Modulation of ascorbic acid accumulation under high irradiance by growth regulators

MARÍA E. SENN; LUIS M. MAZORRA; GUSTAVO GERGOFF GROZEFF; CARLOS BARTOLI

Mar del Plata

Congreso; XXIX Reunión Argentina de Fisiología Vegetal; 2012

Sociedad Argentina de Fisiología Vegetal

MODULATION OF ASCORBIC ACID ACUMULATION UNDER HIGH IRRADIANCE BY GROWTH REGULATORS María E Senn1, Luis M Mazorra1,2, Gustavo Gergoff Grozeff1, Carlos G Bartoli1. 1 INFIVE, Fac de Cs Agrarias y Forestales y Fac de Cs Naturales de la UNLP, La Plata, Argentina. 2 National Institute of Agricultural Sciences. Havana. Cuba. This study evaluates whether the accumulation of ascorbic acid (AA) induced by high irradiance (HI) is modulated by hormone signaling, particularly gibberellins, brassinosteroids and ethylene whose influence on AA synthesis under normal conditions has been demonstrated. Arabidopsis thaliana plants were grown during four weeks under 120 umol m-2 s-1 (PPFD) at 23 °C (10/14hr light / dark) before increasing irradiance to 250 umol m-2 s-1. It was determined that 48 hr under HI treatment was sufficient to increase the AA accumulation in leaves by a 43%. Hormonal treatments were applied by spraying the plants 48 hr prior to the irradiance change. The application of 100/150 μM gibberellic acid produced no change in AA content at HI however, applying paclobutrazol (inhibitor of gibberellin synthesis) produced a differential increase in AA accumulation of 85% (42% above the 43% increase in HI). Treating plants with the ethylene action inhibitor 1-methyl cyclopropene (1-MCP) (by placing plants in 40 L chambers 1μL containing 1μl L-1 1-MCP overnight) produced a differential increase in AA accumulation of 90% (46% above the 43% increase in HI). In brassinosteroid-synthesis dwarf mutant plants (det2), there was no variation in the percentages of AA increase in high irradiance compared with wt plants. In all cases the ratios of reduced and oxidized AA were held constant so that there would be no influence of hormonal or irradiance treatments in the balance of both redox states of the antioxidant. The results indicate that there would be gibberellins and ethylene signaling but not brassinosteroids participation in the AA accumulation induced by high irradiance. Work is under way to study the involvement of abscisic acid. It will be determined if the irradiance dependent AA accumulation is hormonally regulated by changes in photosynthesis and respiration in arabidopsis leaves and at what point on the route of synthesis of AA holds interests hormonal regulation.