stomatal conductance and transpiration (Tn) rate, which presumably decreased the penetration of SO_2 into the leaf. Changes in the levels of several antioxidants and associated enzyme systems were also determined. Stress-insensitive 'M' contained 47% more ascorbate (AsA) and 17% greater ascorbate peroxidase (AP) activity than stress-sensitive 'BS.' Temperature preconditioning increased AP activity in 'BS' by 11% which was comparable to that found in 'M' at 20℃. Thus, the phytoprotection afforded against SO_2 by temperature preconditioning appears to involve both avoidance and detoxification mechanisms

CHANGES IN ABSCISIC ACID, STOMATAL CONDUCTANCE, AND ANTIOXIDANTS DURING LOW TEMPERATURE PRECONDITIONING AGAINST SO_2 INJURY IN CONTRASTING CULTIVARS OF COLEUS

The influence of 5 days of low temperature preconditioning (13℃) on SO_2 sensitivity in relationship to abscisic acid (ABA) concentration, stomatal conductance, transpiration rate, and SO_2 injury was examined in two cultivars of coleus found previously to differ in stress tolerance: SO_2-sensitive \u27Buckley Supreme\u27 (\u27BS\u27) and SO_2-insensitive \u27Marty\u27 (\u27M\u27). \u27BS\u27 plants grown at 20℃ for 5 days and then fumigated with SO_2 for 2hr had 75% overall injury; those grown at 13℃ for 5 days had only 13% SO_2 injury. Corresponding \u27M\u27 plants given 20 and 13℃ pretreatment had 17 and 0% injury, respectively. This decrease in SO_2 sensitivity following preconditioning at 13℃ was associated with an increase in ABA concentration and a decrease in stomatal conductance and transpiration (Tn) rate, which presumably decreased the penetration of SO_2 into the leaf. Changes in the levels of several antioxidants and associated enzyme systems were also determined. Stress-insensitive \u27M\u27 contained 47% more ascorbate (AsA) and 17% greater ascorbate peroxidase (AP) activity than stress-sensitive \u27BS.\u27 Temperature preconditioning increased AP activity in \u27BS\u27 by 11% which was comparable to that found in \u27M\u27 at 20℃. Thus, the phytoprotection afforded against SO_2 by temperature preconditioning appears to involve both avoidance and detoxification mechanisms