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Summary The effect of light on brassinosteroid (BR), indole-3-acetic acid (IAA) and IAA+BR-induced ethylene production in etiolated mung bean ( Vigna radiata L. Rwilcz cv. Berken) hypocotyl segments was evaluated. When 4-day-old, dark grown mung bean seedlings were exposed to 3.7 AE m −2 s −1 of fluorescent light, BR-induced ethylene production by segments taken from these plants was decreased by approximately 35 % with a 15 min exposure period and by up to 75 % following a 60 min exposure period. Segments taken from seedlings which were pretreated for 30 min with irradiances varying from 0 to 80 /,E m −2 s −1 exhibited a maximum inhibition (78 %) in BR-induced ethylene production with a 21 AE m — 2s- 1 exposure and no further decrease at higher irradiances tested. IAA-induced ethylene production was inhibited only with the longest exposure period tested, 3.7 ItE m −2 −1 for 120 min. Inhibition of IAA-induced ethylene production required irradiances as high as 40 AE m −2 s −1 for 30 min. Maximum inhibition of IAA + BR-induced ethylene occurred with the longest exposure time tested (3.7 /,E m −2 s −1 for 120 min) and at the highest irradiance tested (80 ,uE m −2 s −1 The results contained within this study show that in order to optimize BR-induced ethylene production, mung bean seedlings should receive a minimum exposure to light during handling and cutting operations. Conversely, IAA and IAA + BR-induced ethylene do not exhibit the same sensitivity to light. |
